"Andrew Boyd" wrote in message
om...
Dudley Henriques wrote:

established your lower and top gate parameters with a
g/altitude/airspeed profile.

We're wandering off topic, but yes, the concept of a "gate"
is sorely underutilized in the civilian aerobatic world.

Most of the people into civilian aerobatics aren't really
very big into physics, which is a pity, because aerobatics
is really just applied physics. So what happens most of the
time is that people experiment, trial and error, and figure
out what works, and what doesn't, hopefully at a high enough
altitude to recover from any mistakes.

The gate is a wonderful - I would opine essential - tool of
the low-altitude aerobatic pilot. You can program an airplane
similarly to a computer: same inputs, same outputs.

Let's take a reverse outside half cuban eight, for example.

We start level, pull to the 45 up (I personally prefer a tad
steeper, say 55 deg, to reduce x-axis requirements) and my gate
for the push over the top is 1500 feet of altitude and 80 mph in
the Pitts.

The gate altitude is what determines whether or not I hit the ground,
and the entry airspeed determines the G I must pull to obtain the
desired radius, because the velocity squared factor in the lift
equation is cancelled
out the the velocity squared factor in the angular momentum equation
at the stalling AOA. Neat, eh?

I can enter the maneuver faster (90 mph works nicely), and obtain the
same
downward radius by pushing more G on the way down, but it's easier on
the hardware to minimize the negative G. I can push over slower than
80 mph but
I don't like it much - I'm on the edge of a negative stall as the nose
pitches down, which doesn't feel good if it's a bumpy day - turbulence
can cause you to exceed your stalling AOA and you can get into a
drag trap as Cd exponentially soars, which isn't so bad going down
except that Cl is reduced.

Now, thinking about the start of the maneuver, we have to be able to
have enough potential energy to obtain 1500 feet and 80 mph, which
means that
I'd like to see 160 mph of kinetic energy at 250 AGL before I pull up
to
the 55.

The above really isn't very complicated. A very nice, simple
maneuver which has you exiting inverted at 250 AGL. Great view.

We do it in wingtip-to-wingtip formation, which is great fun.

Keeping in mind that with a negative AOA the effect of bank is
reversed, which is a phenomenon which gets more apparent as the
negative G increases. This means that if the wingman gets too
close to the lead and absent-mindedly slightly spirals away from
the lead (a harmless enough adjustment during a positive G formation
maneuver such as a loop) the high pressure on the top of the wing
will cause the wingman to move *closer* to the lead. It's best
to start out doing this stuff with nose-to-tail clearance for
this reason, but that increases the power delta required between
the lead and the wing because of the geometry during the vertical
maneuvers.

What great fun, though!

--
ATP www.pittspecials.com

See Aeroplane Monthly Feb. issue 2004 Article "Precision Decision" by
Col (now Gen) Des Barker. In it, Gen Barker covers fairly completely my
comments on the issues involved in high gating and it's effect on low
altitude vertical recoveries in the P51 Mustang. You might find the
article interesting.
Hope you guys are having a good season. I understand your dad was
Canadian Forces. Ask him if he knew Greg Bruneau. I flew the #10 bird as
a guest of the Snowbirds back in the 70's with Greg. Great guy, and a
wonderful team.
You two remind me of another father and son team from back when.
Don't know if you would remember Bill and Corkey Fornof. They put
together the first F8F civilian Bearcat team ever. Bill is gone now, but
Cork is still out there doing movies. Just emailed with him last week.
Doing fine!
All the best,

Dudley Henriques
International Fighter Pilots Fellowship
Commercial Pilot/ CFI Retired
For personal email, please
replace the at with what goes there and
take out the Z's please!
dhenriquesZatZearthZlinkZdotZnet