Airspeed control during ground launch?

[Roger Worden]

What is the correct relationship between pitch angle and airspeed during
ground launch, either by auto or winch? Different sources make conflicting
statements:

1. Speed control is OPPOSITE to that during aerotow and gliding

* SSA Soaring Flight Manual, page 13-10: "Under most circumstances, the best
way to reduce the airspeed is to raise the nose. During ground launch,
however, the opposite is true ... pulling the nose up results in an increase
in airspeed, assuming the launch vehicle has adequate power."

* FAA Glider Flying Handbook, page 7-16: "The pitch attitude/airspeed
relationship during ground launch is unique. During the launch, pulling back
on the stick tends to increase airspeed, and pushing forward tends to reduce
airspeed. This is the opposite of the normal pitch/airspeed relationship."

* This is what I was taught during autotow training. I can't say that I have
varied the pitch enough in my few launches to have demonstrated it.

2. Speed control is the SAME as during aerotow and gliding

* British Gliding Association Instructors' Manual, page 16-2: "If the launch
speed starts to tail-off, lower the nose." Page 16-3: "monitor the airspeed
trend. If it is falling back towards the minimum safe speed, lower the nose
or relax any back pressure on the stick." BGA does not mention attempting to
slow down: "If the glider is starting to go too fast, maintain the normal
climb attitude, and signal. If it remains too fast, or gets even faster,
release."

* During presentations on winch launch at a recent seminar, two leading
instructors discussed lowering the nose to increase speed and raising the
nose to decrease speed.

* This is what my experience with the Condor flight simulator winch launch
has shown.

It seems to me that this is a critical point on which to be clear, since I
will be winch-launching for the first time soon. I understand that the
vectors involved are different than in aerotowing, because the wings are
converting forward rope travel to angular motion (just like the skeg on a
water ski!). I also understand that a properly balanced glider using a CG
hook for winch launch will tend to nose up initially, and will seek an
optimal climb angle naturally. Altering the climb angle with elevator will
necessarily result in a less-than-optimal altitude gain. But what is the
actual effect of raising or lowering the nose in a stable ground launch
climb?

A. Is it different depending on the angle of climb? In my experience,
autotows tend to achieve a 25- to 30-degree climb angle, winch launch a 40-
to 45-degree climb. Does that cause a difference in the effect of pitch
angle?

B. If #2 above is true, how did the SSA and FFA manuals get it wrong?

C. If #1 is true, is it reversed in Britain? (Just kidding...)

[BT]

As I understand it.. the SSA and FAA manuals do not have it wrong.

A report from the recent Back in the Saddle safety seminar reveals that the
"more modern" winch machines now in Europe actually are more automatic,
maintaining a set tension on the line and varying the speed on the winch.
The reports are that the pitch control for speed control is then more in
tune with the standard practice of raise to slow (more tension, auto
throttle slows down) lower to speed up, less tension more throttle to speed
up the winch and maintain the desired tension.

If you are on an auto tow there is no tension meter or "take up reel" on
auto, so the Speed control would be as described in the SSA and FAA manuals.

BT


"Roger Worden" > wrote in message
et...
> What is the correct relationship between pitch angle and airspeed during
> ground launch, either by auto or winch? Different sources make conflicting
> statements:
>
> 1. Speed control is OPPOSITE to that during aerotow and gliding
>
> * SSA Soaring Flight Manual, page 13-10: "Under most circumstances, the
> best way to reduce the airspeed is to raise the nose. During ground
> launch, however, the opposite is true ... pulling the nose up results in
> an increase in airspeed, assuming the launch vehicle has adequate power."
>
> * FAA Glider Flying Handbook, page 7-16: "The pitch attitude/airspeed
> relationship during ground launch is unique. During the launch, pulling
> back on the stick tends to increase airspeed, and pushing forward tends to
> reduce airspeed. This is the opposite of the normal pitch/airspeed
> relationship."
>
> * This is what I was taught during autotow training. I can't say that I
> have varied the pitch enough in my few launches to have demonstrated it.
>
> 2. Speed control is the SAME as during aerotow and gliding
>
> * British Gliding Association Instructors' Manual, page 16-2: "If the
> launch speed starts to tail-off, lower the nose." Page 16-3: "monitor the
> airspeed trend. If it is falling back towards the minimum safe speed,
> lower the nose or relax any back pressure on the stick." BGA does not
> mention attempting to slow down: "If the glider is starting to go too
> fast, maintain the normal climb attitude, and signal. If it remains too
> fast, or gets even faster, release."
>
> * During presentations on winch launch at a recent seminar, two leading
> instructors discussed lowering the nose to increase speed and raising the
> nose to decrease speed.
>
> * This is what my experience with the Condor flight simulator winch launch
> has shown.
>
> It seems to me that this is a critical point on which to be clear, since I
> will be winch-launching for the first time soon. I understand that the
> vectors involved are different than in aerotowing, because the wings are
> converting forward rope travel to angular motion (just like the skeg on a
> water ski!). I also understand that a properly balanced glider using a CG
> hook for winch launch will tend to nose up initially, and will seek an
> optimal climb angle naturally. Altering the climb angle with elevator will
> necessarily result in a less-than-optimal altitude gain. But what is the
> actual effect of raising or lowering the nose in a stable ground launch
> climb?
>
> A. Is it different depending on the angle of climb? In my experience,
> autotows tend to achieve a 25- to 30-degree climb angle, winch launch a
> 40- to 45-degree climb. Does that cause a difference in the effect of
> pitch angle?
>
> B. If #2 above is true, how did the SSA and FFA manuals get it wrong?
>
> C. If #1 is true, is it reversed in Britain? (Just kidding...)
>
>

[Bruce Greef[_2_]]

Roger Worden wrote:
> What is the correct relationship between pitch angle and airspeed during
> ground launch, either by auto or winch? Different sources make conflicting
> statements:
>
> 1. Speed control is OPPOSITE to that during aerotow and gliding
>
> * SSA Soaring Flight Manual, page 13-10: "Under most circumstances, the best
> way to reduce the airspeed is to raise the nose. During ground launch,
> however, the opposite is true ... pulling the nose up results in an increase
> in airspeed, assuming the launch vehicle has adequate power."
>
> * FAA Glider Flying Handbook, page 7-16: "The pitch attitude/airspeed
> relationship during ground launch is unique. During the launch, pulling back
> on the stick tends to increase airspeed, and pushing forward tends to reduce
> airspeed. This is the opposite of the normal pitch/airspeed relationship."
>
> * This is what I was taught during autotow training. I can't say that I have
> varied the pitch enough in my few launches to have demonstrated it.
>
> 2. Speed control is the SAME as during aerotow and gliding
>
> * British Gliding Association Instructors' Manual, page 16-2: "If the launch
> speed starts to tail-off, lower the nose." Page 16-3: "monitor the airspeed
> trend. If it is falling back towards the minimum safe speed, lower the nose
> or relax any back pressure on the stick." BGA does not mention attempting to
> slow down: "If the glider is starting to go too fast, maintain the normal
> climb attitude, and signal. If it remains too fast, or gets even faster,
> release."
>
> * During presentations on winch launch at a recent seminar, two leading
> instructors discussed lowering the nose to increase speed and raising the
> nose to decrease speed.
>
> * This is what my experience with the Condor flight simulator winch launch
> has shown.
>
> It seems to me that this is a critical point on which to be clear, since I
> will be winch-launching for the first time soon. I understand that the
> vectors involved are different than in aerotowing, because the wings are
> converting forward rope travel to angular motion (just like the skeg on a
> water ski!). I also understand that a properly balanced glider using a CG
> hook for winch launch will tend to nose up initially, and will seek an
> optimal climb angle naturally. Altering the climb angle with elevator will
> necessarily result in a less-than-optimal altitude gain. But what is the
> actual effect of raising or lowering the nose in a stable ground launch
> climb?
>
> A. Is it different depending on the angle of climb? In my experience,
> autotows tend to achieve a 25- to 30-degree climb angle, winch launch a 40-
> to 45-degree climb. Does that cause a difference in the effect of pitch
> angle?
>
> B. If #2 above is true, how did the SSA and FFA manuals get it wrong?
>
> C. If #1 is true, is it reversed in Britain? (Just kidding...)
>
>
Two things active here.

If you have effectively unlimited power on the other end of the string, then
raising the nose forces the glider to describe a larger arc, which it achieves
by accelerating.

If you have limited power (winch power loss, or glider too big for the winch -
unlikely in Europe with newer winches, but I have met some very low power
winches.) OR decreasing effective headwind (remember you are effectively fixed
to the ground in winch launch so wind gradient effects are noticeable) THEN
raising the nose will generally decrease speed, until you stall. Of course, if
you have a powerful winch and the appropriate controller on the other end it may
be able to overcome the wind effect, in which case you will get away with
raising the nose.


So both are correct.
In general, a harder pull will result in a larger arc and higher speed on a well
matched winch. ("Under most circumstances" is the quote.)
In general, decreasing speed on a winch launch is an alarm signal and you should
lower the nose to recover safe airspeed and anticipate launch failure.

Bruce

[John Galloway[_1_]]

The main thing is; on a wire launch - never ever,
under any circumstances, pull the stick back if your
airspeed is very low. The time taken increase the
angle of attack to the point of departure into a spin
is minimal compared with the time that would have been
taken to for the airspeed to rise no matter how powerful
the winch.

John Galloway

At 06:00 30 March 2007, Bruce Greef wrote:
>Roger Worden wrote:
>> What is the correct relationship between pitch angle
>>and airspeed during
>> ground launch, either by auto or winch? Different
>>sources make conflicting
>> statements:
>>
>> 1. Speed control is OPPOSITE to that during aerotow
>>and gliding
>>
>> * SSA Soaring Flight Manual, page 13-10: 'Under most
>>circumstances, the best
>> way to reduce the airspeed is to raise the nose. During
>>ground launch,
>> however, the opposite is true ... pulling the nose
>>up results in an increase
>> in airspeed, assuming the launch vehicle has adequate
>>power.'
>>
>> * FAA Glider Flying Handbook, page 7-16: 'The pitch
>>attitude/airspeed
>> relationship during ground launch is unique. During
>>the launch, pulling back
>> on the stick tends to increase airspeed, and pushing
>>forward tends to reduce
>> airspeed. This is the opposite of the normal pitch/airspeed
>>relationship.'
>>
>> * This is what I was taught during autotow training.
>>I can't say that I have
>> varied the pitch enough in my few launches to have
>>demonstrated it.
>>
>> 2. Speed control is the SAME as during aerotow and
>>gliding
>>
>> * British Gliding Association Instructors' Manual,
>>page 16-2: 'If the launch
>> speed starts to tail-off, lower the nose.' Page 16-3:
>>'monitor the airspeed
>> trend. If it is falling back towards the minimum safe
>>speed, lower the nose
>> or relax any back pressure on the stick.' BGA does
>>not mention attempting to
>> slow down: 'If the glider is starting to go too fast,
>>maintain the normal
>> climb attitude, and signal. If it remains too fast,
>>or gets even faster,
>> release.'
>>
>> * During presentations on winch launch at a recent
>>seminar, two leading
>> instructors discussed lowering the nose to increase
>>speed and raising the
>> nose to decrease speed.
>>
>> * This is what my experience with the Condor flight
>>simulator winch launch
>> has shown.
>>
>> It seems to me that this is a critical point on which
>>to be clear, since I
>> will be winch-launching for the first time soon. I
>>understand that the
>> vectors involved are different than in aerotowing,
>>because the wings are
>> converting forward rope travel to angular motion (just
>>like the skeg on a
>> water ski!). I also understand that a properly balanced
>>glider using a CG
>> hook for winch launch will tend to nose up initially,
>>and will seek an
>> optimal climb angle naturally. Altering the climb
>>angle with elevator will
>> necessarily result in a less-than-optimal altitude
>>gain. But what is the
>> actual effect of raising or lowering the nose in a
>>stable ground launch
>> climb?
>>
>> A. Is it different depending on the angle of climb?
>>In my experience,
>> autotows tend to achieve a 25- to 30-degree climb
>>angle, winch launch a 40-
>> to 45-degree climb. Does that cause a difference in
>>the effect of pitch
>> angle?
>>
>> B. If #2 above is true, how did the SSA and FFA manuals
>>get it wrong?
>>
>> C. If #1 is true, is it reversed in Britain? (Just
>>kidding...)
>>
>>
>Two things active here.
>
>If you have effectively unlimited power on the other
>end of the string, then
>raising the nose forces the glider to describe a larger
>arc, which it achieves
>by accelerating.
>
>If you have limited power (winch power loss, or glider
>too big for the winch -
>unlikely in Europe with newer winches, but I have met
>some very low power
>winches.) OR decreasing effective headwind (remember
>you are effectively fixed
>to the ground in winch launch so wind gradient effects
>are noticeable) THEN
>raising the nose will generally decrease speed, until
>you stall. Of course, if
>you have a powerful winch and the appropriate controller
>on the other end it may
>be able to overcome the wind effect, in which case
>you will get away with
>raising the nose.
>
>
>So both are correct.
>In general, a harder pull will result in a larger arc
>and higher speed on a well
>matched winch. ('Under most circumstances' is the quote.)
>In general, decreasing speed on a winch launch is an
>alarm signal and you should
>lower the nose to recover safe airspeed and anticipate
>launch failure.
>
>Bruce
>

[Bruce]

John Galloway wrote:
> The main thing is; on a wire launch - never ever,
> under any circumstances, pull the stick back if your
> airspeed is very low. The time taken increase the
> angle of attack to the point of departure into a spin
> is minimal compared with the time that would have been
> taken to for the airspeed to rise no matter how powerful
> the winch.
>
That is true, and the stall speed will be a little higher - check the minimum
winch speed for your glider - it should be in the handbook. Try to avoid testing
whether it REALLY is the stall speed on your glider on winch.

> John Galloway
>
> At 06:00 30 March 2007, Bruce Greef wrote:
>
>>Roger Worden wrote:
>>
>>>What is the correct relationship between pitch angle
>>>and airspeed during
>>>ground launch, either by auto or winch? Different
>>>sources make conflicting
>>>statements:
>>>
>>>1. Speed control is OPPOSITE to that during aerotow
>>>and gliding
>>>
>>>* SSA Soaring Flight Manual, page 13-10: 'Under most
>>>circumstances, the best
>>>way to reduce the airspeed is to raise the nose. During
>>>ground launch,
>>>however, the opposite is true ... pulling the nose
>>>up results in an increase
>>>in airspeed, assuming the launch vehicle has adequate
>>>power.'
>>>
>>>* FAA Glider Flying Handbook, page 7-16: 'The pitch
>>>attitude/airspeed
>>>relationship during ground launch is unique. During
>>>the launch, pulling back
>>>on the stick tends to increase airspeed, and pushing
>>>forward tends to reduce
>>>airspeed. This is the opposite of the normal pitch/airspeed
>>>relationship.'
>>>
>>>* This is what I was taught during autotow training.
>>>I can't say that I have
>>>varied the pitch enough in my few launches to have
>>>demonstrated it.
>>>
>>>2. Speed control is the SAME as during aerotow and
>>>gliding
>>>
>>>* British Gliding Association Instructors' Manual,
>>>page 16-2: 'If the launch
>>>speed starts to tail-off, lower the nose.' Page 16-3:
>>>'monitor the airspeed
>>>trend. If it is falling back towards the minimum safe
>>>speed, lower the nose
>>>or relax any back pressure on the stick.' BGA does
>>>not mention attempting to
>>>slow down: 'If the glider is starting to go too fast,
>>>maintain the normal
>>>climb attitude, and signal. If it remains too fast,
>>>or gets even faster,
>>>release.'
>>>
>>>* During presentations on winch launch at a recent
>>>seminar, two leading
>>>instructors discussed lowering the nose to increase
>>>speed and raising the
>>>nose to decrease speed.
>>>
>>>* This is what my experience with the Condor flight
>>>simulator winch launch
>>>has shown.
>>>
>>>It seems to me that this is a critical point on which
>>>to be clear, since I
>>>will be winch-launching for the first time soon. I
>>>understand that the
>>>vectors involved are different than in aerotowing,
>>>because the wings are
>>>converting forward rope travel to angular motion (just
>>>like the skeg on a
>>>water ski!). I also understand that a properly balanced
>>>glider using a CG
>>>hook for winch launch will tend to nose up initially,
>>>and will seek an
>>>optimal climb angle naturally. Altering the climb
>>>angle with elevator will
>>>necessarily result in a less-than-optimal altitude
>>>gain. But what is the
>>>actual effect of raising or lowering the nose in a
>>>stable ground launch
>>>climb?
>>>
>>>A. Is it different depending on the angle of climb?
>>>In my experience,
>>>autotows tend to achieve a 25- to 30-degree climb
>>>angle, winch launch a 40-
>>>to 45-degree climb. Does that cause a difference in
>>>the effect of pitch
>>>angle?
>>>
>>>B. If #2 above is true, how did the SSA and FFA manuals
>>>get it wrong?
>>>
>>>C. If #1 is true, is it reversed in Britain? (Just
>>>kidding...)
>>>
>>>
>>
>>Two things active here.
>>
>>If you have effectively unlimited power on the other
>>end of the string, then
>>raising the nose forces the glider to describe a larger
>>arc, which it achieves
>>by accelerating.
>>
>>If you have limited power (winch power loss, or glider
>>too big for the winch -
>>unlikely in Europe with newer winches, but I have met
>>some very low power
>>winches.) OR decreasing effective headwind (remember
>>you are effectively fixed
>>to the ground in winch launch so wind gradient effects
>>are noticeable) THEN
>>raising the nose will generally decrease speed, until
>>you stall. Of course, if
>>you have a powerful winch and the appropriate controller
>>on the other end it may
>>be able to overcome the wind effect, in which case
>>you will get away with
>>raising the nose.
>>
>>
>>So both are correct.
>>In general, a harder pull will result in a larger arc
>>and higher speed on a well
>>matched winch. ('Under most circumstances' is the quote.)
>>In general, decreasing speed on a winch launch is an
>>alarm signal and you should
>>lower the nose to recover safe airspeed and anticipate
>>launch failure.
>>
>>Bruce
>>
>
>
>

[Chris Reed[_1_]]

Bruce wrote:
> John Galloway wrote:
>> The main thing is; on a wire launch - never ever,
>> under any circumstances, pull the stick back if your
>> airspeed is very low. The time taken increase the
>> angle of attack to the point of departure into a spin
>> is minimal compared with the time that would have been
>> taken to for the airspeed to rise no matter how powerful
>> the winch.
> That is true, and the stall speed will be a little higher - check the
> minimum winch speed for your glider - it should be in the handbook. Try
> to avoid testing whether it REALLY is the stall speed on your glider on
> winch.

The stall speed may not be a *little* higher, but substantially higher.
The BGA instructors book recommends a minimum safe winch launch speed of
stall + 50%.

Stalling on the wire often leads to an immediate spin entry with no time
to recover, so proper training is essential.

Training is also needed to embed appropriately safe actions if the cable
breaks at various heights, as (a) the pitch over to a proper recovery
angle is much higher than a pilot trained on aerotow only would expect,
(b) there is a further trap in these circumstances in that G is reduced
during the pitch over, so that any attempt to turn before full G returns
can lead to a stall and spin (stall speed reduces with lower G), and (c)
on many sites there is a critical height band where there may be only
one safe option for an abbreviated circuit, which needs to be practised
(as do all recoverise from winch launch failures).

From the perspective of several hundred winch launches via different
winches, I'd say there is no consistent answer to what to to with the
elevator to control speed. You need briefing on how that particular
winch works. There are however two clear rules:

1. If speed reduces below the safe minimum, lower the nose, and if the
speed does not pick up immediately, relase and recover.

2. If speed increases above the maximum in the latter half of the launch
(when loads are highest) and the briefed method does not immediately
reduce the speed, lower the nose slightly to reduce the load on the
glider, signal for less speed, and if you don't get is, release as before.

I'd emphasise most strongly that you can't learn safe winch launching
from reading alone - proper training is essential.

[Bill Daniels]

The "glider speeds up with increasing pitch" advice listed below has
annoyed me for a long time. Except for highly unusual circumstances, it's
just plain wrong. In fact, it's dangerously wrong. It is extremely
desirable that the glider pilot be able to control airspeed during a winch
launch in exactly the same way as he does under all other circumstances. He
should never be forced to deal with a reverse response.
Likely this is the result observing launches from poorly constructed winches
using automobile engines and transmissions that are allowed to "run wild"
during the launch. Automobile drive trains are designed for accelerating
heavy vehicles not launching gliders. Automotive drive trains should never
be used without extensive modifications. The Tost organization has written
extensively about this.

Without these modifications, while the gilder is rotating into the climb
portion of the launch, the automatic transmission will still be shifting up
through the gears and the torque converter will still be multiplying torque.
This often results in more line tension than is desirable and the glider
will seem to accelerate alarmingly as the nose is raised. As soon as the
transmission settles in drive and the torque converter locks up, the
pitch/airspeed relationship becomes normal where raising the nose will
reduce airspeed.

Knowledgeable winch builders who still use automotive based power trains
like Tost, gut the transmissions to eliminate all gears except the 1:1 high
gear and fit high stall torque converters that won't cause problems. Other,
still more modern winch builders like Hydrostart of the Netherlands, have
gone further by eliminating all automotive parts. Instead, they use
industrial engines and hydrostatic drives to provide exact control over
cable tension at all points in the launch. These winches provide smooth,
safe launches with a completely logical pitch/airspeed relationship. The
pilot always has control over airspeed.

Bill Daniels


"Roger Worden" > wrote in message
et...
> What is the correct relationship between pitch angle and airspeed during
> ground launch, either by auto or winch? Different sources make conflicting
> statements:
>
> 1. Speed control is OPPOSITE to that during aerotow and gliding
>
> * SSA Soaring Flight Manual, page 13-10: "Under most circumstances, the
> best way to reduce the airspeed is to raise the nose. During ground
> launch, however, the opposite is true ... pulling the nose up results in
> an increase in airspeed, assuming the launch vehicle has adequate power."
>
> * FAA Glider Flying Handbook, page 7-16: "The pitch attitude/airspeed
> relationship during ground launch is unique. During the launch, pulling
> back on the stick tends to increase airspeed, and pushing forward tends to
> reduce airspeed. This is the opposite of the normal pitch/airspeed
> relationship."
>
> * This is what I was taught during autotow training. I can't say that I
> have varied the pitch enough in my few launches to have demonstrated it.
>
> 2. Speed control is the SAME as during aerotow and gliding
>
> * British Gliding Association Instructors' Manual, page 16-2: "If the
> launch speed starts to tail-off, lower the nose." Page 16-3: "monitor the
> airspeed trend. If it is falling back towards the minimum safe speed,
> lower the nose or relax any back pressure on the stick." BGA does not
> mention attempting to slow down: "If the glider is starting to go too
> fast, maintain the normal climb attitude, and signal. If it remains too
> fast, or gets even faster, release."
>
> * During presentations on winch launch at a recent seminar, two leading
> instructors discussed lowering the nose to increase speed and raising the
> nose to decrease speed.
>
> * This is what my experience with the Condor flight simulator winch launch
> has shown.
>
> It seems to me that this is a critical point on which to be clear, since I
> will be winch-launching for the first time soon. I understand that the
> vectors involved are different than in aerotowing, because the wings are
> converting forward rope travel to angular motion (just like the skeg on a
> water ski!). I also understand that a properly balanced glider using a CG
> hook for winch launch will tend to nose up initially, and will seek an
> optimal climb angle naturally. Altering the climb angle with elevator will
> necessarily result in a less-than-optimal altitude gain. But what is the
> actual effect of raising or lowering the nose in a stable ground launch
> climb?
>
> A. Is it different depending on the angle of climb? In my experience,
> autotows tend to achieve a 25- to 30-degree climb angle, winch launch a
> 40- to 45-degree climb. Does that cause a difference in the effect of
> pitch angle?
>
> B. If #2 above is true, how did the SSA and FFA manuals get it wrong?
>
> C. If #1 is true, is it reversed in Britain? (Just kidding...)
>
>

[toad]

Bill,

Are you saying that the winch should be constructed so that "pitch up
= speed up" is impossible, or that the "pitch up = speed up"
relationship is not correct for any winch ?

Todd Smith

[Bill Daniels]

The winch should be constructed such that it is not be possible for the
airspeed to increase as a result of raising the glider's nose. Otherwise,
the winch should be regarded as dangerous.

Some improperly constructed winches, most notably those with automotive V8's
and unmodified automatic transmissions, can briefly cause the airspeed to
increase as the nose is raised causing the pilot to feel the launch is out
of control. This will happen while the transmission is in the lower gears.
This is one of the many reasons Tost removes 1st and 2nd gears from their
transmissions. They also fit a "looser" torque converter to provide
smoother acceleration.

As a glider pitches up on the launch, the load on the cable and on the winch
engine increases. If the winch is tension controlled, the airspeed will
decrease. If, on the other hand, the winch is capable of delilvering
essentially unlimited cable tension as would be the case when the
transmission is in 1st or 2nd gear, the glider may accelerate as the nose is
raised.

Note that this is different from normal acceleration to climb airspeed where
the nose may be rising even as the airspeed is increasing. The difference
is that there is no cause and effect relationship.

Bill Daniels

"toad" > wrote in message
oups.com...
> Bill,
>
> Are you saying that the winch should be constructed so that "pitch up
> = speed up" is impossible, or that the "pitch up = speed up"
> relationship is not correct for any winch ?
>
> Todd Smith
>

[toad]

Ok, thanks. That's the physics as I understood it.

With a modern winch, I won't have to worry about reverse control. But
with an old technology ground launch, I do.

Todd

[Bill Daniels]

"toad" > wrote in message
oups.com...
> Ok, thanks. That's the physics as I understood it.
>
> With a modern winch, I won't have to worry about reverse control. But
> with an old technology ground launch, I do.
>
> Todd
>

Actually, it's neither difficult nor expensive to eliminate the worst
problems with an automatic transmission.

Replacing the stock valve body in the transmission with a "manual valve
body" allows the winch driver to lock out 1st and 2nd gears. (Google "manual
valve body"). These gadgets replace the stock "PRND2L" shift pattern with
"RN321" which can be further restricted to "N3" with a simple shift gate.
This results in the transmission starting in 3rd and remaining there
throughout the launch.

For a bit more money and little more effort, the stock 1800 RPM stall torque
converter can be replaced with a "high stall" TC that lets the transmission
slip up to say 2800 RPM during power up for a softer but still energetic
launch. It also prevents a heavy glider in strong wind conditions from
bogging down the winch engine. Don't do this without adding an effective
transmission cooler.

It won't be perfect, but it's FAR better than the stock setup.

Bill Daniels

[John Galloway[_1_]]

Bill,

If you were to stand beside a Skylaunch winch (which
has a big American petrol/LPG V8 and a fully functioning
3 speed auto box) you would notice that the box is
in 3rd gear by the time that the glider is leaving
the ground and the rest of the launch is normally carried
out in 3rd gear.

John Galloway


At 17:36 30 March 2007, Bill Daniels wrote:
>
>'toad' wrote in message
oups.com...
>> Ok, thanks. That's the physics as I understood it.
>>
>> With a modern winch, I won't have to worry about reverse
>>control. But
>> with an old technology ground launch, I do.
>>
>> Todd
>>
>
>Actually, it's neither difficult nor expensive to eliminate
>the worst
>problems with an automatic transmission.
>
>Replacing the stock valve body in the transmission
>with a 'manual valve
>body' allows the winch driver to lock out 1st and 2nd
>gears. (Google 'manual
>valve body'). These gadgets replace the stock 'PRND2L'
>shift pattern with
>'RN321' which can be further restricted to 'N3' with
>a simple shift gate.
>This results in the transmission starting in 3rd and
>remaining there
>throughout the launch.
>
>For a bit more money and little more effort, the stock
>1800 RPM stall torque
>converter can be replaced with a 'high stall' TC that
>lets the transmission
>slip up to say 2800 RPM during power up for a softer
>but still energetic
>launch. It also prevents a heavy glider in strong
>wind conditions from
>bogging down the winch engine. Don't do this without
>adding an effective
>transmission cooler.
>
>It won't be perfect, but it's FAR better than the stock
>setup.
>
>Bill Daniels
>
>
>

[Bill Daniels]

Actually, John, I've done better than that. I have several cable tension
traces from a Skylaunch made with a tensiometer load cell at the glider.
The data shows horrific tension surges as the transmission shifts up and
down during the launch. These surges were violent enough to break weak
links and the cable. Surges such as these would be unacceptable in a $200
junkyard winch. Given the price of the Skylaunch, we should expect MUCH
better.

I stand by exactly what I wrote. It's extremely foolish to allow a winch
transmission to shift - particularly when it's easy to prevent it. Just
because big American V8's and automatic transmissions are dirt cheap is no
reason to use them without the needed modifications.

BTW, I do like the Skylaunch paint job.

Bill Daniels


"John Galloway" > wrote in message
...
> Bill,
>
> If you were to stand beside a Skylaunch winch (which
> has a big American petrol/LPG V8 and a fully functioning
> 3 speed auto box) you would notice that the box is
> in 3rd gear by the time that the glider is leaving
> the ground and the rest of the launch is normally carried
> out in 3rd gear.
>
> John Galloway
>
>
> At 17:36 30 March 2007, Bill Daniels wrote:
>>
>>'toad' wrote in message
oups.com...
>>> Ok, thanks. That's the physics as I understood it.
>>>
>>> With a modern winch, I won't have to worry about reverse
>>>control. But
>>> with an old technology ground launch, I do.
>>>
>>> Todd
>>>
>>
>>Actually, it's neither difficult nor expensive to eliminate
>>the worst
>>problems with an automatic transmission.
>>
>>Replacing the stock valve body in the transmission
>>with a 'manual valve
>>body' allows the winch driver to lock out 1st and 2nd
>>gears. (Google 'manual
>>valve body'). These gadgets replace the stock 'PRND2L'
>>shift pattern with
>>'RN321' which can be further restricted to 'N3' with
>>a simple shift gate.
>>This results in the transmission starting in 3rd and
>>remaining there
>>throughout the launch.
>>
>>For a bit more money and little more effort, the stock
>>1800 RPM stall torque
>>converter can be replaced with a 'high stall' TC that
>>lets the transmission
>>slip up to say 2800 RPM during power up for a softer
>>but still energetic
>>launch. It also prevents a heavy glider in strong
>>wind conditions from
>>bogging down the winch engine. Don't do this without
>>adding an effective
>>transmission cooler.
>>
>>It won't be perfect, but it's FAR better than the stock
>>setup.
>>
>>Bill Daniels
>>
>>
>>
>
>

[Z Goudie]

Chris Reed wrote:
(a) the pitch over to a proper recovery
>angle is much higher than a pilot trained on aerotow
>only would expect,
>(b) there is a further trap in these circumstances
>in that G is reduced
>during the pitch over, so that any attempt to turn
>before full G returns
>can lead to a stall and spin (stall speed reduces with
>lower G)

Also a reminder that a rapid pitchover from a high
angle/energy cable break can result in a 'Vomit Comet'
reduced/negative G sensation which has over the years
convinced some pilots that the glider is stalled.
They then keep pushing until the glider reaches the
near vertical or the ground whichever comes first.

This difference between stalling and stick induced
negative G may not have been sufficiently well demonstrated
to pilots trained on aerotow.

[Bruce Greef[_2_]]

Bill Daniels wrote:
> Actually, John, I've done better than that. I have several cable tension
> traces from a Skylaunch made with a tensiometer load cell at the glider.
> The data shows horrific tension surges as the transmission shifts up and
> down during the launch. These surges were violent enough to break weak
> links and the cable. Surges such as these would be unacceptable in a $200
> junkyard winch. Given the price of the Skylaunch, we should expect MUCH
> better.
>
> I stand by exactly what I wrote. It's extremely foolish to allow a winch
> transmission to shift - particularly when it's easy to prevent it. Just
> because big American V8's and automatic transmissions are dirt cheap is no
> reason to use them without the needed modifications.
>
> BTW, I do like the Skylaunch paint job.
>
> Bill Daniels
>
>
> "John Galloway" > wrote in message
> ...
>
>>Bill,
>>
>>If you were to stand beside a Skylaunch winch (which
>>has a big American petrol/LPG V8 and a fully functioning
>>3 speed auto box) you would notice that the box is
>>in 3rd gear by the time that the glider is leaving
>>the ground and the rest of the launch is normally carried
>>out in 3rd gear.
>>
>>John Galloway
>>
>>
>>At 17:36 30 March 2007, Bill Daniels wrote:
>>
>>>'toad' wrote in message
oups.com...
>>>
>>>>Ok, thanks. That's the physics as I understood it.
>>>>
>>>>With a modern winch, I won't have to worry about reverse
>>>>control. But
>>>>with an old technology ground launch, I do.
>>>>
>>>>Todd
>>>>
>>>
>>>Actually, it's neither difficult nor expensive to eliminate
>>>the worst
>>>problems with an automatic transmission.
>>>
>>>Replacing the stock valve body in the transmission
>>>with a 'manual valve
>>>body' allows the winch driver to lock out 1st and 2nd
>>>gears. (Google 'manual
>>>valve body'). These gadgets replace the stock 'PRND2L'
>>>shift pattern with
>>>'RN321' which can be further restricted to 'N3' with
>>>a simple shift gate.
>>>This results in the transmission starting in 3rd and
>>>remaining there
>>>throughout the launch.
>>>
>>>For a bit more money and little more effort, the stock
>>>1800 RPM stall torque
>>>converter can be replaced with a 'high stall' TC that
>>>lets the transmission
>>>slip up to say 2800 RPM during power up for a softer
>>>but still energetic
>>>launch. It also prevents a heavy glider in strong
>>>wind conditions from
>>>bogging down the winch engine. Don't do this without
>>>adding an effective
>>>transmission cooler.
>>>
>>>It won't be perfect, but it's FAR better than the stock
>>>setup.
>>>
>>>Bill Daniels
>>>
>>>
>>>
>>
>>
>
>
Hi Bill

I don't understand the mechanics well enough, but this is what we have.

Our little red monster - which looks scrappy but has served well for nearly 30
years consists of:

1x Ford 352 V8 Windsor in stock condition - (Removed from a galaxie I believe.)
1x Standard manual transmission
1x Ford Ranchero one ton truck axle with the differential and one axle locked.

The Single drum is driven from the other hub.

I presume we have the 1,800 RPM stall torque converter as I have not seen any
modifications, and the transmission acts locked from around 2000RPM.

Shifter is 'RN321' manual override.
We launch in 2nd gear - to prevent the engine bogging down. Typically RPM is in
the 3,500 - 3,800 range with a 55-65kt launch in the glider. We only shift to
third manually when needed to retrieve the cable fast. First is locked out.

Am I right in assuming the locked differential and axle are changing the gearing
on the axle. (I think it is a nominal 3.59:1 ratio)

By the way - this setup is nearing the end of it's life at around 50,000 launches.
There is now runout on axle bearings, and oil weeping from the transmission, the
guide rollers are worn beyond machining and the drum rim is deformed. The winch
driver thus gets exposed to quite a lot of vibration, although the cable appears
to absorb most of the vibrations as they are not noticeable in the glider. The
engine is still running well, although it goes through fuel pumps with
distressing frequency (about every 4,000 launches.)

The "capital" cost per launch is tiny.
Fuel is around one litre per launch - less than 1US$.
Maintenance cost is negligible. Filters and batteries mainly.

Now we have to build a replacement - and I wonder where we will find components
as robust.

[Bill Daniels]

"Bruce Greef" > wrote in message
...
> Bill Daniels wrote:
>> Actually, John, I've done better than that. I have several cable tension
>> traces from a Skylaunch made with a tensiometer load cell at the glider.
>> The data shows horrific tension surges as the transmission shifts up and
>> down during the launch. These surges were violent enough to break weak
>> links and the cable. Surges such as these would be unacceptable in a
>> $200 junkyard winch. Given the price of the Skylaunch, we should expect
>> MUCH better.
>>
>> I stand by exactly what I wrote. It's extremely foolish to allow a winch
>> transmission to shift - particularly when it's easy to prevent it. Just
>> because big American V8's and automatic transmissions are dirt cheap is
>> no reason to use them without the needed modifications.
>>
>> BTW, I do like the Skylaunch paint job.
>>
>> Bill Daniels
>>
>>
>> "John Galloway" > wrote in message
>> ...
>>
>>>Bill,
>>>
>>>If you were to stand beside a Skylaunch winch (which
>>>has a big American petrol/LPG V8 and a fully functioning
>>>3 speed auto box) you would notice that the box is
>>>in 3rd gear by the time that the glider is leaving
>>>the ground and the rest of the launch is normally carried
>>>out in 3rd gear.
>>>
>>>John Galloway
>>>
>>>
>>>At 17:36 30 March 2007, Bill Daniels wrote:
>>>
>>>>'toad' wrote in message
oups.com...
>>>>
>>>>>Ok, thanks. That's the physics as I understood it.
>>>>>
>>>>>With a modern winch, I won't have to worry about reverse
>>>>>control. But
>>>>>with an old technology ground launch, I do.
>>>>>
>>>>>Todd
>>>>>
>>>>
>>>>Actually, it's neither difficult nor expensive to eliminate
>>>>the worst
>>>>problems with an automatic transmission.
>>>>
>>>>Replacing the stock valve body in the transmission
>>>>with a 'manual valve
>>>>body' allows the winch driver to lock out 1st and 2nd
>>>>gears. (Google 'manual
>>>>valve body'). These gadgets replace the stock 'PRND2L'
>>>>shift pattern with
>>>>'RN321' which can be further restricted to 'N3' with
>>>>a simple shift gate.
>>>>This results in the transmission starting in 3rd and
>>>>remaining there
>>>>throughout the launch.
>>>>
>>>>For a bit more money and little more effort, the stock
>>>>1800 RPM stall torque
>>>>converter can be replaced with a 'high stall' TC that
>>>>lets the transmission
>>>>slip up to say 2800 RPM during power up for a softer
>>>>but still energetic
>>>>launch. It also prevents a heavy glider in strong
>>>>wind conditions from
>>>>bogging down the winch engine. Don't do this without
>>>>adding an effective
>>>>transmission cooler.
>>>>
>>>>It won't be perfect, but it's FAR better than the stock
>>>>setup.
>>>>
>>>>Bill Daniels
>>>>
>>>>
>>>>
>>>
>>>
>>
>>
> Hi Bill
>
> I don't understand the mechanics well enough, but this is what we have.
>
> Our little red monster - which looks scrappy but has served well for
> nearly 30 years consists of:
>
> 1x Ford 352 V8 Windsor in stock condition - (Removed from a galaxie I
> believe.)
> 1x Standard manual transmission
> 1x Ford Ranchero one ton truck axle with the differential and one axle
> locked.
>
> The Single drum is driven from the other hub.
>
> I presume we have the 1,800 RPM stall torque converter as I have not seen
> any modifications, and the transmission acts locked from around 2000RPM.
>
> Shifter is 'RN321' manual override.
> We launch in 2nd gear - to prevent the engine bogging down. Typically RPM
> is in the 3,500 - 3,800 range with a 55-65kt launch in the glider. We only
> shift to third manually when needed to retrieve the cable fast. First is
> locked out.
>
> Am I right in assuming the locked differential and axle are changing the
> gearing on the axle. (I think it is a nominal 3.59:1 ratio)
>
> By the way - this setup is nearing the end of it's life at around 50,000
> launches.
> There is now runout on axle bearings, and oil weeping from the
> transmission, the guide rollers are worn beyond machining and the drum rim
> is deformed. The winch driver thus gets exposed to quite a lot of
> vibration, although the cable appears to absorb most of the vibrations as
> they are not noticeable in the glider. The engine is still running well,
> although it goes through fuel pumps with distressing frequency (about
> every 4,000 launches.)
>
> The "capital" cost per launch is tiny.
> Fuel is around one litre per launch - less than 1US$.
> Maintenance cost is negligible. Filters and batteries mainly.
>
> Now we have to build a replacement - and I wonder where we will find
> components as robust.

Bruce, It sounds as if the builders of your 'little red monster' got it
right 30 years ago to the standards of that day. If I understand correctly,
your transmission has a manual valve body allowing you to over ride any
automatic shifting. The axle undoubtedly has the differential gears welded
to eliminate their action and make the axle act as a simple right angle
drive. Your simple machine has returned the original investment many
thousands of times over. It deserves an honored retirement. Some current
winch builders could benefit from studying your winch.

When you build your new machine thee are a lot of new ideas to consider.
Electronically controlled, common rail diesels are available either new or
used at reasonable prices. I just located a brand new 425HP Mercedes Benz
14.2 liter diesel for $10,000 USD. These engines produce constant, massive
torque from just above idle to redline. They are very well matched to the
job of launching heavy modern 2-seaters. These engines should last forever
in winch duty. If desired, they can be fueled with biodiesel.

Hydrostatic transmissions and hydrostatic drive systems are now available in
many configurations. They allow absolutely precise control of cable tension
and speed under all conditions.

Since both engines and tranmissions are now electronically controlled, this
makes near full automation both possible and highly desirable. This means
the pilot can expect absolutely smooth, high performance launches every time
regardless of wind, turbulence, thermals, glider type, even rough pilot
technique and inexperienced winch drivers.

There seems to be a trend toward fully enclosed cabs with climate control to
make the winch drivers day more pleasant.

New synthetic cable materials like Dyneema and Spectra have eliminated
virtually all cable related problems. With them, winch builders can make
their creations far more user friendly.

Bill Daniels

[none]

Roger Worden wrote:
> I also understand that a properly balanced glider using a CG
> hook for winch launch will tend to nose up initially, and will seek an
> optimal climb angle naturally. Altering the climb angle with elevator will
> necessarily result in a less-than-optimal altitude gain.
>
This applies to some gliders, e.g. ASK-21, G103, Puchacz, DG500, Pegase,
ASW19/20 and Discus to quote some I know to be benign on the winch, but
not to all gliders.

An ASK-21 trimmed to around 55 kts can be winched without moving the
stick. I haven't done it but our CFI uses this as a demo for students
who are wrecking the launch by misusing the stick. He claps from just
after lift off all the way to the top to prove he isn't flying the glider.

Ka-8s are known to need full forward stick through the ground run and
rotation due to their light weight the large moment arm between wing the
hook. I haven't winched one so can't comment further.

Libelles will snap-rotate as they lift off if you leave trim for
approach speed and leave the stick at that position - at least mine
will. There's nothing in the operator's manual about this. OTOH if I set
full forward trim and apply a little additional pressure past the full
forward trim position I get an nice lift off followed by a nice, slow
rotation into the full climb.

Gliders with heavily cranked sticks (Libelle again) may exaggerate this
effect because the stick will tend to flop backwards during the initial
burst of acceleration and its possible that having to hold the stick
forward may mitigate this tendency.

Get briefed about what the glider you're flying will do during the
launch BEFORE trying it. Snap rotation at lift-off is very dangerous -
the glider can stall and snap roll, which is why the BGA is currently
pushing slow rotation rates.

Remember to RELEASE IMMEDIATELY if a tip touches the ground during the
ground roll. The force vectors make your chances of getting the wing up
again rather remote and you won't have time to think about the
situation, so start the launch with your hand on the release. Mine stays
there all the way up. Remember that on a good winch, 0 to 50 kts is
about 5 seconds: you need to react rather than think if it goes wrong.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

[ucsdcpc]

>Speed control is OPPOSITE to that during aerotow and gliding

I'm sure if I asked this of one of our instructors the answer would be "you
don't" You control the attitude, the winch driver controls the speed. Lowering
the nose is the signal to the driver that you are too slow, wagging the rudder
the signal for too fast. If the winch driver doesn't or cannot respond you
abandon the launch.



Roger Worden wrote:
> What is the correct relationship between pitch angle and airspeed during
> ground launch, either by auto or winch? Different sources make conflicting
> statements:
>
> 1. Speed control is OPPOSITE to that during aerotow and gliding
>
> * SSA Soaring Flight Manual, page 13-10: "Under most circumstances, the best
> way to reduce the airspeed is to raise the nose. During ground launch,
> however, the opposite is true ... pulling the nose up results in an increase
> in airspeed, assuming the launch vehicle has adequate power."
>
> * FAA Glider Flying Handbook, page 7-16: "The pitch attitude/airspeed
> relationship during ground launch is unique. During the launch, pulling back
> on the stick tends to increase airspeed, and pushing forward tends to reduce
> airspeed. This is the opposite of the normal pitch/airspeed relationship."
>
> * This is what I was taught during autotow training. I can't say that I have
> varied the pitch enough in my few launches to have demonstrated it.
>
> 2. Speed control is the SAME as during aerotow and gliding
>
> * British Gliding Association Instructors' Manual, page 16-2: "If the launch
> speed starts to tail-off, lower the nose." Page 16-3: "monitor the airspeed
> trend. If it is falling back towards the minimum safe speed, lower the nose
> or relax any back pressure on the stick." BGA does not mention attempting to
> slow down: "If the glider is starting to go too fast, maintain the normal
> climb attitude, and signal. If it remains too fast, or gets even faster,
> release."
>
> * During presentations on winch launch at a recent seminar, two leading
> instructors discussed lowering the nose to increase speed and raising the
> nose to decrease speed.
>
> * This is what my experience with the Condor flight simulator winch launch
> has shown.
>
> It seems to me that this is a critical point on which to be clear, since I
> will be winch-launching for the first time soon. I understand that the
> vectors involved are different than in aerotowing, because the wings are
> converting forward rope travel to angular motion (just like the skeg on a
> water ski!). I also understand that a properly balanced glider using a CG
> hook for winch launch will tend to nose up initially, and will seek an
> optimal climb angle naturally. Altering the climb angle with elevator will
> necessarily result in a less-than-optimal altitude gain. But what is the
> actual effect of raising or lowering the nose in a stable ground launch
> climb?
>
> A. Is it different depending on the angle of climb? In my experience,
> autotows tend to achieve a 25- to 30-degree climb angle, winch launch a 40-
> to 45-degree climb. Does that cause a difference in the effect of pitch
> angle?
>
> B. If #2 above is true, how did the SSA and FFA manuals get it wrong?
>
> C. If #1 is true, is it reversed in Britain? (Just kidding...)
>
>

[Bill Daniels]

"ucsdcpc" > wrote in message
...
> >Speed control is OPPOSITE to that during aerotow and gliding
>
> I'm sure if I asked this of one of our instructors the answer would be
> "you don't" You control the attitude, the winch driver controls the speed.
> Lowering the nose is the signal to the driver that you are too slow,
> wagging the rudder the signal for too fast. If the winch driver doesn't
> or cannot respond you abandon the launch.
>

And your instructor would be wrong in most cases. Pilots who think they are
controlling attitude are at risk of stalling while on the cable. We are in
a transition period in winch launch where old ideas are giving way to the
new. New gliders launched by new winches operate by somewhat different
rules.

In the modern view, the winch driver controls POWER and the pilot controls
AIRSPEED. The relationship is the same as in airplanes where throttle
controls power and pitch controls airspeed. As the glider leaves the ground
on a winch launch. the pilot smoothly pitches up to hit a target climb
airspeed. In an airplane, this would be Vy. In the typical glider, it
will be between 55 and 65 knots depending somewhat on headwind. It's
helpful to think of the winch driver as your flight engineer with his hands
on the power levers.

A modern trainer such as a ASK-21 would need a very powerful winch indeed
for its pilot to be unable to control airspeed. In most cases, the entire
launch will be flown with neutral elevator leaving considerable up elevator
to control airspeed.

An important exception is with gliders which have hooks too far forward
and/or have too little up elevator authority - for example, most Schweizers.
When flying these gliders the pilot will reach full up elevator before the
airspeed can be controlled. Since the pilot cannot control airspeed, the
winch driver has to. A further complication is that these gliders, which
require the winch driver to control airspeed, will not reach more than 1/2
to 2/3's the height of the modern 2-seater with a properly positioned CG
hook.

This exception case also introduces complications in the event of a cable
break. With the elevator positioned at full up, the glider will pitch up
strongly at the cable break - sometimes beyond the point where a safe
recovery can be made. In any event, a very quick and positive action will
be required of the pilot. This contrasts with gliders like the ASK-21 which
will continue on the same trajectory giving the pilot additional seconds to
handle the cable break.

Bill Daniels

[Andreas Maurer]

Hi Bill,

On Fri, 30 Mar 2007 09:49:23 -0600, "Bill Daniels"
<bildan@comcast-dot-net> wrote:

>The winch should be constructed such that it is not be possible for the
>airspeed to increase as a result of raising the glider's nose. Otherwise,
>the winch should be regarded as dangerous.

Is it such a problem to teach the pilot to pull the release if his
airspeed exceeds the desired prameters? ;)



Bye
Andreas

[Sally W]

At 15:12 02 April 2007, Andreas Maurer wrote:
>Hi Bill,
>
>On Fri, 30 Mar 2007 09:49:23 -0600, 'Bill Daniels'
> wrote:
>
>>The winch should be constructed such that it is not
>>be possible for the
>>airspeed to increase as a result of raising the glider's
>>nose. Otherwise,
>>the winch should be regarded as dangerous.
>
>Is it such a problem to teach the pilot to pull the
>release if his
>airspeed exceeds the desired prameters? ;)

That is exactly what we are taught to do, but making
something as counter-intuitive as 'raise nose go faster'
does strike me as dangerous in the extreme - a huge
amount of the the instruction from 1st flight is based
around 'nose down go faster, nose up go slower'. Would
you like a situation where right stick produced left
bank? I doubt it.

[Bill Daniels]

"Andreas Maurer" > wrote in message
...
> Hi Bill,
>
> On Fri, 30 Mar 2007 09:49:23 -0600, "Bill Daniels"
> <bildan@comcast-dot-net> wrote:
>
>>The winch should be constructed such that it is not be possible for the
>>airspeed to increase as a result of raising the glider's nose. Otherwise,
>>the winch should be regarded as dangerous.
>
> Is it such a problem to teach the pilot to pull the release if his
> airspeed exceeds the desired prameters? ;)
>
>
>
> Bye
> Andreas


Overspeeds shouldn't be a safety problem for a well trained pilot but if it
happens frequently, it will reduce confidence in the winch/driver. For not
quite so well trained pilots, it may become a safety issue. Pilot
confidence in the system is strongly related to the consistency of the
launches. If pilots lose confidence in the winch launch system, they'll go
elsewhere.

The advantages of automatic tension control are so large that there's every
reason to adopt it. Since the tension can't exceed the breaking strength of
the weak link and certainly not the cable, these things become extremely
rare. Automatic tension controlled launches are extremely consistent
regardless of external variables - or winch driver skill.

A collateral problem related to adoption of lightweight 'plastic' winch rope
is that the winch driver can no longer see the rope sag. With heavy steel
cable, winch drivers used cable sag as a gauge of tension. And, absent
airspeed telemetry, the winch driver has no information about the gliders
airspeed. This absence of feedback leads to inconsistent launches.

To deal with lack of feedback and the possibility of overspeeds, winch
drivers just reduce power to increase margins which results in lower
launches. Highly accurate automatic tension control allows the power to be
increased while maintaining launch consistency. Higher power means higher
launches.

Bill Daniels

[Andreas Maurer]

On Mon, 2 Apr 2007 10:01:07 -0600, "Bill Daniels"
<bildan@comcast-dot-net> wrote:


> Pilot
>confidence in the system is strongly related to the consistency of the
>launches. If pilots lose confidence in the winch launch system, they'll go
>elsewhere.

.... or choose to stick to the familiar aerotow...

Might this be one cause why winch launching is used that seldom in the
US?

>The advantages of automatic tension control are so large that there's every
>reason to adopt it.

Hmmm... as usual, I beg to differ. :)
Here in Germany there are hundreds of winches in use with power
ranging from 150 to 400 hp, extremely few of them equipped with
tension control (afaik only the few electric winches), yet the winch
launch works extremely well with very few safety issues.

The major cause for the wide-spread use of winches in Germany is
simplicity: By using standard truck parts such as engine and rear axle
it was (and is) easily possible to build a reliable winch for moderate
costs. Virtually any winch in Germany is homebuilt.

I think adding complex parts (such as automatic gearboxes and tension
control) raises the barrier to build an own winch significantly
(complexity, reliability, engineering effort, cost) while the
efficiency gain is negligible.

I think in order to promote winch launching in the US it might help to
heep the design as simple as possible.



>A collateral problem related to adoption of lightweight 'plastic' winch rope
>is that the winch driver can no longer see the rope sag. With heavy steel
>cable, winch drivers used cable sag as a gauge of tension. And, absent
>airspeed telemetry, the winch driver has no information about the gliders
>airspeed. This absence of feedback leads to inconsistent launches.

Frankly spoken, this is contrary to my own experiences on a vast
number of winches.
A properly designed 280 hp Diesel winch doesn't need any sort of
gearbox and tension control, yet can easlily and safely launch any
glider from Grunau Baby to ASH-25E to satisfying altitudes - even with
an inexperienced winch driver, and even with plastic rope.
Not even a radio communication between pilot and winch is necessary.




Bye
Andreas

[Andreas Maurer]

On 2 Apr 2007 15:31:32 GMT, Sally W
> wrote:


>That is exactly what we are taught to do, but making
>something as counter-intuitive as 'raise nose go faster'
>does strike me as dangerous in the extreme - a huge
>amount of the the instruction from 1st flight is based
>around 'nose down go faster, nose up go slower'.

I still wonder how such a rule cold be created at all.

Where I fly this rule is regarded as an urban legend and student
pilots are told accordingly to lower the nose if they get too slow.



Bye
Andreas

[Bill Daniels]

"Andreas Maurer" > wrote in message
...
> On Mon, 2 Apr 2007 10:01:07 -0600, "Bill Daniels"
> <bildan@comcast-dot-net> wrote:
>
>
>> Pilot
>>confidence in the system is strongly related to the consistency of the
>>launches. If pilots lose confidence in the winch launch system, they'll go
>>elsewhere.
>
> ... or choose to stick to the familiar aerotow...
>
> Might this be one cause why winch launching is used that seldom in the
> US?

Andeas, you are right. This is a big reason.


>
>>The advantages of automatic tension control are so large that there's
>>every
>>reason to adopt it.
>
> Hmmm... as usual, I beg to differ. :)
> Here in Germany there are hundreds of winches in use with power
> ranging from 150 to 400 hp, extremely few of them equipped with
> tension control (afaik only the few electric winches), yet the winch
> launch works extremely well with very few safety issues.

Actually, if you think about it, the diesel winch with a Vioth Turbokuppling
is very close to a tension controlled winch. Diesels have a very flat
torque curve and torque increases linearly with throttle. The Voith
coupling just passes that torque to the drum at a 1:1 ratio. If the winch
driver makes a reasonable guess as to throttle setting based on the glider
to be launched and the wind, the result will be pretty good.

Even in Germany, however, it's likely that the average tension will be 50%
to 70% of the weak link breaking load. Increasing this to 70% to 90% will
significantly increase release heights. 80% - 90% would be even better but
that will likely be more precision than the average human winch driver can
manage. Automated tension control systems can shave it as close as you
like.

>
> The major cause for the wide-spread use of winches in Germany is
> simplicity: By using standard truck parts such as engine and rear axle
> it was (and is) easily possible to build a reliable winch for moderate
> costs. Virtually any winch in Germany is homebuilt.
>
> I think adding complex parts (such as automatic gearboxes and tension
> control) raises the barrier to build an own winch significantly
> (complexity, reliability, engineering effort, cost) while the
> efficiency gain is negligible.
>
> I think in order to promote winch launching in the US it might help to
> heep the design as simple as possible.
>

In the US for the last 50 years or so, 'simple' has meant a V8 engine and
automatic transmission from a wrecked car. The engine will not produce
anything like a flat torque curve and transmission will run wild shifting
whenever it pleases. Combine this with gliders without CG hooks and the
results are very inconsistent leading to absurd 'rules' like "raise nose to
increase speed".

>
>>A collateral problem related to adoption of lightweight 'plastic' winch
>>rope
>>is that the winch driver can no longer see the rope sag. With heavy steel
>>cable, winch drivers used cable sag as a gauge of tension. And, absent
>>airspeed telemetry, the winch driver has no information about the gliders
>>airspeed. This absence of feedback leads to inconsistent launches.
>
> Frankly spoken, this is contrary to my own experiences on a vast
> number of winches.
> A properly designed 280 hp Diesel winch doesn't need any sort of
> gearbox and tension control, yet can easlily and safely launch any
> glider from Grunau Baby to ASH-25E to satisfying altitudes - even with
> an inexperienced winch driver, and even with plastic rope.
> Not even a radio communication between pilot and winch is necessary.
>

I suspect that the average German club member has a far better idea of what
a good launch feels like and how one would drive a winch to obtain that
launch than his US counterpart. In the US, a little intellegence built
into the winch will be a big help to a fledgling winch operation.

This is even more so when it's important to achieve the highest launch
possible to compete with aero tow. Automating cable tension control allows
higher tensions to be used with safety and thus higher launches.

Bill Daniels

[Andreas Maurer[_1_]]

On Mon, 2 Apr 2007 13:29:20 -0600, "Bill Daniels"
<bildan@comcast-dot-net> wrote:

>Actually, if you think about it, the diesel winch with a Vioth Turbokuppling
>is very close to a tension controlled winch. Diesels have a very flat
>torque curve and torque increases linearly with throttle. The Voith
>coupling just passes that torque to the drum at a 1:1 ratio. If the winch
>driver makes a reasonable guess as to throttle setting based on the glider
>to be launched and the wind, the result will be pretty good.

Forget all that high-tech stuff - much too complex for an average
gliding club. Hard to design, hard to build, hard to maintain, hard to
debug, hard to repair. ;)

Here in good ole' Europe usually a standard truck clutch is used (with
a big engine this clutch is either actuated by hydraulics or
pneumatics) to connect the engine to a standard truck rear axle.
Initial acceleration is made by moving the throttle smoothly forward
until a certain RPM is reached which depends upon glider type wind.
During the launche the throttle is slowly brought back to keep the
gliders' speed halfways constant - a couple of RPMs more or less
doesn't matter.


>Even in Germany, however, it's likely that the average tension will be 50%
>to 70% of the weak link breaking load. Increasing this to 70% to 90% will
>significantly increase release heights. 80% - 90% would be even better but
>that will likely be more precision than the average human winch driver can
>manage. Automated tension control systems can shave it as close as you
>like.

I don't think so.
A striong winch is easily able to enable toe glider to exceed its
particular winch-launch Vne. Usually the speed is kept about 10-15 kts
below the Vne. Release altitudes on a standard 3.300 ft rope length
are usually sufficient to thermal (1.000-1.500 ft) or fly a 7 minute
no-thermal traffic circuit.

Completely satisfying for me - and apparently for the other 30.000
glider pilots here... ;)



>In the US for the last 50 years or so, 'simple' has meant a V8 engine and
>automatic transmission from a wrecked car. The engine will not produce
>anything like a flat torque curve and transmission will run wild shifting
>whenever it pleases. Combine this with gliders without CG hooks and the
>results are very inconsistent leading to absurd 'rules' like "raise nose to
>increase speed".

I can imagine that.
Until about 15 years ago the German standard winch also consisted of
an old V8 engine, coupled to a manual gear that was usually locked in
the 2nd gear. When these engines became unavailable (and the gliders
heavier) we switched to Diesel engines.


>In the US, a little intellegence built
>into the winch will be a big help to a fledgling winch operation.

I'm not so sure, Bill.
Intelligence is always a good thing - but what happens if the system
fails or does something unexpected? The more simple the design, the
easier it is for a small club to build and maintain a winch - and to
fix it.
I guess on any airfield in the US there's at least one mechanic who
can repair a Lycoming engine... for if your winch (a new technology
for most clubs) depends on complex closed circuits, you'll probably
get a problem sooner or later - and revert to the trusty Pawnee.



BTW:
Have you tried this to get a winch operation running?

Put an advertisement in the German gliding magazine "Segelfliegen" or
the "aerokurier", offer half a year of free board and lodging, mention
15.000 ft cloud base, and I'm sure you'll immediately find a dozen
enthusiasts who will build a usable winch for you for less than
$25.000 and provide all the training.
It would certainly help if you could offer more than an 1-26 for their
leisure flights. :)



>This is even more so when it's important to achieve the highest launch
>possible to compete with aero tow. Automating cable tension control allows
>higher tensions to be used with safety and thus higher launches.

Nah... forget about the 10 percent height advantage an optimized winch
system can bring.

In 95 percent of the cases a winch launch is completely sufficient to
catch a thermal (...maybe not for a 2-33...).

Key factor for a winch operation are cost savings - and the lower
costs for a winch launch (compared to an aerotow) ought to convince
even the most stubborn club members, don't you think?

You know the deal from your club - nothing better than being able to
offer some highschool kid flying lessons for less than $3 per launch,
don't you agree?
If someone really needs 3.000 ft release altitude, he can still take
the Pawnee.





Bye
Andreas

[Bill Daniels]

Tell you what, Andreas, hop over to the Aero club Salland in the Netherlands
and ask for a launch on their Hydrostart winch. Ask them to explain how it
works.

Process control using simple, rugged PLC's is ubiquitous in manufacturing
facilities the world over. If this stuff were as unreliable as you say,
they'd go back to manual operations in a second. They have money to lose.
Winch tension control is very simple compared to most industrial processes
but uses the same equipment.

BTW, I like your idea of a winch group exchange. Our cloudbases often
exceed 18,000 feet. I have a couple of spare bedrooms...

Bill Daniels


"Andreas Maurer" > wrote in message
...
> On Mon, 2 Apr 2007 13:29:20 -0600, "Bill Daniels"
> <bildan@comcast-dot-net> wrote:
>
>>Actually, if you think about it, the diesel winch with a Vioth
>>Turbokuppling
>>is very close to a tension controlled winch. Diesels have a very flat
>>torque curve and torque increases linearly with throttle. The Voith
>>coupling just passes that torque to the drum at a 1:1 ratio. If the winch
>>driver makes a reasonable guess as to throttle setting based on the glider
>>to be launched and the wind, the result will be pretty good.
>
> Forget all that high-tech stuff - much too complex for an average
> gliding club. Hard to design, hard to build, hard to maintain, hard to
> debug, hard to repair. ;)
>
> Here in good ole' Europe usually a standard truck clutch is used (with
> a big engine this clutch is either actuated by hydraulics or
> pneumatics) to connect the engine to a standard truck rear axle.
> Initial acceleration is made by moving the throttle smoothly forward
> until a certain RPM is reached which depends upon glider type wind.
> During the launche the throttle is slowly brought back to keep the
> gliders' speed halfways constant - a couple of RPMs more or less
> doesn't matter.
>
>
>>Even in Germany, however, it's likely that the average tension will be 50%
>>to 70% of the weak link breaking load. Increasing this to 70% to 90% will
>>significantly increase release heights. 80% - 90% would be even better
>>but
>>that will likely be more precision than the average human winch driver can
>>manage. Automated tension control systems can shave it as close as you
>>like.
>
> I don't think so.
> A striong winch is easily able to enable toe glider to exceed its
> particular winch-launch Vne. Usually the speed is kept about 10-15 kts
> below the Vne. Release altitudes on a standard 3.300 ft rope length
> are usually sufficient to thermal (1.000-1.500 ft) or fly a 7 minute
> no-thermal traffic circuit.
>
> Completely satisfying for me - and apparently for the other 30.000
> glider pilots here... ;)
>
>
>
>>In the US for the last 50 years or so, 'simple' has meant a V8 engine and
>>automatic transmission from a wrecked car. The engine will not produce
>>anything like a flat torque curve and transmission will run wild shifting
>>whenever it pleases. Combine this with gliders without CG hooks and the
>>results are very inconsistent leading to absurd 'rules' like "raise nose
>>to
>>increase speed".
>
> I can imagine that.
> Until about 15 years ago the German standard winch also consisted of
> an old V8 engine, coupled to a manual gear that was usually locked in
> the 2nd gear. When these engines became unavailable (and the gliders
> heavier) we switched to Diesel engines.
>
>
>>In the US, a little intellegence built
>>into the winch will be a big help to a fledgling winch operation.
>
> I'm not so sure, Bill.
> Intelligence is always a good thing - but what happens if the system
> fails or does something unexpected? The more simple the design, the
> easier it is for a small club to build and maintain a winch - and to
> fix it.
> I guess on any airfield in the US there's at least one mechanic who
> can repair a Lycoming engine... for if your winch (a new technology
> for most clubs) depends on complex closed circuits, you'll probably
> get a problem sooner or later - and revert to the trusty Pawnee.
>
>
>
> BTW:
> Have you tried this to get a winch operation running?
>
> Put an advertisement in the German gliding magazine "Segelfliegen" or
> the "aerokurier", offer half a year of free board and lodging, mention
> 15.000 ft cloud base, and I'm sure you'll immediately find a dozen
> enthusiasts who will build a usable winch for you for less than
> $25.000 and provide all the training.
> It would certainly help if you could offer more than an 1-26 for their
> leisure flights. :)
>
>
>
>>This is even more so when it's important to achieve the highest launch
>>possible to compete with aero tow. Automating cable tension control
>>allows
>>higher tensions to be used with safety and thus higher launches.
>
> Nah... forget about the 10 percent height advantage an optimized winch
> system can bring.
>
> In 95 percent of the cases a winch launch is completely sufficient to
> catch a thermal (...maybe not for a 2-33...).
>
> Key factor for a winch operation are cost savings - and the lower
> costs for a winch launch (compared to an aerotow) ought to convince
> even the most stubborn club members, don't you think?
>
> You know the deal from your club - nothing better than being able to
> offer some highschool kid flying lessons for less than $3 per launch,
> don't you agree?
> If someone really needs 3.000 ft release altitude, he can still take
> the Pawnee.
>
>
>
>
>
> Bye
> Andreas

[Markus Graeber]

The only problem with the Hydrostart winch is that it is about the
most expensive winch around (and I haven't heard about them having
sold another one even though they do have a website and seem to have
commercialized the design)... The technology is great if you can
afford it/have the necessary resources available to the club. The guys
who build the Hydrostart are experts in their field and do related
stuff professionally resulting in an awesome winch. But the resources
they had available is not what you find in your average club and, not
surprisingly, the Aero Club Salland is one of the biggest and most
active in NL (hence the 6 drums). Interestingly enough a single drum
setup with retrieve winch could probably achieve the same launch rates
albeit at a far smaller price tag.

Process control using simple, rugged PLC's might be easy to implement
for the expert but you gotta have the expert in the first place. A
simple mechanical setup with off-the-shelf parts can be built/
maintained by a lot more people than a hydrostatic drive with PLC
based controls, no matter how simple they are. If you got the
resources, great, but for the rest of us a more conventional setup
that might lack the last 5% of performance but is reliable in daily
use is more reasonable. Only on very short fields where every meter
counts the significant extra investment those last 5% might cost you
would be really worth paying for. Otherwise I'd rather get another
nice glider for the money saved, as long as decent launches are
assured this will matter more to the members than having the fanciest
winch around.

Markus