STICK AND RUDDER
But the force caused by hitting the tracks
doesn’t accelerate the truck upward as
much when the truck is heavily loaded.
The same general concept can be
applied to the aircraft. The aerodynamic
force we apply by fully deflecting a control
surface—e.g., the elevator—at any given
airspeed is the same regardless of the
weight of the aircraft. However, the lighter
the aircraft, the more that force will accelerate the aircraft in a new direction, thus
imposing a higher load on the airframe.
Loaded lightly, we can expect a bumpier
ride than if we’re more heavily loaded.
The problem is that the maneuvering
speed published in the pilot’s operating
handbook is that of the aircraft at maximum
gross weight. If we’re below maximum gross
weight, maneuvering speed is lower. One
way to calculate VA at a lower speed is by
percentages. The percentage change in
maneuvering speed is half the percentage
change in weight. In other words, if we
reduce our weight by 20 percent, VA
decreases by 10 percent. Many light aircraft
pilots usually fly at well below gross weight,
so maneuvering speed is well below the published figure. If we assume the published VA
applies, we could be setting ourselves up for
more than just bitter disappointment.
MULTIPLE INPUTS
The other place we get into trouble is
thinking that as long as we’re below VA we
can do whatever we wish with the controls
without worry. Again, it isn’t quite that sim-
ple. The determination of VA assumes that
the full, abrupt control movement is in one
axis only and is initiated from a condition
of normal, unaccelerated (1g) flight. The
truth is that if we apply multiple control
inputs—yanking and banking at the same
time, as it were—or if we initiate the control
input with the airframe already loaded, we
can still exceed the structural limits of the
aircraft. Likewise, the determination of VA
assumes that the aircraft is restored to nor-
mal flight following the abrupt input. If we
apply a staccato of control inputs, we can
exceed the design limits of the airframe
structures, and bring our flying career to an
untimely end. These
facts were painfully
brought to light in
WHEN TO USE MANEUVERING SPEED
Instructors are quick to tell us that the air-
craft should be slowed to below VA before
performing any type of flight maneuvers,
such as steep turns, lazy-eights, or chandelles.
They will also explain that whenever condi-
tions became turbulent, it is appropriate to
slow the aircraft to below maneuvering
speed. Certainly, thunderstorms and training
maneuvers aren’t likely to sneak up on us, but
there are times when a sudden maneuver can
come straight out of the blue.
Robert N. Rossier, EAA 472091, has been flying for
more than 30 years and has worked as a flight instructor,
commercial pilot, chief pilot, and FAA flight check airman.
