CG hook on aero tows??

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.

At 09:18 07 January 2004, Marc Ramsey wrote:
Chris Rollings wrote:
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.

Marc Ramsey wrote
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

I hate to agree with Chris Rollings but he sums it
up quite well.

The questions posed by Marc Ramsey, difficult to obtain
that no one will even try, so they will not get answered.

Whatever we write here, I cannot see the owners of
C of G only aircraft rushing out to retrofit a nose
hook. Having towed on both, the worst being an Olympia
2B with only a C of G hook and a powerful tug, I prefer
the nose hook every time.

Some years ago, mid 1908’s I believe, the Australian
Gliding Association, following a number of tug upsets
produced a very graphic illustration showing the various
stages of a tug being upset by a glider on tow, wherever
the hook. It clearly and simply illustrated the difficulties
this caused the pilots at each end of the combination.


C of G hooks merely increase the likely hood of this
happening with an inattentive pilot.

The short answer is educating the pilots on the particular
hook to be used and hammering home the consequences
of inattention to all.

The Australian poster should be displayed at all gliding
sites.

To try to answer the question that started this thread,
the B4 pilots problems could be solved by asking the
tug to accelerate a little faster from the start, having
due regard to the problems this may cause. IE Things
may go wrong even quicker!

Dave

Karel,

I think you may have paid the extra for the belly hook
not the nose hook. I am on the Schempp-Hirth waiting
list at present and when I enquired about the cost
of adding a nose hook I was told that all gliders had
the nose hook as standard and that the additional cost
option was for a belly hook. They would build a glider
with the belly hook only for no extra cost on special
request but it would be placarded as not certified
for aerotowing.

John Galloway

At 10:30 07 January 2004, K.P. Termaat wrote:
Just recently we (my son and I) bought a Ventus-2cxT.
Nice glider. My first
flight with it was on airtow. Used nosehook which we
paid for seperately. No
tendency of dropping a wing. However very nervous on
pitch during the tow.
Not a pleasure and was happy to release. I guess a
novice would certainly
have had problems with it.

So one may say that each glider has its own way of
being pulled into the
air. Being towed is certainly a safety issue. So I
wonder why not everybody
concludes that for airtows nosehooks should be mandatory
and CG hooks should
not be allowed. We are talking about money I guess.
We spent many thousands
of euros on the glider itself and try to save some
euros in not having a
nose hook installed and still like to take off in an
airtow. To my humble
idea our lives and especially those of towpilots are
to valuable to run an
additional risk of not using a nose hook in air tows.

Karel, NL

I am not a sufficiently expert statistician to be certain, but I think
the UK data leads to two conclusions about tug upset fatal accidents:

1. There have been too few such fatalities - I think about 6-10 over 30
years - to draw conclusions with a high probablility of being certain of
the correlation - and I can't stipulate how "high" is high;

2. Notwithstanding 1. above, as far as I know 100 percent of UK tug
upset fatal accidents in the last 30 years happened with belly hooks. We
changed our procedures and recommendations before we could gather more
data and satisfy statistical pedants with some more fatalities which
might have improved the correlation calculations. Since the changes,
fatal tug upsets have almost entirely disappeared from the UK fatal
accident reports.

There have been tugging accidents other than upsets, with nose hooks as
well as belly hooks, but these do not affect such inferences as one can
draw from 1 and 2 above.

By the way, I fly mostly a Ka6E with a belly hook. I am very careful
not to kill my friends who tug, being all too well aware of the danger.
One of the changes was to alter our preferred tow position, as has been
referred to by others, to only just above the prop wash - termed the
"low High-tow" position, IIRC. Before the changes, we normally kept the
glider at or slightly above the tug height once established on tow.

Chris N.

Chris,

Your wasting your breath in this thread - just listen
and learn from the wise ones.

John Galloway

At 19:30 07 January 2004, Chris Nicholas wrote:
I am not a sufficiently expert statistician to be certain,
but I think
the UK data leads to two conclusions about tug upset
fatal accidents:

1. There have been too few such fatalities - I think
about 6-10 over 30
years - to draw conclusions with a high probablility
of being certain of
the correlation - and I can't stipulate how 'high'
is high;

2. Notwithstanding 1. above, as far as I know 100
percent of UK tug
upset fatal accidents in the last 30 years happened
with belly hooks. We
changed our procedures and recommendations before we
could gather more
data and satisfy statistical pedants with some more
fatalities which
might have improved the correlation calculations.
Since the changes,
fatal tug upsets have almost entirely disappeared from
the UK fatal
accident reports.

There have been tugging accidents other than upsets,
with nose hooks as
well as belly hooks, but these do not affect such inferences
as one can
draw from 1 and 2 above.

By the way, I fly mostly a Ka6E with a belly hook.
I am very careful
not to kill my friends who tug, being all too well
aware of the danger.
One of the changes was to alter our preferred tow position,
as has been
referred to by others, to only just above the prop
wash - termed the
'low High-tow' position, IIRC. Before the changes,
we normally kept the
glider at or slightly above the tug height once established
on tow.

Chris N.

The Australian Poster Dave refers to was actually line
drawings of the photo's taken of the tests I described.

Chris Rollings

At 10:30 07 January 2004, Dave Martin wrote:
At 09:18 07 January 2004, Marc Ramsey wrote:
Chris Rollings wrote:
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.

Marc Ramsey wrote
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

I hate to agree with Chris Rollings but he sums it
up quite well.

The questions posed by Marc Ramsey, difficult to obtain
that no one will even try, so they will not get answered.

Whatever we write here, I cannot see the owners of
C of G only aircraft rushing out to retrofit a nose
hook. Having towed on both, the worst being an Olympia
2B with only a C of G hook and a powerful tug, I prefer
the nose hook every time.

Some years ago, mid 1908’s I believe, the Australian
Gliding Association, following a number of tug upsets
produced a very graphic illustration showing the various
stages of a tug being upset by a glider on tow, wherever
the hook. It clearly and simply illustrated the difficulties
this caused the pilots at each end of the combination.


C of G hooks merely increase the likely hood of this
happening with an inattentive pilot.

The short answer is educating the pilots on the particular
hook to be used and hammering home the consequences
of inattention to all.

The Australian poster should be displayed at all gliding
sites.

To try to answer the question that started this thread,
the B4 pilots problems could be solved by asking the
tug to accelerate a little faster from the start, having
due regard to the problems this may cause. IE Things
may go wrong even quicker!

Dave

The Capstan and Olypia 2 really have 'compromise' hooks,
halfway between nose hook and C of G hook. Not quite
so good for winch launching but not as wildly unstable
on aerotow as a true C of G hook.

Not sure about the accident statisics for those days,
my close involvement only began when I started work
at Booker in 1970 - certainly there were aerotow accidents
back then.

Chris Rollings

At 10:48 07 January 2004, Silent Flyer wrote:

Chris Rollings wrote in message
...

SNIP
Let's look at the numbers. I will use the UK as an
example, since I have a fairly accurate knowledge
of
the statistics there, but the pricipals are the same
for any of the World's gliding nations.
SNIP

Chris

I learnt to fly at an all aerotow operation back in
1967 at the old
Leicestershire club at Rearsby. Training was on a Slingsby
Capstan and
pupils were then sent solo in an Olympia 2b, (in my
case after twenty seven
flights). These of course like virtually all gliders
of that time had only
CoG hooks.

What do the accident statistics say when comparing
that period with the
present day ?

Don Brown

Todd is right in every respect, at least one of the
aerotow upset fatals involved a largly winch launch
experienced pilot and the cicumstances he surmised.

Chris Rollings

At 15:06 07 January 2004, Todd Pattist wrote:
Eric Greenwell wrote:

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

There are a couple of things that might make the U.S.
experience a little different in view of our training
and
operating procedures and the different experience of
our
pilot base. Many/most U.S. pilots are unfamiliar with
winch
launching and are extremely uncomfortable with any
kind of
nose high attitude on launch. I have occasionally
wondered
if some 'kiting on tow' accidents might be related
to the
pilots control response in a situation that is dangerous
for
an aerotow, but not for a winch launch. Another potential
difference is the prevalence of U.S. training in the
venerable 2-33, which typically produces a very high
nose up
attitude as the roll commences and requires a strong
forward
stick to compensate.

Of course, despite those comments, we also experience
too
many towing accidents. The CG hook can be implicated
in more
than the kiting accidents, and I know several pilots
who
have purchased or retrofitted the nose hook after a
loss of
directional control during the initial roll on a CG
hook
aerotow launch.
Todd Pattist - 'WH' Ventus C
(Remove DONTSPAMME from address to email reply.)

Yes the pull can be enough to affect stability, that
was what the test I descibed demonstrated.

Chris Rollings

At 18:36 07 January 2004, Greg Arnold wrote:
Marc Ramsey wrote:



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?


Is the pull on a CG hook during aerotow ever great
enough to have much
effect on the longitudinal stability of the glider?
I have never
noticed such an effect, so I wonder if pilots who fly
from a winch (very
quick acceleration and doubtless a significant effect
on longitudinal
stability) are unfairly extrapolating their experience
there to the
aerotow situation.

Doubtless a nose hook is better for aerotow, but I
wonder if the alleged
advantages aren't being oversold by some posters to
this thread.

The point is not 'does a Cof G hook cause a glider
to pitch up on tow'. The point is that if something
(an accidental pilot input, or a gust not corrected
for immediately because the pilot in momentarily distracted)
causes the glider to pitch up, will it carry on pitching
further up of its own accord, stay it the attitude
it has reached, or start to pitch back down of its
own accord? If the first of those three, how easy
is it to stop it pitching up? In the tests on the
Ka8, it seemed to me to be (almost?) impossible to
stop it, once the pitch angle exceeded about 30 degrees.


Don't know about most of the other types mentioned
in this thread. I've flown most of them, but even
I didn't include 'simulated tug upset whilst aerotowing
on C of G hook' in my normal type conversion exercises
- I think I would have found it hard to get a tow after
a while if I had.

Chris Rollings

At 00:00 08 January 2004, Mike Borgelt wrote:
On Tue, 6 Jan 2004 18:39:17 -0000, 'W.J. \(Bill\) Dean
\(U.K.\).'
wrote:

There have been several fatal 'aerotow upset' accidents
in the U.K. where
it seems certain that towing on a hook intended for
winch launching was a
factor.

These include:
Lasham new year 1963/4 Auster towing a Ka 6cr or Skylark
2 (I forget which),
Tug at Aboyne towing a Ka 6e,
Tugs (Super Cubs) towing K 18s at Portmoak and Dunstable
(within a few
months of each other), this led to the tests by Chris
Rollings, Verdun Luck
and Brian Spreckley at Booker see
http://www.glidingmagazine.com/ListF...Dtl.asp?id=327
.

Will that do, or how many others do you need?

So that is 4 in 40 years.

I think we've managed to kill that many towplane pilots
in Aus in the
last 15 in mid airs. At least one, maybe more would
have had a good
chance of survival if he had had a parachute. Something
that still
isn't required here.

The common link with the upsets mentioned seems to
be high wing wooden
gliders of low wing loading with deep fuselages. These
may be prone to
pitch up.

How long were the ropes in these situations?

Were there other circumstances that contributed?

Could they have been compensated for?

Any glider which launches well on a cable using the
aft launching hook, will
do the same behind a tug maybe killing the tug pilot
in the process. If
you really think that the glider pilot can control
or stop this process once
it starts, READ THE ARTICLE LINKED ABOVE; I suggest
that the pilots who
conducted those tests were more experienced, more current
and just plain
better than you.

You are suggesting that on a winch launch with much
higher loads in
the cable that these gliders are not controllable in
pitch?

To my certain knowledge it is possible to fit a forward
hook for aerotow to
the ASW 15, 17, ASK 18, ASW 19, 20, and 22 and the
Pegase; the ASK 21 and 23
and I think later types were fitted with it as standard.
I don't know of
any examples of these in club (as distinct from private
owner) use which
have not been modified.

I once owned an ASW20B. The GFA required the nose hook
to be fitted.
The Scheicher factory job on this was pitiful. Nobody
who bought
gliders from this batch of 6 put up with it. The releases
were taken
out and glassed over. When finishing the area it became
apparent that
the skin had been distorted by the additional release
bulkheads.
I don't ever recall the 20B having the slightest tendency
to pitch up
on aerotow on the belly release.

I have no aversion to properly engineered nose hooks
like in
Glasflugel and Schempp gliders but poorly designed
retrofits are a bad
idea particularly when no testing has been done on
that particular
type to see if indeed the 'solution' is effective
or even necessary.

The BGA considers 150 foot ropes acceptable. I consider
these
dangerously short, 200 feet is more like it with around
240 to 260
being much better.

Now consider this::

The world's politicians and bureaucrats are forever
looking for ways
to meddle in our lives to keep themselves in jobs.
If we place
requirements on our own operations (Like compulsory
nose releases)that
are not firmly founded in proper testing and rational
analysis we
weaken our case in resisting the idiot requirements
that come in a
never ending stream from these people.

I've yet to meet anyone who has flown on a 250 foot
rope who hasn't
admitted it was easier than on shorter ropes. When
I aerotow I want to
go soaring for maybe several hours and maybe the enviroment
on the
ground was stressful due to heat, humidity etc. I really
don't need a
5 minute adrenaline thrill to begin a cross country.
I would like
tows to be a non event. Longer ropes and tow pilots
who don't try to
thermal or do other sudden manouevers all aid in this.

The scariest tow I ever had was in my Salto (with nose
release) behind
a tow pilot who was not paying attention and who pulled
back hard on
leaving the ground as we encountered a gust leaving
me dangling low
from the end of the rope with decreasing airspeed.
Followed by a hard
push just as I was climbing slowly back up into station(low
tow)
leaving me very high followed by another hard pull
which put me very
low again wherupon I released and did a 180 back to
the strip.
Probably my shortest ever aerotow flight, closest to
disaster and on
the 130 foot or so ropes that were fashionable at the
time. I never
ever want to do this again. It was 30 years ago and
I remember it
clearly.
A rope twice as long likely would have made this a
non event.

The surprisingly easy tows were at Minden in an ASW20(belly
release)
through the rotor behind a 182. Long rope, no problem
at all.

Mike Borgelt