Pawnee Tow Hook STC

[Shawn Curry]

Greetings,

Does anybody have any information about Tost or Schweizer tow hook STCs
for a Pawnee? Our A&P hasn't found any info. Does it require a field
approval or is their an STC out there?

Thanks,
Shawn

[W.J. (Bill) Dean (U.K.).]

I know nothing at all about the regulations, paperwork etc. required for
fitting tow hooks in the USA. However, if you fit a Schweizer hook PLEASE
make sure that it is modified to make it easier to release under load.
Remember that it is a banner towing hook, and no-one gets killed if you
can't release the banner!

There is a modification to the Schweizer hook in the U.K., this was done
after we killed a few tug pilots.

The modification to Schweizer type banner towing hooks is approved and
highly recommended by the BGA.

It may be found at:
British Gliding Association.
http://www.gliding.co.uk/
Go to: Info for Clubs & Members.
http://www.gliding.co.uk/bgainfo/news.htm
Go to: Technical.
http://www.gliding.co.uk/bgainfo/technical/news.htm
Go to: Airworthiness Directives.
http://www.gliding.co.uk/bgainfo/technical/ads.htm
Go to: Motor Glider and Tug issues.
http://www.gliding.co.uk/bgainfo/technical/manufacturers/motorgliderandtug.pdf
See: Page 2 - item 14. Schweitzer type banner towing hooks.

You will not be able to view the mod. on-line, or download it; but I am sure
they will mail it to you (let me know if you have problems).

The release wire is attached to a double flat bar which pivots on a bolt at
the bottom through the fixed part of the hook. Half way along the bar is a
round stud which has to slide forward on the upward releasing fitting in
order to release. It is high friction between this stud and the releasing
fitting which causes the problem (high release loads when the towrope is
under high tension). The fix is to put in a roller bearing instead of the
round stud, so that it rolls off the releasing fitting instead of sliding.

W.J. (Bill) Dean (U.K.).
Remove "ic" to reply.

Post by Shawn Curry
Greetings,
Does anybody have any information about Tost or Schweizer tow hook STCs
for a Pawnee? Our A&P hasn't found any info. Does it require a field
approval or is their an STC out there?
Thanks,
Shawn

[Kirk Stant]

Post by W.J. (Bill) Dean (U.K.).
There is a modification to the Schweizer hook in the U.K., this was done
after we killed a few tug pilots.

There is also a modification to the Schweizer hook (actually, a mod to
the mount) that is approved in the US, it consists of turning the
release assembly upside down, so that any upward load is taken against
the fixed part of the release and not the hinged arm. This prevents an
excessive upward load from jamming the release. Contact Turf Soaring
at http://www.turfsoaring.com/ for more info on this mod (it was
apparently invented by one of Turf's tow pilots).

All of Turf's Pawnees have this mod installed.

Kirk

[7Zulu]

Post by W.J. (Bill) Dean (U.K.).
I know nothing at all about the regulations, paperwork etc. required for
fitting tow hooks in the USA. However, if you fit a Schweizer hook PLEASE
make sure that it is modified to make it easier to release under load.
Remember that it is a banner towing hook, and no-one gets killed if you
can't release the banner!
There is a modification to the Schweizer hook in the U.K., this was done
after we killed a few tug pilots.
The modification to Schweizer type banner towing hooks is approved and
highly recommended by the BGA.
British Gliding Association.
http://www.gliding.co.uk/
Go to: Info for Clubs & Members.
http://www.gliding.co.uk/bgainfo/news.htm
Go to: Technical.
http://www.gliding.co.uk/bgainfo/technical/news.htm
Go to: Airworthiness Directives.
http://www.gliding.co.uk/bgainfo/technical/ads.htm
Go to: Motor Glider and Tug issues.
http://www.gliding.co.uk/bgainfo/technical/manufacturers/motorgliderandtug.pdf
See: Page 2 - item 14. Schweitzer type banner towing hooks.
You will not be able to view the mod. on-line, or download it; but I am sure
they will mail it to you (let me know if you have problems).
The release wire is attached to a double flat bar which pivots on a bolt at
the bottom through the fixed part of the hook. Half way along the bar is a
round stud which has to slide forward on the upward releasing fitting in
order to release. It is high friction between this stud and the releasing
fitting which causes the problem (high release loads when the towrope is
under high tension). The fix is to put in a roller bearing instead of the
round stud, so that it rolls off the releasing fitting instead of sliding.
W.J. (Bill) Dean (U.K.).
Remove "ic" to reply.

Post by Shawn Curry
Greetings,
Does anybody have any information about Tost or Schweizer tow hook STCs
for a Pawnee? Our A&P hasn't found any info. Does it require a field
approval or is their an STC out there?
Thanks,
Shawn

...

Phila. Glider has installed Tost on Pawnee, contact me for details

[Sam Fly]

Shawn,

The only STC I have found is one Schweizer owns for the Piper PA-18.
It appears the FAA is going to stop field approvals for tow hooks.
Their latest statement," there must be an STC or be listed in the Type
Certification Data Sheet for the aircraft". This could be costly.

Sam Fly
Texas Soaring Association

Post by Shawn Curry
Greetings,
Does anybody have any information about Tost or Schweizer tow hook STCs
for a Pawnee? Our A&P hasn't found any info. Does it require a field
approval or is their an STC out there?
Thanks,
Shawn

[Cliff Hilty]

I can remember the people at Turf talking about getting
FAA approval for modifing the Schweizer tow hook by
inverting it and other improvements. I suggest you
contact Turf directly for this info. Roy would surely
be able to steer you in the right direction. Turf Soaring
School 602-439-3621.

Post by Sam Fly
Shawn,
The only STC I have found is one Schweizer owns for
the Piper PA-18.
It appears the FAA is going to stop field approvals
for tow hooks.
Their latest statement,' there must be an STC or be
listed in the Type
Certification Data Sheet for the aircraft'. This could
be costly.
Sam Fly
Texas Soaring Association

Post by Shawn Curry
Greetings,
Does anybody have any information about Tost or Schweizer
tow hook STCs
for a Pawnee? Our A&P hasn't found any info. Does
it require a field
approval or is their an STC out there?
Thanks,
Shawn

...

[Stewart Kissel]

Thanks for the posts,
If anyone has some digital images of Schweitzer or
Tost hook installations on a Pawnee, they would be
greatly appreciated. Also any comments on how the
paperwork was processed. It appears no STC exists.
This is for a US aircraft.

Post by Cliff Hilty
I can remember the people at Turf talking about getting
FAA approval for modifing the Schweizer tow hook by
inverting it and other improvements. I suggest you
contact Turf directly for this info. Roy would surely
be able to steer you in the right direction. Turf Soaring
School 602-439-3621.

Post by Sam Fly
Shawn,
The only STC I have found is one Schweizer owns for
the Piper PA-18.
It appears the FAA is going to stop field approvals
for tow hooks.
Their latest statement,' there must be an STC or be
listed in the Type
Certification Data Sheet for the aircraft'. This could
be costly.
Sam Fly
Texas Soaring Association

Post by Shawn Curry
Greetings,
Does anybody have any information about Tost or Schweizer
tow hook STCs
for a Pawnee? Our A&P hasn't found any info. Does
it require a field
approval or is their an STC out there?
Thanks,
Shawn

...

[Rod Pool]

Shawn
These links address the problem-
Much thanks to Jim Burch and his contributuon to soaring.

http://home.att.net/~jdburch/index.htm
http://home.att.net/~jdburch/towhook.htm
http://home.att.net/~jdburch/Form337.htm
http://home.att.net/~jdburch/Towstudy.htm

This applys to the Schweizer hooks:

"On rare occasions it is possible for a glider on aerotow takeoff to
get so high that the tow plane tail is lifted even with full up
elevator by the tow pilot. It is also possible in this situation for
the tow plane release to jam and prevent release by the tow pilot. One
solution to ensure that the tow pilot can release when this happens is
to invert the release hook. To review an article on this subject from
the May 1996 issue of Soaring, select Towhook Article. Select FAA Form
337 for documentation of such a modification to a Pawnee tow plane,
and Towing Analysis for the study upon which the article is based."

In my opinion the TOST hooks by far are the better answer although
initial cost and maintainence costs are a factor.
Good Luck.
Rod

[Andy Durbin]

Post by Shawn Curry
Greetings,
Does anybody have any information about Tost or Schweizer tow hook STCs
for a Pawnee? Our A&P hasn't found any info. Does it require a field
approval or is their an STC out there?
Thanks,
Shawn

FAA form 337 for installing an inverted Schweizer hook can be found at

http://home.att.net/~jdburch/Form337.htm

The site also contains related links.



Andy

[B Lacovara]

PGC got field approvals in 2003 for the installation of Tost hooks on both a
Pawnee and a Cessna L-19. From a safety standpoint the Tost installation is
the way to go.

Bob