Bertie the Bunyip wrote:
Dudley Henriques wrote in
:


Didn't see the T6 roll on these links, but I think I remember the
crash. The 6 has a lousy roll rate and loses energy like a brick when
rolling and doing 2 in a row while down in the weeds can bite you in
the butt dishing out. More than one guy's lost a T6 this way.

Yeah, gave you the wrong one the sifrst time and couldn't get it when I
replied. Youtube seemed to be down or something. Still is. He just did a
single roll. It's pretty obvious from the get go that he hasn't got a
chance. By the time he's 90 deg left the nose is well down on the
horizon and he's commited to some major thrashinbg around on the
elevators and rudder to keep the thing goin which degenerates into
dishing out of the bottom in a big way towards the end. I am surprised
about your comments on it losing energy, though..
The Cobra; his best chance would have been to anticipate the torque
roll carrying all that MP and throttle back to idle before it torqued
out on him, then rolling to the nearest horizon after a mistake like
he made on the way up. In certain conditions you just don't get a
second chance in prop fighters.


OK, that makes sense. I get the feeling he was a bit surprised by the
time he reached the 3/8ths point of the loop and had no real plan out.
They do teach this nowadays, right? I was quizzed mercilessly about
escape routes from all sorts of fjukkups (all of which I had a good
answer for) by the FAA inspector that signed my waiver. Do inspectors
even do those anymore? Evrythng else seems to be done by someone else
these days.





Bertie


The Cobra was a perfect example of something every pilot who flies these
hot prop fighters in demonstrations should be told on the very first day
a check pilot works with them.
First thing you learn is that if you have to think about it, you
shouldn't be doing it...period! The second thing you learn is that money
and horsepower don't necessarily equate.
All of these guys have egos. If they didn't, they wouldn't be
demonstrating a prop fighter at low altitude. Ego is fine, but you leave
that on the ground or sooner or later it dies with you in these airplanes.
The first thing you do when you work with these pilots is take away that
ego and replace it with a deep respect for the airplane. Trust me, those
things can kill you quicker than a rattlesnake strike. Complacency will
kill you in prop fighters. The only way you can demonstrate a prop
fighter at low altitude and live to retire and talk about it is to
develop a keen respect for the airplane even more keen than any airplane
you have ever flown or ever will fly.
The next thing is consistency. Bob Hoover is alive today because of
consistency. Every maneuver he does is like it was cut out of a
template. His g profiles in his pulls and his top gate parameters are as
consistent as a finely tuned swiss watch. He seldom varies more than a
few feet in altitude and a few knots in airspeed, and his application of
g is totally predictable.
Predictability is the key to survival when demonstrating an airplane
like a Mustang, Spitfire, or a King Cobra.
There is a killer up there and it rides with you all the time. Neglect
it for only an instant and you're history. It's a game that has to be
played right the first time....every time....period!

You have an issue with these high powered prop fighters that you don't
have in any other kind of airplane when it comes to demonstration flying
at low altitude. This issue concerns what happens when these airplanes
get too slow, have too much angle of attack on the wing, and are
carrying high amounts of manifold pressure.
Just to give you some idea of exactly how powerful these airplanes are,
consider for a moment that a P51 will actually jump it's wheel chocks at
40 inches. You can't hold it!
Now, put one of the fighters on top approaching a critical low altitude
top gate after losing all your maneuvering airspeed to positive g on the
way up there; now throw in a high power setting and a mushing nose rate
as an 11 foot prop disk rotates through the air in pitch and what do you
get? You get a King Cobra severely being impacted by torque in roll,
severe P Factor with the prop sensing a relative wind; and as the prop
disk rotates; gyroscopic precession 90 degrees to the pitch axis. As if
all this wasn't enough, with the high power setting, he had spiraling
slipstream forces acting on the airplane in yaw as well.
As the man says, "this just ain't no place for a sane person to be"

The Cobra had all these things in play, and it really messed him up
badly from what I saw. He had all this mess going on at the same time.

It looked like he tried to salvage it, but instead of cutting the power
and rolling to the nearest horizon throttled back as he should have
done, then repositioning, continuing his routine by recapturing the show
line and continuing, he tried to stay with it and ride it out. The
result was a rolling yawing motion almost surely behind the max CL curve
with a lot of mush on the airplane. Naturally this worked itself out for
him as the wing recovered some workable angle of attack but by then it
was way too late. He had no g available that would recover the airplane
on the front side of a high speed stall before impacting the ground; a
classic coffin corner vertical recovery failure.

So Important is the issue of vertical recovery for demonstration pilots
flying WW2 prop fighters that I have written extensively on the subject
for two publications.
The titles are supplied here for anyone interested in this area of
flight safety.

1. "Zero Error Margin", the definitive study on air show accidents and
demonstration flying by Gen Des Barker of the South African Air Force

2. "Precision Decision" Aeroplane Monthly Feburary 2004




--
Dudley Henriques