Another stall spin

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.