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

Terry, the dynamic of the towplane slowing was not lost on me. The only source for the kiting energy of the glider is the tug. Any climb rate for the glider above that being provided by the engine of the tug will come out of the tug in the form of lost airspeed. That is probably the first thing the towpilot will notice. But, the same loss of speed could occur as a result of the glider's powerful dive brakes openning, so that cannot be used as a trigger for an auto system. Also, slowing the tug will not make it pitch down, unless the slowing is to below the stall speed of the tug. It will make it start to drop, as lift is now less than weight. And, Terry, if you were nose down, your tail likely was pulled up. In an amount that kept the glider in your mirror. Your airpseed loss was the transfer of your kinetic energy to the increased kinetic and potential energy of the glider. The nose down was likely a combo of the glider pulling your tail up and possibly stalling of the wing of the tug. You effectively became a moving anchor point for the glider.

GC, stalled tail and accelerated stalls are not at all the same. Maybe you need some training? :-) My belief is that a kiting glider with a wing that is 3-5 times the size of the tugs tail can provide far greater tug pitch authority than the tail on the tug. You don't have to stall the tug's tail in order to produce more force with something else than it can produce.

You can test the stalled tail theory by flying the tug sans glider at tow speed. Push the stick rapidly forward to create the nose down pitch rate, then pull rapidly back to arrest it. If the stick back pull does not stop the nose down pitch, the tail was stalled. If it does, the tail is not stalled. This may not be the case for an aerobatic plane intentionally doing an outside snap.

As to "well trained glider pilots", ask Terry about the "well trained pilot" he was tugging who thought he pulled the release, so he started his climbing turn away. Well trained or not these things do happen. Not often, but they do happen. And when they happen at low altitude, the result is usually fatal. First step in training is to burn it into the heads of all glider pilots that on air tow, you don't even consider turning away from the towplane until you have seen the rope going away. Amazingly simple but forgotten more than most would imagine.

Kirk, I don't think we want to consider a bridle from the tips. This would require HUGE spar changes, as you could easily impart 500 lbs aft force at both wing tips. This will pretty likely fold the wings aft and make for a very high speed, although only vertical and down capable, tug. Maybe the missle you were hoping to use? :-)

Mark, fairleads over the tail have issues, too, as boxing the wake will quickly show. But, maybe the air load and the pull of the rope in the other direction will sort of cancel, and not risk bending the fin? However, if there is restriction to up or down pull, you have lost the benefit.

As to other failure modes of an automatic system and the "need to train for them", well, don't we already train for rope breaks? If the system is designed well, it won't make a disconnect any more likely than it is now. And, it is not a change to the airframe, but only an additional means of operating the release. I tend to think that this would be much easier to certify, once you have shown sufficient reliability of the system by design, and that it does not substantially increase the risk of an unplanned seperation of the tug and the glider in practice.

So, with what we have available to us today, why are we afraid to try and design a system to reduce this risk?

Steve Leonard