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normal category airplane must be strong enough to sustain
a load factor of 3.8 times its weight. That is, every pound
of weight added to an aircraft requires that the structure
be strong enough to support an additional 3.8 pounds.
An aircraft operated in the utility category must sustain a
load factor of 4.4, and acrobatic category aircraft must be
strong enough to withstand 6.0 times their weight.
The lift produced by a wing is determined by its airfoil
shape, angle of attack, speed through the air, and the air
density. When an aircraft takes off from an airport with a
high density altitude, it must accelerate to a speed faster
than would be required at sea level to produce enough
lift to allow takeoff; therefore, a longer takeoff run is
necessary. The distance needed may be longer than the
available runway. When operating from a high-density
altitude airport, the Pilot’s Operating Handbook (POH)
or Airplane Flight Manual (AFM) must be consulted to
determine the maximum weight allowed for the aircraft
under the conditions of altitude, temperature, wind, and
runway conditions.
Effects of Weight
Most modern aircraft are so designed that if all seats
are occupied, all baggage allowed by the baggage
compartment is carried, and all of the fuel tanks are
full, the aircraft will be grossly overloaded. This type of
design requires the pilot to give great consideration to the
requirements of the trip. If maximum range is required,
occupants or baggage must be left behind, or if the
maximum load must be carried, the range, dictated by the
amount of fuel on board, must be reduced.
Some of the problems caused by overloading an aircraft
are:
• the aircraft will need a higher takeoff speed, which
results in a longer takeoff run.
• both the rate and angle of climb will be reduced.
• the service ceiling will be lowered.
• the cruising speed will be reduced.
• the cruising range will be shortened.
• maneuverability will be decreased.
• a longer landing roll will be required because the
landing speed will be higher.
• excessive loads will be imposed on the structure,
especially the landing gear.
The POH or AFM includes tables or charts that give the
pilot an indication of the performance expected for any
weight. An important part of careful preflight planning
includes a check of these charts to determine the aircraft is
loaded so the proposed flight can be safely made.
Weight Changes
The maximum allowable weight for an aircraft is
determined by design considerations. However, the
maximum operational weight may be less than the
maximum allowable weight due to such considerations as
high-density altitude or high-drag field conditions caused
by wet grass or water on the runway. The maximum
operational weight may also be limited by the departure or
arrival airport’s runway length.
One important preflight consideration is the distribution
of the load in the aircraft. Loading the aircraft so the gross
weight is less than the maximum allowable is not enough.
This weight must be distributed to keep the CG within the
limits specified in the POH or AFM.
If the CG is too far forward, a heavy passenger can
be moved to one of the rear seats or baggage can be
shifted from a forward baggage compartment to a rear
compartment. If the CG is too far aft, passenger weight or
baggage can be shifted forward. The fuel load should be
balanced laterally: the pilot should pay special attention
to the POH or AFM regarding the operation of the fuel
system, in order to keep the aircraft balanced in flight.
Weight and balance of a helicopter is far more critical
than for an airplane. With some helicopters, they may be
properly loaded for takeoff, but near the end of a long
flight when the fuel tanks are almost empty, the CG may
have shifted enough for the helicopter to be out of balance
laterally or longitudinally. Before making any long flight,
the CG with the fuel available for landing must be checked
to ensure it will be within the allowable range.
Airplanes with tandem seating normally have a limitation
requiring solo flight to be made from the front seat in
some airplanes or the rear seat in others. Some of the
smaller helicopters also require solo flight be made from a
specific seat, either the right, left, or center. These seating
limitations will be noted by a placard, usually on the
instrument panel, and they should be strictly adhered to.
As an aircraft ages, its weight usually increases due to
trash and dirt collecting in hard-to-reach locations, and
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Aircraft Weight and Balance Handbook(5)
