(re: negative G)
the key was to relax
Correct. When you start doing aerobatics, the first
thing you learn is to tense up before you do a maneuver,
to keep the blood up to your brain.
That's good for pulling on the stick, but really bad for
pushing on the stick. If you grunt before a push, you're
really going to pressurize your poor skull with blood.
You want to set up the cockpit so that you can totally
relax before a push, to keep your blood pressure as low
as possible. The little jets that I fly, for example, have very
nice stirrups to keep your feet on the rudder pedals under
negative G. And you want your lap belt insanely tight,
and your shoulder harnesses reasonably tight. Tiny
details, like your sunglasses and mike boom moving
around under -ve G, need to be addressed. Your headset
must be tethered in some manner. I like the perrone
mesh "snoopy" helmets, but some people use chin
straps. Heck, a line of duct tape will even do it!
Positive G is great fun. It's sort of like lifting weights.
Once you get onto the "grunt", you can rapidly increase
the +ve G that you pull: 2, then 4, then 6, then 8, then 10.
A guy I know pulls +11 and pushes -7 on every flight.
He's broken every part of his Pitts, and reinforced it.
Negative G is really strange. You must build the -ve G
very slowly, to avoid really screwing yourself up. Your
blood pressure soars to insane levels, so if you have any
kind of flaw in your brain - aneurism, etc - you will find
it right away. If I overdo it, I blow blood vessels in the
skin on my face, esp underneath my eyes. Looks really
weird.
But the real danger of ramping up the -ve G too fast
is your inner ear - the wobblies. No one knows much
about them, because the western military doesn't do
-ve G, and the civilians that get the wobblies don't
want to talk about it, and have their medicals pulled.
Start with -1G. Roll upside down, a 2 pt roll, and stay
there for a bit. Try to figure out - attitudes and movements -
which pitch attitude you need to maintain altitude. Common
error is to not push -1G and to lose altitude. A little bit
of nose down trim can help reduce the stick push force.
Obviously this is speed and aircraft type (flat bottom wing?)
dependent.
Ok, so try to fly straight and level inverted for 10 seconds,
then 20 seconds, then 30 seconds, hesitating during that
2 pt roll. Obviously you need to worry about aircraft systems
limitations. Not all aircraft can tolerate indefinite -ve G.
You're going to get disoriented upside down. You are
going to get lost. Seriously. Best thing you can do, is
after taking off, is roll inverted and navigate to the
practice area and back again. It's like learning to fly
all over again.
Some level inverted turns are a good idea. Start with
30, then 45, then 60 degree inverted turns. Remember
to co-ordinate with OPPOSITE rudder. It is really easy
to slip/skip inverted turns. Some people install inverted
balls (inclinometers). Watch the altitude! It is really
easy to spiral dive out of inverted steep turns.
60 degree inverted turns is -2G, which is getting better.
You want to start with -1G, then -1.5G, then -2G, then
-2.5G, then -3G, etc. If you go right to -6G you are NOT
going to be a happy puppy.
Another exercise, once you can fly inverted, is to push to
45 up, hold it for a moment, then level off inverted again
at a higher altitude and slower airspeed. Pause, then let
the nose drop to a 45 downline and push level again.
This is really excellent practice. One very simple maneuver
I like is max airspeed at the surface, and pull for an inside
1/2 cuban-8. But instead of 1/2 rolling upright from the
resulting inverted 45 downline, push to level inverted. Or,
keep pushing to a 45 inverted upline, and do a nice 1 1/2
roll to the upright 45.
Once you have mastered the inverted pushes to 45, time
to take the next step to the outside 1/2 cuban-8. Dive
for some airspeed. 1/2 roll inverted, and push through the
vertical - lots of right rudder required, esp with a metal prop -
to the 45 upright downline. Call it quits there. Practice
until you've got it nailed, no spiralling. If anything goes
wrong, you are going up with decreasing airspeed which
is good for the Vg diagram - you will "fall upwards"
Once you master the outside 1/2 cu-8, time to continue
the push for the complete outside loop, which is interesting
because your altitude is going away fast, the airspeed is
increasing, and the negative G is building up fast. This is
a much more dangerous maneuver than the outside 1/2 cu-8,
and care must be taken with the top gate - is the altitude
at least the minimum, and is the airspeed down below the
maximum?
Not many people master the outside loop. If you do, you
are in a pretty elite group of masochistic pilots!