TOST vs. Schweizer Hooks on Tow Planes.

[Jason Scott]

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.

[Paul Agnew]

https://groups.google.com/d/topic/rec.aviation.soaring/bo90yIUlxRo/discussion

There was a lively discussion concerning the two tow hook options. It's worth reading before everyone chimes in here.

Paul A.
Jupiter, FL

[Walt Connelly]

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

[[email protected]]

"> The push back will be the cost of the Tost system"
Push back is not about cost, push back is about the lack of information on legally installing the Tost system on all current towplanes in light of you wanting the FAA to ban all Schweizer hooks. As I said to you last time this came up, if you want to make towing safer collect and make available STCs and successful 337s for Tost hook installations. Instead of whining to a higher power for a solution that screws clubs be the solution that helps clubs.

[[email protected]]

Mr. Connelly, for my own knowledge where does the 1500/1200 lb. limitation on the Schwiezer system come from. Ive tried to find a reference in the past but couldnt find one.

To respectfully add to the debate, I'd challenge anyone in favor of ousting the Schwiezer system if they feel the same way about aero tow with a Tost c.g. hook? Here the superior Tost system has been perhaps miss used and this installation has caused more glider accidents and fatalities than Schwiezer release on tow plane accidents.
I appreciate the position of the "hands off" crowd, what I'd like to see is if those in favor of banning the Schwiezer system on the tow plane also believe they should be beholden to a regulation or policy affecting the method by which they are towed in their glider (when it's their expense).
These two items would have the single biggest impact on soaring safety that I can think of at the lowest cost and highest participation level if it were either a regulatory or insurance requirement. The problem is pilots are cheap and nobody thinks it will happen to them.

-Doug

[Dan Marotta]

I question why the FAA would care if a Schweizer release was mounted
inverted.Â* I would also bet that it would be a very simple 337 which
would allow the modification.

That said, when I installed Garmin G5 instruments in the 180 to replace
the vacuum instruments, I found that I could not move the vacuum
attitude indicator to the right hand panel as a backup. According to
Garmin's installation manual the instrument had to be moved one position
left and one row down.Â* That's what the STC called for.Â* What a bunch of
crap.

On 5/1/2019 7:57 AM, wrote:
>
> "> The push back will be the cost of the Tost system"
> Push back is not about cost, push back is about the lack of information on legally installing the Tost system on all current towplanes in light of you wanting the FAA to ban all Schweizer hooks. As I said to you last time this came up, if you want to make towing safer collect and make available STCs and successful 337s for Tost hook installations. Instead of whining to a higher power for a solution that screws clubs be the solution that helps clubs.

--
Dan, 5J

[Paul Agnew]

On Wednesday, May 1, 2019 at 9:59:05 AM UTC-4, wrote:
> Mr. Connelly, for my own knowledge where does the 1500/1200 lb. limitation on the Schwiezer system come from. Ive tried to find a reference in the past but couldnt find one.
>

There are numerous mentions on RAS regarding the placarded #1200 limit on Pawnee. Ex:

https://groups.google.com/d/topic/rec.aviation.soaring/cSmTbQEuaK4/discussion

PA

[Paul Agnew]

Does anyone know the limits on these STC'd hooks? They claim to be better than Schweizer hooks, but don't list any numbers to substantiate it. (I've emailed an inquiry to them.)

https://pacificaerialtowhooks.com/

[Dan Daly[_2_]]

On Wednesday, May 1, 2019 at 12:02:59 PM UTC-4, Paul Agnew wrote:
> Does anyone know the limits on these STC'd hooks? They claim to be better than Schweizer hooks, but don't list any numbers to substantiate it. (I've emailed an inquiry to them.)
>
> https://pacificaerialtowhooks.com/

If you read the documents section on that website it says 1200 lbs max. http://pacificaerialtowhooks.com/wp-content/uploads/2018/03/FW_FWI660_13_Rev_IR__ICA.pdf . Page 203.

[Charlie M. (UH & 002 owner/pilot)]

I have not read all the links on tow hooks for towplanes.......

Most STC's are paperwork.
What works is "sorta based on normal tow position" from what I see.

The issue here is.....when does "out of position by a fair amount create an issue for either end!"....

Forget high tow vs. low tow.....separate discussion (hammered many times on RAS....)....

Some is design, some is maintenance, some is how you fly a certain tow type.....

An inverted Schweitzer hook may be fine, if maintained.....same as a Tost or others....
A towed ship waaaayyyyy out of position may FUBAR ANY hook system.....

[Charlie Quebec]

A CG hook and high tow is a recipe for disaster. I only have CG on my Dg200, no problem at all with low tow.
We don’t allow anything other than Tost here, thank goodness.

[[email protected]]

Why is CG and high tow a bad thing???

[Walt Connelly]

" The push back will be the cost of the Tost system"
Push back is not about cost, push back is about the lack of information on legally installing the Tost system on all current towplanes in light of you wanting the FAA to ban all Schweizer hooks. As I said to you last time this came up, if you want to make towing safer collect and make available STCs and successful 337s for Tost hook installations. Instead of whining to a higher power for a solution that screws clubs be the solution that helps clubs.

Your characterization of my "whining" to a higher power speaks of one unconcerned with safety. I pointed out clearly the glaring knowledge of a problem which has resulted in the death of tow pilots. The FAA AO acknowledges the problem as does the SSA/SSF (which is a joke). The SSA is a toothless tiger along for the ride while collecting dues and selling magazines in my Constitutionally protected opinion. The FAA has the teeth if they choose to chew.

I'm more concerned with saving lives than anything else having been a second or two from losing mine. If your mechanics can't find the appropriate STCs and 337s perhaps you need to find another mechanic.

I've been contacted by one tow pilot who has acknowledge my actions which influenced his facility to make the changes I recommended. By his acknowledgement it saved his life shortly thereafter. I've heard from commercial operators who experienced this event and realized the potential. They did the work needed to make the changes to a safer, more accessable system.

Have a nice day.

Walt Connelly
Former tow pilot
Now happily flying Whirlybirds.

[Walt Connelly]

Mr. Connelly, for my own knowledge where does the 1500/1200 lb. limitation on the Schwiezer system come from. Ive tried to find a reference in the past but couldnt find one.

To respectfully add to the debate, I'd challenge anyone in favor of ousting the Schwiezer system if they feel the same way about aero tow with a Tost c.g. hook? Here the superior Tost system has been perhaps miss used and this installation has caused more glider accidents and fatalities than Schwiezer release on tow plane accidents.
I appreciate the position of the "hands off" crowd, what I'd like to see is if those in favor of banning the Schwiezer system on the tow plane also believe they should be beholden to a regulation or policy affecting the method by which they are towed in their glider (when it's their expense).
These two items would have the single biggest impact on soaring safety that I can think of at the lowest cost and highest participation level if it were either a regulatory or insurance requirement. The problem is pilots are cheap and nobody thinks it will happen to them.

-Doug

The Schweizer hook is limited to a 1200 lb rope which by the 80-200 rule would limit the max gross weight of the glider in tow to 1500 lbs. This came from the Schweizer factory recommendations. You could use a stronger rope but would have to then use a weak link of appropriate strength. I believe the Tost system has a limit of 900kg which is just short of 2000 lbs covering most all current gliders. Any supplier should be able to supply you with the pertinent published limitations. Wings and Wheels would be a good source.

I don't follow you on the Schweizer vs Tost system regarding accidents. I have not seen those statistics, perhaps you could site them? I will say that in 7000 tows I have never had a problem with a CG hook glider but then again most of these are flown by more experienced pilots. It will be the student on solo or occasionally an older pilot who should no longer be flying who will upend you.

Walt Connelly

[Charles Longley]

You don’t mention what type of fleet you have. Putting a Tost tow hook on a Pawnee, Super Cub or Husky is very simple mechanically and paperwork wise.

[Paul Agnew]

On Wednesday, May 1, 2019 at 12:02:59 PM UTC-4, Paul Agnew wrote:
> Does anyone know the limits on these STC'd hooks? They claim to be better than Schweizer hooks, but don't list any numbers to substantiate it. (I've emailed an inquiry to them.)
>
> https://pacificaerialtowhooks.com/

I just heard back from Pacific Aerial Towhooks.

#1200 glider weight limit using AC 43.13-2B, 804(d). Their release handles look to be at least 5:1 by design.

PA

[[email protected]]

On Monday, April 29, 2019 at 1:37:55 PM UTC-7, Jason Scott wrote:
> 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.

Pacific Aerial Tow Hooks has an FAA approved STC with a hook that has lower release forces than the Schwitzer hook. The tested release load on a new PATH hook is only 56 lbs with a 1000 lb tow load at 20 degrees. The whole kit is STCed on a wide variety of aircraft.

[[email protected]]

On Wednesday, May 1, 2019 at 9:02:59 AM UTC-7, Paul Agnew wrote:
> Does anyone know the limits on these STC'd hooks? They claim to be better than Schweizer hooks, but don't list any numbers to substantiate it. (I've emailed an inquiry to them.)
>
> https://pacificaerialtowhooks.com/

Paul as I replied to your email,
The pacific Aerial Tow Hook is rated for a limit load of 1440 lbs. using AC 43.13-2B, 804(d) the glider can be 1200 lbs or a banner can be 720 lb, (although we recommend a banner limit of 600 lb.) The rope for glider towing is limited to 960 lbs breaking strength.

The geometry of the Schweizer hook has a load ratio on the release of .377 and the PATH tow hook has a load ratio of .265, so the release loads on the Schweizer are 42% more. Also the ring is held in one location and can't move around like the Schweizer hook.