View Full Version : Winch Launch Safety Study
In the recent Aerokurier, there is a very good 2 part article on winch
safety, which I think everyone should read who is interested in winch
launches. I read it in the hard cover version in German, so I don't
know if an online version is available.
The main takeaways for me are the following statistics:
- Winch launches are the safest launch type
- Tension controlled winches are far safer than speed controlled ones,
such as the new electric, hydro and diesel designs. They recommend
modifying them to tension controlled ones, as the data is clear.
- initial tension at he beginning of the launch should be about
between 0.5g and 1g - depending on type.
- At the beginning of the launch, there is a danger that if the
acceleration is too strong, it could exceed the elevator authority of
gliders to stay in a safe angle of attack. A high speed (or in the
case of a rope break) low speed stall could occur - which are almost
always fatal in this phase. Plenty of evidence of this is features in
the article, including the fact that GROB models are never involved in
this type of accident because of their large elevators and low mounted
wings, generally limiting pitch up forces.
- Permissible tension forces, tow speeds the weak links should be
changed to allow for faster tows (though not in the beginning phase) -
Especially in the case of GROB models as the weak link used for GROBs
are too weak as seen in those often breaking and those models often
involved in accidents involving broken weak links. Stronger ones from
1.6-1.9g should be used for GROBS.
- The biggest causes of accidents during winch launches are :
1. Winch malfunctions
2. Rope Breaks
These two points can be addressed by proper care and maintenance of
the equipment.
And again, speed controlled winch designs, like the newer ones, are
far more accident prone, than tension controlled ones. What is needed
is tension, not constant speed, so the metric being measured is the
wrong one and it is more difficult for the winch operator to adjust
from one model to the next based just on speed.
Also speed controlled winches give the opposite response to pilot
inputs compared to tension controlled winches. On a Speed controlled
winch, pulling will increase airspeed and pushing will decrease it. On
a Tension controlled one, pulling will reduce airspeed, while pushing
will increase it. They both produce opposite results per pilot input.
In the beginning phase of the launch, the tension controlled one has
obvious clear advantages and is far safer statistically. Having said
all this, winch launches are safer than aerotows.
Someone please ask commercial operators stateside to offer winch
launches, please.........like at Llano, Cal City, Minden,
etc.........you can pick up a used Tost winch starting around 7k Euros
- a lot cheaper than rebuilding, insuring and operating a Pawnee.
Tom Vallarino
bildan
March 18th 09, 03:26 AM
On Mar 17, 7:45*pm, wrote:
> In the recent Aerokurier, there is a very good 2 part article on winch
> safety, which I think everyone should read who is interested in winch
> launches. I read it in the hard cover version in German, so I don't
> know if an online version is available.
>
> The main takeaways for me are the following statistics:
>
> - Winch launches are the safest launch type
> - Tension controlled winches are far safer than speed controlled ones,
> such as the new electric, hydro and diesel designs. They recommend
> modifying them to tension controlled ones, as the data is clear.
> - initial tension at he beginning of the launch should be about
> between 0.5g and 1g - depending on type.
> - At the beginning of the launch, there is a danger that if the
> acceleration is too strong, it could exceed the elevator authority of
> gliders to stay in a safe angle of attack. A high speed (or in the
> case of a rope break) low speed stall could occur - which are almost
> always fatal in this phase. Plenty of evidence of this is features in
> the article, including the fact that GROB models are never involved in
> this type of accident because of their large elevators and low mounted
> wings, generally limiting pitch up forces.
> - Permissible tension forces, tow speeds the weak links should be
> changed to allow for faster tows (though not in the beginning phase) -
> Especially in the case of GROB models as the weak link used for GROBs
> are too weak as seen in those often breaking and those models often
> involved in accidents involving broken weak links. Stronger ones from
> 1.6-1.9g should be used for GROBS.
>
> - The biggest causes of accidents during winch launches are :
>
> 1. Winch malfunctions
> 2. Rope Breaks
>
> These two points can be addressed by proper care and maintenance of
> the equipment.
>
> And again, speed controlled winch designs, like the newer ones, are
> far more accident prone, than tension controlled ones. What is needed
> is tension, not constant speed, so the metric being measured is the
> wrong one and it is more difficult for the winch operator to adjust
> from one model to the next based just on speed.
>
> Also speed controlled winches give the opposite response to pilot
> inputs compared to tension controlled winches. On a Speed controlled
> winch, pulling will increase airspeed and pushing will decrease it. On
> a Tension controlled one, pulling will reduce airspeed, while pushing
> will increase it. They both produce opposite results per pilot input.
>
> In the beginning phase of the launch, the tension controlled one has
> obvious clear advantages and is far safer statistically. Having said
> all this, winch launches are safer than aerotows.
>
> Someone please ask commercial operators stateside to offer winch
> launches, please.........like at Llano, Cal City, Minden,
> etc.........you can pick up a used Tost winch starting around 7k Euros
> - a lot cheaper than rebuilding, insuring and operating a Pawnee.
> Tom Vallarino
Tension controlled winches are certainly safer and provide higher
launches than speed controlled ones - any winch with an automatic
transmission is speed controlled since that's what the automotive
drive train was designed to do.
I'm not sure I follow the rest of your post. Hopefully an English
translation will be available.
Bill Daniels
The article says that the older gasoline powered winches with
automatic transmissions are tension controlled types, or at least
allow themselves to be controlled that way. I'm not familiar with
transmissions to know either way, just citing what the article says.
They go on to recommend that the existing electric ones and the
Diesels commonly used at least install a tension meter. Further, the
older Hercules winches should be abandoned as they are not up to par,
break down often and are not of the highest standard. These are mainly
from eastern Europe.
To take away, besides maintaining the equipment, is to realize that an
avoidable danger is in accelerating too fast in the first few seconds,
because this can (emphasis on "can") cause an unavoidable pitch up
movement that can not be compensated for with the available elevator
authority - resulting in either a high speed and nose high stall at
low altitude due to an excessive angle of attack or a rope break (weak
link). the former is almost always fatal. The latter not, but can be
if the pilot does not react properly and can contribute to
accidents.
Derek Copeland[_2_]
March 18th 09, 06:30 AM
At 03:26 18 March 2009, bildan wrote:
>
>Tension controlled winches are certainly safer and provide higher
>launches than speed controlled ones - any winch with an automatic
>transmission is speed controlled since that's what the automotive
>drive train was designed to do.
>
>I'm not sure I follow the rest of your post. Hopefully an English
>translation will be available.
>
Short of fitting a speed controlling governor, I don't think that any
current winches are 'speed controlled'. Some earlier diesel powered
winches did have this arrangement, but it was found not to work. During a
properly controlled winch launch the motor and drum speeds reach a maximum
as the glider lifts off, and then decrease during the rest of the launch,
due to vector effects and wind gradients.
Winches with automatic transmissions , such as the Tost and the Skylaunch,
will give perfect good constant pull/tension launches as long as you use an
appropriate throttle or power setting. The Tost depends on the skill of the
driver to do this, but the Skylaunch has an adjustable throttle stop that
you can pre-program according to the glider type and headwind.
Derek Copeland
The article is especially critical of the electric winches that they
say are only speed controlled. They said they tried to talk to the
manufacturer (in Germany), but they refused to discuss the issue. They
also mention hydro winches some of which have the same set up - only
speed controlled - at least that's how I understood the article - and
some Diesels. Though they mention that some set ups do have both a
speed and tension indicators - sort of a hybrid.
It is clear that they implied that gasoline driven winches with
automatic transmissions, which are widespread, are the safest ones and
explain the theory as to why, namely because they are tension
controlled. I'm just the messenger.................
I remember reading about winches with torque converters, I think the
Tosts - which is a component of the automatic transmission, so not
speed controlled, but torque regulated via the transmission =
controlling tension on the cable, not the drum or cable speed.
Point is, primarily speed controlled or regulated winches are the most
dangerous type in the statistics table they produced in the article.
One final point from the article:
Only the winch operator/winch can ensure that the first seconds of the
launch are not in the red zone. The pilot can do absolutely nothing if
the winch catapults the glider into the air in a manner that exceeds
the elevator authority and the maximum angle of attack is exceeded at
50 feet in 2 seconds or less. If that happens, rare as it has
occurred, it has always been fatal. A tension controlled winch would
not do this..........ditto if the launch is too strong, causing a rope
break or weak link break............
John Roche-Kelly
March 18th 09, 10:15 AM
Interesting. In the UK the accident statistics confirm that there are more
serious injuries/fatalities/damaged gliders per 100000 launches by winch
than by aerotow!
Automatic transmissions would provide constant torque rather than tension
or speed. And then only at a fixed throttle setting.
The predominant accidents with winches are 1) wing drop during ground run;
pilots must release before the wing touches the ground 2) stall during
rotation, it is hard to know whether these are elected rotation or
automatic rotation 3) power loss below 100' and inappropriate pilot
response and 4) power loss mid launch.
Mechanical or electrical devices to maintain torque, speed or tension are
all very well in their place but there is no unique solution as different
conditions apply at different parts of the launch. There is no substitute
for pilot and winch driver training and awareness.
I recommend that all UK pilots read the annual BGA report on glider
accidents and that they promote the training initiatives from the BGA
which appear to be reducing the number of accident and incidents in our
sport.
Best wishes
JohnR-K
Martin Gregorie[_4_]
March 18th 09, 11:53 AM
On Wed, 18 Mar 2009 10:15:07 +0000, John Roche-Kelly wrote:
> 2) stall during rotation, it is hard to know whether these are
> elected rotation or automatic rotation
>
Note to any Libelle drivers out there who are thinking of trying winch
launching for the first time.
Libelles winch well provided the pilot has been given a proper briefing
by somebody who is familiar with winch launching them. However, with
incorrect technique they can snap-rotate at lift-off. There is nothing in
the owners manual about this.
--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |
Karl Striedieck
March 18th 09, 03:07 PM
If you don't have a modern tension-controlled winch you can still get a safe
launch by using the "poor mans" tension control as we do with our 650HP,
supercharged Chevrolet Suburban auto tows. We brief the driver on the
airspeed range we want and then during the launch the pilot holds down the
mic button and continuously transmits the indicated airspeed. It works
great and enhances safety.
Karl Striedieck
> wrote in message
...
> In the recent Aerokurier, there is a very good 2 part article on winch
> safety, which I think everyone should read who is interested in winch
> launches. I read it in the hard cover version in German, so I don't
> know if an online version is available.
>
> The main takeaways for me are the following statistics:
>
> - Winch launches are the safest launch type
> - Tension controlled winches are far safer than speed controlled ones,
> such as the new electric, hydro and diesel designs. They recommend
> modifying them to tension controlled ones, as the data is clear.
> - initial tension at he beginning of the launch should be about
> between 0.5g and 1g - depending on type.
> - At the beginning of the launch, there is a danger that if the
> acceleration is too strong, it could exceed the elevator authority of
> gliders to stay in a safe angle of attack. A high speed (or in the
> case of a rope break) low speed stall could occur - which are almost
> always fatal in this phase. Plenty of evidence of this is features in
> the article, including the fact that GROB models are never involved in
> this type of accident because of their large elevators and low mounted
> wings, generally limiting pitch up forces.
> - Permissible tension forces, tow speeds the weak links should be
> changed to allow for faster tows (though not in the beginning phase) -
> Especially in the case of GROB models as the weak link used for GROBs
> are too weak as seen in those often breaking and those models often
> involved in accidents involving broken weak links. Stronger ones from
> 1.6-1.9g should be used for GROBS.
>
> - The biggest causes of accidents during winch launches are :
>
> 1. Winch malfunctions
> 2. Rope Breaks
>
> These two points can be addressed by proper care and maintenance of
> the equipment.
>
> And again, speed controlled winch designs, like the newer ones, are
> far more accident prone, than tension controlled ones. What is needed
> is tension, not constant speed, so the metric being measured is the
> wrong one and it is more difficult for the winch operator to adjust
> from one model to the next based just on speed.
>
> Also speed controlled winches give the opposite response to pilot
> inputs compared to tension controlled winches. On a Speed controlled
> winch, pulling will increase airspeed and pushing will decrease it. On
> a Tension controlled one, pulling will reduce airspeed, while pushing
> will increase it. They both produce opposite results per pilot input.
>
> In the beginning phase of the launch, the tension controlled one has
> obvious clear advantages and is far safer statistically. Having said
> all this, winch launches are safer than aerotows.
>
> Someone please ask commercial operators stateside to offer winch
> launches, please.........like at Llano, Cal City, Minden,
> etc.........you can pick up a used Tost winch starting around 7k Euros
> - a lot cheaper than rebuilding, insuring and operating a Pawnee.
> Tom Vallarino
bildan
March 18th 09, 03:16 PM
On Mar 17, 11:12*pm, wrote:
> The article says that the older gasoline powered winches with
> automatic transmissions are tension controlled types, or at least
> allow themselves to be controlled that way. I'm not familiar with
> transmissions to know either way, just citing what the article says.
>
> They go on to recommend that the existing electric ones and the
> Diesels commonly used at least install a tension meter. Further, the
> older Hercules winches should be abandoned as they are not up to par,
> break down often and are not of the highest standard. These are mainly
> from eastern Europe.
>
> To take away, besides maintaining the equipment, is to realize that an
> avoidable danger is in accelerating too fast in the first few seconds,
> because this can (emphasis on "can") cause an unavoidable pitch up
> movement that can not be compensated for with the available elevator
> authority - resulting in either a high speed and nose high stall at
> low altitude due to an excessive angle of attack or a rope break (weak
> link). the former is almost always fatal. The latter not, but can be
> if the pilot does not react properly and can contribute to
> accidents.
The pleasing part is that the new German statistics show winch launch
actually safer than air tow. I've always felt that this should be the
case if the equipment was well maintained and the pilots were trained
to the same level as is common with air tow.
However there seems to be a lot of technical confusion in the article.
"Tension Controlled" means that rope tension is continuously monitored
and controlled through an automatic feedback loop. There are very few
winches that do this. Two American built super winches are both
tension controlled with feedback systems.
Automatic transmissions are designed to help a vehicle driver maintain
highway speed on varying road grades - that's speed control and the
exact opposite of tension control. There is no torque regulation in
an automatic transmission and there is no way to modify one to provide
it. To refer to them as "tension controlled is plain wrong.
Automatic transmissions taken from road vehicles simply don't belong
in glider winches.
Electric winches could easily be tension controlled by just monitoring
the current flowing to the motor as could hydrostatic winches by
monitoring hydraulic pressure although a running line tensiometer
would be a better solution. My understanding is that the ESW-2B is
tension controlled. I know for a fact that both American super
winches under development ARE tension controlled.
Specific attacks on electric winches show a complete lack of
understanding of electric power. The innate characteristics of
electric motors make them ideal for torque control.
"Older gasoline powered winches" most likely mean underpowered winches
that are actually "tension limited" such that the glider pilot can
control airspeed with pitch. To refer to these as tension controlled
is unwarranted and will confuse the issue. These are not "tension
controlled".
The hysterics about initial acceleration needs hard data not theory or
speculation to back it up. The experiments I have done with "pitch
strings" used as an angle of attack indicator suggest that the AOA is
nowhere near stall regardless of initial acceleration. In fact,
greater acceleration actually reduces peak AOA.
The preceding paragraph needs to be qualified by saying there are a
small number of types with well deserved reputations for
uncontrollable pitch-up under hard acceleration. There are relatively
few of these and they are .
Chris Reed[_2_]
March 18th 09, 03:17 PM
Martin Gregorie wrote:
> On Wed, 18 Mar 2009 10:15:07 +0000, John Roche-Kelly wrote:
>
>> 2) stall during rotation, it is hard to know whether these are
>> elected rotation or automatic rotation
>>
> Note to any Libelle drivers out there who are thinking of trying winch
> launching for the first time.
>
> Libelles winch well provided the pilot has been given a proper briefing
> by somebody who is familiar with winch launching them. However, with
> incorrect technique they can snap-rotate at lift-off. There is nothing in
> the owners manual about this.
>
>
The same is true for the Ka8. I haven't winched one for some time, but
still have the scars where my knuckles would hit the instrument panel
even on a normal speed launch start!
Karl,
that airspeed communication on a winch would work well on the latter
part of a winch launch, but not for the first dew seconds, which is
the most dangerous part, if the winch driver applies too much power at
the outset. I'm just doing the best I can in translating the technical
terms. When they talk about tension controlled winches the word they
use is "Laststeurung" for speed controlled, they use the term:
"Drehzahlregelung" (OK better translation would be RPM controlled).
Bill,
They devote almost an entire page to explaining that the Electric
winch (they don't name it, but it's obviously the E2B) is indeed RPM
controlled in the initial launch phase and they tried to talk to the
manufacturer. The accident statistics are published in the article
with charts and graphs and it's clear as day that the first few
seconds of the launch are the most critical and require the most care
and that winches which are RPM controlled are involved in more
accidents in exactly this phase of the launch by a factor of 7. It's
not even close. Diesel powered RPM controlled winches are involved in
more accidents in this phase by a factor of 2.5 than tension
controlled ones - the latter of which are the vast majority operated
in Germany.
I'm not a transmission expert, so I do not know if certain
transmissions can be operated to hold a certain torque or cable
tension or not. The article does not get into the intricacies of
transmissions, but it does go into how the electric winch functions,
which is too lengthy and technical for me to translate here. The end
result is that it functions as an RPM controlled winch. They also
mention electric winches could be built to be tension controlled,
apparently the E-2B is not.
If you freeze the gas pedal on a GM SUV in flat terrain, you'll
maintain a steady speed. But then, if you start going up hill, you'll
slow down if the gas position is maintained as before and not
increased. It seems to me, the transmission does not maintain a
constant speed of the SUV or RPM of the wheels at the same power
setting, rather it is a torque converter from engine to wheels and
maintains constant torque to the wheels at a constant power setting -
regardless of wheel RPM (vehicle speed).
Derek Copeland[_2_]
March 18th 09, 06:30 PM
Two points Bill,
1) Why do you think that automatic transmissions in vehicles (or winches)
try to maintain a constant speed? If you come to a hill and keep the
throttle setting the same, the vehicle will slow down! As a glider rotates
into the full climb and demands more power, the winch cable will also slow
down if you maintain the same throttle setting. Are you sure you are not
getting confused with cruise control?
2) Obviously you have never watched a dangerously steep, overpowered,
over-rotation on a winch launch. I have!
Generally these involve lighter, high wing gliders such as K6s, K7s and
K8s. Usually they go into a near vertical climb, often despite the pilot
holding the stick on the forward stop, followed by a weak link failure. On
one occasion a K8 got into such a steep climb that the belly hook just back
released, due to the extreme angle between the fuselage and the cable.
These events normally leave the glider pointing almost vertically at the
sky at about 100ft with no further means of propulsion! Fortunately at our
club, none of these glider flicked, and were being flown by youngish,
switched on pilots who managed to get them down safety. I dread to think
what would have happened if a numpty had been flying them.
I know a lady who was almost knocked unconcious during at the start of a
very overpowered winch launch, when she banged her head very hard on the
canopy frame of her K6. Also there have been a couple of fatal flick spin
accidents in the UK where it is believed that the pilots slipped back in
their seats and pulled the stick hard back as a result. These were both in
glass single seaters with rather reclining seatpans.
There is no case for exceeding about 0.8g acceleration during the ground
run. This gets you up to flying speed in about 3 to 4 seconds. Most pilots
find this enough!
Derek Copeland
At 15:16 18 March 2009, bildan wrote:
>.
>
>The pleasing part is that the new German statistics show winch launch
>actually safer than air tow. I've always felt that this should be the
>case if the equipment was well maintained and the pilots were trained
>to the same level as is common with air tow.
>
>However there seems to be a lot of technical confusion in the article.
>
>"Tension Controlled" means that rope tension is continuously monitored
>and controlled through an automatic feedback loop. There are very few
>winches that do this. Two American built super winches are both
>tension controlled with feedback systems.
>
>Automatic transmissions are designed to help a vehicle driver maintain
>highway speed on varying road grades - that's speed control and the
>exact opposite of tension control. There is no torque regulation in
>an automatic transmission and there is no way to modify one to provide
>it. To refer to them as "tension controlled is plain wrong.
>Automatic transmissions taken from road vehicles simply don't belong
>in glider winches.
>
>Electric winches could easily be tension controlled by just monitoring
>the current flowing to the motor as could hydrostatic winches by
>monitoring hydraulic pressure although a running line tensiometer
>would be a better solution. My understanding is that the ESW-2B is
>tension controlled. I know for a fact that both American super
>winches under development ARE tension controlled.
>
>Specific attacks on electric winches show a complete lack of
>understanding of electric power. The innate characteristics of
>electric motors make them ideal for torque control.
>
>"Older gasoline powered winches" most likely mean underpowered winches
>that are actually "tension limited" such that the glider pilot can
>control airspeed with pitch. To refer to these as tension controlled
>is unwarranted and will confuse the issue. These are not "tension
>controlled".
>
>The hysterics about initial acceleration needs hard data not theory or
>speculation to back it up. The experiments I have done with "pitch
>strings" used as an angle of attack indicator suggest that the AOA is
>nowhere near stall regardless of initial acceleration. In fact,
>greater acceleration actually reduces peak AOA.
>
>The preceding paragraph needs to be qualified by saying there are a
>small number of types with well deserved reputations for
>uncontrollable pitch-up under hard acceleration. There are relatively
>few of these and they are .
>
>
On the other end of the scale, only 8.7% of the accidents with winch
launches involves a wing drop to the ground.
bildan
March 18th 09, 07:14 PM
On Mar 18, 11:44*am, wrote:
> Karl,
> that airspeed communication on a winch would work well on the latter
> part of a winch launch, but not for the first dew seconds, which is
> the most dangerous part, if the winch driver applies too much power at
> the outset. I'm just doing the best I can in translating the technical
> terms. When they talk about tension controlled winches the word they
> use is "Laststeurung" for speed controlled, they use the term:
> "Drehzahlregelung" (OK better translation would be RPM controlled).
>
> Bill,
> They devote almost an entire page to explaining that the Electric
> winch (they don't name it, but it's obviously the E2B) is indeed RPM
> controlled in the initial launch phase and they tried to talk to the
> manufacturer. The accident statistics are published in the article
> with charts and graphs and it's clear as day that the first few
> seconds of the launch are the most critical and require the most care
> and that winches which are RPM controlled are involved in more
> accidents in exactly this phase of the launch by a factor of 7. It's
> not even close. Diesel powered RPM controlled winches are involved in
> more accidents in this phase by a factor of 2.5 than tension
> controlled ones - the latter of which are the vast majority operated
> in Germany.
I agree that the first few seconds are the most critical but there's
nothing here that suggests a rigorous understanding of what exactly
happens in those seconds. Statistics are nearly useless since the
sample is WAY too small for meaningful answers. In any event, the
proximate cause of 99% of all glider accidents is random pilot error
which is not amenable to statistical analysis.
What is needed, and the Germans are extremely good at this, is a full
technical investigation with fully instrumented gliders and winches.
We need actual tension, airspeed and AOA measurements. A few days of
high quality engineering measurement is worth millions of words of
speculation, opinion or statistics. Unfortunately, the mere mention
of winch launch seems to bring out huge amounts of speculation and
opinion.
Tension controlled means that there is a means of directly measuring
tension real time and a means to control it - preferably automatically
with a feedback loop. I have spent 10 years studying winch design and
I believe there are very few such tension controlled winches in
existence. This is most likely a translation problem.
>
> I'm not a transmission expert, so I do not know if certain
> transmissions can be operated to hold a certain torque or cable
> tension or not. The article does not get into the intricacies of
> transmissions, but it does go into how the electric winch functions,
> which is too lengthy and technical for me to translate here. The end
> result is that it functions as an RPM controlled winch. They also
> mention electric winches could be built to be tension controlled,
> apparently the E-2B is not.
I do not believe this is acutally the case although the article may
say it.
>
> If you freeze the gas pedal on a GM SUV in flat terrain, you'll
> maintain a steady speed. But then, if you start going up hill, you'll
> slow down if the gas position is maintained as before and not
> increased. It seems to me, the transmission does not maintain a
> constant speed of the SUV or RPM of the wheels at the same power
> setting, rather it is a torque converter from engine to wheels and
> maintains constant torque to the wheels at a constant power setting -
> regardless of wheel RPM (vehicle speed).
True, but an automatic transmission ASSISTS the driver in maintaining
speed on a hill by downshifting and allowing the torque converter to
slip thus multiplying torque at the wheels.
Here's where this goes wrong in a glider winch. The air is never
still, and being glider pilots, we want to launch into thermic
conditions. If the winch is equipped with an automatic transmission
salvaged from a road vehicle, and the glider encounters a thermal
during the launch, the transmission will see this as increased load
just like a hill and increase torque and therefore increasing rope
tension. In effect, pulling the glider down through the thermal
causing an airspeed spike - the exact opposite of what you want which
is to reduce rope tension letting the glider climb in the thermal.
Conversely, if the glider encounters sink, the automatic transmission
will REDUCE torque and therefore tension - again the exact opposite of
what you want which is to increase tension helping the pilot maintain
safe airspeed.
Further, if the pilot tries to reduce excessive airspeed by increasing
pitch, the transmission will see this as increased load and ramp up
tension frustrating the pilot. If the pilot lowers the nose in an
effort to increase airspeed, the transmission will decrease tension
again frustrating the pilots efforts to control airspeed.
Automatic transmissions are marvelous devices when used in road
vehicles but they are grossly misapplied when used in a glider winch.
It introduces a "wild card" that neither the winch operator nor the
pilot can predict or control.
US winch designers are using hydrostatic or electric drive with active
tension control to provide exactly the correct rope tension on every
launch regardless of atmospherics, glider type or pilot technique.
This is FAR safer than older winch designs.
Bill Daniels
Karl Striedieck
March 18th 09, 09:55 PM
I agree that the first part of a launch that might involve excessive
acceleration and subsequent uncontrollable over rotation would not be safer
with our continuous airspeed transmission procedure. Things get out of
control way too fast for any radio transmission to help. The radio comes
into play after the glider is climbing out and the airspeed is within the
range the pilot requested.
Also, auto launches generally can't put as much horsepower into the glider
as a winch, and thus the chances of over rotation with the stick full
forward are not as great. However, it happened to me once when my ASW-17 was
being launched by a 180 HP Jeep. It was scary to have the stick full forward
and be pointed up too steep near the ground. But this time the weak link
held and the Jeep didn't stumble, so it worked OK (and made a believer out
of me!).
Karl Striedieck
> wrote in message
...
> Karl,
> that airspeed communication on a winch would work well on the latter
> part of a winch launch, but not for the first dew seconds, which is
> the most dangerous part, if the winch driver applies too much power at
> the outset. I'm just doing the best I can in translating the technical
> terms. When they talk about tension controlled winches the word they
> use is "Laststeurung" for speed controlled, they use the term:
> "Drehzahlregelung" (OK better translation would be RPM controlled).
>
> Bill,
> They devote almost an entire page to explaining that the Electric
> winch (they don't name it, but it's obviously the E2B) is indeed RPM
> controlled in the initial launch phase and they tried to talk to the
> manufacturer. The accident statistics are published in the article
> with charts and graphs and it's clear as day that the first few
> seconds of the launch are the most critical and require the most care
> and that winches which are RPM controlled are involved in more
> accidents in exactly this phase of the launch by a factor of 7. It's
> not even close. Diesel powered RPM controlled winches are involved in
> more accidents in this phase by a factor of 2.5 than tension
> controlled ones - the latter of which are the vast majority operated
> in Germany.
>
> I'm not a transmission expert, so I do not know if certain
> transmissions can be operated to hold a certain torque or cable
> tension or not. The article does not get into the intricacies of
> transmissions, but it does go into how the electric winch functions,
> which is too lengthy and technical for me to translate here. The end
> result is that it functions as an RPM controlled winch. They also
> mention electric winches could be built to be tension controlled,
> apparently the E-2B is not.
>
> If you freeze the gas pedal on a GM SUV in flat terrain, you'll
> maintain a steady speed. But then, if you start going up hill, you'll
> slow down if the gas position is maintained as before and not
> increased. It seems to me, the transmission does not maintain a
> constant speed of the SUV or RPM of the wheels at the same power
> setting, rather it is a torque converter from engine to wheels and
> maintains constant torque to the wheels at a constant power setting -
> regardless of wheel RPM (vehicle speed).
bagmaker
March 18th 09, 11:06 PM
Interestingly, my vehicle (VW 6 speed) has an amazing automatic with full electronic control. I now believe such a modern automatic would pass power between engine and spool despite my previos limits of winch design left only to full electric or hydraulic (both with tension feedback).
The current crop of automatic gearboxes could be controlled by an economical PLC (sub $500) and loadcell feedback. Rope speed control is into the 3d PLC graph as well, with wind and ambeint temperature. These gearboxes stay in the gear electronically selected, regardless, and I believe they could be used without a torque converter although I am open to suggestion that this would be an advantage.
A wrecked V10 Diesel Touareg drivetrain from VW is the perfect winch option.
This drive will give the winch operator a simple "EB28" or "libelle" or even better, "tail registration number" input into the winch then hit the go button. His only other input into the launch is an emergency stop or emergency manual override.
The winch PLC (Computer) then confirms the registration is of the glider type memorised (safety feedback from the operator) and automatically selects the correct torque/speed curve to launch that glider. Off it goes, same every launch.
The winch operator can then download the data daily on a memory stick and invoice the pilot for the launch with full information -hieght, time, windspeed, temp, etc.
Should the pilot advise the launch needed a different parameter, this can be uploaded for his next launch.
Over time this data may be on servers world wide and the known safety margins set. Should the pilot be requesting a curve outside this window of safety he could be appraised of a possible issue with his launch technique or his glider airworthiness!
There is no way this safe, reliable launch can be acheived with the outdated drives of a 18th century automatic transmission, period.
They may have been up to the job, sure, but if you are to build a new one, dont start backwards!
Plenty to read at the yahoo winch design group
http://groups.yahoo.com/group/winchdesign/
bagger
bildan
March 18th 09, 11:53 PM
On Mar 18, 12:30*pm, Derek Copeland > wrote:
> 2) Obviously you have never watched a dangerously steep, overpowered,
> over-rotation on a winch launch. I have!
No, I haven't seen any of the weird things you describe. They all
seem to happen in your immediate vicinity. I wonder why.
Derek Copeland[_2_]
March 19th 09, 01:00 AM
At 23:53 18 March 2009, bildan wrote:
>On Mar 18, 12:30=A0pm, Derek Copeland wrote:
>
>> 2) Obviously you have never watched a dangerously steep, overpowered,
>> over-rotation on a winch launch. I have!
>
>No, I haven't seen any of the weird things you describe. They all
>seem to happen in your immediate vicinity. I wonder why.
>
Probably because I'm a gliding instructor at a large and very busy club
that does a lot of winch launching. I also visit other clubs that winch
launch.
I should add that probably 99% of winch launches go to plan (including
deliberate practice launch failures by instructors) without any
difficulties. About 1% suffer cable or weak link breaks, or other
technical failures of one sort or another. Given proper training these
should be just an inconvenience, rather than an emergency situation.
Once it was recognised that over powered winch launches were a problem for
lighter gliders, we reduced the power settings used for these types and
opened the winch engine throttles a bit more slowly. I haven't seen a
'rocket launch' for quite a few years now.
Derek Copeland
Karl,
I agree that vehicles are not prone to make gliders do space shuttle
like launches, due to all the inertia of that set up. Though thanks
for sharing that even there it is possible, not just with winches.
Bill,
The articles has an emphasis on heavy analysis that I am not going to
translate now, nor do I even have permission from Aerokurier to do
that. It's not my article. But trust me, it is very thorough and they
also calculated different scenarios. When there is and accident with
heavy damage or a fatality, the cause is investigated thoroughly and
that cause is listed in the tables in the article. There is no
statistical hoky poky. What for?
I would not presume to start with the assumption that the statistics
are somehow skewed, wrong, massaged or manipulated. If you want to
blast off on winch launch full power from zero on a 300HP (or more)
winch, vastly exceeding 1g and doing a space shuttle launch
simulation, that's your business. The analysis clearly shows that
doing that is 2.5-7 times more dangerous than accelerating under 1g
for the first few seconds. After that, the article says that tension
and airspeed can be higher than is the norm today with no problem,
provided a weak link is used that can handle it.
When I have some time, I'll post at least the accident tables and the
winch accident rate comparisons by winch type. It's easier to see what
I'm saying with the tables in front of you, rather than just my choppy
interpretation and translation of th text. It's very technical.
Speaking of experiences, flying all manner of gliders in Germany and
having participated and watched thousands of winch launches myself -
I've seen and participated in my fair share of space shuttle launches
"Kavalierstart", even with the stick full forward. Unlike Karl, I was
young and not so smart and I wasn't scared at all the few times it
happened to me and we criticized pilots when we saw it happen to them
(like they did it on purpose...free beer). Though I knew it wasn't
right and battled the nose down as soon as I could, there is nothing I
could do about it. That it was dangerous I knew, but I was thrilled to
be blasting off like that since it happened so fast and there was
nothing I could do about it anyway but push the stick full forward.
Simply put, if the rope tension in the first few seconds exceeds 1g
rope tension (not aircraft mass acceleration), the pilot is like a
passenger and can do nothing to correct the situation while the AOA is
pushed to the limit or much closer to the limit. Hopefully, the AOA is
not exceeded for any reason, that is the wing does not stall, because
if it does, the outcome is certain death within the first 7 seconds or
so.
Please understand that the 0.5g-1g tension is measured as rope tension
and not as felt inside the glider as mass acceleration. If you have a
strong head wind, it doesn't take much initial speed or mass
acceleration to create a space shuttle simulation (perhaps that's what
happened to Karl) as the maximum rope tension will occur at a much
slower drum (car) speed and set in much quicker than with no wind.
That is why tension controlled winches are safer as they easily
compensate for this - they deliver a certain rope tension and that's
it, regardless of wind and the drum speed will vary on it's own. It's
like the car rolling up hill - the tension will be the same, only
it'll roll slower up the hill and faster down or flat. RPM winches do
not compensate for any of this. On climb out it's fine, but not in the
first few seconds.
Surfer!
March 19th 09, 08:18 AM
In message >, Derek Copeland
> writes
>At 23:53 18 March 2009, bildan wrote:
>>On Mar 18, 12:30=A0pm, Derek Copeland wrote:
>>
>>> 2) Obviously you have never watched a dangerously steep, overpowered,
>>> over-rotation on a winch launch. I have!
>>
>>No, I haven't seen any of the weird things you describe. They all
>>seem to happen in your immediate vicinity. I wonder why.
>>
>Probably because I'm a gliding instructor at a large and very busy club
>that does a lot of winch launching. I also visit other clubs that winch
>launch.
>
>I should add that probably 99% of winch launches go to plan (including
>deliberate practice launch failures by instructors) without any
>difficulties. About 1% suffer cable or weak link breaks, or other
>technical failures of one sort or another. Given proper training these
>should be just an inconvenience, rather than an emergency situation.
I have over 300 winch launches - not many by some people's standards but
still a fair number. I have had only 1 genuine launch failure (caused
by the club member driving the winch, not by me or by equipment
failure), so either I'm due a run of cable breaks and the like, or the
percentage of failures is better for some pilots/ glider types than
others... (or a bit of both of course)
<snip>
--
Surfer!
Email to: ramwater at uk2 dot net
kestrel19
March 19th 09, 01:06 PM
On Mar 18, 11:39*pm, wrote:
> Karl,
> I agree that vehicles are not prone to make gliders do space shuttle
> like launches, due to all the inertia of that set up. Though thanks
> for sharing that even there it is possible, not just with winches.
>
search RAS on groups.google.com for phoebus c accident for just such
an accident
it's not entirely clear whether it was an all-flying tail stall or
over rotation into a stall
Frank Whiteley
Bruce
March 19th 09, 03:03 PM
bildan wrote:
> On Mar 18, 12:30 pm, Derek Copeland > wrote:
>
>> 2) Obviously you have never watched a dangerously steep, overpowered,
>> over-rotation on a winch launch. I have!
>
> No, I haven't seen any of the weird things you describe. They all
> seem to happen in your immediate vicinity. I wonder why.
Hi Bill
Derek is not alone here.
As additional example - Std Cirrus can also be coaxed into too steep a
climb with too much power too fast.
In this case it is often a combination of
- poor seatbelt location, which allows the pilot to slide back on launch.
- full flying elevator - which is possible to stall if one holds the
stick full forward. (Low speed + big angular deflection)
- aft CG with a light pilot
Maybe if you only ever see launches of modern glass, or heavy two
seaters, with experienced winch drivers who know the different types,
you will not see this. I have yet to meet the perfect winch driver. At a
busy club, or where the winch driver is inexperienced with the glider
type or just inexperienced it is easy on a powerful winch to apply too
much initial power. And a little too fast on the throttle at the start
is very dangerous for a range of gliders.
Basically excessive acceleration can use most or all of the available
control authority. One more thing, like a gust / thermal / cable break
and you exceed the authority and have an accident. Best to avoid. Best
way to avoid is to train winch driving technique correctly. Denial gets
people hurt.
Power limited winches are no fun either...
Bruce
bildan
March 19th 09, 03:18 PM
On Mar 18, 11:39*pm, wrote:
> Karl,
> I agree that vehicles are not prone to make gliders do space shuttle
> like launches, due to all the inertia of that set up. Though thanks
> for sharing that even there it is possible, not just with winches.
>
> Bill,
> The articles has an emphasis on heavy analysis that I am not going to
> translate now, nor do I even have permission from Aerokurier to do
> that. It's not my article. But trust me, it is very thorough and they
> also calculated different scenarios. When there is and accident with
> heavy damage or a fatality, the cause is investigated thoroughly and
> that cause is listed in the tables in the article. There is no
> statistical hoky poky. What for?
>
> I would not presume to start with the assumption that the statistics
> are somehow skewed, wrong, massaged or manipulated. If you want to
> blast off on winch launch full power from zero on a 300HP (or more)
> winch, vastly exceeding 1g and doing a space shuttle launch
> simulation, that's your business. The analysis clearly shows that
> doing that is 2.5-7 times more dangerous than accelerating under 1g
> for the first few seconds. After that, the article says that tension
> and airspeed can be higher than is the norm today with no problem,
> provided a weak link is used that can handle it.
>
> When I have some time, I'll post at least the accident tables and the
> winch accident rate comparisons by winch type. It's easier to see what
> I'm saying with the tables in front of you, rather than just my choppy
> interpretation and translation of th text. It's very technical.
>
> Speaking of experiences, flying all manner of gliders in Germany and
> having participated and watched thousands of winch launches myself -
> I've seen and participated in my fair share of space shuttle launches
> "Kavalierstart", even with the stick full forward. Unlike Karl, I was
> young and not so smart and I wasn't scared at all the few times it
> happened to me and we criticized pilots when we saw it happen to them
> (like they did it on purpose...free beer). Though I knew it wasn't
> right and battled the nose down as soon as I could, there is nothing I
> could do about it. That it was dangerous I knew, but I was thrilled to
> be blasting off like that since it happened so fast and there was
> nothing I could do about it anyway but push the stick full forward.
>
> Simply put, if the rope tension in the first few seconds exceeds 1g
> rope tension (not aircraft mass acceleration), the pilot is like a
> passenger and can do nothing to correct the situation while the AOA is
> pushed to the limit or much closer to the limit. Hopefully, the AOA is
> not exceeded for any reason, that is the wing does not stall, because
> if it does, the outcome is certain death within the first 7 seconds or
> so.
>
> Please understand that the 0.5g-1g tension is measured as rope tension
> and not as felt inside the glider as mass acceleration. If you have a
> strong head wind, it doesn't take much initial speed or mass
> acceleration to create a space shuttle simulation (perhaps that's what
> happened to Karl) as the maximum rope tension will occur at a much
> slower drum (car) speed and set in much quicker than with no wind.
> That is why tension controlled winches are safer as they easily
> compensate for this - they deliver a certain rope tension and that's
> it, regardless of wind and the drum speed will vary on it's own. It's
> like the car rolling up hill - the tension will be the same, only
> it'll roll slower up the hill and faster down or flat. RPM winches do
> not compensate for any of this. On climb out it's fine, but not in the
> first few seconds.
I didn't accuse anyone of "hoky-poky" and certainly not the publishers
of Aerokurier. I just said that statistics don't work very well for
accident analysis since the data set is too small to draw meaningful
conclusions. To the extent that you analyze anything with accident
statistics, it's pilot skill. That dominates the results not
equipment or procedures. Inconsistent and variable pilot skills
introduces way too much "noise" in the data. Statistics are simply
the wrong tool.
The right tool for this problem is engineering. Every single
parameter can be analyzed with measurement data. If excessive
acceleration does, in fact, reduce AOA margin, that would be very
straight forward to measure. Just install an AOA indicator,
commercial units are available, and simultaneously measure
acceleration with a tensiometer or with a simple video camera. Start
slow and work up. If the stall margin is getting smaller, you'll know
when to stop. Rock solid engineering data will also validate
mathematical models - or not.
I happen to think that the "Kavalierstart" you speak of is pure pilot
error. The pilot causes, or allows, the glider to rotate into a steep
climb before he has safe airspeed. Once over-rotated and stalled,
there is insufficient elevator authority to reverse the situation -
he's riding a kite not flying a glider. A good pilot can prevent this
at accelerations right up to the breaking strength of the weak link.
I know because I've done it.
Requite qualification: There MAY be a very small number of gliders
whose inertially induced pitch-up under hard acceleration exceeds the
elevator authority to prevent it. .
Derek Copeland[_2_]
March 19th 09, 06:00 PM
Bill,
Over accelerated "Kavalierstart" winch launches often have nothing to do
with 'pilot error'. If you are already holding the stick hard against the
forward stop to try and stop the glider over-rotating, what else can you
do, apart from pulling off? Even that would leave you in a very tricky
situation, with the glider very nose high and very close to the ground!
It is quite difficult to overpower a K21, a Grob G103 or a DG1000, mainly
because they are quite heavy and need a lot of horsepower to accelerate
them. Anything lighter than this, and fitted with a belly hook, is
potentially at risk with modern powerful winches, and I include K13
two-seaters in this. I would not recommend launching on a nose hook by the
way, as you will get a very poor launch and they normally don't have a
back release mechanism.
The problem can be avoided anyway by limiting the winch power or tension
setting to what the glider type can safely handle. The Skylaunch winch
does this very well, as long as the driver sets the throttle tabs
correctly.
Derek Copeland
At 15:18 19 March 2009, bildan wrote:
>
>I didn't accuse anyone of "hoky-poky" and certainly not the
publishers
>of Aerokurier. I just said that statistics don't work very well for
>accident analysis since the data set is too small to draw meaningful
>conclusions. To the extent that you analyze anything with accident
>statistics, it's pilot skill. That dominates the results not
>equipment or procedures. Inconsistent and variable pilot skills
>introduces way too much "noise" in the data. Statistics are simply
>the wrong tool.
>
>The right tool for this problem is engineering. Every single
>parameter can be analyzed with measurement data. If excessive
>acceleration does, in fact, reduce AOA margin, that would be very
>straight forward to measure. Just install an AOA indicator,
>commercial units are available, and simultaneously measure
>acceleration with a tensiometer or with a simple video camera. Start
>slow and work up. If the stall margin is getting smaller, you'll know
>when to stop. Rock solid engineering data will also validate
>mathematical models - or not.
>
>I happen to think that the "Kavalierstart" you speak of is pure pilot
>error. The pilot causes, or allows, the glider to rotate into a steep
>climb before he has safe airspeed. Once over-rotated and stalled,
>there is insufficient elevator authority to reverse the situation -
>he's riding a kite not flying a glider. A good pilot can prevent this
>at accelerations right up to the breaking strength of the weak link.
>I know because I've done it.
>
>Requite qualification: There MAY be a very small number of gliders
>whose inertially induced pitch-up under hard acceleration exceeds the
>elevator authority to prevent it. .
>
Bill,
the statistics covers accidents and launches in the period from
2002-2008. Brought to an annualized figure that means there were an
average of 1,449,500 glider launches every year for the period. That
is, the analysis covers about 10,146,500 launches of all types in
Germany and the accidents that resulted from these. That's a pretty
big sample. The sample also covers 60 winches in France, listed
separately. (the only accidents in France involved electric winces)
In Germany, for the period (2002-2008), there was a yearly average of:
712,500 - Winch Launches
237,000 - Aero tows
500,000 - Motorglider take offs (fixed position motors)
The number of motorized glider take offs is not indicated, but the
number of their accidents is, which comes out to 5.3% of all glider
launch accidents involves this type of launch.
I don't think the sample is too small.
Your statement that one could simply install an AOA indicator to allow
the pilot to avoid exceeding the AOA misses the point entirely. The
point is that exceeding the AOA occurs because of what the winch does,
not the pilot - namely, excessive initial launch speed/tension/power
resulting in an uncontrollable excessive initial pitch up movement
that ends with a stall and flip into the ground at high speed within
seconds.
The only aircraft type pattern mentioned is that involving GROBs.
These types were never involved in flip ins during inititial launch.
Another anomaly is that in 45% of all accidents involving broken weak
links Grobs were involved - indicating the certified strength of the
weak links for Grobs are not strong enough.
I think the analysis is very thorough and makes strong
recommendations. What you are doing, strong initial acceleration
launches (which I presume exceed 1g rope tension), is what they are
saying should be avoided. Later in the launch phase, it's OK to
increase tension beyond 1g, but not in the initial danger zone.
bildan
March 19th 09, 07:42 PM
On Mar 19, 12:26*pm, wrote:
> Bill,
> the statistics covers accidents and launches in the period from
> 2002-2008. Brought to an annualized figure that means there were an
> average of 1,449,500 glider launches every year for the period. That
> is, the analysis covers about 10,146,500 launches of all types in
> Germany and the accidents that resulted from these. That's a pretty
> big sample. The sample also covers 60 winches in France, listed
> separately. (the only accidents in France involved electric winces)
>
> In Germany, for the period (2002-2008), there was a yearly average of:
> 712,500 - Winch Launches
> 237,000 - Aero tows
> 500,000 - Motorglider take offs (fixed position motors)
>
> The number of motorized glider take offs is not indicated, but the
> number of their accidents is, which comes out to 5.3% of all glider
> launch accidents involves this type of launch.
>
> I don't think the sample is too small.
>
> Your statement that one could simply install an AOA indicator to allow
> the pilot to avoid exceeding the AOA misses the point entirely. The
> point is that exceeding the AOA occurs because of what the winch does,
> not the pilot - namely, excessive initial launch speed/tension/power
> resulting in an uncontrollable excessive initial pitch up movement
> that ends with a stall and flip into the ground at high speed within
> seconds.
>
> The only aircraft type pattern mentioned is that involving GROBs.
> These types were never involved in flip ins during inititial launch.
> Another anomaly is that in 45% of all accidents involving broken weak
> links Grobs were involved - indicating the certified strength of the
> weak links for Grobs are not strong enough.
>
> I think the analysis is very thorough and makes strong
> recommendations. What you are doing, strong initial acceleration
> launches (which I presume exceed 1g rope tension), is what they are
> saying should be avoided. Later in the launch phase, it's OK to
> increase tension beyond 1g, but not in the initial danger zone.
I think understand, Tommyto is Derek Copeland using one of his
hundreds of aliases.
The statistics are interesting but prove little without actual
engineering measurements. What the statistics do suggest is that
pilot incompetence is sadly not rare and that someone should do some
actual certified engineering measurements.
To increase the weak link strength without engineering data to insure
that is in fact safe is grossly irresponsible - and illegal in every
country in the world except the UK. In any event, the final and only
authority on that subject is holder of the type certificate - Grob
itself. (US pilots note that weak link strengths are set under JAR-22
to a prescribed value with a +or- 10% tolerance as part of a types
airworthiness certificate - read your POH.)
To suggest that pilots are crashing due to the weak links being too
weak would be hilarious if not so tragic and I'm quite sure the LBA
and/or DAeC made no such suggestion.
Weak link failure accidents are 100% pilot error and 0% hardware
deficiency. Pilots must EXPECT wire or weak link failures and be
prepared to deal with them safely. Pilots who can't handle a launch
failure with big safety margins should be grounded for extensive
retraining.
I did NOT suggest using an AOA indicator to help the pilot avoid
"exceeding the AOA" [OF STALL?] although that is a great idea. What I
did suggest is using it as an engineering measurement tool to
determine if increased acceleration was causing an increase in AOA.
My measurements suggest the exact opposite - that increasing the
acceleration REDUCES the maximum AOA. Other measurements suggest that
even gliders with a strong inertial pitch up tendency will break their
weak link under strong acceleration long before running out of
elevator.
If you want statistics, they seem to show that over rotation leading
to stalls on the wire occur mainly on weak winches and auto tow -
always as the result of premature pilot induced pitch up - as in
counting 6 seconds and pulling up without consulting the ASI.
"I think understand, Tommyto is Derek Copeland using one of his
hundreds of aliases. "
Let us get at least this part straight - my name is Thomas Vallarino,
not Derek Copeland and I do not even know the gentleman.
"My measurements suggest the exact opposite - that increasing the
acceleration REDUCES the maximum AOA."
You can believe whatever you want to. You are free to disregard the
calculations in the analysis, the accident data and the experiences of
those here in this thread who describe specific cases of
uncontrollable pitch up movements, despite full forward stick - from
Karl's ASW-17 incident to the same experience of others including
myself with a variety of other models. It's not always the pilot's
fault when this happens as the pilot runs out of elevator authority.
The article calculated the pitch arm moment of many gliders and what
tension would be necessary to exceed the elevator authority at the
beginning of the launch. That's why they recommend a range of initial
rope tension of no more than 0.5-1.0g for singles and 0.7-1.0g for
doubles at the beginning of the launch.
Just think about it. Why does the tail go down into the ground at the
beginning of the launch, despite full forward stick? Because there is
little to no air moving over the elevator to overcome the pitch up
moment produced by the rope tension when the glider fist begins to
move forward at 0.1 seconds into the launch. This effect can continue
after the glider leaves the ground if the rope tension is too high.
If there is no stall and accident, then yes the airspeed will continue
to build up very quickly and so will elevator authority and the AOA
can be moved back to larger margins quickly by the pilot, so long as
tension doesn't continue to increase. However, there is a specific
rope tension for any airspeed within the first phase of the launch
(initial angle vector of rope VS horizontal), after which the maximum
AOA will be exceeded due to the pitch up moment and limited elevator
authority to prevent a stall.
In all my years, I have never even seen an accident on the winch,
where anything was damaged. Plenty of incidents, but everything
always turned out well. So what we're talking about here is to make it
even safer than it already is.
Thomas Vallarino
Manhattan Beach, California
bildan
March 19th 09, 10:41 PM
On Mar 19, 3:14*pm, wrote:
> "I think understand, Tommyto is Derek Copeland using one of his
> hundreds of aliases. "
>
> Let us get at least this part straight - my name is Thomas Vallarino,
> not Derek Copeland and I do not even know the gentleman.
Well, that's incredibly good news for many reasons.
>
> "My measurements suggest the exact opposite - that increasing the
> acceleration REDUCES the maximum AOA."
>
> You can believe whatever you want to.
Hard engineering data ALWAYS trumps calculations and predictions no
matter how logical they seem. I'll believe measured data instead of
calculated results any day.
"Just think about it. Why does the tail go down into the ground at the
beginning of the launch, despite full forward stick?"
And why does it stop there? It hit the ground, right? Now you have
hard acceleration and NO rotation. As the speed increases, the pilot
continues to hold full down elevator which increases in effectiveness
with the square of the airspeed.
As the glider leaves the ground, the inertial rotation will begin but
if the acceleration continues, the elevator effectiveness will also
continue to increase with the square of the airspeed. Rotation can't
happen instantly because the glider has mass and rotational inertia.
In fact, the pilot has to start backing off the down elevator to allow
the glider to rotate into the climb.
Now, contrast this with a slow acceleration. The glider staggers into
the air and the nose-up inertial couple starts the rotation but the
low speed and acceleration doesn't provide adequate control. The nose
rises as the pilot struggles to control it with inadequate
airspeed.....
I've collected stories on this type of accident for decades and they
ALWAYS happen with slow acceleration.
Bill,
If the initial rope tension is too low, the pilot should just release
and not stagger around for long periods. Elevator authority should not
be a problem when rope tension is low. From experience, I have never
seen uncontrollable pitch ups on slow tows, only on fast ones.
Martin Gregorie[_4_]
March 19th 09, 11:49 PM
On Thu, 19 Mar 2009 15:41:38 -0700, bildan wrote:
> As the glider leaves the ground, the inertial rotation will begin but if
> the acceleration continues, the elevator effectiveness will also
> continue to increase with the square of the airspeed. Rotation can't
> happen instantly because the glider has mass and rotational inertia. In
> fact, the pilot has to start backing off the down elevator to allow the
> glider to rotate into the climb.
>
That depends on what you're flying and how lead footed the winch driver
is. I have an early (H.201) Std Libelle.
I remember having a fairly 'vigorous' launch on a calm day from a V8
Supacat. I started with full forward trim as usual but possibly with not
quite as much additional forward pressure as I normally use. The glider
started to pitch up shortly after lifting off. Applying full down
elevator maintained but didn't reduce the pitch-up rate until the full
climb attitude, when rotation eased off and I was able to ease back to no
stick pressure. This started to happen around 50 kts, the rotation rate
was acceptable and the full climb angle post rotation was steep but not
excessive. I had around 65 kts when rotation had stopped.
My Std. Libelle normally lifts off both wheels almost simultaneously,
even with full forward trim plus a bit of forward pressure. I usually
have no problems holding or reducing that attitude as the speed builds up
past 50 kts. However, on this occasion I want to emphasize that I went
fairly briskly to full forward stick as rotation started and REMAINED
THERE through rotation into full climb. At that attitude when I eased
back to the trimmed position as the rotation slowed. If the acceleration
had been higher I could have been in real trouble.
Now, I always ask to be launched "like a Junior but 10 kts slower", which
gives a nice lift-off and constant attitude until 50 kts and rising is on
the clock. At that point a reduction in forward pressure gives a nice,
controllable rotation into full climb. Easing the stick back as the
rotation slows gives a nice full climb attitude at just over 60 kts.
Vwinch is 65.
Caveat: I've never winched an H.201B, which has a bigger tail than the
H.201, so its winch behavior may be different.
--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |
bildan
March 20th 09, 03:35 AM
On Mar 19, 5:49*pm, Martin Gregorie
> wrote:
> On Thu, 19 Mar 2009 15:41:38 -0700, bildan wrote:
> > As the glider leaves the ground, the inertial rotation will begin but if
> > the acceleration continues, the elevator effectiveness will also
> > continue to increase with the square of the airspeed. *Rotation can't
> > happen instantly because the glider has mass and rotational inertia. In
> > fact, the pilot has to start backing off the down elevator to allow the
> > glider to rotate into the climb.
>
> That depends on what you're flying and how lead footed the winch driver
> is. I have an early (H.201) Std Libelle.
>
> I remember having a fairly 'vigorous' launch on a calm day from a V8
> Supacat. I started with full forward trim as usual but possibly with not
> quite as much additional forward pressure as I normally use. The glider
> started to pitch up shortly after lifting off. Applying full down
> elevator maintained but didn't reduce the pitch-up rate until the full
> climb attitude, when rotation eased off and I was able to ease back to no
> stick pressure. This started to happen around 50 kts, the rotation rate
> was acceptable and the full climb angle post rotation was steep but not
> excessive. I had around 65 kts when rotation had stopped.
>
> My Std. Libelle normally lifts off both wheels almost simultaneously,
> even with full forward trim plus a bit of forward pressure. I usually
> have no problems holding or reducing that attitude as the speed builds up
> past 50 kts. However, on this occasion I want to emphasize that I went
> fairly briskly to full forward stick as rotation started and REMAINED
> THERE through rotation into full climb. At that attitude when I eased
> back to the trimmed position as the rotation slowed. If the acceleration
> had been higher I could have been in real trouble.
>
> Now, I always ask to be launched "like a Junior but 10 kts slower", which
> gives a nice lift-off and constant attitude until 50 kts and rising is on
> the clock. At that point a reduction in forward pressure gives a nice,
> controllable rotation into full climb. Easing the stick back as the
> rotation slows gives a nice full climb attitude at just over 60 kts.
> Vwinch is 65.
>
> Caveat: I've never winched an H.201B, which has a bigger tail than the
> H.201, so its winch behavior may be different.
>
> --
> martin@ * | Martin Gregorie
> gregorie. | Essex, UK
> org * * * |
Martin, your post has all the ingredients I'm talking about. If you
know your glider, you'll know if it will require down elevator and
roughly how much. It's probably a good idea to start the roll with
full down elevator to eliminate 'reaction time'. The problem occurs
when the nose is allowed to rise too far and the pilot then tries to
correct the situation.
This has been a hard fought discussion but I kept at it because there
is a lot of good things in it that winch novices need to think about.
bildan
March 20th 09, 03:58 AM
On Mar 19, 5:04*pm, wrote:
> Bill,
> If the initial rope tension is too low, the pilot should just release
> and not stagger around for long periods. Elevator authority should not
> be a problem when rope tension is low. From experience, I have never
> seen uncontrollable pitch ups on slow tows, only on fast ones.
Right, and you DON'T start the rotation. If you do, that's when the
problem starts and you run out of elevator control.
Derek Copeland[_2_]
March 20th 09, 01:00 PM
As I have tried to explain to Bill on numerous occasions, and on various
forums, the uncontrollable over-rotation you get from an over-powered
winch launch is caused by the pull line to the belly hook being below the
glider's centre of gravity and centre of pressure. This causes a rotation
for mechanical rather than aerodynamic control reasons. This is why high
winged gliders, such as the K6 and K8 are most at risk.
If you get such a launch, even holding the stick hard forward all the time
from 'take up slack' will not prevent the over-rotation, although it
might slightly reduce your chances of instant death from a flick spin.
Such events can be easily avoided by by controlling the winch so that the
ground run acceleration is not more than about 1.0g (or less for the types
mentioned above). This will still get you airborne and climbing within
about 3-4 seconds, which most pilots find quite fast enough! It will also
make very little difference to the achieved height.
Derek Copeland
At 22:41 19 March 2009, bildan wrote:
>As the glider leaves the ground, the inertial rotation will begin but
>if the acceleration continues, the elevator effectiveness will also
>continue to increase with the square of the airspeed. Rotation can't
>happen instantly because the glider has mass and rotational inertia.
>In fact, the pilot has to start backing off the down elevator to allow
>the glider to rotate into the climb.
>
>Now, contrast this with a slow acceleration. The glider staggers into
>the air and the nose-up inertial couple starts the rotation but the
>low speed and acceleration doesn't provide adequate control. The nose
>rises as the pilot struggles to control it with inadequate
>airspeed.....
>
>I've collected stories on this type of accident for decades and they
>ALWAYS happen with slow acceleration.
>
>
>
>
Del C[_2_]
March 20th 09, 07:30 PM
Sorry, I forgot to add that there are a few types where holding the stick
hard forward to contain an over-rotation is not a good idea, as you can
stall the elevator/tailplane and make the situation even worse! These are
mostly gliders with all-flying tailplanes, such as the Standard Cirrus.
Again, all these unpleasantries can be avoided by just a slight moderation
of the ground run acceleration, if you have a powerful winch.
Derek C
At 13:00 20 March 2009, Derek Copeland wrote:
>As I have tried to explain to Bill on numerous occasions, and on various
>forums, the uncontrollable over-rotation you get from an over-powered
>winch launch is caused by the pull line to the belly hook being below
the
>glider's centre of gravity and centre of pressure. This causes a
rotation
>for mechanical rather than aerodynamic control reasons. This is why high
>winged gliders, such as the K6 and K8 are most at risk.
>
>If you get such a launch, even holding the stick hard forward all the
time
>from 'take up slack' will not prevent the over-rotation, although it
>might slightly reduce your chances of instant death from a flick spin.
>
>Such events can be easily avoided by by controlling the winch so that
the
>ground run acceleration is not more than about 1.0g (or less for the
types
>mentioned above). This will still get you airborne and climbing within
>about 3-4 seconds, which most pilots find quite fast enough! It will
also
>make very little difference to the achieved height.
>
>Derek Copeland
>
Dick Johnson said in 2001:
In my opinion it is reasonably safe to ground launch a Phoebus A,B, or
C sailplane as long as the initial acceleration is not too great. The
all-moving horizontal tail on these sailplanes have more propensity to
stall than those of sailplanes equipped with conventional fixed
stabilizer/elevator configurations. When the all-moving stabilizer
stalls during an excessively high acceleration take-off, pushing the
control stick forward usually just puts the horizontal tail deeper
into its stall, and therefore it is even more ineffective.
At low airspeeds, the nose up couple produced by a strong tow rope
pull and a high sailplane CG location can easily overpower the
aerodynamic nose down capability of an elevator control system, and
that leads to an uncontrollable nose up pitch during take-off. In a
number of instances, this has lead to the sailplane stalling and
crashing; usually with fatal results. The Phoebus is not the only
sailplane that is susceptible to this fault, so be careful of high
initial tow acceleration - auto as well as winch. I have been there!
Dick Johnson
bildan
March 22nd 09, 01:23 AM
On Mar 20, 4:52*pm, wrote:
> Dick Johnson said in 2001:
>
> In my opinion it is reasonably safe to ground launch a Phoebus A,B, or
> C sailplane as long as the initial acceleration is not too great. The
> all-moving horizontal tail on these sailplanes have more propensity to
> stall than those of sailplanes equipped with conventional fixed
> stabilizer/elevator configurations. When the all-moving stabilizer
> stalls during an excessively high acceleration take-off, pushing the
> control stick forward usually just puts the horizontal tail deeper
> into its stall, and therefore it is even more ineffective.
>
> * At low airspeeds, the nose up couple produced by a strong tow rope
> pull and a high sailplane CG location can easily overpower the
> aerodynamic nose down capability of an elevator control system, and
> that leads to an uncontrollable nose up pitch during take-off. In a
> number of instances, this has lead to the sailplane stalling and
> crashing; usually with fatal results. The Phoebus is not the only
> sailplane that is susceptible to this fault, so be careful of high
> initial tow acceleration - auto as well as winch. I have been there!
> * Dick Johnson
Careful, Dick Johnson was a very old personal friend of mine. I
discussed this with him on many occasions and his opinion in no way
differed from mine.
As I have said many times, There are a very few gliders with control
difficulties and the Phoenix is one of them. Most of the other
problem glider were of that generation or earlier. There are very few
of them left.
Just because a few gliders have a problem is no reason to operate as
if they all do.
bildan
March 22nd 09, 01:24 AM
On Mar 20, 7:00*am, Derek Copeland > wrote:
> As I have tried to explain to Bill on numerous occasions, and on various
> forums, the uncontrollable over-rotation you get from an over-powered
> winch launch is caused by the pull line to the belly hook being below the
> glider's centre of gravity and centre of pressure. This causes a rotation
> for mechanical rather than aerodynamic control reasons. This is why high
> winged gliders, such as the K6 and K8 are most at risk.
>
> If you get such a launch, even holding the stick hard forward all the time
> from 'take up slack' will not prevent the over-rotation, although it
> might slightly reduce your chances of instant death from a flick spin.
>
> Such events can be easily avoided by by controlling the winch so that the
> ground run acceleration is not more than about 1.0g (or less for the types
> mentioned above). This will still get you airborne and climbing within
> about 3-4 seconds, which most pilots find quite fast enough! It will also
> make very little difference to the achieved height.
>
> Derek Copeland
>
> At 22:41 19 March 2009, bildan wrote:
>
> >As the glider leaves the ground, the inertial rotation will begin but
> >if the acceleration continues, the elevator effectiveness will also
> >continue to increase with the square of the airspeed. *Rotation can't
> >happen instantly because the glider has mass and rotational inertia.
> >In fact, the pilot has to start backing off the down elevator to allow
> >the glider to rotate into the climb.
>
> >Now, contrast this with a slow acceleration. *The glider staggers into
> >the air and the nose-up inertial couple starts the rotation but the
> >low speed and acceleration doesn't provide adequate control. *The nose
> >rises as the pilot struggles to control it with inadequate
> >airspeed.....
>
> >I've collected stories on this type of accident for decades and they
> >ALWAYS happen with slow acceleration.
And just as often I've challenged you to produce ANY engineering data
to support your mere opinion. You have not and I believe you cannot.
Bill,
Aside from your rude remarks and your inability to admit your mistakes
on several points (an automatic transmissions do not operate like a
cruise control), etc.....I have only posted that an article on winch
safety came out and was making people aware of it, nothing more. And I
am not the author either. However, the accident stats and their
carefully determined causes are what they are. So are the real world
experiences in a variety of gliders described in this thread suffering
from too strong initial launch acceleration. And they were not only
with types of planes that you think it can only happen to.
Dick Johnson's own words:
"...be careful of high initial tow acceleration..."
Now let me ask you a question for once: What rope tension, measured in
g do you recommend for the first seconds of the launch? Or do you
advocate RPM controlled winches over tension controlled ones?
Bill,
I also wonder if you have considered gusts and turbulence on elevator
authority. The winch RPM speed is not affected by this and will
continue accelerating if that 's what you want, when gusts or
turbulence affect the elevator. Even Tension controlled winches may
not be able to reduce tension quickly enough if this happens. That's
why the initial tension should not be too high to begin with.
I would like to hear your description of how winch settings should be
with some metrics. I know you advocate high initial tow acceleration
launches. But that doesn't really tell me the specifics.
Del C[_2_]
March 22nd 09, 10:00 AM
As far I can find out, Bill has only done a few hundred launches on rather
underpowered and overgeared old US Gehrlein type winches, plus a couple of
launches on his 'US Superwinch' in a Grob G103 before the drum was
crushed by the synthetic cable, something else I warned him about! The
G103, being low winged and quite heavy, is not prone to over-rotation
accidents anyway, as identified in the Aerokourier report.
I have personally witnessed several vastly overpowered launches involving
K6 and K8 gliders, and have sat through 3 myself, in a K8, a Standard
Cirrus and a DG101. They really do go into a near vertical climb, often
despite the best efforts of the pilot to control the rotation.
Particularly in the DG case I was lucky not to join the accidents
statistics, as I slipped back up the seat as the glider rotated and was
only able to keep the stick just off the backstop with my fingertips.
Just about everyone in Europe, where we we have a lot of winch launching
experience, disagrees with Bill's views. As to engineering data, I have
seen none whatsoever from Bill, whereas I have supplied quite a lot plus
illustrative videos on the Yahoo Winch Design Group.
If you know the position of the belly hook and the centres of gravity and
pressure in a given glider, it should be possible to calculate the
rotational couple for various levels of pull, and at what level it will
overpower the elevator.
Derek Copeland
At 01:24 22 March 2009, bildan wrote:
>On Mar 20, 7:00=A0am, Derek Copeland wrote:
>> As I have tried to explain to Bill on numerous occasions, and on
various
>> forums, the uncontrollable over-rotation you get from an over-powered
>> winch launch is caused by the pull line to the belly hook being below
>the
>> glider's centre of gravity and centre of pressure. This causes a
>rotation
>> for mechanical rather than aerodynamic control reasons. This is why
high
>> winged gliders, such as the K6 and K8 are most at risk.
>>
>> If you get such a launch, even holding the stick hard forward all the
>tim=
>e
>> from 'take up slack' will not prevent the over-rotation, although it
>> might slightly reduce your chances of instant death from a flick spin.
>>
>> Such events can be easily avoided by by controlling the winch so that
>the
>> ground run acceleration is not more than about 1.0g (or less for the
>type=
>s
>> mentioned above). This will still get you airborne and climbing within
>> about 3-4 seconds, which most pilots find quite fast enough! It will
>also
>> make very little difference to the achieved height.
>>
>> Derek Copeland
>>
>> At 22:41 19 March 2009, bildan wrote:
>>
>> >As the glider leaves the ground, the inertial rotation will begin but
>> >if the acceleration continues, the elevator effectiveness will also
>> >continue to increase with the square of the airspeed. =A0Rotation
can't
>> >happen instantly because the glider has mass and rotational inertia.
>> >In fact, the pilot has to start backing off the down elevator to
allow
>> >the glider to rotate into the climb.
>>
>> >Now, contrast this with a slow acceleration. =A0The glider staggers
>into
>> >the air and the nose-up inertial couple starts the rotation but the
>> >low speed and acceleration doesn't provide adequate control. =A0The
>nose
>> >rises as the pilot struggles to control it with inadequate
>> >airspeed.....
>>
>> >I've collected stories on this type of accident for decades and they
>> >ALWAYS happen with slow acceleration.
>
>And just as often I've challenged you to produce ANY engineering data
>to support your mere opinion. You have not and I believe you cannot.
>
Willy VINKEN[_2_]
March 22nd 09, 06:22 PM
Can anyone tell me more about how a Standard Cirrus handles when
winched?
We use a GMC V8 325 HP petrol engine with standard automatic gearbox.
No problems until now with K8, K6 and Astir Jeans.
I plan to fit my Cirrus with a CG hook. Cirruses imported to France
where all equipped with a nose hook.
Willy VINKEN OO-ZNY
On 22 Mar 2009 10:00:06 GMT, Del C > wrote:
>As far I can find out, Bill has only done a few hundred launches on rather
>underpowered and overgeared old US Gehrlein type winches, plus a couple of
>launches on his 'US Superwinch' in a Grob G103 before the drum was
>crushed by the synthetic cable, something else I warned him about! The
>G103, being low winged and quite heavy, is not prone to over-rotation
>accidents anyway, as identified in the Aerokourier report.
>
>I have personally witnessed several vastly overpowered launches involving
>K6 and K8 gliders, and have sat through 3 myself, in a K8, a Standard
>Cirrus and a DG101. They really do go into a near vertical climb, often
>despite the best efforts of the pilot to control the rotation.
>Particularly in the DG case I was lucky not to join the accidents
>statistics, as I slipped back up the seat as the glider rotated and was
>only able to keep the stick just off the backstop with my fingertips.
>
>Just about everyone in Europe, where we we have a lot of winch launching
>experience, disagrees with Bill's views. As to engineering data, I have
>seen none whatsoever from Bill, whereas I have supplied quite a lot plus
>illustrative videos on the Yahoo Winch Design Group.
>
>If you know the position of the belly hook and the centres of gravity and
>pressure in a given glider, it should be possible to calculate the
>rotational couple for various levels of pull, and at what level it will
>overpower the elevator.
>
>Derek Copeland
Del C[_2_]
March 22nd 09, 07:30 PM
At 18:22 22 March 2009, Willy VINKEN wrote:
>Can anyone tell me more about how a Standard Cirrus handles when
>winched?
>We use a GMC V8 325 HP petrol engine with standard automatic gearbox.
>No problems until now with K8, K6 and Astir Jeans.
>I plan to fit my Cirrus with a CG hook. Cirruses imported to France
>where all equipped with a nose hook.
>
>Willy VINKEN OO-ZNY
>
As long as you don't get an overpowered winch launch it's fine. The
ailerons are slightly ineffective at low speed, so try to choose a fit
looking wing runner if you can. If it's one of the all-flying tailplane
versions, just hold the stick about two-thirds forward and leave it there
until you are established in the full climb. Just concentrate on keeping
the wings level and the glider running straight during the ground run and
rotation. If there is any chance of dropping a wingtip onto the ground,
pull off immediately. It will naturally rotate quite enthusiatically after
lift off, but avoid ramming the stick hard forward to contain this, as this
is what can stall the tailplane.
Don't try to winch launch on a nose hook, because it will give a very
poor launch, and there is no back release mechanism on a the type of nose
hook fitted to this type.
The Standard Cirrus doesn't have the best positioned shoulder strap
mountings, so make sure you do your safety harness up as tightly as
possible to avoid slipping back up the seat, due to the acceleration.
Derek Copeland
John Vella Grech
March 23rd 09, 11:15 AM
At 18:22 22 March 2009, Willy VINKEN wrote:
>Can anyone tell me more about how a Standard Cirrus handles when
>winched?
>We use a GMC V8 325 HP petrol engine with standard automatic gearbox.
>No problems until now with K8, K6 and Astir Jeans.
>I plan to fit my Cirrus with a CG hook. Cirruses imported to France
>where all equipped with a nose hook.
>
>Willy VINKEN OO-ZNY
>We operated a Standard Cirrus for 3 years on the winch and found no
handling problems provided the elevator was moved progressively. The AMT
is quite powerfull and has been known to stall on full down deflection ,
but we never experienced it .
>
>On 22 Mar 2009 10:00:06 GMT, Del C wrote:
>
>>As far I can find out, Bill has only done a few hundred launches on
>rather
>>underpowered and overgeared old US Gehrlein type winches, plus a couple
>of
>>launches on his 'US Superwinch' in a Grob G103 before the drum was
>>crushed by the synthetic cable, something else I warned him about! The
>>G103, being low winged and quite heavy, is not prone to over-rotation
>>accidents anyway, as identified in the Aerokourier report.
>>
>>I have personally witnessed several vastly overpowered launches
involving
>>K6 and K8 gliders, and have sat through 3 myself, in a K8, a Standard
>>Cirrus and a DG101. They really do go into a near vertical climb, often
>>despite the best efforts of the pilot to control the rotation.
>>Particularly in the DG case I was lucky not to join the accidents
>>statistics, as I slipped back up the seat as the glider rotated and was
>>only able to keep the stick just off the backstop with my fingertips.
>>
>>Just about everyone in Europe, where we we have a lot of winch
launching
>>experience, disagrees with Bill's views. As to engineering data, I
have
>>seen none whatsoever from Bill, whereas I have supplied quite a lot
plus
>>illustrative videos on the Yahoo Winch Design Group.
>>
>>If you know the position of the belly hook and the centres of gravity
and
>>pressure in a given glider, it should be possible to calculate the
>>rotational couple for various levels of pull, and at what level it will
>>overpower the elevator.
>>
>>Derek Copeland
>
Gavin Short[_2_]
March 24th 09, 06:45 AM
At 19:30 22 March 2009, Del C wrote:
>At 18:22 22 March 2009, Willy VINKEN wrote:
>>Can anyone tell me more about how a Standard Cirrus handles when
>>winched?
>>We use a GMC V8 325 HP petrol engine with standard automatic gearbox.
>>No problems until now with K8, K6 and Astir Jeans.
>>I plan to fit my Cirrus with a CG hook. Cirruses imported to France
>>where all equipped with a nose hook.
>>
>>Willy VINKEN OO-ZNY
>>
>As long as you don't get an overpowered winch launch it's fine. The
>ailerons are slightly ineffective at low speed, so try to choose a fit
>looking wing runner if you can. If it's one of the all-flying tailplane
>versions, just hold the stick about two-thirds forward and leave it
there
>until you are established in the full climb. Just concentrate on keeping
>the wings level and the glider running straight during the ground run
and
>rotation. If there is any chance of dropping a wingtip onto the ground,
>pull off immediately. It will naturally rotate quite enthusiatically
after
>lift off, but avoid ramming the stick hard forward to contain this, as
>this
>is what can stall the tailplane.
>
>Don't try to winch launch on a nose hook, because it will give a very
>poor launch, and there is no back release mechanism on a the type of
nose
>hook fitted to this type.
>
>The Standard Cirrus doesn't have the best positioned shoulder strap
>mountings, so make sure you do your safety harness up as tightly as
>possible to avoid slipping back up the seat, due to the acceleration.
>
>Derek Copeland
>
I concur with Derek. I brace my right arm against my thigh and hold the
stick part way down so any bumps on the ground run will have much less
effect. (I learnt on a UK hill site). Mine has a all flying tail and I do
what Derek describes. I don't need to adjust the position of the stick
(in terms of pitch) until well into the climb and that is just fine
tuning.
Yes, tighten the straps before launch and press firmly back on the pedals
before launch to compress parachute/back rest arrangements (I have 50mm of
dynafoam behind me) to ensure you don't slip back on launch.
No problems with a V8 power Tost winch.
Fitting winglets last season made the ailerons more responsive at low
speed.
Read the flight manual about launching (which basically says what Derek
and I have). Also look at the Standard Cirrus website
http://www.standardcirrus.org
and also look at the Std Cirrus Forum. There is a search facility so look
for 'launch'.
The Std Cirrus hook is well protected by 2 parallel metal strips.
Practice getting the cable on yourself so you can describe to helpers how
they should fit the cable. They tend to get a bit confused because they
can't see the hook like K8s and Astirs etc.
As my first CFI says: Its a glider - go any fly it as you would a glider!
Gavin
Std Cirrus, CNN now G-SCNN, #173
LSV Viersen, Keiheuvel, Belgium
MaD
March 24th 09, 12:45 PM
In addition to what Gavin and Derek said I think it is also important
to know that the location of your Centre of Gravity has a significant
influence on the winch launch characterisitics of the Standard Cirrus.
Make sure it is no-where near the rear end of the allowable range. I
can't remember the figures but recall having it close to mid-range and
always felt comfortable.
To prevent sliding into the baggage compartment I always took the
pedals right back and trapped myself between pedals and rear canopy
rim during winch launch.
Marcel Dünner
Derek Copeland[_2_]
March 24th 09, 01:45 PM
Some of you might be interested in the latest British Gliding Association
(BGA) Winch Launching Safety Campaign, which includes some frightening
simulations of what can go wrong if you approach winching in a too
cavalier manner. Taking off with the stick hard back, possibly as a result
of sliding back up the seat, is one of them, and has been responsible for
several fatal accidents in the UK. See:
http://www.gliding.co.uk/bgainfo/safety/winch-safety.htm
Derek Copeland
At 12:45 24 March 2009, MaD wrote:
>In addition to what Gavin and Derek said I think it is also important
>to know that the location of your Centre of Gravity has a significant
>influence on the winch launch characterisitics of the Standard Cirrus.
>Make sure it is no-where near the rear end of the allowable range. I
>can't remember the figures but recall having it close to mid-range and
>always felt comfortable.
>To prevent sliding into the baggage compartment I always took the
>pedals right back and trapped myself between pedals and rear canopy
>rim during winch launch.
>
>Marcel D=FCnner
>
ucsdcpc
March 24th 09, 04:17 PM
...... and do the quiz .....
chris
On 24/03/2009 1:45 PM, Derek Copeland wrote:
> Some of you might be interested in the latest British Gliding Association
> (BGA) Winch Launching Safety Campaign, which includes some frightening
> simulations of what can go wrong if you approach winching in a too
> cavalier manner. Taking off with the stick hard back, possibly as a result
> of sliding back up the seat, is one of them, and has been responsible for
> several fatal accidents in the UK. See:
>
> http://www.gliding.co.uk/bgainfo/safety/winch-safety.htm
>
> Derek Copeland
>
> At 12:45 24 March 2009, MaD wrote:
>> In addition to what Gavin and Derek said I think it is also important
>> to know that the location of your Centre of Gravity has a significant
>> influence on the winch launch characterisitics of the Standard Cirrus.
>> Make sure it is no-where near the rear end of the allowable range. I
>> can't remember the figures but recall having it close to mid-range and
>> always felt comfortable.
>> To prevent sliding into the baggage compartment I always took the
>> pedals right back and trapped myself between pedals and rear canopy
>> rim during winch launch.
>>
>> Marcel D=FCnner
>>
bildan
March 24th 09, 04:18 PM
On Mar 21, 9:00*pm, wrote:
> Bill,
> Aside from your rude remarks and your inability to admit your mistakes
> on several points (an automatic transmissions do not operate like a
> cruise control), etc.....
I didn't say anything remotely like that. I said they ASSIST the
driver in maintaining speed by increasing torque multipication when
climbing hills.
>
> Now let me ask you a question for once: What rope tension, measured in
> g do you recommend for the first seconds of the launch? Or do you
> advocate RPM controlled winches over tension controlled ones?
I advocate tension controlled winches and the tension should be the
maximum safe value.
bildan
March 24th 09, 04:26 PM
On Mar 21, 9:29*pm, wrote:
> Bill,
> I also wonder if you have considered gusts and turbulence on elevator
> authority. The winch RPM speed is not affected by this and will
> continue accelerating if that 's what you want, when gusts or
> turbulence affect the elevator. Even Tension controlled winches may
> not be able to reduce tension quickly enough if this happens. That's
> why the initial tension should not be too high to begin with.
RPM is of interest only as far as it is necessary to protect the
engine. It is of no interest in the launch profile. Properly
engineered automatic tension control winches can for all practical
purposes INSTANTLY reduce or increase tension in response to gusts.
>
> I would like to hear your description of how winch settings should be
> with some metrics. I know you advocate high initial tow acceleration
> launches. But that doesn't really tell me the specifics.
Tension, and therefore acceleration, is limited by the prescribed weak
link strength to no more than about 1.2 G. George Moore has
extensively studied this and shows that a slight tension reduction at
rotation is needed although more actual measurements are needed to
validate that.
bildan
March 24th 09, 04:35 PM
On Mar 22, 4:00*am, Del C > wrote:
> As far I can find out, Bill has only done a few hundred launches on rather
> underpowered and overgeared old US Gehrlein type winches, plus a couple of
> launches on his 'US Superwinch' in a Grob G103 before the drum was
> crushed by the synthetic cable, something else I warned him about! The
> G103, being low winged and quite heavy, is not prone to over-rotation
> accidents anyway, as identified in the Aerokourier report.
>
> I have personally witnessed several vastly overpowered launches involving
> K6 and K8 gliders, and have sat through 3 myself, in a K8, a Standard
> Cirrus and a DG101. They really do go into a near vertical climb, often
> despite the best efforts of the pilot to control the rotation.
> Particularly in the DG case I was lucky not to join the accidents
> statistics, as I slipped back up the seat as the glider rotated and was
> only able to keep the stick just off the backstop with my fingertips.
>
> Just about everyone in Europe, where we we have a lot of winch launching
> experience, disagrees with Bill's views. As to engineering data, I have
> seen none whatsoever from Bill, whereas I have supplied quite a lot plus
> illustrative videos on the Yahoo Winch Design Group. *
>
> If you know the position of the belly hook and the centres of gravity and
> pressure in a given glider, it should be possible to calculate the
> rotational couple for various levels of pull, and at what level it will
> overpower the elevator.
>
> Derek Copeland
>
> At 01:24 22 March 2009, bildan wrote:
>
> >On Mar 20, 7:00=A0am, Derek Copeland *wrote:
> >> As I have tried to explain to Bill on numerous occasions, and on
> various
> >> forums, the uncontrollable over-rotation you get from an over-powered
> >> winch launch is caused by the pull line to the belly hook being below
> >the
> >> glider's centre of gravity and centre of pressure. This causes a
> >rotation
> >> for mechanical rather than aerodynamic control reasons. This is why
> high
> >> winged gliders, such as the K6 and K8 are most at risk.
>
> >> If you get such a launch, even holding the stick hard forward all the
> >tim=
> >e
> >> from 'take up slack' will not prevent the over-rotation, although it
> >> might slightly reduce your chances of instant death from a flick spin.
>
> >> Such events can be easily avoided by by controlling the winch so that
> >the
> >> ground run acceleration is not more than about 1.0g (or less for the
> >type=
> >s
> >> mentioned above). This will still get you airborne and climbing within
> >> about 3-4 seconds, which most pilots find quite fast enough! It will
> >also
> >> make very little difference to the achieved height.
>
> >> Derek Copeland
>
> >> At 22:41 19 March 2009, bildan wrote:
>
> >> >As the glider leaves the ground, the inertial rotation will begin but
> >> >if the acceleration continues, the elevator effectiveness will also
> >> >continue to increase with the square of the airspeed. =A0Rotation
> can't
> >> >happen instantly because the glider has mass and rotational inertia.
> >> >In fact, the pilot has to start backing off the down elevator to
> allow
> >> >the glider to rotate into the climb.
>
> >> >Now, contrast this with a slow acceleration. =A0The glider staggers
> >into
> >> >the air and the nose-up inertial couple starts the rotation but the
> >> >low speed and acceleration doesn't provide adequate control. =A0The
> >nose
> >> >rises as the pilot struggles to control it with inadequate
> >> >airspeed.....
>
> >> >I've collected stories on this type of accident for decades and they
> >> >ALWAYS happen with slow acceleration.
>
> >And just as often I've challenged you to produce ANY engineering data
> >to support your mere opinion. *You have not and I believe you cannot.
Derek, I have more experience with ground launch than you are likely
to achieve in your lifetime.
No, Derek, Only YOU disagree. All you are doing is "Bible Pounding"
hoping that by repeating the same thing over and over ever more loudly
people will accept it on faith. I think people are smart enough to
demand proof. I accept nothing on faith. I want engineering
measurements to support each and every detail.
Furthermore you are the sales representative for a particularly bad
winch design seeking to discredit all other approaches any way you
can. If you aren't being paid for this, you should demand to be.
bildan
March 24th 09, 04:48 PM
On Mar 20, 7:00*am, Derek Copeland > wrote:
> As I have tried to explain to Bill on numerous occasions, and on various
> forums, the uncontrollable over-rotation you get from an over-powered
> winch launch is caused by the pull line to the belly hook being below the
> glider's centre of gravity and centre of pressure. This causes a rotation
> for mechanical rather than aerodynamic control reasons. This is why high
> winged gliders, such as the K6 and K8 are most at risk.
I understand this exactly and have wrote about it for many years.
Almost all gliders currently in use have no risk at all of
"mechanical" over-rotation. Does a G103 have "Uncontrollable Over-
rotation"?
The "Over powered" launches you speak of are strictly limited by the
weak link to slightly over one G which is a trivial value. Nothing
violent happens at one G unless the pilot initiates it.
Derek Copeland[_2_]
March 24th 09, 05:30 PM
At 16:35 24 March 2009, bildan wrote:
>
>Derek, I have more experience with ground launch than you are likely
>to achieve in your lifetime.
>
>No, Derek, Only YOU disagree. All you are doing is "Bible Pounding"
>hoping that by repeating the same thing over and over ever more loudly
>people will accept it on faith. I think people are smart enough to
>demand proof. I accept nothing on faith. I want engineering
>measurements to support each and every detail.
>
>Furthermore you are the sales representative for a particularly bad
>winch design seeking to discredit all other approaches any way you
>can. If you aren't being paid for this, you should demand to be.
>
Bill,
1) So how many winch launches HAVE you done? I have made over 5000 autotow
and winch launches at a number of sites over a 28 year period, both solo
and as an instructor (combined that is).
2) What engineering measurements can you provide? To the best of my
knowledge, nobody has yet found a 100% successful way of measuring winch
cable tension. The cable speeds are too high for Rolling Line
Tensiometers, so this generally has to be derived from torque or throttle
settings.
3) Other than being a satisfied user of Tost and Skylaunch winches, I have
no financial connections to any manufacturer.
Derek Copeland
Bill said:
"... the tension should be the maximum safe value."
OK, let me try this again. Maybe you'll understand this question:
1. In your opinion, what is the maximum safe value expressed in g, for
he initial launch phase?
2. Who else agrees with your position that the initial launch phase
should be aggressive? In this thread alone, nobody agrees with you.
Where are all these people? Mr. George Moore has also said he
advocates a slower launch than you do on the Yahoo groups site.
"Bill has advocated higher ground acceleration rates than I am
generally comfortable with."
I haven't heard a single person support what you advocate. Whatever
you find, please with verifiable quotes.
- And I don't know were your get your sense of what rude is, but
publicly and falsely claiming I am misrepresenting my identity without
any proof on your part what so ever, certainly is rude behavior.
Derek Copeland[_2_]
March 25th 09, 07:45 AM
No a Grob G103 is not prone to 'uncontrollable over-rotation' after
lifting off on a winch launch, because it has low set wings, hence a low
centre of gravity, a slightly forward set belly hook, and it's quite
heavy. Depending on the model, it either launches on a relatively weak red
or brown link, so it is prone to weak link failures, as is identified in
the Aerokourier report. So you need to be careful about overpowering it
for a different reason.
However there are many types that are prone to over-rotation, particularly
K6, K7, K8, K13, Standard Cirrus, and many other types of single seater.
In that it is very rare to break a weak link during the ground run,
however violent, it is likely that you can get much faster acceleration
than 1.2g. I think this is because of the fact that the glider is on
wheels and unloads the weak link as it rolls and accelerates forward. If
you where pulling against a concrete block set into the ground, you would
break the weak link every time at the same force. If the weak link does
break as a result of an overpowered launch, it usually does so sometime
during or just after the rotation, which is at the worst possible time! If
you drive a winch (which I do) you can feel the load on the cable increase
as the glider rotates, even if the throttle or tension setting remains
constant.
Have a look at the following video showing a K13 being winch launched:
http://www.youtube.com/watch?v=KUsqw0OwMZA
Note that after a slightly protracted 'take up slack' the tailwheel goes
down onto the ground when the winch driver opens the throttle and stays
there until the glider lifts off, if anything slightly mainwheel first.
This is despite the elevator being held slightly lower than neutral (stick
forward of centre), as it should be. If you have a K13 available, try
sitting two 180lb men plus parachutes in it and then push down down on the
tail until the tailwheel touches the ground. You will find that this
requires quite a lot of force, which illustrates just how powerful the
rotational couple must be.
Derek Copeland
At 16:48 24 March 2009, bildan wrote:
>On Mar 20, 7:00=A0am, Derek Copeland wrote:
>> As I have tried to explain to Bill on numerous occasions, and on
various
>> forums, the uncontrollable over-rotation you get from an over-powered
>> winch launch is caused by the pull line to the belly hook being below
>the
>> glider's centre of gravity and centre of pressure. This causes a
>rotation
>> for mechanical rather than aerodynamic control reasons. This is why
high
>> winged gliders, such as the K6 and K8 are most at risk.
>
>I understand this exactly and have wrote about it for many years.
>Almost all gliders currently in use have no risk at all of
>"mechanical" over-rotation. Does a G103 have "Uncontrollable Over-
>rotation"?
>
>The "Over powered" launches you speak of are strictly limited by the
>weak link to slightly over one G which is a trivial value. Nothing
>violent happens at one G unless the pilot initiates it.
>
bagmaker
March 25th 09, 09:59 AM
Bill said:
"... the tension should be the maximum safe value."
OK, let me try this again. Maybe you'll understand this question:
1. In your opinion, what is the maximum safe value expressed in g, for
he initial launch phase?
2. Who else agrees with your position that the initial launch phase
should be aggressive? In this thread alone, nobody agrees with you.
Where are all these people? Mr. George Moore has also said he
advocates a slower launch than you do on the Yahoo groups site.
"Bill has advocated higher ground acceleration rates than I am
generally comfortable with."
I haven't heard a single person support what you advocate. Whatever
you find, please with verifiable quotes.
- And I don't know were your get your sense of what rude is, but
publicly and falsely claiming I am misrepresenting my identity without
any proof on your part what so ever, certainly is rude behavior.
I would support a fair bit of what Bill says, which may be why my previos post has been ignored.
Many of our sports members fall into the old dogs and new tricks area, I have a feeling the more experience one has in anything, the more they push against change, especially as we grow older.
I must disagree with Dereks' statement on measuring tension as well, it is a simple thing to do. Perhaps it hasnt been done, sure, but its not hard. (Caveat- I sell loadcells and measurement equipment for a living)
As I have stated, If we can identify we have a problem (we do, people have died) why would we not change? Technology is allowing change, embrace it.
If, with respect of time, we see we were wrong and can change back, what harm? At least we tried.
We can set up winches to do any damn thing we like, every time, regardless of wind gusts, temperature changes, altitute differences, ballast, number of pilots, student requirements, winchperson ability, emergency airspace violations etc, etc. So lets!
If you dis-agree, dont fly off the new winch, simple!
Bagger
Derek Copeland[_2_]
March 25th 09, 02:45 PM
In the UK, Holland and Germany about two-thirds of glider launches are done
by winch, so we have a fair bit of experience in this technique. Prior to
about the early 1980s winches were fairly asthmatic things, but the sort
of ideas that Bill is advocating now where tried out as more powerful, big
engined winches such as the Tost and Van Gelder, became available, and
where quickly found to be somewhat dangerous! As the Americans are at last
starting to get into winching, I am just trying to stop them re-inventing a
rather dangerous wheel. All you have to do in reality is to slightly
restrict the power given to those types of glider that can't safely use
it!
Even a fully automated, computerised winch can fall foul of finger trouble
in inputing the launch data, so even there it is best to err slightly on
the size of caution.
Bill has suggested that slowly accelerated launches are more likely to
cause flick spins. That being the case we should have had plenty of these
when we autotowed, where the acceleration is very slow, but we didn't!
If you have a system or a gadget that you can clamp to a winch to directly
measure cable tension, I for one would like to know about it. RLTs seem to
be limited to about 40mph maximum cable speed, which is not enough. The
other approach is to mount a load cell in the glider's hook mount, or at
the glider end of the cable with a radio transmitter to transmit data back
to the winch. The former would be rather expensive for glider owners and
for clubs with a lot of gliders, while the latter would be prone to
breakages when dropped from 2000ft!
Derek Copeland
At 09:59 25 March 2009, bagmaker wrote:
>
>I would support a fair bit of what Bill says, which may be why my
>previos post has been ignored.
>
>Many of our sports members fall into the old dogs and new tricks area,
>I have a feeling the more experience one has in anything, the more they
>push against change, especially as we grow older.
>
>I must disagree with Dereks' statement on measuring tension as well, it
>is a simple thing to do. Perhaps it hasnt been done, sure, but its not
>hard. (Caveat- I sell loadcells and measurement equipment for a
>living)
>
>As I have stated, If we can identify we have a problem (we do, people
>have died) why would we not change? Technology is allowing change,
>embrace it.
>If, with respect of time, we see we were wrong and can change back,
>what harm? At least we tried.
>
>We can set up winches to do any damn thing we like, every time,
>regardless of wind gusts, temperature changes, altitute differences,
>ballast, number of pilots, student requirements, winchperson ability,
>emergency airspace violations etc, etc. So lets!
>
>If you dis-agree, dont fly off the new winch, simple!
>
>
>Bagger
>
>
>
>
>--
>bagmaker
>
bildan
March 25th 09, 04:43 PM
On Mar 25, 3:59*am, bagmaker >
wrote:
> ;687487 Wrote:
>
>
>
>
>
> > Bill said:
> > "... the tension should be the maximum safe value."
>
> > OK, let me try this again. Maybe you'll understand this question:
>
> > 1. In your opinion, what is the maximum safe value expressed in g, for
> > he initial launch phase?
> > 2. Who else agrees with your position that the initial launch phase
> > should be aggressive? In this thread alone, nobody agrees with you.
> > Where are all these people? Mr. George Moore has also said he
> > advocates a slower launch than you do on the Yahoo groups site.
> > "Bill has advocated higher ground acceleration rates than I am
> > generally comfortable with."
>
> > I haven't heard a single person support what you advocate. Whatever
> > you find, please with verifiable quotes.
>
> > - And I don't know were your get your sense of what rude is, but
> > publicly and falsely claiming I am misrepresenting my identity without
> > any proof on your part what so ever, certainly is rude behavior.
>
> I would support a fair bit of what Bill says, which may be why my
> previos post has been ignored.
>
> Many of our sports members fall into the old dogs and new tricks area,
> I have a feeling the more experience one has in anything, the more they
> push against change, especially as we grow older.
>
> I must disagree with Dereks' statement on measuring tension as well, it
> is a simple thing to do. Perhaps it hasnt been done, sure, but its not
> hard. (Caveat- I sell loadcells and measurement equipment for a
> living)
>
> As I have stated, If we can identify we have a problem (we do, people
> have died) why would we not change? Technology is allowing change,
> embrace it.
> If, with respect of time, we see we were wrong and can change back,
> what harm? At least we tried.
>
> We can set up winches to do any damn thing we like, every time,
> regardless of wind gusts, temperature changes, altitute differences,
> ballast, number of pilots, student requirements, winchperson ability,
> emergency airspace violations etc, etc. So lets!
>
> If you dis-agree, dont fly off the new winch, simple!
>
> Bagger
>
> --
> bagmaker
Thanks for that.
This discussion always gets the "Safety Nazis" wringing their hands
and wailing every time. ( But never, ever, producing any hard data.)
The thing is - it's mostly a trivial "tempest in a teapot".
To get the absolute maximum acceleration possible for a glider, just
divide a gliders flying weight into its specified weak link strength.
(Tost weak links are now calibrated to +or- 5%) That value is always
around 1.2G - if you don't believe it, read your manual. If you try
to accelerate the glider with more force than that, the link breaks in
the takeoff roll and the glider never gets airborne.
Since even the most conservative old fart thinks than .8 to .9 G is OK
for most gliders, this whole frightful affair is all about an
approximately .3G range which is buried in the 'noise'. Most pilots
can't detect the difference.
I've had brand new Tost weak links fail in the rotation phase on many
occasions as a result of too much cable tension from one of those
"underpowered US winches". I was nowhere near the limit of down
elevator authority. The most recent involved a 2-33 whose CG is at
least 3 feet above the hook and whose tiny horizontal tail severely
limits down elevator authority.
Again, the disclaimer, there are a very few mostly old gliders with a
problem which thankfully are very rare in the US. Pilots of these
should check with knowledgeable people for the special launching
technique required. Virtually all gliders in the US winch just fine.
I strongly suspect the problem is isolated to the UK, where they do
fly old gliders, and has to do with a particular new 'powerful winch'
which is capable of enormous force in first gear and which shifts to
second gear at some unknown and uncontrollable point during the
rotation phase. The tension data which IS available for this winch
looks pretty scary.
Dereks voluminous criticism of computer controlled automatic tension
winches stems from the fact that HIS favorite winch has no such
controls and he's afraid that US winch builders using Automatic
Tension Control will steal the market.
Everyone has experienced the imprecise surging when backing a car with
an automatic transmission to align a tow ball with a trailer hitch.
Imagine trying to control the acceleration a 1000 pound glider with a
drive train intended for a 6000 pound road vehicle.
Anyone who thinks any of this is not true, needs to produce some valid
measurements to the contrary. I believe validated data.
John Galloway[_1_]
March 26th 09, 12:15 AM
At 16:43 25 March 2009, bildan wrote:
>Everyone has experienced the imprecise surging when backing a car with
>an automatic transmission to align a tow ball with a trailer hitch.
>Imagine trying to control the acceleration a 1000 pound glider with a
>drive train intended for a 6000 pound road vehicle.
>
>Anyone who thinks any of this is not true, needs to produce some valid
>measurements to the contrary. I believe validated data.
Bill,
I have been involved in a lot of discussion a debate here in Scotland abut
the merits or otherwise of Skylaunch winches and I have been launched by
one and have launched about 8 gliders with one. As you well know because
you have been told this on another forum the auto box is a complete
non-issue. It changes into third during the ground run and stays in fixed
ratio top gear throughout the launch - only exeptionally changing down
under very heavy loading during the main part of the launch. The early
upwards gear changes are undetectable to the glider pilot.
I don't know what you consider to be validated data if not 40 odd winches
over many years of use without problems with controllability related to the
auto box. I can understand your wish to promote the merits of tension
controlled winches but to do so by denigrating a clearly successful
alternative design reveals more about your mindset than the winch in
question. It is a shame that you have no practical experience of the
Skylaunch which in our club trials worked equally successfully for K8s to
Duo Disci
I am pretty sure that the long term future of winching will rest with much
more complex designs but there is none currently available that is proven
by experience in terms of time of use and numbers built. The Hydrostart
is certainly not yet convincing and is very expensive and, correct me if I
am wrong, the US version is not launching yet. Considering the cost of
winches, and the fact that once a club becomes winch orientated then
proven reliabilty is critical, then I would reckon that it will be 5-10
years before it becomes wise to risk the purchase of what is now an
experimental winch design. That is not to say that the the US tension
controlled winch will not be successful from the start - just that it is
better to let others act as the early adopters.
John Galloway
"This discussion always gets the "Safety Nazis" wringing their hands
and wailing every time. ( But never, ever, producing any hard data.)
"
Bill, for once, please, answer the simple question:
What the initial tension, measured in G that you consider ideal on
initial launch? Are you afraid to answer this question that I am now
asking of you for the third time already? You can't complain about
others not providing data (which is not true) if you refuse to even
begin to do so yourself. So put up already.
Derek Copeland[_2_]
March 26th 09, 07:00 AM
Can I add that after a very sucessful 6 month trial with a loaned
secondhand Skylaunch winch, Lasham Gliding Society has ordered 2 new ones
that will be arriving shortly.
Lasham is the largest and probably most professional gliding club in the
UK, so its Committee and Management would not have not have entered into
this major financial investment lightly or without considering the
alternatives. I am not a member of the Management or the Committee by the
way.
Can I further add that this winch will smoothly launch anything from
lightweight little vintage single seaters up to big and heavy DG1000Ts,
Duo Discus turbos, and ASH25 turbos. As John says below, the automatic
gearbox changes up into top very early during the ground run and normally
stays there for the rest of the launch. The gearchanges are imperceptable
to the pilot and we have not found a problem with weak links breaking
during the ground run, or at any other stage of the launch for that
matter.
Derek Copeland
P.S. I still want to know how many winch launches Bill Daniels has
actually taken? He demands exact data from others, but won't give out any
himself!
At 00:15 26 March 2009, John Galloway wrote:
>At 16:43 25 March 2009, bildan wrote:
>
>>Everyone has experienced the imprecise surging when backing a car with
>>an automatic transmission to align a tow ball with a trailer hitch.
>>Imagine trying to control the acceleration a 1000 pound glider with a
>>drive train intended for a 6000 pound road vehicle.
>>
>>Anyone who thinks any of this is not true, needs to produce some valid
>>measurements to the contrary. I believe validated data.
>
>Bill,
>
>I have been involved in a lot of discussion a debate here in Scotland
abut
>the merits or otherwise of Skylaunch winches and I have been launched by
>one and have launched about 8 gliders with one. As you well know
because
>you have been told this on another forum the auto box is a complete
>non-issue. It changes into third during the ground run and stays in
fixed
>ratio top gear throughout the launch - only exeptionally changing down
>under very heavy loading during the main part of the launch. The early
>upwards gear changes are undetectable to the glider pilot.
>
>I don't know what you consider to be validated data if not 40 odd
winches
>over many years of use without problems with controllability related to
>the
>auto box. I can understand your wish to promote the merits of tension
>controlled winches but to do so by denigrating a clearly successful
>alternative design reveals more about your mindset than the winch in
>question. It is a shame that you have no practical experience of the
>Skylaunch which in our club trials worked equally successfully for K8s
to
>Duo Disci
>
>I am pretty sure that the long term future of winching will rest with
much
>more complex designs but there is none currently available that is
proven
>by experience in terms of time of use and numbers built. The Hydrostart
>is certainly not yet convincing and is very expensive and, correct me if
I
>am wrong, the US version is not launching yet. Considering the cost of
>winches, and the fact that once a club becomes winch orientated then
>proven reliabilty is critical, then I would reckon that it will be 5-10
>years before it becomes wise to risk the purchase of what is now an
>experimental winch design. That is not to say that the the US tension
>controlled winch will not be successful from the start - just that it is
>better to let others act as the early adopters.
>
>John Galloway
>
MaD
March 26th 09, 12:16 PM
> To get the absolute maximum acceleration possible for a glider, just
> divide a gliders flying weight into its specified weak link strength.
> (Tost weak links are now calibrated to +or- 5%) That value is always
> around 1.2G - if you don't believe it, read your manual.
Hmmm... Must really go and check the manuals. Or my maths.
IIRC mine (a newer AS model) says 750 or 800daN allowable, my flying
weight is normally around 390kg. So that's close to 2g.
We use 1000daN weak links for the ASK21 (empty 360kg according to AS
homepage), so with two occupants around 540kg. That's also around
1.9g!
Regards
Marcel Dünner
John Roche-Kelly
March 27th 09, 11:00 AM
I think you may be missing the point here.
The weak link is to protect the glider airframe from exceeding maximum
loading ie towards the top of the launch, with the cable almost vertical
and the wing loading at its maximum. Using these calculations to determine
the best acceleration at the start of the launch is bad math(s).
The acceleration on the ground should be safe. Too high and the inertia of
the stick and the pilot's hand will cause backward movement, with
self-evident results. Too slow and aileron authority is not achieved
quickly enough to prevent wing drop and possible cartwheel!
Typically aileron authority is present just below the stall speed so the
acceleration should be sufficient to get to that speed before a wing can
drop, say 2 seconds or so. Now do the math(s) for your glider. Typical
stall speeds are below 35 kt (17 metres per second). This gives an
acceleration of less than 1g which will comfortably be tolerated by any
pilot. If continued the acceleration will have the glider fully flying and
high enough to begin the rotation into full climb in another second or
two.
Broken weak links at the start of the ground run are generally due to a
snatched All Out. The launch marshal must ensure that there is no slack in
the cable before giving All Out by waiting for a genuine movement of the
glider. The wing tip holder must move forward with the glider for as long
as possible. The wing tip holder should abort the launch if he or she has
to hold the wings level, they should do so naturally or the wing will drop
on release.
Best wishes
JohnR-K
Derek Copeland[_2_]
March 27th 09, 01:15 PM
A few points to add to this.
1) The pilot should also be prepared to abandon the launch if a wing drops
during the ground run. In the UK it is recommended that the pilot keeps his
hand on the release knob during the ground run.
2) I always hold the stick in an appropriate setting for the glider type,
generally always forward of centre, and then rest my arm or elbow against
either my thigh or the side of the cockpit. That way I will not
inadvertantly pull the stick back due to the effects of acceleration and
inertia.
3) Always do your straps up as tightly as possible for a winch launch, and
if the rudder pedals are easily adjustable, set them a bit closer than
normal. If you need back cushions, make sure that they are made of a firm
material. Several fatal winch launching accidents in the UK have been
caused by pilots slipping back up the seat, or sinking back into soft foam
cushions, again due to rapid acceleration and inertia. Possibly another
good reason for limiting acceleration rates!
Derek Copeland
At 11:00 27 March 2009, John Roche-Kelly wrote:
>I think you may be missing the point here.
>The weak link is to protect the glider airframe from exceeding maximum
>loading ie towards the top of the launch, with the cable almost vertical
>and the wing loading at its maximum. Using these calculations to
determine
>the best acceleration at the start of the launch is bad math(s).
>The acceleration on the ground should be safe. Too high and the inertia
of
>the stick and the pilot's hand will cause backward movement, with
>self-evident results. Too slow and aileron authority is not achieved
>quickly enough to prevent wing drop and possible cartwheel!
>Typically aileron authority is present just below the stall speed so the
>acceleration should be sufficient to get to that speed before a wing can
>drop, say 2 seconds or so. Now do the math(s) for your glider. Typical
>stall speeds are below 35 kt (17 metres per second). This gives an
>acceleration of less than 1g which will comfortably be tolerated by any
>pilot. If continued the acceleration will have the glider fully flying
and
>high enough to begin the rotation into full climb in another second or
>two.
>Broken weak links at the start of the ground run are generally due to a
>snatched All Out. The launch marshal must ensure that there is no slack
in
>the cable before giving All Out by waiting for a genuine movement of the
>glider. The wing tip holder must move forward with the glider for as
long
>as possible. The wing tip holder should abort the launch if he or she
has
>to hold the wings level, they should do so naturally or the wing will
drop
>on release.
>
>Best wishes
>
>JohnR-K
>
MaD
March 27th 09, 04:07 PM
On 27 Mrz., 12:00, John Roche-Kelly >
wrote:
> I think you may be missing the point here.
> The weak link is to protect the glider airframe from exceeding maximum
> loading ie towards the top of the launch, with the cable almost vertical
> and the wing loading at its maximum. Using these calculations to determine
> the best acceleration at the start of the launch is bad math(s).
Yes, yes, of course. I didn't mean to give the impression I would like
to be accelerated to the limits of the weak link - that would be
quite frightful. But bildan was throwing wrong figures about and
claiming (indirectly) the weak link limits the acceleration to safe
levels.
Marcel
Alan Garside
March 27th 09, 05:30 PM
Also the wing tip runner should hold the wing at the correct height, too
many hold a high wing too low and a low wing too high.
At 11:00 27 March 2009, John Roche-Kelly wrote:
>I think you may be missing the point here.
>The weak link is to protect the glider airframe from exceeding maximum
>loading ie towards the top of the launch, with the cable almost vertical
>and the wing loading at its maximum. Using these calculations to
determine
>the best acceleration at the start of the launch is bad math(s).
>The acceleration on the ground should be safe. Too high and the inertia
of
>the stick and the pilot's hand will cause backward movement, with
>self-evident results. Too slow and aileron authority is not achieved
>quickly enough to prevent wing drop and possible cartwheel!
>Typically aileron authority is present just below the stall speed so the
>acceleration should be sufficient to get to that speed before a wing can
>drop, say 2 seconds or so. Now do the math(s) for your glider. Typical
>stall speeds are below 35 kt (17 metres per second). This gives an
>acceleration of less than 1g which will comfortably be tolerated by any
>pilot. If continued the acceleration will have the glider fully flying
and
>high enough to begin the rotation into full climb in another second or
>two.
>Broken weak links at the start of the ground run are generally due to a
>snatched All Out. The launch marshal must ensure that there is no slack
in
>the cable before giving All Out by waiting for a genuine movement of the
>glider. The wing tip holder must move forward with the glider for as
long
>as possible. The wing tip holder should abort the launch if he or she
has
>to hold the wings level, they should do so naturally or the wing will
drop
>on release.
>
>Best wishes
>
>JohnR-K
>
Jon Simpson[_2_]
March 27th 09, 09:50 PM
"Alan Garside" > wrote in message
...
> Also the wing tip runner should hold the wing at the correct height, too
> many hold a high wing too low and a low wing too high.
>
>
> At 11:00 27 March 2009, John Roche-Kelly wrote:
>>I think you may be missing the point here.
>>The weak link is to protect the glider airframe from exceeding maximum
>>loading ie towards the top of the launch, with the cable almost vertical
>>and the wing loading at its maximum. Using these calculations to
> determine
>>the best acceleration at the start of the launch is bad math(s).
>>The acceleration on the ground should be safe. Too high and the inertia
> of
>>the stick and the pilot's hand will cause backward movement, with
>>self-evident results. Too slow and aileron authority is not achieved
>>quickly enough to prevent wing drop and possible cartwheel!
>>Typically aileron authority is present just below the stall speed so the
>>acceleration should be sufficient to get to that speed before a wing can
>>drop, say 2 seconds or so. Now do the math(s) for your glider. Typical
>>stall speeds are below 35 kt (17 metres per second). This gives an
>>acceleration of less than 1g which will comfortably be tolerated by any
>>pilot. If continued the acceleration will have the glider fully flying
> and
>>high enough to begin the rotation into full climb in another second or
>>two.
>>Broken weak links at the start of the ground run are generally due to a
>>snatched All Out. The launch marshal must ensure that there is no slack
> in
>>the cable before giving All Out by waiting for a genuine movement of the
>>glider. The wing tip holder must move forward with the glider for as
> long
>>as possible. The wing tip holder should abort the launch if he or she
> has
>>to hold the wings level, they should do so naturally or the wing will
> drop
>>on release.
>>
>>Best wishes
>>
>>JohnR-K
>>
To the tune of 'Donald whers yoo trooses' (Scottish folk song)
"Let the wing go high let the wing go low"......you get the drift.
JRS
Derek Copeland[_2_]
March 28th 09, 08:30 AM
Despite the alleged 'bildan tension spikes' from the automatic gearboxes
fittes to many current winches, in my experience weak link breaks during
the ground run are extremely rare. If you do get a very overpowered
launch, the weak link will normally break towards the end of the rotation
or early in the full climb. The best video example I can find on youtube
is:
http://www.youtube.com/watch?v=jvK1ONl1CqE
This launch was on a diesel powered winch (also favoured by bildan) where
you typically get a rather slow initial ground run acceleration, followed
by a sudden snatch into the air and often a considerable overspeed for
lighter gliders.
The video also shows what happens if you don't lower the nose quickly
enough after a launch failure. The pilot allows the glider to stall, after
which it never regains enough airspeed to round out. The glider (ASW15)
suffered a collapsed undercarriage and other minor damage, and the pilot a
bruised back. Fortunately nothing more serious, as it looks at one point as
if the glider might spin.
Otherwise weak links normally only break near the top of the launch, where
they are doing their job in protecting the airframe.
Derek Copeland
At 16:07 27 March 2009, MaD wrote:
>On 27 Mrz., 12:00, John Roche-Kelly
>wrote:
>> I think you may be missing the point here.
>> The weak link is to protect the glider airframe from exceeding maximum
>> loading ie towards the top of the launch, with the cable almost
vertical
>> and the wing loading at its maximum. Using these calculations to
>determine
>> the best acceleration at the start of the launch is bad math(s).
>
>Yes, yes, of course. I didn't mean to give the impression I would like
>to be accelerated to the limits of the weak link - that would be
>quite frightful. But bildan was throwing wrong figures about and
>claiming (indirectly) the weak link limits the acceleration to safe
>levels.
>
>Marcel
>
David Chapman
March 28th 09, 07:00 PM
A Yahoo groups forum on Glider Winch engineering. Some posts review tension
control, ?? .......
http://dir.groups.yahoo.com/group/winchengineer/message/36
http://dir.groups.yahoo.com/group/winchengineer/message/38
and even one thinking about using battery power?
http://dir.groups.yahoo.com/group/winchengineer/message/40
Did anyone get a electric battery launch before?
David.
At 08:30 28 March 2009, Derek Copeland wrote:
>Despite the alleged 'bildan tension spikes' from the automatic
gearboxes
>fittes to many current winches, in my experience weak link breaks during
>the ground run are extremely rare. If you do get a very overpowered
>launch, the weak link will normally break towards the end of the
rotation
>or early in the full climb. The best video example I can find on youtube
>is:
>
> http://www.youtube.com/watch?v=jvK1ONl1CqE
>
>This launch was on a diesel powered winch (also favoured by bildan)
where
>you typically get a rather slow initial ground run acceleration,
followed
>by a sudden snatch into the air and often a considerable overspeed for
>lighter gliders.
>
>The video also shows what happens if you don't lower the nose quickly
>enough after a launch failure. The pilot allows the glider to stall,
after
>which it never regains enough airspeed to round out. The glider (ASW15)
>suffered a collapsed undercarriage and other minor damage, and the pilot
a
>bruised back. Fortunately nothing more serious, as it looks at one point
>as
>if the glider might spin.
>
>Otherwise weak links normally only break near the top of the launch,
where
>they are doing their job in protecting the airframe.
>
>Derek Copeland
>
>
>At 16:07 27 March 2009, MaD wrote:
>>On 27 Mrz., 12:00, John Roche-Kelly
>>wrote:
>>> I think you may be missing the point here.
>>> The weak link is to protect the glider airframe from exceeding
maximum
>>> loading ie towards the top of the launch, with the cable almost
>vertical
>>> and the wing loading at its maximum. Using these calculations to
>>determine
>>> the best acceleration at the start of the launch is bad math(s).
>>
>>Yes, yes, of course. I didn't mean to give the impression I would like
>>to be accelerated to the limits of the weak link - that would be
>>quite frightful. But bildan was throwing wrong figures about and
>>claiming (indirectly) the weak link limits the acceleration to safe
>>levels.
>>
>>Marcel
>>
>
Derek Copeland[_2_]
March 28th 09, 07:45 PM
At 19:00 28 March 2009, David Chapman wrote:
>A Yahoo groups forum on Glider Winch engineering. Some posts review
tension
>control, ?? .......
>http://dir.groups.yahoo.com/group/winchengineer/message/36
>http://dir.groups.yahoo.com/group/winchengineer/message/38
>
>and even one thinking about using battery power?
>http://dir.groups.yahoo.com/group/winchengineer/message/40
>Did anyone get a electric battery launch before?
>
There is a German made electric winch called the ESW2B that essentially
runs on battery power, albeit an array of 12 volt lead-acid ones. They
need to be constantly charged up while in use, either from the mains or a
portable generator. I believe that you can't do too many launches per
hour without boiling the battery acid.
A winch needs at least 300hp or 230kW to launch a modern two-seater
glider, so it's a bit too much for normal mains electricity!
Derek Copeland
Gerhard Wesp[_9_]
March 29th 09, 04:28 AM
On 22 Mrz., 03:24, bildan > wrote:
> And just as often I've challenged you to produce ANY engineering data
> to support your mere opinion. *You have not and I believe you cannot.
That seems like elementary rigid body mechanics to me. In this case
calculations trump measurements due to the well-understood nature of
the
physics and the inherent errors of any measurement.
A simple longitudinal simulation model should be well sufficient to
gain
good insight into these types of accidents. Would be an interesting
subject
for a followup article.
Best regards
--Gerhard Wesp
Gerhard Wesp[_9_]
March 29th 09, 04:43 AM
On 26 Mrz., 02:55, wrote:
> What the initial tension, measured in G that you consider ideal on
> initial launch? Are you afraid to answer this question that I am now
> asking of you for the third time already? You can't complain about
> others not providing data (which is not true) if you refuse to even
> begin to do so yourself. So put up already.
Ahem... Tension is measured in Newton, not in G. G == acceleration,
or m/s^2. Yes, the forward acceleration of the glider in the initial
takeoff run
can be measured in G, but the connection between the cable tension and
acceleration involves glider and cable mass and wind, so there's no
one-to-one correspondence.
Best regards
--Gerhard Wesp
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