Flight Training - July 2013 - 30

to about the same pitch attitude, and
subsequently descended behind a tree
line with a high sink rate. Another witness reported seeing the airplane come
over the tree line behind his residence
and impact the ground in a nose-low
attitude. A post-accident examination
of the airplane and engine revealed no
mechanical malfunctions or failures that
would have precluded normal operation.
The witness's observations are consistent
with the pilot attempting to climb at too
steep a pitch angle, which resulted in an
aerodynamic stall. According to calculations, the airplane’s weight was about
110 pounds over the maximum allowable
takeoff weight, which would have resulted
in reduced climb performance.”
RUN THE NUMBERS. To calculate whether

your airplane is overweight, find its basic
empty weight (BEW). For nonexperimental, factory-built, and certified airplanes,
the BEW is in the weight and balance data
specific to that particular airplane.
Add the weight of everything you put
in the airplane to the BEW. This includes
the weight of passengers, bags, and fuel
(avgas weighs an average of six pounds
per gallon). Compare that weight to the
maximum allowable weight (max gross)
found in the aircraft's manual—the operating limitations.
If you have too much weight, it’s decision time. Can you leave behind enough
baggage or fuel—or even passengers—to
get the airplane within limits? By the way,
if you do this quick calculation before
fueling or agreeing to take passengers, it
makes your decision-making much easier.
WHERE SHOULD THE WEIGHT GO? We
can’t treat the subject of weight fairly
without also covering balance—in
other words, where you put the weight.
“Balance” to pilots is the balance of the airplane along its longitudinal axis, its pitch,
and your three options are: too far aft, too
far forward, and within the envelope. The
envelope, based on the airplane’s center
of gravity, is defined in the airplane's
handbook.
If you load the airplane with weight
that is too far forward, the elevator has
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Center of gravity

Center of pressure

IF YOU LOAD your aircraft too far forward, the
airplane's elevator has to push down harder on
the air to keep the nose up. You've overloaded the
aircraft—not with weight inside, but with the air
forces outside of the aircraft. Now imagine the
effects on landing.

WE CAN'T TREAT THE SUBJECT OF WEIGHT FAIRLY WITHOUT
ALSO COVERING BALANCE—IN OTHER WORDS, WHERE
YOU PUT THE WEIGHT.
to push down harder on the air to keep
the nose up. That “tail down force” is
actually lift directed downward for the
express purpose of balancing the airplane.
The more tail down force you use, the
more upward lift the wings must produce to counteract that force. When you
load an airplane too far forward, it is as if
you have overloaded it. In fact, you have
overloaded it—not with mass inside the
airplane but rather with air forces outside.
The result is the same. Up elevator travel
could also be limited, presenting many
problems on takeoff and landing.
Another unfortunate example from the
NTSB files:
“On February 2, 2005... a Bombardier Challenger CL-600-1A11, N370V,
ran off the departure end of Runway 6
at Teterboro Airport (TEB), Teterboro,
New Jersey, at a groundspeed of about
110 knots; through an airport perimeter
fence; across a six-lane highway (where
it struck a vehicle); and into a parking
lot before impacting a building. The two
pilots were seriously injured, as were two
occupants in the vehicle. The cabin aide,
eight passengers, and one person in the
building received minor injuries. The
airplane was destroyed by impact forces
and post-impact fire….The National Trans-

portation Safety Board determines that
the probable cause of the accident was
the pilots’ failure to ensure the airplane
was loaded within weight-and-balance
limits and their attempt to take off with
the center of gravity well forward of the
forward takeoff limit, which prevented
the airplane from rotating at the intended
rotation speed.”
When you load an airplane too far aft
of its limits, the airplane no longer acts as
if it is too heavy. The problem becomes
insufficient stability. With a heavy tail,
the nose wants to rise. This may seem like
a good thing initially, until you realize
that the airplane’s elevator (or stabilator) has stops for both up and down. This
means that there is a limit to how much
the elevator can counteract that nose-up
pitch. If you have more weight in the back
than the elevator can overcome, there’s no
stopping the upward trend of the nose—in
other words, there’s no bringing the nose
back down, and stall recovery could be
impossible. Again, from the NTSB:
“The pilot and a passenger, a perspective
[sic] flight student, completed a preflight
inspection of [a Cessna 177 Cardinal,
N3431T]. Another passenger subsequently
approached the airplane with two heavy
bags. The first passenger put the larger

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Flight Training - July 2013

Table of Contents for the Digital Edition of Flight Training - July 2013