How Low to Spin??

Marc Ramsey wrote:
Mark James Boyd wrote:
Marc Ramsey wrote:

No, I'm saying (based on experience) it's a lot easier to let yourself
slip (well, actually skid) into a dangerous uncoordinated turn from a
shallow bank, than it is from a steeper bank.

Hmmm...this could be true. It may be that rudder authority is pretty
good at low speeds, and with light foot pressures. At higher speeds,
the foot pressure required to really change the airspeeds dramatically
on the wingtips may make skids less likely to happen by mistake.

If one believes uncoordinated flight is the sole cause of stall/spin/spiral
close to the ground, then only rudder is the culprit. I don't think
this is the case...

It is far safer to be in a properly
coordinated turn with a 40 to 50 degree bank angle. Every glider I've
ever flown gives a much better warning of impending departure in a tight
turn, plus the visual (nose above horizon) and physical (G forces
slacking off) cues are much more pronounced.

The US Glider Flying Handbook recommends medium banks in the
pattern, and 1/4 to 1/2 mile pattern legs (distance from runway).
I'm gonna stick with this myself.

And how many pilots did this save from a spin? How many pilots
have died because of spins from the 40-50 degree bank angle vs.
the shallow bank angle?

Most pilots die spinning on the base to final turn, and they almost
always manage to do it from a slow shallow turn, rather than a slow
steep turn.

Hmmm...you made me look at the accident reports again. A third
possibility came up. In some cases it seems that the glider may
have never fully stalled, but simply overbanked, and the pilot
didn't stop the overbanking tendency, and went into a steep
spiral nose down.

There were 11 fatal accidents in the pattern caused by stall/spin/spiral
since 1990. One, on Aug 10, 1996, was simply a C.G. to rearward.

Aug 12, 01 bank, stall/spin, downwind to base, tight pattern
Jan 28, 01 60 deg left bank, 45 down, but ailerons were right turn
Oct 4, 96 45 deg bank, 60 deg dive
Jul 31, 96 sharp left turn, then steep descent
Jun 29, 96 steep left turn, stall
Sep 14, 95 left turn, stall during 180 after contest
May 21, 94 steep right turn, then spin
May 3, 94 flat skidding downwind to base, two month old pilot license
May 12, 91 left turn to final, stall
Sep 2, 90 180 deg climbing 180 after contest

One flat skidding turn, the others were in a bank. At least one
looks like an aileron spin (this can be done with feet off the rudders
completely, but is very hard to time correctly). Several don't
look like spins at all, but overbanking that led to a steep spiral
close to the ground. In others, it seems possible the steep bank was
after the spin entry, perhaps not before it.

Eric pointed out that past 45 degrees, many gliders just don't
have enough elevator to stall. This may be true, but it seems
at least some of these were overbanking, a dragging aileron,
and steep spirals instead.


But, hey, we can agree to disagree, as long as we're not in the same
glider...

Well, for now anyway, I can't see myself doing steep banks in the
pattern. And since the FAA says so, I'm gonna teach no more than
medium banks, and mild or moderate roll rates. At the recommended
pattern size, I don't see why this isn't sufficient.

I think we all agree that low and slow is no way to have a
long life...we just disagree whether most of these accidents
are caused by bad rudder(I don't think so) or by
coarse application of dragging aileron/overbanking...
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Mark Boyd
Avenal, California, USA