At 12:33 22 February 2014, GC wrote:
On 22/02/2014 20:21, Chris Rollings wrote:
The time difference to go from low tow to kiting compared to high tow
to
kiting is about 1 second - try it at safe altitude.

I read your posts carefully, Chris and I don't recall any low tow
experiments. The closest was your description of the glider with the
PA-18 as "in a slightly low normal tow position" which I take to be high
tow for you. So I don't think you speak with any special authority on
low tow. Correct me if I'm wrong. I have a lot of experience with low
tow and your 1 second is wrong unless a normally competent pilot intends
- suicidally - to deliberately go kiting. To use your own words: it's
"...something unlikely to occur accidentally, even with an inexperienced
glider pilot."

...As observed you can't
take-off in low tow so the highest risk time, just after take off when
the
combination is accelerating, is exactly the same.

....and no worse. And needs the same training whether it ends in high or

low tow.

The transition from
normal tow to low tow, early in the climb, puts the glider into the
turbulence of the prop-wash which may well cause the, less than one
second,
loss of control which is all that is needed to start the kiting.

You originally said 2 to 3 seconds from high tow so it's got to be at
least 4 seconds from low tow on your own figures above - but we won't
quibble about trivia. All I can say is that it's not our - very
considerable - experience. You're welcome to learn nothing from anybody
else (a very English habit, that) but in that case let's drop the
pretence that kiting is a seriously difficult problem to solve and
worthy of vast quantities of speculative rubbish.

It takes 2 - 3 seconds from high tow and as you say probably 4 seconds from
low tow, but after the first 1 second it's inevitable unless the release is
pulled then and that is equally true of low and high tow. May I suggest
that you take a light weight glider up on a C of G hook and, at a safe
height, in low tow, pitch the glider up about 25 degrees and observe what
happens, then report back on here.

The point that is overlooked is that, faced with a totally unexpected and
very alarming picture, pilots do not react in one second or even two and
when they do react the physical act or reaching for the release and pulling
it takes at least a couple more seconds, probably more - too late, it's all
over. Taking off with a hand on the release might just help, though I
doubt it would help enough and I'm pretty sure it would cause significantly
more accidents with unintentional releases.


Finally,
low tow on a glider with a C of G hook, leaves the rope wrapped around
the
side of the cockpit, not really a good idea and C of G hooks are where
the
danger lies.
The cheapest mechanical solution is, fit a nose hook to any glider that
is
going to be aerotowed.

That's why aerotow is only permitted on nose hooks in Oz. It's the
obvious counterpart of low tow. You don't travel much, do you? I have
done low tows on a CG hook (at Hus Bos) and they were a non-event.

My best estimate of low level kiting fatal/serious accident frequency
is
of
the order of one in a million. "Tens of thousands of aerotows" is not
a
big enough sample to draw conclusions.

Mmm. Statistics aren't your strong point, are they Chris?

Why do you say that?


I must say I'm quite stunned by your negativity re low tow, especially
if you were once CFI at Booker. I read and was impressed by your tests.
You seemed to take the problem really seriously. This is the reality:
there is a simple solution (not perfect) available immediately to
minimise the risk of kiting. If it's a serious problem, it should be
implemented while the fancy gimcrackery is developed and I'm surprised
you're fighting it. Otherwise, it's not a problem you actually take all
that seriously. As you said, one in a million. Australia thinks it's
serious enough to have actually done something. It appears you don't.
That's fair enough, it's your call, so let's forget all the bull**** and
talk about something else.

I have always taught low tow as useful for avoiding a slack line when
towing cross-country, I'm not against it. I simply don't believe that it
significantly, if at all reduces the risk of a kiting incident. I would be
pleased to see a description of some flight tests that proved me wrong.


GC


At 07:58 22 February 2014, GC wrote:
On 22/02/2014 16:17, Alan wrote:

...You don't get kiting if you fly normal "high" tow behind the
towplane,
if you remain in control.

If you don't remain in control, starting from low tow is not
going
to
make a lot of difference.

Experience (tens of thousands of aerotows) shows there is an enormous
difference. The inadequate control and time to go from high tow to
kiting is orders of magnitude different from that required to go from
low tow to kiting. In fact, I've never heard of that ever happening.
Even with low time students. Kiting from high tow, however, is
apparently so common as to need a whole new system of electronic
whizzbangery and gallons of bandwidth to stop.

If the tug has just lifted off, being in low tow sounds a bit
difficult,
but that would be a particularly hazardous time.

Yes. Liftoff is a time to be wary and we train accordingly.
Nevertheless, all I can say is that low tow has prevented kiting
accidents for many years. But don't take my word for it, keep this
ridiculous discussion going with another screwball idea for pivoting,
autoswivelling, pitch-sensing, stick-following nonsense.

If the issue is serious - as it was in Australia - flying low tow will
solve it. If it isn't - see my previous post.

GC



As for automatic methods to mitigate the problem, perhaps the
solution
is not to modify tow planes, but to modify gliders. If the glider is
in a very high pitch attitude on tow, it might be a good time to
automatically
release.

Another modification might be to attach the tow rope to the top
of
the
glider.
This would cause the tow force to pitch the glider down.


Is this more of a problem when folks try to tow a slow glider
like
a
2-33 at
high speeds?

Alan