Nimbus 4DT accident 31 July 2000 in Spain.

On Tue, 5 Jul 2005 18:24:21 UTC, (Andreas Maurer)
wrote:

As Bert already stated: As long as you stay within the safe speed
range, there is no way to exceed the stress limits of the glider -
simply there isn't enough lift available.

Um, must check, but am pretty sure angle of attack influences lift as
well...

Besides: I've never seen an ASW-20 break a weak link on my home
airfield. We were using the blue ones for the 20.

So why would anyone fly with a 33% over strength link?

Would you fly with 250kg of unofficial extra ballast in the fuselage?
That's not the point since this "unofficial ballast" never shows up if
the speed is kept in the safe range.

Unless the glider hits a gust, or the pilot pulls back too hard, or
the throttle of the winch suddenly shoots open or ...

One example of how a designer got it wrong is the SF-34:
Officially the only allowed weak link is the blue one. Unfortunately
with this weak link it is nearly impossible to complete a winch launch
- the weak link fails in the moment the glider starts to accelerate.
Solution: a stronger weak link, and careful speed control.

It's been ages since I did a winch launch in an SF34 and I really
can't remember much about it, but surely in that case the manufacturer
should be approached about changing the link officially, and issuing a
strengthening modification if required?

I wonder if Centrair changed this on the Alliance 34? I must check the
handbook - we have one at my current (all aerotow!) club.

Ian
--

If you fly at max allowed speed at Ca(max), even a gust cannot produce more
lift.

Just to get your numbers straightened out: The wing attachement is designed
for a maximum load of 5.3g, that equivalents in the case of an ASW20 beyond
1000kg of non lift producing parts (which are around 200 kg of mass).

Ad it's pretty clear that if you don't use a weak link, you need to watch
your speed _and_ your angle of attack.


--
Bert Willing

ASW20 "TW"


"Ian Johnston" a écrit dans le message de news:
dzZo7CxomoOm-pn2-sdKTFDfjQBvY@localhost...
On Tue, 5 Jul 2005 18:24:21 UTC, (Andreas Maurer)
wrote:

As Bert already stated: As long as you stay within the safe speed
range, there is no way to exceed the stress limits of the glider -
simply there isn't enough lift available.

Um, must check, but am pretty sure angle of attack influences lift as
well...

On 5 Jul 2005 21:16:28 GMT, "Ian Johnston"
wrote:


As Bert already stated: As long as you stay within the safe speed
range, there is no way to exceed the stress limits of the glider -
simply there isn't enough lift available.

Um, must check, but am pretty sure angle of attack influences lift as
well...

Indeed... but if you stay within the allowed speed range, you'll get a
stall if you pull too hard instead of overstressing the glider.


Besides: I've never seen an ASW-20 break a weak link on my home
airfield. We were using the blue ones for the 20.

So why would anyone fly with a 33% over strength link?

Ask Bert - he's got his reasons!


Unless the glider hits a gust, or the pilot pulls back too hard, or
the throttle of the winch suddenly shoots open or ...

Nope.
Either of these cases results either in a stall (pulling back too
hard) or overspeed... but does not lead to overstress. If you leave
the safe speed range, you pull the release... problem solved
immediately.


It's been ages since I did a winch launch in an SF34 and I really
can't remember much about it, but surely in that case the manufacturer
should be approached about changing the link officially, and issuing a
strengthening modification if required?

Indeed... but nothing has happened.

I wonder if Centrair changed this on the Alliance 34? I must check the
handbook - we have one at my current (all aerotow!) club.

Please do - I'd be interested if it's different for the Alliance 34.




Bye
Andreas