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Old May 1st 19, 01:28 PM
Walt Connelly Walt Connelly is offline
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First recorded activity by AviationBanter: Aug 2010
Posts: 365
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Quote:
Originally Posted by Jason Scott View Post
Currently operating 3 tow planes, all with Schweizer hooks installed. I would love to get access to some concrete information on the issues with the Schweizer hooks, comparison between the two, and any concerns with the TOST system. My goal is to likely switch over the fleet, having personally experienced a situation with a glider losing directional control on tow, and causing momentary upset to the towplane. In my opinion, the TOST system is superior, and tangible information is the best way to present this opinion to the other parties involved in our operation.

In the FAA Advisory Circular, Date 3/3/08 AC No 43.13-2b, Page 76, Par 808 states as follows:

“ WHEN THE GLIDER UNDER TOW OPERATES ABOVE A CERTAIN ANGLE TO THE TOW PLANE, THE RING MAY SLIDE UPWARDS ON THE HOOK, CAUSING EXCESSIVE LOAD ON THE HOOK AND DIFFICULTY IN RELEASING THE TOW ROPE RING.”

The Soaring Society of America thru their Soaring Safety Foundation, Tow Pilot Training Course additionally acknowledge IN RED as follows:

“If at any time the nose of the tow plane is pulled uncontrollably by the glider to a dangerously high or low pitch attitude, - PULL THE RELEASE! “

It goes on to say:

“Depending on the installation of the tow hitch, it may be possible for the release mechanism to become jammed due to the excessively high position of the glider, (American style hook). “

Here we have two "authorities" acknowledging the problem which has been a contributing factor to the death of tow pilots in the past. This condition has existed for a few decades at least with knowledge of and a lack of interest in correcting the matter. If this is not 'concrete" enough then I don't know what would be.

Every report I have read notes a "delay in releasing" on the part of the tow pilot. I would submit that there was no delay in the attempt, rather a mechanism which is meant to release but will not as noted in the above documents.

My letter to the FAA recommended at a MINIMUM that there be blanket permission for a qualified A&P IA to invert the Schweizer hook AND to allow for the increase in the length of the release handle, increasing the mechanical advantage and allowing for access to the tow pilot in the upright and seated position. It is absurd to have it down on the floor and with a 5-1 mechanical advantage which has been shown to be inadequate to affect a release. The TOST system would be preferable especially if you consider that you may not tow any glider with a max gross weight of 1500 lbs with the Schweizer hook as this system is limited to a 1200 lb rope.

The push back will be the cost of the Tost system and while you're at it don't forget to improve the position and mechanical advantage of the release handle. But If you don't value the life of your tow pilots...

Walt Connelly
Former tow pilot (7K tows)
Now happily flying helicopters