TOST vs. Schweizer Hooks on Tow Planes.

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/re...aK4/discussion

PA

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/

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-...ev_IR__ICA.pdf . Page 203.

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.....

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

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.