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Old July 10th 03, 02:05 AM
Spencer Suderman
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I *think* Doug has just admitted to performing aerobatics while looking
at the instruments.....I have been using a technique that's been around
since man started flying. It involves using the gluteous maximus and
it's relationship to the ergonomic interface installed within the
cockpit of the airplane....

I like to perform barrel rolls when I take people for rides. It is not
very physiologically demanding while being very visually exciting. I
have gotten the g meter to read as high as +1.5 and as low as +/- 0
after much practice at my stick technique. I usually do the manuever at
+2 g's and +.5 g and it "feels" right.

-Spencer



DSowder wrote:
Seems to me that at the top of the roll, he would have had to be rolling at
a rate
sufficient to have centripital force equal to 2 g; such that when you
subtract the normal downward
1 g, there's a resultant 1 g left acting in the conventional direction



You're mixing force and acceleration. First of all, it is not possible to do a
barrel roll with a constant 1g, simply because an airplane is "pulling" 1g in
level flight. A barrel roll involves a climb, so at the instant of departure
from level flight, the "g" increases a bit, regardless of how gentle the
manouver might be. Similarly, near the finish of the barrel roll, the nose will
be down and must be brought back to level flight; that takes more than 1g,
since level flight itself is 1g.

That being said, the "g" the pilot talks about is what he sees on the "g"
meter, which measures the force resulting from acceleration in the direction of
the "z" axis. If the plane is inverted (and level) and showing 1g positive, the
actual acceleration toward the earth is, as you've surmised, 2g's, or 64 ft.
per second per second. But the resulting apparent force on the pilot and on the
g meter is (the result of) 1g. So, the g meter really measures force resulting
from acceleration, rather than acceleration itself. You clearly know how to
analyze this, so now that you know how a g meter works, it'll be easy.
Obviously, an airplane in level flight, at which time its g meter indicates 1g,
is NOT accelerating toward the ground at 32 ft. per second per second. Nor is a
g meter sitting on my desk, indicating 1 g. BTW, the g meter reads zero when
flying a vertical line up or down, and it reads -1 when flying straight and
level inverted.

This brings up an interesting observation that I made an evening or two ago
while practicing snap rolls and trying to snap with the minimum possible stick
pull (thus, minimum energy loss). When snapping on a 45 degree up line, more
stick movement is needed than when snapping on a level line. Why? Well, the
stick is pulled to load the wings to a critical angle of attack close to a
stall, so that when the rudder is kicked, one wing stalls (or nearly so) and
the other grabs a chunk of lift to autorotate the airplane. When on a 45 degree
upline at a constant airspeed (it's almost possible), the g meter reads only
.707 g (got my bifocals tuned up for that observation). Hence, it takes more
stick pull (motion, not force) to load the wing to the critical angle of
attack, since the angle of attack was less to start with.

Nuff said, maybe someone who is actually an expert will chime in...

Doug Sowder