CG hook on aero tows??

There is an article in the archives of Gliding & Motorgliding International
on Aerotow "Upset" Accidents by Chris Rollings which may be found at:
http://www.glidingmagazine.com/ListF...Dtl.asp?id=327 .
All tug pilots, and glider pilots who launch by aerotow, should read this
article.

For the U.K. the B.G.A. give advice to be found in "Laws and Rules for
Glider Pilots" 14th edition June 2003 (cannot be read on-line):

Under "Recommended Practices":

RP12. The minimum length of aerowtow rope recommended is 150ft. However,
under special circumstances a short rope may be used. The operators'
attention is drawn to the following factors which may cumulatively
contribute to a hazardous situation:

(a) Low experience of glider and/or tug pilot
(b) Gliders fitted with C of G hook only
(c) Glider's C of G towards the aft limit
(d) Turbulent air in the take-off area
(e) Rough ground in the take-off area
(f) Significant cross-wind component.

RP13. After releasing the cable, the glider should turn away so that the
tug aircraft pilot can see clearly that the glider is free.

Under "Operational Regulations":

4.16 The sum of tows made by the tug pilot and the glider pilot, in their
respective capacities, shall not be less than six.

My own opinion is that if a forward aerotow hook is fitted it should always
be used for aerotowing. If the glider does not have an aerotow hook, but
can be fitted with one as a modification then this should be done if it is
to be launched by aerotow.

It is quite normal for tug pilots to refuse to launch a glider if the rope
is on the aft hook when an aerotow hook is available.

I cannot think of any circumstance when the use of the forward hook rather
than the aft one for aerotow launching could cause a problem.

The longer the rope the easier the flying is for the glider pilot (except
perhaps in violent rotor?). The 150 ft rope is a compromise between safety
and operational convenience which has been found to be satisfactory in
practice in the U.K.

The above BGA recommendations and my opinions are based on the assumption
that the glider pilot has been properly trained and checked for currency
etc. The requirements etc. are to be found in the BGA Instructors' Manual
(which is not available to be read on-line).

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


"Bill Daniels" wrote in message
hlink.net...

snip

There's a BGA write-up on CG hooks and pitch-up incidents that should be
required reading for anyone contemplating airtow with a CG hook. Maybe
one of our British friends can provide a link to it.

Bill Daniels

If I am well informed in Germany CG hooks are not allowed for airtow
anymore.
The exception is that if your glider does not have a nose hook, you may use
the CG hook provided that you can show that you made at least six airtows in
the last three month prior to this occasion (or wordings like this).

Karel, NL



"Ian Strachan" schreef in bericht
...
In article , Andy
Durbin writes

snip

I have flown the last 15 or so years with aerotow on a cg hook. My new
ASW-28 has forward and CG hooks but I have never used the forward
hook.

What you have been doing in your ASW-28 would not be allowed at Lasham
and many other clubs (or if I were towing you!). If you have a forward
hook (often called the air tow hook), at most gliding organisations with
which I have been associated, you must use it for air tows except for
well-controlled exercises to show the difference. A true CG hook
position is for winch launching.

Normally, if both hooks are fitted the rear one will be "really rear"
because the manufacturer will assume that it will only be used for winch
or auto-tow. What does it say in your flight manual?

If only one hook is fitted then it will be somewhat forward of the pure
"C of G" position because its location is a compromise for both air tow
and winch and it will be tested for both before the initial C of A is
given for the type.

The reason not to use a CG hook for air tows if a front hook is
available is not so much directional stability while on the ground, but
the potentially much more dangerous "tug upset" which can, and has,
killed tug pilots in the past.

I think that the tug pitch-upset situation has been extensively covered
before on this newsgroup. If the glider becomes high enough behind the
tug, the tow pilot pulls back on the stick to counter the nose-down
pitch and can run out of back-stick. The tug's tailplane (horizontal
stabilizer) can then stall, leading to a sharp and uncontrollable steep
nose-down pitch which, if near the ground (say 600 ft or less) is often
fatal for the tug pilot.

We have had such fatals in the UK at both Lasham, Dunstable and
elsewhere, hence the universal use of nose hooks for air towing where
such a hook is fitted to the glider.

There was even a debate within the BGA after the last UK fatal tug
upset, on whether gliders with only a CG hook should be allowed to be
air towed at all. The upshot was the present situation combined with
careful briefing and air tow practice concentrating on sitting close on
top of the tug slipstream and never getting high. Tug pilots watch the
rear-view mirror very carefully at and after takeoff and I am quite
willing to dump anyone who gets really high, particularly close to the
ground.

Finally, on rope length I agree with Mike Borgelt. The longer the rope
the easier an air tow is to fly in the glider. Last year I had a tow in
Poland in a Puchatz at their Zar mountain soaring centre on a VERY short
rope, and flying the tow was "very active". The field at Zar is a
respectable length so I do not know why they insist on using such short
ropes. The only reason for a short rope that I can think of is to tow
out of a VERY short field, and in my view even that is questionable, if
the field is THAT short it may not be safe to tow out of anyway.
Finally, Lasham make up air tow ropes to be 50m long (164 ft). From
memory, the BGA minimum tow rope length recommendation is 150 ft.

Andy, I really suggest that you start using your air tow (front) hook
when you take an air tow !

--
Ian Strachan
Lasham Tow Pilot

Ian Strachan wrote:


Andy, I really suggest that you start using your air tow (front) hook
when you take an air tow !

I presume you can have an upset incident even with a nosehook. Are
there any statistics that show the safety advantage of a nose hook
compared to a CG hook?

Greg Arnold
330 aerotows with CG hooks, and never any problems except when taking
off without a wing runner

Ian Strachan wrote in message

big snip, but all noted

Andy, I really suggest that you start using your air tow (front) hook
when you take an air tow !

I knew this would get a reply from someone. I am aware of the
conditions of the LBA certification for the ASW 28 and also aware that
BGA has prohibited, or discouraged, import of gliders that don't have
a forward hook for aerotow.

A Schleicher agent advised me not to buy the forward hook option. I
chose to have it fitted because I didn't want any risk that FAA would
grant an airworthiness certificate for aerotow. LBA certification
prohibits the use of CG hook for aerotow but I don't believe my FAA
experimental airworthiness certification has such a limitation.

I use the ASW 28 cg hook for 2 reasons:

1. With over 1500 hours in the ASW 19 I am very familiar with aero tow
with CG hooks. (the CG hook on both gliders is just forward of the
main wheel inside the gear doors)

2. The forward hook is a poor design which is difficult to hook up and
poorly sealed.


Andy (GY)

In article , Andy
Durbin writes

snip

LBA certification
prohibits the use of CG hook for aerotow

Does not that tell you something, then?

1. With over 1500 hours in the ASW 19 I am very familiar with aero tow
with CG hooks.

So I have no doubt also thought the glider pilots who got out of
position and killed the tug pilot.

Just do not come to my club and expect to tow on your aft hook, or
anywhere where I am towing. I would have thought where life-and-death
was concerned you could be a tad more humble about your undoubted
handling abilities. But perhaps unlike the rest of us, you never have
an off-day ......

--
Ian Strachan

"W.J. (Bill) Dean (U.K.)." wrote in
message ...
| There is an article in the archives of Gliding &
Motorgliding International
| on Aerotow "Upset" Accidents by Chris Rollings which may
be found at:
|
http://www.glidingmagazine.com/ListF...Dtl.asp?id=327 .
| All tug pilots, and glider pilots who launch by aerotow,
should read this
| article.
|
| For the U.K. the B.G.A. give advice to be found in "Laws
and Rules for
| Glider Pilots" 14th edition June 2003 (cannot be read
on-line):
|
| Under "Recommended Practices":
|
| RP12. The minimum length of aerowtow rope recommended is
150ft. However,
| under special circumstances a short rope may be used.
The operators'
| attention is drawn to the following factors which may
cumulatively
| contribute to a hazardous situation:
|
| (a) Low experience of glider and/or tug pilot
| (b) Gliders fitted with C of G hook only
| (c) Glider's C of G towards the aft limit
| (d) Turbulent air in the take-off area
| (e) Rough ground in the take-off area
| (f) Significant cross-wind component.
|
| RP13. After releasing the cable, the glider should turn
away so that the
| tug aircraft pilot can see clearly that the glider is
free.
|
| Under "Operational Regulations":
|
| 4.16 The sum of tows made by the tug pilot and the
glider pilot, in their
| respective capacities, shall not be less than six.
|
| My own opinion is that if a forward aerotow hook is fitted
it should always
| be used for aerotowing. If the glider does not have an
aerotow hook, but
| can be fitted with one as a modification then this should
be done if it is
| to be launched by aerotow.
|
| It is quite normal for tug pilots to refuse to launch a
glider if the rope
| is on the aft hook when an aerotow hook is available.
|
| I cannot think of any circumstance when the use of the
forward hook rather
| than the aft one for aerotow launching could cause a
problem.
|
| The longer the rope the easier the flying is for the
glider pilot (except
| perhaps in violent rotor?). The 150 ft rope is a
compromise between safety
| and operational convenience which has been found to be
satisfactory in
| practice in the U.K.
|
| The above BGA recommendations and my opinions are based on
the assumption
| that the glider pilot has been properly trained and
checked for currency
| etc. The requirements etc. are to be found in the BGA
Instructors' Manual
| (which is not available to be read on-line).
|
| W.J. (Bill) Dean (U.K.).
| Remove "ic" to reply.

In Australia, all new gliders and any gliders which change
ownership must be fitted with a nose hook if aero tow is to
be used. C of A not valid otherwise.
John G.

Andy Durbin wrote:

I use the ASW 28 cg hook for 2 reasons:

1. With over 1500 hours in the ASW 19 I am very familiar with aero tow
with CG hooks. (the CG hook on both gliders is just forward of the
main wheel inside the gear doors)

I also had 1000+ hours on my ASW 20 CG hook (and another 600 on other
gliders) when I had a forward hook installed.

2. The forward hook is a poor design which is difficult to hook up

True, but I noticed each line person knew how to do it the second time
they hooked me up, and no one complained.

and
poorly sealed.

Not that bad, but I did spend an hour one day sealing against air
instrusion (for winter flying) when I had the seat pan out for an annual.

Why go to any trouble at all? I found the forward hook (about 1 to 2
feet back from the nose) was better in a crosswind, better if the wing
runner was clumsy, better if I got distracted on tow, better in rough
air, and I never ran over the tow rope, which happened once in a while
with the CG hook.

--
-----
change "netto" to "net" to email me directly

Eric Greenwell
Washington State
USA

Finally, on rope length I agree with Mike Borgelt. The longer the rope
the easier an air tow is to fly in the glider. Last year I had a tow in
Poland in a Puchatz at their Zar mountain soaring centre on a VERY short
rope, and flying the tow was "very active". The field at Zar is a
respectable length so I do not know why they insist on using such short
ropes. The only reason for a short rope that I can think of is to tow
out of a VERY short field, and in my view even that is questionable, if
the field is THAT short it may not be safe to tow out of anyway.
Finally, Lasham make up air tow ropes to be 50m long (164 ft). From
memory, the BGA minimum tow rope length recommendation is 150 ft.


I, too, have been towed by a short rope (10M!) in Poland; but only out
of a dirt field. Mind you, getting towed out of a soft dirt field is,
by itself, a new experience (in the States we would say "go get your
trailer", but in Poland, do as the Poles do. The tow pilot, who spoke
very little English, said "Rope OK?". I figured the guy had to have
his reasons, hopefully not to make me look silly, so I said: "Rope
OK". A short rope on a runway would be intimidating enough, but we are
talking about a soft plowed field! With the help of a bunch of Polish
children (they showed up every time I landed out) I positioned the
glider (Jantar Std III) on the hardest furrow in the field. After some
instruction by the tow pilot to the oldest child on how to hold the
wing (one hand in the back pocket) we were ready to go.
The tow plane was a 9 cylinder radial tail dragger Yak (lots of
power!). The first thing that happened was that one of the amin gear
dug in, causing the tow plane to veer that direction. Of course, I
followed (so much for the hard furrow theory. Then the other wheel
would dug in and we would go that direction. This ment that I would
bounce over from furrow to furrow. At the same time, my gear would dug
in, increasing tow tension until the gear pulled out. This would pull
me violently unto my nose, which would cause me to bounce back onto
the tail, which would bounce me back onto the nose and back onto the
tail. At the same time one of the wing tips would drag into the dirt.
At least 10 times I told myself this was just too intolerable and I
should release; but each time I said (to myslef) I would hang on for
just one more second, and if it didn't improve then I would release.
Throughout this whole experience our speed was increasing, which was
both good and bad. Good: we needed speed to fly. Bad: the jolts got
more violent. Finally, I saw the tow plane go airborne. This was great
except for one thing: I was still on the ground! Hanging on, I felt my
main clear the dirt. But I could hear (yes, hear), the tail dragging
through the ground. Then the noise stopped: I was airborne!
Once airborne you might think that your troubles were over: wrong! At
that distance you can see ever rivet of the tow plane. You are totally
concentrating on following every little movement of the tow plane,
especially the wing waggle (tow release). Because after they waggle
their wings they do a split-S to go after the next glider! Sure
enough, he waggled his wings and I released. Now, where is the
airfield (it has to be close, doesn't it)? The airfield is a square km
of grass, which happens to look like every other farm in the area! I
started looking for another field to land in. Then I spotted the
airfield, to my great relief.
BTW, why the short rope? Simple: on take off I always had clear
visibility; if the long rope had been used the dust from the prop wash
would have made me IFR.

ASW 27B is only certificated for aerotow operation when the forward tow
release is used!

ASW 27 flight manual 4.4.1.2. states,THE SAILPLANE IS ONLY CERTIFICATED FOR=20
AEROTOW OPERATION WHEN THE FORWARD TOW RELEASE IS USED, now i know we all us=
ed=20
to tow from belly hooks years ago, but think on , if you aerotow from the c/=
g=20
hook on ASWs with forward hooks you are flying an uncertified glider and may=
be=20
not be insured, big risk for a =A350,000 glider,and what about the tug pilot=
!