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

On Tuesday, 11 February 2014 18:41:48 UTC, son_of_flubber wrote:
On Tuesday, February 11, 2014 3:56:33 AM UTC-5, Chris Rollings wrote:



What was needed was a hook that

responded to the vertical component of the load, not the angle at which it

was applied...



This statement defines the starting point, not the ending point.



How about a weather proof calibrated mechanical device placed between the Tost release hook and the tug that pulls the Tost release lever when the vertical component exceeds a limit? There is a well-proven mechanism that does something like that on my downhill ski bindings. A rocket-scientist is not required.



Is it a matter of the FAA and insurance underwriters making any change to the status quo cost-prohibitive? What sort of gauntlet does one need to run?

My statement that an automatic releasing hook was beyond our capabilities refered to the situation over 30 years ago, it is quite possible that technology has moved on a bit since then and it is now possible. It would certainly constiute a modification to the aircraft under UK/European rules, and I strongly suspect ander FAA rules too. As such it would need approval, time consuming and possibly expensive.

Chris Rollings wrote:

Third test: Terrier Tow-Plane, K 8b on C of G hook. I pitched the glider
about 25 degrees nose up. The glider continued to pitch up fairly rapidly
(as at the start of a winch launch) and substantial forward movement of the
stick only slightly slowed the rate of pitch. The glider achieved about 45
degrees nose up, speed increased rapidly from 55 knots to about 75 knots
and the glider was pulled back towards level flight (again as at the top of
a winch launch). I released at that point. The entire sequence of events
occupied a VERY short period of time (subsequently measured as 2 - 3
seconds). The Tow Pilot reported a marked deceleration and start of
pitching down which he attempted to contain by moving the stick back; this
was followed immediately by a very rapid pitch down accompanied by
significant negative “G�. The tow-plane finished up about 70 degrees
nose down and took about 400 feet to recover to level flight. We both
found the experience alarming, even undertaken deliberately at 4000 feet.
Our conclusion was that the combination of the initial pitch down and the
upward deflection of the elevator caused the horizontal stabilizer/elevator
combination to stall and the abrupt removal of the down-force it provided
caused the subsequent very rapid pitch-down and negative “G�.

I was the pilot of a tug involved in exactly the scenario described by
Chris above. The culprit was a K6 using a belly hook, and the only
reason I am here to tell the tale is that it occurred at 400ft. It was
actually a dual tow with the K6 on the short rope and a K13 on the
long rope in low-tow position. The K6 had recovered from some earlier
excursions, but all seemed to be going well before it happened.

The "up-ending" was instantaneous, there was no way to have reached
any type of release before the rope broke, and in any case I can
assure you that when descending vertically on full throttle at 400ft,
your first reaction it to close the throttle.

Our CFI in the K13 said he hadn't seen the underside of a PA18 in plan
form quite so close before.

In those days we used to store spare ropes and things behind the rear
seat of the PA18, and my situation was not improved by the whole lot
coming forward and landing on my head and all over the cockpit.

A good friend of mine later died towing a K6 with a PA18, which
incident quite probably was the trigger for Chris' investigations.

Ain't no doubt about how quickly the tug gets upset when the glider decides
to fly hither and yon.

My event involved a highly experienced retired FAA guy with type ratings in
every aircraft imagineable. It was his first flight in a borrowed HP-14
and, during the departure turn at about 700' AGL he flew high and wide to
the right, outside of the turn. Before I could reach the release lever,
he'd turned hard left and dove across the tail of the Pawnee wrapping the
tow rope around his left wing and, after it cut the top and bottom skins of
the wing clear to the spar, cutting the rope in two in the middle. The
final yank on the rope caused the tug to yaw hard right and pitch slightly
up (from about 45 degrees down).

Not realizing how close he'd come to killing us both, he proceeded to have a
nice 4-hour flight. After landing he asked our line guy to help with
derigging. That's when Steve called him to the left side of the glider and
pointed out the damage.

I had a few words with him, too.

"Colin Wray" wrote in message
...
Chris Rollings wrote:

Third test: Terrier Tow-Plane, K 8b on C of G hook. I pitched the glider
about 25 degrees nose up. The glider continued to pitch up fairly rapidly
(as at the start of a winch launch) and substantial forward movement of
the
stick only slightly slowed the rate of pitch. The glider achieved about
45
degrees nose up, speed increased rapidly from 55 knots to about 75 knots
and the glider was pulled back towards level flight (again as at the top
of
a winch launch). I released at that point. The entire sequence of events
occupied a VERY short period of time (subsequently measured as 2 - 3
seconds). The Tow Pilot reported a marked deceleration and start of
pitching down which he attempted to contain by moving the stick back; this
was followed immediately by a very rapid pitch down accompanied by
significant negative â?oGâ??. The tow-plane finished up about 70 degrees
nose down and took about 400 feet to recover to level flight. We both
found the experience alarming, even undertaken deliberately at 4000 feet.
Our conclusion was that the combination of the initial pitch down and the
upward deflection of the elevator caused the horizontal
stabilizer/elevator
combination to stall and the abrupt removal of the down-force it provided
caused the subsequent very rapid pitch-down and negative â?oGâ??.

I was the pilot of a tug involved in exactly the scenario described by
Chris above. The culprit was a K6 using a belly hook, and the only
reason I am here to tell the tale is that it occurred at 400ft. It was
actually a dual tow with the K6 on the short rope and a K13 on the
long rope in low-tow position. The K6 had recovered from some earlier
excursions, but all seemed to be going well before it happened.

The "up-ending" was instantaneous, there was no way to have reached
any type of release before the rope broke, and in any case I can
assure you that when descending vertically on full throttle at 400ft,
your first reaction it to close the throttle.

Our CFI in the K13 said he hadn't seen the underside of a PA18 in plan
form quite so close before.

In those days we used to store spare ropes and things behind the rear
seat of the PA18, and my situation was not improved by the whole lot
coming forward and landing on my head and all over the cockpit.

A good friend of mine later died towing a K6 with a PA18, which
incident quite probably was the trigger for Chris' investigations.

On Wednesday, February 12, 2014 12:03:17 PM UTC-5, Dan Marotta wrote:
Ain't no doubt about how quickly the tug gets upset when the glider decides

to fly hither and yon.



My event involved a highly experienced retired FAA guy with type ratings in

every aircraft imagineable. It was his first flight in a borrowed HP-14

and, during the departure turn at about 700' AGL he flew high and wide to

the right, outside of the turn. Before I could reach the release lever,

he'd turned hard left and dove across the tail of the Pawnee wrapping the

tow rope around his left wing and, after it cut the top and bottom skins of

the wing clear to the spar, cutting the rope in two in the middle. The

final yank on the rope caused the tug to yaw hard right and pitch slightly

up (from about 45 degrees down).

Yikes. Over confidence and diminished capacity are a bad combination.

Annual flight reviews would head off more accidents than better tow hooks.

I think we could combine an optical target designator from an air to air missile, and some explosive bolts, and come up with a solution here, loose the target lock with a speed above 20 Kts, and ring in the hook, and you fire the bolts. Maybe we could get DARPA to fund it. Forget the flashing light on the back of the tow plane, we will use the flare system from a C130 to let everyone know what just happened. I'm in, anybody know how to write a grant proposal? Explosive bolts, missile parts, really cool flares, what's not to like?

On Wednesday, February 12, 2014 11:43:18 AM UTC-6, SF wrote:
I think we could combine an optical target designator from an air to air missile, and some explosive bolts, and come up with a solution here, loose the target lock with a speed above 20 Kts, and ring in the hook, and you fire the bolts. Maybe we could get DARPA to fund it. Forget the flashing light on the back of the tow plane, we will use the flare system from a C130 to let everyone know what just happened. I'm in, anybody know how to write a grant proposal? Explosive bolts, missile parts, really cool flares, what's not to like?

And we mount it with a Picatinny rail - painted desert camo.

Totally tacticool!

Kirk

The camo paint would not be approved for use in CA or NY. Too evil looking,
don'tcha know... It would probably be OK in NJ as long as the release
mechanism did not incorporate a "hollow point".


"kirk.stant" wrote in message
...
On Wednesday, February 12, 2014 11:43:18 AM UTC-6, SF wrote:
I think we could combine an optical target designator from an air to air
missile, and some explosive bolts, and come up with a solution here, loose
the target lock with a speed above 20 Kts, and ring in the hook, and you
fire the bolts. Maybe we could get DARPA to fund it. Forget the
flashing light on the back of the tow plane, we will use the flare system
from a C130 to let everyone know what just happened. I'm in, anybody know
how to write a grant proposal? Explosive bolts, missile parts, really
cool flares, what's not to like?

And we mount it with a Picatinny rail - painted desert camo.

Totally tacticool!

Kirk

If this was an industrial control problem. I would try two things.
1: Mount a Tost CG release on the tow plane upside down and at an angle where the upwards angle of the tow rope would initiate a back release. The angle required, reliability, tendency for unintended operation,and whether or not this would actually work, to be determined by testing. Based on something like this that was attempted and reported on here earlier, I have a low confidence in this scheme working out.
2: Using a TOST release, add an electric solenoid activation device somewhere in the cable run to the release. The solenoid could be activated by a "full back stick" limit switch and a short time delay circuit on the tow plane, the normal manual pull handle in the cockpit, or a switch on the stick. Again, testing would have to be done to confirm that this scheme would actually work.
I have no idea how any of this could be accomplished given it's an airplane and the FAA is involved. Their requirements are baffling to someone that does not live in that world.

Ultimately, taking the human element out of the equation could prove impossible. The cure being worse that the disease is also a real possibility due to unintended consequences. However we have always done it this way, isn't a good answer either.

That might be the scenario to build an auto release. it would require an electronic gyro which any more is inexpensive and easy to implement along with the full back stick switch, if the Tow plane pitches down more than a certain amount (Maybe 20 degrees down pitch) and with full aft stick initiates and auto release.

Brian

At 03:57 18 February 2014, Brian wrote:
That might be the scenario to build an auto release. it would require an
el=
ectronic gyro which any more is inexpensive and easy to implement along
wit=
h the full back stick switch, if the Tow plane pitches down more than a
cer=
tain amount (Maybe 20 degrees down pitch) and with full aft stick
initiates=
and auto release.

Brian


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.