wrote:
Snap Roll.

I can't find the maneuver as it was depicted in the show either in my
Aerobat manual or in Neil William's book.

The snap roll in the Aerobat manual is what I was thinking of when
Bertie mentioned snap roll -- essentially an accelerated spin in the
direction of flight which involves inversion about the longitudinal
axis. Maybe there are other versions of snap rolls that don't "invert"
you about the longitudinal axis. I dunno.

Let me describe the P51 maneuver this way: Imagine a car driving along
a gentle curve being chased by another car -- the first car hits a
patch of ice and does a rapid 360, recovering in the same direction as
it started.

That's pretty much what the plane did (although it climbed some during
whatever kind of stall this was). Anyway now imagine the headlights of
the spinning car are machine guns: as the spinning car gets to about
270 degrees from original heading and the chasing car is starting to
go past the guns start to fire, continuing to fire as the first car
spins back to its orginal heading, nailing the second car the whole
way as it goes by.

The P51 was never "upside down" as you'd expect in a snap roll. Maybe
a spin out?

Bang -- down went the 109.

Speaking of airframes coming apart, I don't recall ever reading about
such things happening in WWII dogfights. It seems it would given the
complexity and fear of the situation. Did it happen much? Maybe that
kind of thing wasn't reported because it's not exactly a heroic end to
an aircraft / pilot.

I understand disintegration was far more common in WWI.

It's hard to visualize a 51 doing a maneuver as you describe it; in the
horizontal plane and flat. A normal snap in the Mustang would be done
with no fuel at all in the fuselage tank (if installed) at an airspeed
below maneuvering speed preferably with power on up to about 46 inches
with the prop set at 2700 RPM or above; applying full back stick and as
the stall breaks hard rudder and aileron together into the snap
direction desired; preferably to the left side which gives a torque
assist and really twists the airplane around in a hurry.
The real danger is that with all that yaw induced and the power up, you
can easily snap the airplane right into a spin with power on, which is a
REAL no no in this aircraft. If this happens, the only way to recover
the airplane is to pull the power immediately and begin a power off
recovery. The altitude loss for a spinning Mustang can be tremendous and
if you don't have some air under you, you could be in for a real short day!
I haven't seen this episode, but just from what you have said, it would
appear that the 51 was defensive and possibly turning with the 109 with
the 109 at his corner speed and the Mustang above his corner velocity.
(Corner speed for both airplanes is the airspeed for each where the
application of maximum available positive g produces a maximum turn rate
and minimum turn radius. If the 109 was at his corner and the Mustang
above the Mustang's corner, the 109 could arc in the plane of the 51's
turn and pull lead due to his tighter turn radius.
If this was the scenario, the 51 was defensive against an aggressive
shooter inside gun range and depending on the angle off and closure
rate, the 51 couldn't force an overshoot until he got the airplane down
to it's corner speed as above corner the 51 would be g limited. (below
corner he would be aerodynamically limited.
Yanking into a defensive snap roll to shake the shooter would be a
desperation maneuver as it would leave the Mustang with an extremely low
Ps with no further maneuvering potential due to specific energy loss. In
other words, meat on the table for the shooter.
Your description of how the Mustang maneuvered through this snap roll of
his is puzzling to me, as the normal flight path for the airplane would
be a snap basically without a change in the velocity vector. In other
words, the Mustang should have snapped all the way around and recovered
basically along the same flight path as its entry.
What COULD have happened if the 109 was in close was that the 51 snapped
a half snap with a very high nose attitude bleeding energy like a stuck
pig and the 109 could have over shot him low. Then as the 51 went
inverted, if he pulled back pressure, he just might have slewed the
aircraft back down and fired as he pulled, nailing the 109 as he went by
low.
Mind you, I'm just guessing here, but this would be one plausible
scenario :-))
Anyway, they tell me the show is well done. Enjoy it in good health.
DH

--
Dudley Henriques