Another stall spin

On 9/13/2012 8:52 AM, Mark Jardini wrote:
I had an incipient departure just the other day. I fly an Apis M. In
deconstructing the event, I saw the nose dropping and not responding
to back pressure so I put the stick forward and it was all over in a
second.

Your response is "the universal ticket for departure control"...works
(rapidly/"instantly") in any glider, regardless of wing appurtenances.

I found this true even with "so notorious a departer" as the two 2-32's my
club has had over the years, one of which "always" departed enthusiastically
left wing low if Joe Pilot insisted on ignoring prior aerodynamic warnings.
Merely relaxing aft pressure completely eliminated its "departure thrills", to
the point that a marginally aware accompanying pilot might never even be aware
what had transpired.

Another good reason to be primed to "relax back pressure" is gust-induced
"significant separation" absolutely halted upward progress in my 15-meter
unballasted ship when it occurred - for ~30 seconds, as measured by altimeter
and sweep second hand. (Gravity never stops!) A "calibrated butt" could easily
feel this effect, while a calibrated ear could actually hear it as well. And,
of course, it could be felt throughout the plane's control system. Awesome way
to depress your average climb rate!

Maybe pilots in the intermountain west get more unbidden opportunites to
practice "the stick bump" while thermalling, simply because in my experience
on the downwind side of the Continental Divide, gust-induced incipient stalls
are "the norm" during routine thermalling on days with any significant
westerly (which is to say most of them!).
- - - - - -

I think when the aircraft doesn't do what it should for the
input, there should be a reflex alternative action. Either flaps or
stick forward is probably ok. The stick feels more like it has more
authority to me.

In a fully established spin, flaps have to come off as you will likely
exceed the white arc in recovery.

The dicey scenarios are the ones where you have to think out what is
going on before acting. The whole thinking thing is easily derailed.

Mark


Good thinking!

Regards,
Bob W.

I think we need to make a very clear distinction between incipient spin and developed spin. The SSA has a bronze badge study guide of which one of the questions is... "What corrective action should be taken if, while thermalling at minimum sink speed in turbulent air, the left wing drops while turning to the left" The answer to this question is NOT apply opposite rudder. The correct answer is "lower the nose before applying opposite rudder and aileron pressure"

I have never practiced spins in a glider. I'm wondering, for those who have done so. Is it common to become confused as to which direction you are spinning? I practice spins in Condor and this often happens. I'm curious if Condor spin characteristcs are very realistic. Based on recovery procedures, I'm guessing not. Incipient spins happen a lot in Condor, especially with full water working narrow thermals. Full water makes it much harder to recover.

.... Aaron

On 9/12/2012 2:06 AM, BruceGreeff wrote:
Hi Eric

Sorry to be obscure - I think we actually agree entirely. Follow the
standard procedure until the spin stops.

I am sure you are way more experienced than I. So - free opinion and
worth every cent you paid.

Aviate first comment applies to thinking all the time - rather than
applying rote process.

In my experience - It helps to always try to have the objective in
mind when you do something in the cockpit. In a departure from
controlled flight, that is turning into "something" the first thing
to do is to correct the condition that caused the departure. In the
instances we were discussing that is a stalled wing. If your primary
objective is to un-stall the wing then, again in my limited
experience, the manual on a flapped ship says something along the
lines of "reduce the flap setting".

So my thinking is first move flaps to neutral or negative as
indicated. This will reduce AoA, and MAY arrest the departure.

Then one should assess what the aircraft is actually doing.

If and only if you are simultaneously rotating about all three axes
with relatively stable speed and the G force is not increasing and
the other indicators unique to the type of aircraft you are flying
indicate that you are in fact spinning - then the logical thing to do
is to initiate the standard spin recovery.

If you are in a steeply descending turn with airspeed increasing and
experiencing elevated G load, you are probably in a spiral dive.

If you are - like Bruno - simply in a bit of a slip, with one wing
low and airspeed and control normal, well straighten up and fly
right.

In the vast majority of gliders the reduction in AoA from flap change
will arrest the departure. The aircraft may be at an unusual
attitude, but it is fully under control. (as was the case in the
video)

Following a rote spin recovery in this situation is irrational , and
with a flapped ship it may be especially dangerous. Many gliders
will accelerate rapidly enough that - especially if you have not
reduced the flap setting - you will exceed limiting speed for the
aircraft configuration and damage something. In at least two cases I
have seen this was at least a contributory factor in a fatality.

Therefore I advocate - first reduce AoA, by changing flap - that way
you have taken the action most likely to recover with the minimum
disturbance and very importantly, you have configured your aircraft
for the possible / probable high speed that will eventuate if you do
have to recover from a fully developed spin or spiral dive. And then
continue with the rest of the standard recovery process until the
spin is arrested.

Again I think we agree - the critical point for me is that in a
flapped aircraft the flaps should be the first control input, and
that the result of each input should be assessed lest you do
something inappropriate to the circumstances simply because it is the
next action on the standard recovery procedure.

It's my understanding from my flight manual that the flap reduction and
the standard spin recovery motions are to be applied simultaneously.
Applying the flap reduction first can work (at least, under some
circumstances), but it is not what is specified in the manual, and I
have had no problems by doing the two things simultaneously. Why wait to
see if the flap reduction fails? That will only increase the height lost
and allow the glider to go further into the spin.

As a thought - consider what might have happened with Bruno if he had
immediately centralised the controls without changing flap first.

I have not watched the video, but the standard spin recovery does not
include centralizing the controls (the ailerons - yes, the stick and
rudder - no). Had Bruno done standard spin recovery, my belief is the
glider would have recovered immediately, and he could have continued
thermalling with very little height loss or disruption.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)

On 9/13/2012 9:39 PM, akiley wrote:
I think we need to make a very clear distinction between incipient spin and
developed spin. The SSA has a bronze badge study guide of which one of the
questions is... "What corrective action should be taken if, while
thermalling at minimum sink speed in turbulent air, the left wing drops
while turning to the left" The answer to this question is NOT apply
opposite rudder. The correct answer is "lower the nose before applying
opposite rudder and aileron pressure"

Whether we're talking "an uncommanded (by Joe Pilot) departure" or "a fully
developed spin", neither can happen unless one wing is sufficiently above its
critical angle of attack that lift-reduction/increased-drag leads to loss of
lateral stability (hence the uncommanded wing drop). Anything serving to
maintain the more-stalled wing in that condition will also serve to maintain
(in a fully developed spin) or worsen (in the case of an uncommanded
departure) the condition.

Presuming Joe Pilot doesn't want the condition to worsen or continue, a useful
way to think of "corrective action" is to prioritize the sequence of potential
actions by those most likely to reduce the critical AoA ASAP. Then the SSA's
answer makes perfect sense. Why?

Recovery can NOT occur until the wings are both again flying (i.e. below their
critical AoA). (Understanding - and *believing* the preceding claim is crucial
to burning the proper corrective actions into one's noodle.)

While "instant opposite rudder" *might* prove useful (by slewing the nose
around and thereby potentially reducing the lower wing's AoA due to the
hoped-for velocity increase), success along those lines presumes sufficient
rudder authority and aerodynamic energy/conditions to halt-then-overcome the
rotational inertia of the already-/increasingly-rotating glider.

OTOH, reducing AoA directly via the stick is almost *guaranteed* to have "an
instantaneous effect" because gravity never quits, and - in this situation -
is working *for* you. Once you're unstalled, the rudder has a better chance of
assisting with recovery...
- - - - - -


I have never practiced spins in a glider. I'm wondering, for those who
have done so. Is it common to become confused as to which direction you
are spinning?

Making no claims to be a spinning expert, and noting all my spins have been
upright (i.e. not inverted), I've never come close to being confused on spin
direction. Obviously (he sez! :-)) it IS possible to become confused, but I'd
guess most easily so in any simulator lacking "G-clues". Perhaps the real
world equivalent would be by entering a spin only after "sufficient preceding
aerobatics" to overwhelm Joe Pilot's experience base.

In "normal thermalling (and by extension, landing pattern) flight" when you
experience an uncommanded wing drop (meaning, possibly an uncommanded
departure/incipient spin), between a) the obvious "falling to one side"
sensation, and b) the rotation of the world beyond the canopy, direction has
always seemed to me immediately obvious...and of course, you probably had been
cheating toward the spin direction with rudder, too, right?!? (Meaning, a
halfway aware pilot should already know "without having to think about it"
when he's in a situation predisposing him to an uncommanded departure, and
WHY!!! What may happen next - and in what direction - "should be obvious...")

The above presumes we're NOT talking about the possibility of "over the top"
spin entries. While they're possible - and demonstrable in some gliders -
they're not the ones that commonly kill in the landing pattern, nor are they
commonly experienced while thermalling. Key word being "commonly"...

Stated another way, "in real life" you're "almost always" going to spin the
direction you're already turning. "No confusion necessary!"


I practice spins in Condor and this often happens. I'm
curious if Condor spin characteristcs are very realistic. Based on
recovery procedures, I'm guessing not. Incipient spins happen a lot in
Condor, especially with full water working narrow thermals. Full water
makes it much harder to recover.

... Aaron



HTH!
Bob W.