[NSRCA-discussion] Snap

[Martin X. Moleski, SJ]

rjo626 at aol.com wrote:

> I forgot to mention... there was a discernable pitch break. Come to think of
> it, I've seen novice pilots stall and snap their models on take offs and
> landings with no pitch break... Is the pitch break only needed to stall the
> wing at flying speed?

In my opinion, no.

I learned about accelerated stalls from committing several
of them with an overweight and short-lived Fun One.  I didn't
round the leading edge of the wing sufficiently, among many
other mistakes that I made.

http://moleski.net/rc/b4aftr.htm

The inputs I was making that caused the accelerated stalls
that didn't damage the plane beyond repair were on landing
approaches at low speed.  I put in a little bit of aileron
to finish turning to final and the plane would snap in
the OPPOSITE direction.  For a long time, I thought it
was a radio glitch.  I couldn't see why left aileron
would make the plane snap right.  Now I know that the
downgoing aileron (in this example, the right aileron)
causes more drag that the other aileron, decelerating
just that wing and causing it to stall.  Because the
left wing was still flying, it threw the plane to the
right.

In a snap-roll, only one wing loses lift.  It is the
lift generated by the wing that is still flying that
throws the wing around.

A lifting surface can stall at any speed.  All you
need is excess angle-of-attack for that flight
regime.

I think that those who want a two-wing stall demonstrated
before the snap roll are mixed up about what stalling
contributes to the maneuver.

If you have a full-wing stall prior to the snap, you are
not going to find the plane continuing on the same line
on which it entered the stall/snap combination.

Instead, you'll have a stall/spin that leaves the plane
on a lower line.

I have had lots of planes that would snap with elevator-only.
Actually, I still have two of them: Combat Gremlins.  I have
to remember to pull gingerly with them.  And if they snap,
then I have to relax on the elevator to get them to recover.
So far, so good, but I've had a few close calls.

Requiring that a snap be produced by elevator-only seems
wrong-headed to me.  Some planes are more docile than
others.

				Marty