Improved Towhook from Aircraft Spruce

[Burt Compton - Marfa]

North America: Anyone have experience with this new, improved tow
hook based upon the Schweizer hook? Your FAA Approval process?

From the catalog at www.aircraftspruce.com (see photos there)

Aircraft Spruce Pilot Supplies - Towing Equipment
GLIDER & BANNER TOW HOOKS

These tow hooks are available in two models. One is a bolt-on tow hook
with a mounting lug which is ideal for attachment to a tail tie down
point. The other model is a weld-on tow hook designed to be directly
welded to a custom mounting bracket.

These two hooks are similar in design to the Schweizer manufactured
two hooks that are no longer available. Design improvements were made
to increase emergency release capability at all towing loads and
angles.

These new tow hooks have greater release arm leverage and a unique
hardened roller release design to reduce release force at all tow
angles. Additionally, the geometry of the tow hook housing was
improved to keep the tow ring in the optimum position to minimize
release force.

FAA approval can be obtained for the complete tow hook and release
system by following the guidelines in FAA Advisory Circular 43.13-2A,
Chapter 8, titled, "Glider and Banner Tow-Hitch Installations" and the
included tow hook installation instruction.

Description Part No. Price
GLIDER TOW HOOK (WELD ON) 13-04974 $302.81
GLIDER TOW HOOK (BOLT ON) 13-04975 $340.40

[Andy[_1_]]

On Nov 22, 6:24 am, Burt Compton - Marfa > wrote:
> North America: Anyone have experience with this new, improved tow
> hook based upon the Schweizer hook? Your FAA Approval process?

No experience with this release but I've noticed that some hook
installations don't release until most of the release handle motion
range is used up. Since this release has a longer arm then more
release handle motion will be required. I wonder if that will require
a redesigned release handle or perhaps just more careful attention to
cable adjustment.

Andy

[[email protected]]

The roller is a huge designe improvement too, both for setting the
latch and pushing open.

Would like to see a heavier guage of material on the sides. The
Schweizer hooks WILL bend and/or jam with the just the right angle of
side load.


Michael

Andy wrote:
> On Nov 22, 6:24 am, Burt Compton - Marfa > wrote:
> > North America: Anyone have experience with this new, improved tow
> > hook based upon the Schweizer hook? Your FAA Approval process?
>
> No experience with this release but I've noticed that some hook
> installations don't release until most of the release handle motion
> range is used up. Since this release has a longer arm then more
> release handle motion will be required. I wonder if that will require
> a redesigned release handle or perhaps just more careful attention to
> cable adjustment.
>
> Andy

[HL Falbaum]

They should be compared to that which really works--a Tost release. If they
are not better than a Tost, it doesn't matter if they are better than the
old Schweizer hook.
my 0.02USD
--
Hartley Falbaum
"KF" USA

"Burt Compton - Marfa" > wrote in message
...
> North America: Anyone have experience with this new, improved tow
> hook based upon the Schweizer hook? Your FAA Approval process?
>
> From the catalog at www.aircraftspruce.com (see photos there)
>
> Aircraft Spruce Pilot Supplies - Towing Equipment
> GLIDER & BANNER TOW HOOKS
>
> These tow hooks are available in two models. One is a bolt-on tow hook
> with a mounting lug which is ideal for attachment to a tail tie down
> point. The other model is a weld-on tow hook designed to be directly
> welded to a custom mounting bracket.
>
> These two hooks are similar in design to the Schweizer manufactured
> two hooks that are no longer available. Design improvements were made
> to increase emergency release capability at all towing loads and
> angles.
>
> These new tow hooks have greater release arm leverage and a unique
> hardened roller release design to reduce release force at all tow
> angles. Additionally, the geometry of the tow hook housing was
> improved to keep the tow ring in the optimum position to minimize
> release force.
>
> FAA approval can be obtained for the complete tow hook and release
> system by following the guidelines in FAA Advisory Circular 43.13-2A,
> Chapter 8, titled, "Glider and Banner Tow-Hitch Installations" and the
> included tow hook installation instruction.
>
> Description Part No. Price
> GLIDER TOW HOOK (WELD ON) 13-04974 $302.81
> GLIDER TOW HOOK (BOLT ON) 13-04975 $340.40
>
>
>
>
>
>

[Doug Hoffman[_2_]]

Andy wrote:

> No experience with this release but I've noticed that some hook
> installations don't release until most of the release handle motion
> range is used up. Since this release has a longer arm then more
> release handle motion will be required. I wonder if that will require
> a redesigned release handle or perhaps just more careful attention to
> cable adjustment.

I've always liked the Scheder-design HP nose or chin hooks. They seem
simple in design and as far as I know are quite robust. The neat thing
is upon release they completely retract into the fuse and cover the
opening with a flush plate.

I would guess that Bob K. of HP Aircraft owns the rights to the design.
I'm surprised that I don't see this hook retrofitted to a lot of other
glider types.

Regards,

-Doug

[Wayne Paul]

"Doug Hoffman" <no.spam> wrote in message
.. .
>
> I've always liked the Scheder-design HP nose or chin hooks. They seem
> simple in design and as far as I know are quite robust. The neat thing is
> upon release they completely retract into the fuse and cover the opening
> with a flush plate.
>
> I would guess that Bob K. of HP Aircraft owns the rights to the design.
> I'm surprised that I don't see this hook retrofitted to a lot of other
> glider types.
>

Doug,

The 1-35A, SparrowHawk and, I believe, Zuni have tow hooks simular the Dick
Schreder's HP/RS series design.

Wayne
HP-14 "6F"
http://www.soaridaho.com/Schreder

[HL Falbaum]

I believe the hook described in thr Aircraft Spruce catalogue is for the
Towplane. The problem is release ability under extreme vertical or
horizontal (side) loads by a very out-of-position glider. This is of great
interest to towpilots.

--
Hartley Falbaum


"Wayne Paul" > wrote in message
...
>
> "Doug Hoffman" <no.spam> wrote in message
> .. .
>>
>> I've always liked the Scheder-design HP nose or chin hooks. They seem
>> simple in design and as far as I know are quite robust. The neat thing
>> is upon release they completely retract into the fuse and cover the
>> opening with a flush plate.
>>
>> I would guess that Bob K. of HP Aircraft owns the rights to the design.
>> I'm surprised that I don't see this hook retrofitted to a lot of other
>> glider types.
>>
>
> Doug,
>
> The 1-35A, SparrowHawk and, I believe, Zuni have tow hooks simular the
> Dick Schreder's HP/RS series design.
>
> Wayne
> HP-14 "6F"
> http://www.soaridaho.com/Schreder
>
>

[[email protected]]

Long time readers of this news group will remeber posting from me on
the subject of Tost tow hooks verses all the others. My opinion is
tilll the same, nothing compairs to a Tost tow hook either on the
glider or on the tow plane, for safety and reliability. As mentioned
in other replys to this subject the other tow hooks have have an
increase in the force needed to actuate the release that is portional
to the tension on the tow line. This is not good. None of the other
tow hooks have a schedule of maintaince, none of the others lock over
center and hold the tow ring in a position for easy and clean release
of the tow rope. The Schweizer and Schreader style hooks just can not
compaire to a Tost.

One reason you do not see these other tow releases retrofitted to a
lot of other gliders is that except for the Schweizer gliders, they
are not legal to use in Type Certificated gliders. For a Type
Certificated glider that was originally fitted with a Tost hook, to
have the other sype hook installed would require a fair ammount of
paperwork. A knowlegable FAA inspector would not accept only a form
337 for this change.

The Tost is so good that it has been copired by Ottfur in England and
by SZD and other former East Block glider manufactuers.

Yes, they are more expensive, but I think you really do get what you
pay for, and I think that considering the tow release's critical part
in safe launching, the extra cost is a small price to pay.

Robert Mudd
Moriarty, New Mexico
Expirencing our first snow fall of the season today.

> I've always liked the Scheder-design HP nose or chin hooks. �They seem
> simple in design and as far as I know are quite robust. �The neat thing
> is upon release they completely retract into the fuse and cover the
> opening with a flush plate.
>
> I would guess that Bob K. of HP Aircraft owns the rights to the design.
> � I'm surprised that I don't see this hook retrofitted to a lot of other
> glider types.
>
> Regards,
>
> -Doug

[Bill Daniels]

Robert Mudd is dead on.

I would add that there is considerable safety and operational value in
standardization. On any airfield today, Tost is the dominant
ringset/release system. If a second system is used, it adds ring switching
to the rope handling chore. There is always a temptation to use a Tost
ringset on a Schweizer which WILL occasionally jam the release.
Standardizing on Tost is expensive but safer and more convenient.

Bill D


> wrote in message
...
Long time readers of this news group will remeber posting from me on
the subject of Tost tow hooks verses all the others. My opinion is
tilll the same, nothing compairs to a Tost tow hook either on the
glider or on the tow plane, for safety and reliability. As mentioned
in other replys to this subject the other tow hooks have have an
increase in the force needed to actuate the release that is portional
to the tension on the tow line. This is not good. None of the other
tow hooks have a schedule of maintaince, none of the others lock over
center and hold the tow ring in a position for easy and clean release
of the tow rope. The Schweizer and Schreader style hooks just can not
compaire to a Tost.

One reason you do not see these other tow releases retrofitted to a
lot of other gliders is that except for the Schweizer gliders, they
are not legal to use in Type Certificated gliders. For a Type
Certificated glider that was originally fitted with a Tost hook, to
have the other sype hook installed would require a fair ammount of
paperwork. A knowlegable FAA inspector would not accept only a form
337 for this change.

The Tost is so good that it has been copired by Ottfur in England and
by SZD and other former East Block glider manufactuers.

Yes, they are more expensive, but I think you really do get what you
pay for, and I think that considering the tow release's critical part
in safe launching, the extra cost is a small price to pay.

Robert Mudd
Moriarty, New Mexico
Expirencing our first snow fall of the season today.

> I've always liked the Scheder-design HP nose or chin hooks. ?They seem
> simple in design and as far as I know are quite robust. ?The neat thing
> is upon release they completely retract into the fuse and cover the
> opening with a flush plate.
>
> I would guess that Bob K. of HP Aircraft owns the rights to the design.
> ? I'm surprised that I don't see this hook retrofitted to a lot of other
> glider types.
>
> Regards,
>
> -Doug

[Doug Hoffman[_2_]]

wrote:
> Long time readers of this news group will remeber posting from me on
> the subject of Tost tow hooks verses all the others. My opinion is
> tilll the same, nothing compairs to a Tost tow hook either on the
> glider or on the tow plane, for safety and reliability.

Hi Robert,

Actually I did do a search of the message archives before posting and
didn't see anything about problems with a Schreder tow hook. Yes, I saw
your comments, but they were directed at the Schweizer hook.


> As mentioned
> in other replys to this subject the other tow hooks have have an
> increase in the force needed to actuate the release that is portional
> to the tension on the tow line.

Interesting. I have flown several different Schreder gliders and never
had a problem with that.


> This is not good. None of the other
> tow hooks have a schedule of maintaince, none of the others lock over
> center and hold the tow ring in a position for easy and clean release
> of the tow rope. The Schweizer and Schreader style hooks just can not
> compaire to a Tost.

What are the failure modes of the Schreder nose hook (not the Schweizer
or Applebay hook)? How does the failure rate of the Schreder hook
compare to the Tost hook? I think there are quite a few Schreder pilots
out there now who would be keenly interested in knowing about this.



> One reason you do not see these other tow releases retrofitted to a
> lot of other gliders is that except for the Schweizer gliders, they
> are not legal to use in Type Certificated gliders. For a Type
> Certificated glider that was originally fitted with a Tost hook, to
> have the other sype hook installed would require a fair ammount of
> paperwork. A knowlegable FAA inspector would not accept only a form
> 337 for this change.

Of course. Sorry if you thought I meant otherwise.

Regards,

-Doug

[Doug Hoffman[_2_]]

Bill Daniels wrote:
> Robert Mudd is dead on.
>
> I would add that there is considerable safety and operational value in
> standardization. On any airfield today, Tost is the dominant
> ringset/release system. If a second system is used, it adds ring switching
> to the rope handling chore. There is always a temptation to use a Tost
> ringset on a Schweizer which WILL occasionally jam the release.
> Standardizing on Tost is expensive but safer and more convenient.

Well, good luck getting Schweizer gliders banned from airfields unless
they have a Tost conversion. But I agree that not having to hassle with
switching rings on the end of the tow rope would be best. Btw, The
three Schreder gliders that I have flown accepted either the Tost ring
or the Schweizer ring without problems.

Regards,

-Doug

[Udo]

I would like to shed some more light on the Schreder Hook.
The Schreder hook in fact has the same features as the Toast hook.
Back pressure will release the ring, this back pressure can easily be
metered by changing a simple hardware store spring.
Ring size is not critical, nothing gets twisted or jammed to prevent
release
An other feature, due to the rotating point of the hook being near to
where the line of force is located when the glider is high above the
tow plane. The release load become less as the glider climbs above
the two plane, as well the hook can be shaped that will allow an
automatic released if a certain angle is reached and it would still
function for all normal towing conditions.

As Doug Hoffman already mentioned the hook installation needs only a
small opening, when the hook rotates and retracts,
a cover automatically swings into place and makes it rather slick
looking arrangement.
Udo


On Nov 24, 10:09 am, Doug Hoffman <no.spam> wrote:
> wrote:
> > Long time readers of this news group will remeber posting from me on
> > the subject of Tost tow hooks verses all the others. My opinion is
> > tilll the same, nothing compairs to a Tost tow hook either on the
> > glider or on the tow plane, for safety and reliability.
>
> Hi Robert,
>
> Actually I did do a search of the message archives before posting and
> didn't see anything about problems with a Schreder tow hook. Yes, I saw
> your comments, but they were directed at the Schweizer hook.
>
> > As mentioned
> > in other replys to this subject the other tow hooks have have an
> > increase in the force needed to actuate the release that is portional
> > to the tension on the tow line.
>
> Interesting. I have flown several different Schreder gliders and never
> had a problem with that.
>
> > This is not good. None of the other
> > tow hooks have a schedule of maintaince, none of the others lock over
> > center and hold the tow ring in a position for easy and clean release
> > of the tow rope. The Schweizer and Schreader style hooks just can not
> > compaire to a Tost.
>
> What are the failure modes of the Schreder nose hook (not the Schweizer
> or Applebay hook)? How does the failure rate of the Schreder hook
> compare to the Tost hook? I think there are quite a few Schreder pilots
> out there now who would be keenly interested in knowing about this.
>
> > One reason you do not see these other tow releases retrofitted to a
> > lot of other gliders is that except for the Schweizer gliders, they
> > are not legal to use in Type Certificated gliders. For a Type
> > Certificated glider that was originally fitted with a Tost hook, to
> > have the other sype hook installed would require a fair ammount of
> > paperwork. A knowlegable FAA inspector would not accept only a form
> > 337 for this change.
>
> Of course. Sorry if you thought I meant otherwise.
>
> Regards,
>
> -Doug

[Bob Kuykendall]

Robert has a good point: Everyone willing to more for a sailplane than
for a house should demand the very best in accessories and options.

Wandering off-topic, the other day I was flipping through a book
called "Graphic War," which shows and describes the technical drawings
used in the technical manuals of WWII aircraft. I was probably geeking
out from the tech writer perspective, but some of the stories behind
the documentation are as interesting as the stories behind the
aircraft themselves. Okay, maybe not, but I'd argue the case.

Anyhow, one of the drawings was a cutaway of the tailwheel and swivel
of the Junkers JU52. While the text described it only in terms of its
advantages over the tailskid, the drawing showed, in addition to the
tailwheel, a tow hitch mechanism with geometry identical to that of a
scaled-up Tost E85, right down to the actuation sector and the
mirrored torsion spring that holds the release knuckle down.