On Fri, 29 Jul 2011 00:12:35 +0200, Werner Schmidt
wrote:

in which part of the german world ;-) do you live?

Landau, Pfalz.



Think your statistics ain't representative ... :-)

I think they are - ours are similar to yours:
Perhaps half a dozen of more or less serious radio failures per year
in my club. Multiplay this probability with the probability of having
to call a pilot with an important advice, and chances are pretty small
that you are not going to reach the pilot in question. In my
experience 8 out of 10 radio calls worked.


[sigh] ... the same pilot ... :-/

Yup.
This guy has got a written checklist that is half a meter long (and
comprises at least 50 items) - yet things like "airbrakes closed and
locked" or "wind direction and strength" didn't make it onto the check
list... says it all, doesn't it?


So how he managed not to misunderstand the radio calls? ;-

Clear communication. Fortunately the guys on my home airfield are
disciplined enough that only one of them yells into the radio.

He's flying a Ventus - first case of extended aerobrakes was an
aerotow behind an FK-9 (this combination doesn't really climb anymore
if the glider's airbrakes are extended), the second case was a winch
launch (lots of water on board, of course)...........


I agree, radios are rather reliable, but your eyes are more. And under
bad circumstances a radio call may be poorly readable, misunderstood,
... so two simple signals (rudder wag / wing rock) should be safer. But
the accidents corresponding with them *did* occur ...

This is what puzzles me - I had thought that these optical signs were
extremely reliable (I had even thought about introducing them in my
club)... poor training of the glider pilots?


I don't have the solution. In my opinion one should:

1. give no signal before misinterpretation is not likely to be harmful
(i.E. before sufficient height is gained), whenever possible

2. if necessary, give a radio call (like "glider on tow, check your
airbrakes") /followed/ by the corresponding signal (rudder wag)

I'm not sure about rudder wag.
A precise radio call ("Delta 7989 check your airbrakes") is probably
less prone to trigger an immediate wrong reaction of the pilot than an
optical hint like rudder wag.

We once had a pretty low release of a glider pilot because the
towplane crossed some turbulence that rocked its wings...

I guess in the end it comes down to one point: Training.


Cheers
Andreas