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