Does anyone use a tug tow hook that releases automatically whenglider kites?

On Tuesday, February 18, 2014 7:17:16 AM UTC-6, Don Johnstone wrote:
At 11:54 18 February 2014, Pieter Oosthuizen wrote:

Thanks Chris - appreciate your comments!



Apologies if I interpreted it incorrectly.



PO



I think Chris has made it pretty clear that the fitting of an automatic

system is not at this time a practical solution. I think he has also made

it pretty clear that once the sequence starts the result, as far as the tug

is concerned, is inevitable.



This is one of those situations where tug pilots are going to have to

decide what risks they are willing to take. I would support any tug pilot

who said that he would not tow a glider on a CoG or Compromise hook. On the

other hand I would not tell him he could not do it. There is also a

responsibility for those of us who teach aerotowing to really get across to

students the danger, to the tug pilot, of getting out of position. I am not

sure we have done this in the past, I know I have not been as pedantic as I

should in getting this point home.

Tug pilots do not always know the people they are towing so they are

perhaps not aware of the experience, or lack of it, of the pilot on the

back. In those circumstances the saviour should be the authoriser. We all

know that does not work. Perhaps tug pilots need to be more circumspect in

who they are prepared to tow.

It occurred to me that attaching the tow rope to the tug near the center of gravity (top of turtle deck on a Pawnee for example) would make kiting a non-event. That's how all the RC gliders are towed since you cannot control the position of the glider really well in relation to the towplane while standing on the ground. Interference of the tow rope with rudder and elevator does not seem to be a problem for RC fliers.

On Tuesday, 18 February 2014 11:25:24 UTC-5, wrote:
On Tuesday, February 18, 2014 7:17:16 AM UTC-6, Don Johnstone wrote:

It occurred to me that attaching the tow rope to the tug near the center of gravity (top of turtle deck on a Pawnee for example) would make kiting a non-event. That's how all the RC gliders are towed since you cannot control the position of the glider really well in relation to the towplane while standing on the ground. Interference of the tow rope with rudder and elevator does not seem to be a problem for RC fliers.


Um... wouldn't that cause a great risk of fouling the tail feathers of the tug? No more "boxing the wash".

At 16:41 18 February 2014, C-FFKQ 42 wrote:
On Tuesday, 18 February 2014 11:25:24 UTC-5, wrote:
On Tuesday, February 18, 2014 7:17:16 AM UTC-6, Don Johnstone wrote:
=20
It occurred to me that attaching the tow rope to the tug near the
center
=
of gravity (top of turtle deck on a Pawnee for example) would make kiting
a=
non-event. That's how all the RC gliders are towed since you cannot
contr=
ol the position of the glider really well in relation to the towplane
while=
standing on the ground. Interference of the tow rope with rudder and
elev=
ator does not seem to be a problem for RC fliers.


Um... wouldn't that cause a great risk of fouling the tail feathers of
the
=
tug? No more "boxing the wash".

OK here is a whacky idea. A V shaped boom with the point to the rear of the
rudder, the release mounted at this point. The two front points mounted to
a pivot, through the fuselage above the wing, near the CoG. The V
arrangement can pivot up, but not down. The space between the arms has to
be sufficient to allow full rudder. Would only work for low wing
monoplanes.

On Tuesday, February 18, 2014 1:50:52 PM UTC-7, Don Johnstone wrote:

OK here is a whacky idea. A V shaped boom with the point to the rear of the

rudder, the release mounted at this point. The two front points mounted to

a pivot, through the fuselage above the wing, near the CoG. The V

arrangement can pivot up, but not down. The space between the arms has to

be sufficient to allow full rudder. Would only work for low wing

monoplanes.

Well as long as were are drawing on envelopes, how about a bridle attached to each wingtip of the towplane, with the towhook at the apex of the bridle, able to slide side to side (to prevent rudder stalls) while the bridle pivots up during kiting so the force just pulls the towplane higher! To drop the glider, release one end of the bridle and the towhook just slips off.

Or just teach the stupid glider pilot to fly the correct tow position!

Of course, a good winch solves this problem nicely....

Kirk

On Tuesday, February 18, 2014 6:56:56 PM UTC-5, kirk.stant wrote:
On Tuesday, February 18, 2014 1:50:52 PM UTC-7, Don Johnstone wrote: OK here is a whacky idea. A V shaped boom with the point to the rear of the rudder, the release mounted at this point. The two front points mounted to a pivot, through the fuselage above the wing, near the CoG. The V arrangement can pivot up, but not down. The space between the arms has to be sufficient to allow full rudder. Would only work for low wing monoplanes. Well as long as were are drawing on envelopes, how about a bridle attached to each wingtip of the towplane, with the towhook at the apex of the bridle, able to slide side to side (to prevent rudder stalls) while the bridle pivots up during kiting so the force just pulls the towplane higher! To drop the glider, release one end of the bridle and the towhook just slips off. Or just teach the stupid glider pilot to fly the correct tow position! Of course, a good winch solves this problem nicely.... Kirk

The Dragonfly towplane for hang & ultralite gliders uses a bridle attached above the top of the rudder and just below the bottom of the rudder, withbthe tow rope free to ride up and down on the bridle. Hang gliders sometimes get way out of shape, but the tug isn't affected.
UH

On Tue, 18 Feb 2014 08:41:57 -0800, C-FFKQ (42) wrote:

On Tuesday, 18 February 2014 11:25:24 UTC-5, wrote:
On Tuesday, February 18, 2014 7:17:16 AM UTC-6, Don Johnstone wrote:

It occurred to me that attaching the tow rope to the tug near the
center of gravity (top of turtle deck on a Pawnee for example) would
make kiting a non-event. That's how all the RC gliders are towed since
you cannot control the position of the glider really well in relation
to the towplane while standing on the ground. Interference of the tow
rope with rudder and elevator does not seem to be a problem for RC
fliers.


Um... wouldn't that cause a great risk of fouling the tail feathers of
the tug? No more "boxing the wash".

From what I know of model aircraft I suspect, but can't prove it, that
the fin on an RC model is (relatively) considerably stronger than the fin
on a towplane. Structurally, most RC model fins are either solid balsa
sheet or a foam-filled fibreglass moulding. If its a sheet balsa fin its
almost guaranteed to be a lot harder and denser than I'd ever use on a
model I was building myself.

An RC model can be dumped on the strip in a manner that would wreck any
GA aircraft. They are very frequently landed this way. Rounding out? Whats
that? Land the model badly on grass enough to flip it over onto its back
and the fin is almost guaranteed to be undamaged. Could you say the same
about a typical towplane's fin?



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

On Tuesday, 18 February 2014 12:07:20 UTC+2, Chris Rollings wrote:
That might work but I suspect it would be impossible, in the real World, to
get a sufficiently high degree of reliability that we did not get more
accidents from innocent gliders be jettisoned at low altitudes than we
currently get from kiting accidents.

Hi Chris

This is not a personal attack - I appreciate your valuable input but ...

With modern technology we can reliably detect pitch, roll, acceleration of a tug plane IMO.
e.g. My Note 2 has a magnetometer, electronic gyros, accelerometers, barometer, and GPS. I downloaded an artificial horizon app for my Android phone and when it blends all the sensor data you get a very reliable pitch and roll output.
It doesn't even experience gyro drift because it is able to compensate using the magnetometer to sense gravity.

Another example are all the Ardupilot projects.
If they are capable of flying DIY autonomous drones around for under $300 then I think the technology is available and good enough for us to use.

Even so, I'd rather have a 1 in 1000 chance of accidentally being dumped than kill a tug pilot and myself through a momentary lapse of judgement/attention.

I happen to fly at the club in South Africa which had the low altitude, tug upset on Sunday 16th Feb 2014, resulting in the death of the tug pilot in a Cessna 182A.
I simply refuse to believe that we can fly to the moon and back but can't devise a reliable automatic tow release mechanism.
How many more tug pilots around the world do we have to kill before we devise a mechanism which works?

To detect a tug upset reliably I think one would only need:
1. To sense the tug elevator at the back stop +
2. The pitch of the tug (say 20 degrees down and increasing) +
3. The load on the rope (glider still attached).
I can't imagine the above being present in any normal operational situation.

Paul

At 07:23 19 February 2014, Surge wrote:
On Tuesday, 18 February 2014 12:07:20 UTC+2, Chris Rollings wrote:
That might work but I suspect it would be impossible, in the real
World,
to
get a sufficiently high degree of reliability that we did not get more
accidents from innocent gliders be jettisoned at low altitudes than we
currently get from kiting accidents.

Hi Chris

This is not a personal attack - I appreciate your valuable input but ...

With modern technology we can reliably detect pitch, roll, acceleration
of
a tug plane IMO.
e.g. My Note 2 has a magnetometer, electronic gyros, accelerometers,
barometer, and GPS. I downloaded an artificial horizon app for my Android
phone and when it blends all the sensor data you get a very reliable
pitch
and roll output.
It doesn't even experience gyro drift because it is able to compensate
using the magnetometer to sense gravity.

Another example are all the Ardupilot projects.
If they are capable of flying DIY autonomous drones around for under $300
then I think the technology is available and good enough for us to use.

Even so, I'd rather have a 1 in 1000 chance of accidentally being dumped
than kill a tug pilot and myself through a momentary lapse of
judgement/attention.

I happen to fly at the club in South Africa which had the low altitude,
tug
upset on Sunday 16th Feb 2014, resulting in the death of the tug pilot in
a
Cessna 182A.
I simply refuse to believe that we can fly to the moon and back but can't
devise a reliable automatic tow release mechanism.
How many more tug pilots around the world do we have to kill before we
devise a mechanism which works?

To detect a tug upset reliably I think one would only need:
1. To sense the tug elevator at the back stop +
2. The pitch of the tug (say 20 degrees down and increasing) +
3. The load on the rope (glider still attached).
I can't imagine the above being present in any normal operational
situation.

Paul


Paul, by the time your items 1, 2 & 3 are present it is probably too late,
the tail-plane is almost certainly stalled and even if the glider were
jettisoned at that instant, the tow-plane would probably still pitch down
another 40 or 50 degrees before recovery (I say probably, could someone
please test it with a camera plane alongside at safe altitude, done
deliberately it should be possible to pull the release at exactly the right
moment - might take three or four goes to get on exactly right).

The thing that is constantly under-estimated by those that haven't
experienced it is how quickly it all happens. LESS THAN 3 SECONDS FROM ALL
NORMAL TO ALL OVER. People take at least that long to react to something
unexpected unless it is something they have practiced frequently, certainly
not the case in kiting incidents.

It is clear from what we have seen on this thread that we have identified
an occurrence which has resulted in the death of tug pilots. If we do
nothing tug pilots will continue to be killed and the question is, "Are we
resigned to classing these future deaths as a normal operating hazard?" For
my part I would not be particularly comfortable with this, especially as I
could be the pilot on the back.

We have established, thanks to Chris that the event, from start to finish,
happens over a very short period. He estimates 2 - 3 seconds and I have no
reason to doubt this assessment. Chris is a very experienced pilot of both
gliders and tugs and he further states that once the event starts it is
unlikely that either pilot can react in time to prevent a predictable
outcome. That predictable outcome is the tug pointing vertically at the
ground at full throttle. The only unknown in any of these events is whether
or not there is sufficient height for the tug pilot to recover from this
situation before the ground gets in the way. If there is insufficient
height the tug pilot is going to die.

There has been much discussion concerning an auto release mechanism. Chris
has said that he does not think that a mechanical "angle detection" system
would work in time, I concur with that view. The problem is not just the
height above the tug that the glider reaches but the rate of change in
height. It has been suggested that by the time the glider has reached the
height behind the tug to cause a problem it is too late to do anything
about it.

There is one possibility, measurement of the rate of change in height
relative to the tug. The technology for this exists and is abundant, we see
this every day in the boxes on the side of the road, I speak of course of
speed cameras. It would not be difficult to have a device that operated the
release if there was a rate of change in excess of what we consider normal.
You could even take two measurements or more to detect an increasing rate
of change (Unsafe) to a decreasing rate of change (Less Unsafe). The device
would trigger the release instead of the camera. Ideally this would be
mounted in the glider but given the cost implications it would be
acceptable in the tug. There is an opportunity to give the glider the rope
before the tug gets into an irrecoverable situation.

This would not be cheap, and I am sure there are other options we have yet
to discover, but is the option of doing nothing acceptable? We do not know
the cause of this occurrence in every case, we do know the effect and the
outcome. We do know the factors that are likely to contribute to the cause,
for example CoG hooks, but addressing this alone, as Chris has pointed out,
is not the complete answer. We are left with mitigating the effects and I
think we owe it to the people who provide our tows to do all we can.

Lastly I would like to thank Chris Rollings for sharing his research.
Without his work we would be dealing with theories, which are less
compelling than real results.

I think the Gyro, and full back stick switch has some potential but has some issues, such as calibrating the Gyro, and possible Test/fault issues that would need to be overcome.

Another one to consider would be a time delay switch on the Throttle. Once the throttle has been set to climb power for more than say 5 seconds (time might need to be adjusted) then if the stick is moved to full aft, a release is initiated.
The throttle delay is to prevent releases during the 1st part of the ground roll. I can't think of any other time when the tow plane would have full back stick and full throttle that the pilot would not want the glider to be released. One advantage of this system is that the tow pilot should know this combination will cause a release and bring a higher awareness to the possibility of the glider kiting.

Another issue to be addressed by either of these systems is that it will require a powerful actuator to ensure a release actually occurs when needed.

Just brain storming some idea's

Brian