AOPA Pilot Magazine - May 2013 - 84

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TECHNIQUE

Once an aerobatic student is looking
in the right places, the next step is calibrating his or her arm for the pull, and
the loop involves lots of pulling: hard at
the bottom when the airplane is going
fast, and light at the top when it’s slow.
(There’s no pushing on the stick in a loop,
only varying amounts of pulling.)
The sweet spot for the pull is typically
about 3.5 Gs. Pull harder and you induce
unwanted, energy-killing drag, as well as
greater stress on the airframe. Pull too
lightly and you may run out of airspeed
before making it over the top. Most aerobatic airplanes have G meters, and a glance
during the initial pull should be enough to

If the airplane you’re flying is equipped
with an angle-of-attack indicator, it will
illustrate an abstract concept that pilots
learn to recite during ground school but
rarely fully comprehend—which is that
an airplane can stall in “any attitude” and
at “any airspeed.” For me, it took stalling
on the back side of a loop (while pointed
straight down at a high power setting) for
that idea to sink in.
During the initial pull into a loop, the
airplane has a high airspeed, a high angle
of attack, and is producing a large amount
of lift (and high Gs). As the airplane floats
over the top of the maneuver, it’s at low
speed, a low angle of attack, and produc-

Most aerobatic airplanes have G meters, and a glance
during the initial pull should be enough to tell you
(like Goldilocks) whether you are pulling too hard,
too soft, or just right.

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tell you (like Goldilocks) whether you are
pulling too hard, too soft, or just right.
As the airplane approaches the top
of the maneuver, you should feel light in
your seat. The target here is weightlessness—zero Gs. Airspeed at this point can
be critically low, sometimes below stall
speed. But at zero Gs, the wings aren’t
making any lift, and wings that aren’t
making lift can’t stall.
Gravity hasn’t forgotten you or your
airplane, however, and as the heavy front
end begins to point toward the ground
and airspeed increases, airflow attaches
to the wings in the normal fashion and
you can start pulling out of the dive. The
pull is gentle at first, and more firm as airspeed builds.
Pulling too hard at any point in a loop
can create some surprising results. At the
top of a loop, excessive pulling can lead to
an unwanted departure that sometimes
turns into a half snap roll—or a spin—
and the pilot finds himself level (and very
slow) at the point in which he expects to be
inverted and accelerating. Pulling too hard
on the back side of a loop can make it feel
as though you’re driving down a rutted and
bumpy country road. Relax the back pressure slightly and the ride will smooth out.
84 | AOPA PILOT May 2013

ing almost no lift (and no Gs). Gaining
speed on the back side of the loop, airspeed becomes high again, angle of attack
increases, and the amount of lift (and Gs)
goes up along with them.
A constant-speed prop is a real luxury in a loop as you can go to high power
and rpm and simply “set it and forget it.”
Fixed-pitch props usually require full
power in the initial climb and throttling
back during the descent to avoid exceeding rpm redlines.
The loop introduces pilots to new
sensations such as relatively high Gs and
weightlessness, all in the same maneuver. It forces pilots to seek and interpret
attitude information in new ways (pitch
and yaw information comes from looking out the sides of the aircraft, and roll
by looking overhead). Angle of attack
should approach, but never exceed, the
critical angle.
Loops enable pilots to feel how the
wing flies throughout its full range of
speed and angle of attack, and experience—
and even enjoy! —the physical demands
imposed by both high Gs and weightlessness. It’s quite a ride.
AOPA
EMAIL dave.hirschman@aopa.org
http://www.AmericanFlyers.net http://www.AmericanFlyers.net http://www.GuardianAvionics.com http://www.GuardianAvionics.com
AOPA Pilot Magazine - May 2013

Table of Contents for the Digital Edition of AOPA Pilot Magazine - May 2013
