Nimbus 4DT accident 31 July 2000 in Spain.

I would question the 99% but surely theproblem is that
the 1% tend to be spectacular, and stings a bit.

At 02:06 24 June 2005, Andreas Maurer wrote:
On 23 Jun 2005 21:27:25 GMT, Don Johnstone
wrote:


Now here's a question. Given the answer above why when
the wing drops at the start of a take off run (winch
or aero-tow) does everyone almost without exception
try and lift the downgoing wing with aileron?

.... because it works in 99 percent of the cases?


Bye
Andreas

At 22:24 23 June 2005, Ian Johnston wrote:

snip

OK, so how would you described the difference. How
far does the wing
have to drop before /you/ use spin recovery rather
than stall
recovery? I'm genuinely interested: it's not supposed
to be a trick question in any way.

Ian

Its not about how far the wing has dropped, its about
whether the glider has started to rotate about the
dropped wing.

A wing drop stall has a lot of roll, some pitch but
not much yaw so your first action is to unstall the
wings by moving the stick forward.

If you've been slow to intiate the recovery, the glider
will start to yaw/rotate around the dropped wing and
once this has happened, your first action should be
full opposite rudder.

Ed

Edward Lockhart writes
Its not about how far the wing has dropped, its about whether the
glider has started to rotate about the dropped wing.

I think //that's// the answer the question was looking for.

If you've been slow to intiate the recovery, the glider will start to
yaw/rotate around the dropped wing and once this has happened, your
first action should be full opposite rudder.

Or the nose drop self-corrects the stall and the glider develops into a
spiral dive, in which case centring the controls and kicking in a
boot-full of opposite rudder is only going to delay recovery in the face
of a now rapidly approaching Vne.

Despite knowing the difference, being practised and familiar with the
characteristics, recovery and differences of both, it's the prospect of
mistaking a spiral dive for a spin in the adrenaline rush of the moment
that actually still scares me, despite the fact that I quite enjoy being
upside down in a glider



--
Bill Gribble
http://www.scapegoatsanon.demon.co.uk
- Learn from the mistakes of others.
- You won't live long enough to make all of them yourself.

A careful read of the Minden accident report will reveal what two very
experinced pilots did. The owner P1 was a famous glider pilot, and P2 was a
WW II trained Naval Aviator, also famous. Eyewitness reports (in the NTSB
report) stated that the rotation had stopped, the glider nosed down, then
the wings bent up to about 45 deg, then failed. The spoilers were found
actuated. The wings broke just outboard of the spoiler. The report refers to
an interconnction between the flaps and the spoiler, full spoiler also
produces full flap. The report also states time for the glider to accelerate
to Vne and Vd, indicating quite rapid acceration.

Further in the report it is indicated that the N4DM was certified by JAR
with exceptions for stall/spin behavior.

The implication is that the pilot(s) stopped the yaw, the glider dropped
it's nose and started accelerating as expected, and then at or above Vd,
spoilers were actuated, and the wings broke. Neither pilot got out.

The Spanish accident reports notes that the spoilers were found in the
locked position.

So, in summary, one pilot pulled the stick and broke the aircraft, and one
pilot pulled the spoilers and broke the aircraft. Faced with going through
Vd and breaking the aircraft, or trying to recover and breaking the
aircraft--maybe the best chioce is to jump while it's still intact?

--
Hartley Falbaum



"Robert William" wrote in message
...
At 02:06 24 June 2005, Andreas Maurer wrote:
On Thu, 23 Jun 2005 16:34:41 -0500, Bob Johnson
wrote:

Frankly spoken, pulling the stick back hard enough
to break off the
wings shows that the pilot was lacking the most basic
skills to fly
that bird.


well, possibly, but having got to the position where
you could either go through Vd or pull back what would
YOU do?

"Ian Johnston" wrote in message
news:dzZo7CxomoOm-pn2-QjvLCM11RPHz@localhost...
On Thu, 23 Jun 2005 21:27:25 UTC, Don Johnstone
wrote:

The answer is again simple and goes to recognition.
A stall with wing drop is just that and provided action
is taken to solve that problem, unstall the wing, the
a spin will be prevented. A spin is the result of failure
at the first step for whatever reason. Everyone properly
trained will know the difference.

OK, so how would you described the difference. How far does the wing
have to drop before /you/ use spin recovery rather than stall
recovery? I'm genuinely interested: it's not supposed to be a trick
question in any way.

Ian

What do we think about picking up the wing with rudder when in a stall with
wing drop? It's not the BGA method and I'm troubled by someone who
recommends it.

Stephen

Hmmm,

disagree in practice if not in principle. Bending and twisting moments
are much greater with increasing span. And a certain degree of symmetry
is assumed in measuring load limits. Contol inputs will significanly
change the lift distribution across the span (the squatcheloid). So
will twist in the wing. Al Blackburn's point, and I take it to heart,
is that design requirements don't look at failure modes under a variety
of assymetric lift distributions.

Consider the deployment of one spoiler cap during the spiral dive
recovery with deflected ailerons to recover from a steep bank.

The lesson I take away is to be very thoughful in applying the controls
under high load.

HL Falbaum wrote:

Further in the report it is indicated that the N4DM was certified by JAR
with exceptions for stall/spin behavior.

How so? You cannot get a glider certificated without adhering to all JAR
22 requirements.

So, in summary, one pilot pulled the stick and broke the aircraft, and one
pilot pulled the spoilers and broke the aircraft.

Wrong. Neither of the two would have done any damage. They broke the
glider by doing both things at the same time.

Stefan

Most important is recognition of prestall and initial departure. Since
the spin is a product of yaw moment at departure, you can prevent a
spin with coordinated controls alone. IE, modern aircraft must be
"helped" into the spin. (Put another way, the vertical stabilizer
creates enough yaw dampening to prevent autorotaion at stall so long no
pro spin control imputs are made. Since there are two yaw controls,
that would mean pro rudder or anti stick.) Thus, any prestall or
initial departure that is met with a release of back pressure and use
of coordinated controls to level the wings will produce the desired
effect before a spin or spiral dive can develop. Even if you choose not
to release back pressure, you shouldn't spin. Instead, you might find
yourself in a secondary stall. The longer it takes to apply these
simple actions, the less likely that it will produce an immediate
remedy, as the aircraft will continue into either a spin or spiral dive.

That would be sasquatcheloid assymetry, typically only encountered in
the high Sierra during the winter. It would be much more manageable (if
not entirely polite), if they hitched their rides in pairs.

Stephen ] writes
What do we think about picking up the wing with rudder when in a stall
with wing drop? It's not the BGA method and I'm troubled by someone
who recommends it.

I'm not sure I understand what you mean. Say, right wing drops in a
stall so this "method" would advocate kicking in left rudder as you move
the stick forwards to alleviate the stall?

Personally, the last thing I'd do when the aircraft was in a stalled
state, whether or not a wing drop was involved, would be to
intentionally use the rudder in an uncoordinated fashion. That is,
unless I actually wanted to spin.

--
Bill Gribble
http://www.scapegoatsanon.demon.co.uk
- Learn from the mistakes of others.
- You won't live long enough to make all of them yourself.