Kyle Boatright wrote:
"Maxwell" wrote in message
...
wrote in message
oups.com...
when you did it, did you wait until manovering speed before pulling
all the way back? I'd worry, in the Mooney, if the pilot in command
(he loves being called that) pulled back to the stops at cruise. If
you kept your wits about you, I'd guess firm back until I think 130
knots, then to the aft limit in that airplane, would probably only
break a gyro or two, and not the backbone of the airplane. I don't
know if its gyros are rated for more than 60 degrees back or pitch.
First things first, don't over stress the aircraft under any
circumstances, it shouldn't be necessary. You shouldn't need more than 2.5
Gs max, if that much. But keep the Gs on. As the aircraft slows,
maintaining those Gs assures you the tightest possible loop radius, and is
the quickest way over the top. In this case, unlike demonstration
aerobatics, you want an elliptical loop. You shouldn't hit the stops
until you get very near the top, and very slow, if even then. Nine times
out of ten these days, you won't hurt the gyros, but there is no guarantee
unless they are designed for such duty or can be caged.

I would offer a different opinion... My big fear with new acro pilots is the
inverted accelerated stall. A 140 knot loop in an Arrow or Mooney is going
to get slow on top. Probably very close to stall speed. The way to keep the
speed higher at the top of the loop is with a fairly aggressive pull at the
beginning of the loop - say 3.5 g's, easing off as airspeed slows. Trying to
use the elevator to tighten the loop at the top is likely to result in a
stall, and possible inverted spin.

For what it is worth, I often float over the top of a loop at 60 knots,
which is about 10 knots above stall speed. At that point, the elevator is
more or less neutral, and the airplane is performing a -2g arc. One of the
g's comes from aerodynamic lift and the other comes from gravity... That's
only a .5 G different arc than the beginning of the loop, which was a 2.5 g
arc: 3.5 aerodynamic g's in the "up" direction minus 1 g from gravity...

KB


I would agree with this as well. Pulling in tight at the apex of a loop
can easily result in a positive g snap roll, as the angle of attack is
increasing through the vertical line. Add to this that as the lift
vector passes below the horizon through the apex an additional positive
g is available, you can easily pull into a snap this way. The preferred
method would indeed be a brisk pull into the maneuver keeping the g down
so as to avoid a high induced drag index, then easing off the g past the
pure vertical line.
As for the inverted spin; it's possible if things get away from you at
the apex, but with the stall being produced by tighter positive g
instead of a push into a negative side snap, the result would most
likely be an erect spin entry if you botched the snap recovery.
Dudley Henriques