CG hook on aero tows??

On 6 Jan 2004 12:41:34 -0700, (Mark James Boyd)
wrote:


First of all, if the manual says to not use the C.G. hook
for aerotow, I personally wouldn't try it, even once.
But that's just me.

In the case of the 28 it's not a question of danger: Hundreds of 24's
(which has only a different wing, but identical fuselage, CG and tail)
are flying with CG hook only.

But what do you do with a glider like our ASW-27?
If only a CG hook is installed (yes, there are at least 150 27's
flying like this), it's fully certified for aerotow on the CG hook.
Since the new rules came out, all new 27's have a nose hook installed
and therefore this one MUST be used for aerotow.

Does the installed nose hook suddenly make the aerotow on the CG hook
dangerous?

(Consequence: Many owners of new 27's removed the nose hook).

The same goes for nearly all current gliders that were previously
built with only a CG hook and which are currently produced with a nose
hook.

A new glider with a different
placement of the CG hook relative to the CG may
be a completely different ride. If you do try it, keep
meticulous records, and send a report to the manufacturer.
I bet they'd like to know, since maybe their test pilot
was too chicken to do it himself.

If a CG hook is certified, the manufacturer has tested it for all
possible CG's.

Another thought...is it possible to rig a towline in such a way
that it has TWO rings? So that one could release the nose
ring and then be on the belly ring? Could one then
launch (the super dangerous part) using the nose ring and
then release this and experiment using the belly ring up at
high altitude?

Why would anyone do that?
The disadvantages of a nose hook is that it oftern creates significant
noise, draft, a little drag, costs money to build and to maintain.
Inflight it's nice to have.


Of course all of this begs the question: if the glider
HAS a nose hook for aerotow, why not just use it?

See above..
I admit that I've covered the nose hook with tape to get rid of the
noise and the draft when I was flying on very cold days - Schleicher
screwed up the design in my opinion.

An aerotow on the nose hook is probably less prone to pull the
towplane's tail up - but so far I have not seen one single accident
(!) statistic that could prove this point. I guess that by today
enough gliders with a nose hook should be in duty to see if the nose
hook really make a difference concerning accident rates.

The only information that I've seen so far is the Idaflieg flight test
that demonstrated that a gloder on a nose hook takes a lot more effort
and time to pull the tail of the tow plane up.

Bye
Andreas

On 6 Jan 2004 08:21:29 GMT, Ray Payne
wrote:

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

This is correct.
And an ASW-27 where no nose hook is installed is certified for aerotow
operation on the CG hook.

Bye
Andreas

I got a question for any mate from OZ. IIRC low tows
are mandatory done there. So how does that work with
a CG hook?

Ted,

It's tough to say what the real cause of your upset was, but goodness
knows we're going to try.

Your tow pilot makes a good point, and one you should take to heart.
Before your next take off, note a physical feature on the runway where
the tow plane starts its take off roll. Most tow pilots apply full
power immediately. Since the tow plane is moving slowly at this point,
it is generating a good bit of turbulence that you are going to have
to negotiate at less than flying speed and probably well below a speed
where your controls will have anything close to full authority. Tail
draggers like the B4 are especially prone to upset at this point. As I
roll toward the tow plane start point, I try to anticipate the upset
(almost always a drop of the right wing) and catch it as it starts
rather than letting it catch me unawares.

The B4 has an especially strong elevator. If you get out of sorts, you
have to be extra careful not to over control. PIOs are common in the
model, especially during the first few aerotows.

On 6 Jan 2004 12:41:34 -0700, (Mark James Boyd)
wrote:


First of all, if the manual says to not use the C.G. hook
for aerotow, I personally wouldn't try it, even once.
But that's just me.


But what do you do with a glider like our ASW-27?
If only a CG hook is installed (yes, there are at least 150 27's
flying like this), it's fully certified for aerotow on the CG hook.
Since the new rules came out, all new 27's have a nose hook installed
and therefore this one MUST be used for aerotow.

Does the installed nose hook suddenly make the aerotow on the CG hook
dangerous?


OK, be prepared for me to completely change my tune. Are you guys
telling me the manual says that if it has only a CG hook, you can
aerotow with it, but if both hooks are present, the manual
prohibits aerotow on the CG hook for the ASW-27? And the
W&B limits and CG hook locations are identical for both
gliders?

If THIS is the case, a certainly can't argue with those
who see it as a simple paper shuffle. But I'd also say that in
this case a factory test pilot has surely flown that exact type of glider
with the CG hook in the exact position and flown it aerotow
that way. This means anyone who does it is NOT therefore a
test pilot.

Sounds like removing the nose hook just to "legally" aerotow
off the CG hook is a ridiculous paper shuffle hassle...
And yes, I did read the reasons why one might want to remove it.
Hmmm...so much for the manual, eh?

I probably should resist the urge to jump in on this thread, but what
the heck. I've made several hundred aerotows using CG hook only
equipped gliders, and have had exactly 3 incidents which might have been
avoided with a nose hook. Two were my first flights in newly purchased
gliders, where I guessed wrong about the takeoff trim position, got
quite high on takeoff, but managed to recover with full forward stick.
The other time I got sideways early in the ground roll with half water,
released, and got stopped before going too far off the runway.

Being the skeptical sort, I went to the US National Transportation
Safety Board site, and did a query for all reports of accidents during
the past 20 years with the words "tow" and "glider" in them. This
yielded 280 hits. I eliminated those accidents that happened after safe
release, where there was a mechanical failure (disconnected controls,
etc.), where one of the pilots was likely to be impaired (heart attack,
etc.), or where the glider ran off the side of the runway early in the
takeoff roll. This left 17 accidents. Of those, 8 gliders (two
probably with CG hook, one more possible) had large pitch excursions on
takeoff, were released and subsequently crashed without damage to the
towplane.

That left 9 in which a glider high and out of position pulled up the
tail of the towplane causing it to crash. Of these, 3 very likely had
CG hooks (Std Cirrus, Open Cirrus, Ka-6E), 2 likely had nose hooks
(G103C and 1-26), and the remainder either the glider type was not
stated, or may have had either type of hook (Twin Astir).

The thing that struck me about these accidents was how many of them were
due to the pilot fiddling with an open canopy, or inadvertently deployed
spoilers. If the pilots simply payed attention to flying the aircraft,
most of the above would never have happened. The other thing that is
clear is that those freakin' Schweizer towplane hooks are a menace to
tow pilots, and *should* be banned.

These statistics don't suggest to me that we should prohibit aerotow of
CG hook only gliders in the US. A significant proportion of the single
seat gliders here only have CG hooks, as some of the European
manufacturers charged a fairly hefty premium to put in a nose hook until
recently (if they offered them at all), and, well, a lot of glider
pilots are kind of cheap.

As for the other side of the Atlantic, it would be interesting to see
some actual statistics...

Marc

On 6 Jan 2004 20:01:17 -0700, (Mark James Boyd)
wrote:

OK, be prepared for me to completely change my tune. Are you guys
telling me the manual says that if it has only a CG hook, you can
aerotow with it, but if both hooks are present, the manual
prohibits aerotow on the CG hook for the ASW-27? And the
W&B limits and CG hook locations are identical for both
gliders?

Exactly.
The early 27's (as well as 24's, and probably all other glides that
are currently being produced in Germany) were only equipped with a CG
hook.
We retro-fitted one of our two DG-300's with a nose hook in order to
make it flyable for student pilots again who had been flying it safely
in aerotow the year before, but suddenly were forbidden to aerotow it
due to the new rules that demanded a nose hook for student pilots.


Sounds like removing the nose hook just to "legally" aerotow
off the CG hook is a ridiculous paper shuffle hassle...

More or less. If the nose hook was installed when the ship was
delivered, it must stay installed (yet some pilots seem to have found
an agreement with their inspector to remove the nose hook).

And yes, I did read the reasons why one might want to remove it.
Hmmm...so much for the manual, eh?

More or less.
The fact is undisputed that the nose hook indeed makes aerotows a
little easier and safer, therefore a nose hook definitely is an
improvement... but this does not mean that a CG hook per se is unsafe.

Bye
Andreas

Marc Ramsey wrote:

That left 9 in which a glider high and out of position pulled up the
tail of the towplane causing it to crash. Of these, 3 very likely had
CG hooks (Std Cirrus, Open Cirrus, Ka-6E), 2 likely had nose hooks
(G103C and 1-26), and the remainder either the glider type was not
stated, or may have had either type of hook (Twin Astir).

Very interesting numbers. Too bad we don't know what proportion of
launches are nose-hook or CG hook, then we could see if one was
over-represented.

The thing that struck me about these accidents was how many of them were
due to the pilot fiddling with an open canopy, or inadvertently deployed
spoilers. If the pilots simply payed attention to flying the aircraft,
most of the above would never have happened. The other thing that is
clear is that those freakin' Schweizer towplane hooks are a menace to
tow pilots, and *should* be banned.

Amen.

These statistics don't suggest to me that we should prohibit aerotow of
CG hook only gliders in the US. A significant proportion of the single
seat gliders here only have CG hooks, as some of the European
manufacturers charged a fairly hefty premium to put in a nose hook until
recently (if they offered them at all), and, well, a lot of glider
pilots are kind of cheap.

The US might have less trouble with CG hooks than a country where aero
tow isn't as common.

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

Eric Greenwell
Washington State
USA

Chris Rollings wrote:
I am a staunch defender of anyone's right to risk his
or her own life in pursuit of any goal they hold dear
(including saving money). In launching on a C og G
hook you are risking the tow-pilots life more than
your own, and this I will not defend.

I personally prefer to fly aerotow with nose hooks, and both of the
gliders I now fly have them. But, I'm not convinced that anyone has
provided actual evidence of an observed safety issue with CG hooks.
Some numbers like these for, say, the past 20 years in the UK:

How many aerotow operations were there per year?
What percentage of aerotow operations used CG hooks?
How many aerotow upset accidents were there during that period?
What percentage of the aerotow upset accidents involved CG hooks?

If these figures aren't available, is the use of CG hooks being
discouraged based simply on the assumed lack of positive longitudinal
stability during aerotow?

Marc

On Wed, 7 Jan 2004 03:01:17 UTC, (Mark James
Boyd) wrote:

: Are you guys
: telling me the manual says that if it has only a CG hook, you can
: aerotow with it, but if both hooks are present, the manual
: prohibits aerotow on the CG hook for the ASW-27?

Under what circumstances would one tow with a CG hook when a nose hook
was available?

Ian
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