The aerodynamics of a towplane in a kiting glider situation

On Monday, May 18, 2020 at 8:30:04 AM UTC-4, Jonathon May wrote:
At 10:11 18 May 2020, Sci Fi wrote:
At 06:18 18 May 2020, 2G wrote:
On Sunday, May 17, 2020 at 6:20:53 PM UTC-7,

w=
rote:
Presumably, cable force has an upper bound of 80% to
200% of the glider
g=
ross weight (FAR 91.309).
=20

If that 80-200% is correct it could mean any weak link, for a
350kg glide
could be from 280 kg to 700kg breaking strain. Perhaps the
lower figur
should be used for aero-tows, as it is sooo much safer.
However I don'
know if weak links of less than 500kg are made.


I have seen a 4 ton winch moved on a 2 seater launch(1000Kg)
links you can stop a tug and strip it of all its airspeed quite easily.
Tost make a series of links down to 80kg for hang-gliders ,but I
do not think that is the answer.

The only way I can see it working is an ,and+and+and system.

If the elevator is hard up+the angle is above a set figure +the
load is above set figure the rope is released.

You would need a load sensor ,a light beam over the rope to limit
the deflection and a micro switch on the elevator.If all 3 occurred
together the rope is released.You would probably need a
magnetic coupling.
And you would still get nuisance releases.

Commendable that such thought is being put in but it's design, creation, approval and implementation at the end of the day. There is a point below which nothing is going to save the life of a tow pilot, human nature being what it is. I would have thought the potential for such an upset being caused by a flight instructor would be near zero... The old duffers YES, (and they abound) 15 year old students, YES but not instructors. The USAFA and Front Royal incidents are proof positive that there is a disconnect when it comes to recognizing the need to release when you kite above the tow plane, reaction time is everything. If the glider doesn't release it is necessary that the tow pilot has an unfettered system, at least not a system that has been proven in the past to fail. That would be the TOST system or at least if a Schweizer hook is used it be inverted and a release handle with adequate mechanical advantage and accessibility. Again this would not have helped the most recent accident victim but the next time a glider kites at a recoverable altitude let's hope the tow pilot has an out.

Walt Connelly
Former Tow Pilot
Now Happy Helicopter Pilot