Nimbus 4DT accident 31 July 2000 in Spain.

The book says it should be red. And as long as I'm operating my private
ship, it's me who is responsible for which weak link I ask for. Launch
marshals may comment on that, but not decide. Winch drivers are told which
glider is on the other side of the rope, and when they should start to pull.

I have seen (from the ground) quite a couple of critical situations
resulting from fatigued weak link breakage, and I prefer to watch angle of
attack and speed, and pull the knob myself if necessary. And even if the
book doesn't like it, that even works while being launched into thermals or
Mistral rotors.

--
Bert Willing

ASW20 "TW"


"Ian Johnston" a écrit dans le message de news:
dzZo7CxomoOm-pn2-DhT3lGVC8vpw@localhost...
On Tue, 5 Jul 2005 10:27:40 UTC, "Bert Willing"
wrote:

I take of with my ASW20 on a black link. And it's not the winch driver
who
decides about this.

If that is the correct link for the glider, then fine. If it's not,
and I were either launch marshall or winch driver, then I can assure
you that I, personally, would have nothing to do with launching you.

The correct weak link for an ASH-25, as specified by the designer and
manufacturer, is brown, 850dN.

Ian


--

On Tue, 5 Jul 2005 12:45:41 UTC, "Bert Willing"
wrote:

The book says it should be red.

Which is 750dN, and you are launching with black, which is 1000dN.
That 250dN (33%) extra probably represents around 50 - 75% overload at
the wing fuselage junction. With all due respect, that's an insane
risk to take. Would you fly your glider with a cockpit load or ballast
250kg above the maximum permitted? Would your insurance company let
you? Would your national aviation authority let you?

And as long as I'm operating my private
ship, it's me who is responsible for which weak link I ask for.

Indeed, but as long as you are being launched by other people it is
their responsibility to assess your request and, if it's unsafe,
refuse it, just as it would be their duty to refuse to launch you if
you were drunk, or if your airbrakes were open.

Launch
marshals may comment on that, but not decide.

On the contrary, I believe that launch marshalls /should/ decide.
Nobody should be complicit in dangerous behaviour of this sort.

I have seen (from the ground) quite a couple of critical situations
resulting from fatigued weak link breakage, and I prefer to watch angle of
attack and speed, and pull the knob myself if necessary.

Well good luck - and here's hoping that by the time you pull the knob
the hook (and wheel on an ASW20?) isn't on its way to the ground along
with sundry control connections. That's if a good unexpected bump on
the way up hasn't taken your wings off.

Ian

First of all, if the weak link breaks, the overload would be 33% (I don't
know what you do to get 50-75%).
Secondly, the point is not to get the weak link breaking at all. As long as
you stay within the limits of max winch tow speed, the overload is zero.
You might be not aware, but there is a good number of clubs who don't use
any weak links _at all_ (or launch marshalls...).

And I stand my point - it is my responsability to deal with my security, my
insurance and my legal authorities. Good luck? Go tell that to those who had
an accident initiated by a weak link failure. After 25 years of flying, I
still have to learn about a case of structural overload during winch launch.
However, I can accept that if I don't fly my glider, that I am imposed to
the owner's rules.

--
Bert Willing

ASW20 "TW"


"Ian Johnston" a écrit dans le message de news:
dzZo7CxomoOm-pn2-8g13dep07KYM@localhost...
On Tue, 5 Jul 2005 12:45:41 UTC, "Bert Willing"
wrote:

The book says it should be red.

Which is 750dN, and you are launching with black, which is 1000dN.
That 250dN (33%) extra probably represents around 50 - 75% overload at
the wing fuselage junction. With all due respect, that's an insane
risk to take. Would you fly your glider with a cockpit load or ballast
250kg above the maximum permitted? Would your insurance company let
you? Would your national aviation authority let you?

And as long as I'm operating my private
ship, it's me who is responsible for which weak link I ask for.

Indeed, but as long as you are being launched by other people it is
their responsibility to assess your request and, if it's unsafe,
refuse it, just as it would be their duty to refuse to launch you if
you were drunk, or if your airbrakes were open.

Launch
marshals may comment on that, but not decide.

On the contrary, I believe that launch marshalls /should/ decide.
Nobody should be complicit in dangerous behaviour of this sort.

I have seen (from the ground) quite a couple of critical situations
resulting from fatigued weak link breakage, and I prefer to watch angle
of
attack and speed, and pull the knob myself if necessary.

Well good luck - and here's hoping that by the time you pull the knob
the hook (and wheel on an ASW20?) isn't on its way to the ground along
with sundry control connections. That's if a good unexpected bump on
the way up hasn't taken your wings off.

Ian

Bert Willing wrote:

First of all, if the weak link breaks, the overload would be 33% (I don't
know what you do to get 50-75%).
Secondly, the point is not to get the weak link breaking at all. As long
as you stay within the limits of max winch tow speed, the overload is
zero. You might be not aware, but there is a good number of clubs who
don't use any weak links _at all_ (or launch marshalls...).

And I stand my point - it is my responsability to deal with my security,
my insurance and my legal authorities. Good luck? Go tell that to those
who had an accident initiated by a weak link failure. After 25 years of
flying, I still have to learn about a case of structural overload during
winch launch. However, I can accept that if I don't fly my glider, that I
am imposed to the owner's rules.

Interesting. I find it odd that German rules, which are often clearly more
strict than other soaring environs, would allow this departure.

Frank

On Tue, 5 Jul 2005 16:35:18 UTC, "Bert Willing"
wrote:

First of all, if the weak link breaks, the overload would be 33% (I don't
know what you do to get 50-75%).

I said already. The overload on the aircraft as a whole is 33%,
However, that's a lot more than 1.3G structurally, because at 1.3G
much of the applied load is on, and then balanced by, the wings.

Secondly, the point is not to get the weak link breaking at all. As long as
you stay within the limits of max winch tow speed, the overload is zero.

Except you can stay within that limit with 250dN load more on the
winch hook and the wing attachments than the designers of the aircraft
thought safe.

Would you fly with 250kg of unofficial extra ballast in the fuselage?

You might be not aware, but there is a good number of clubs who don't use
any weak links _at all_ (or launch marshalls...).

Then they are idiots.

Ian

On 5 Jul 2005 17:11:09 GMT, "Ian Johnston"
wrote:

Secondly, the point is not to get the weak link breaking at all. As long as
you stay within the limits of max winch tow speed, the overload is zero.

Except you can stay within that limit with 250dN load more on the
winch hook and the wing attachments than the designers of the aircraft
thought safe.

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.

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.

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.

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.



Bye
Andreas

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

In article ,
"Bert Willing" wrote:

I have seen (from the ground) quite a couple of critical situations
resulting from fatigued weak link breakage, and I prefer to watch angle of
attack and speed, and pull the knob myself if necessary.

With all due respect, Bert, if a weak link breakage creates a "critical"
situation, then the pilot has a training issue which needs to be
resolved. Sounds like some cable break practice is in order.

A launch isn't supposed to be a hazardous maneuver. If there's -any-
stage during the launch where someone wouldn't be comfortable with
the cable breaking, they need to find an instructor and get some
remedial training.

- mark