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on every flight to know the maximum allowable gross weight
of the aircraft and its CG limits. This allows the pilot to
determine on the preflight inspection that the aircraft is
loaded in such a way that the CG is within the allowable
limits.
Weight and balance technology, like all other aspects of
aviation, has become more complex as the efficiency and
capability of aircraft and engines have increased. Therefore,
this requires all pilots and AMTs to understand weight and
balance control, and to operate and maintain their aircraft
so its weight and CG location are within the limitations
established when the aircraft was designed, manufactured,
and certified by the FAA.
Why is Weight and Balance Important?
Weight and balance is one of the most important factors
affecting safety of flight. An overweight aircraft, or one
whose center of gravity is outside the allowable limits, is
inefficient and dangerous to fly. The responsibility for
proper weight and balance control begins with the engineers
and designers and extends to the pilot who operates and the
Aviation Main-tenance Technician (AMT) who maintains the
aircraft.
Modern aircraft are engineered utilizing state-of-the-art
technology and materials to lift the maximum amount of
weight and carry it the greatest distance at the highest speed.
As much care and expertise must be exercised in operating
and maintaining these efficient aircraft as was taken in their
design and manufacturing.
Various types of aircraft have different load requirements.
Transport aircraft must carry huge loads of passengers and
cargo for long distances at high altitude and high speed.
Military aircraft must be highly maneuverable and extremely
sturdy. Corporate aircraft must carry a reasonable load at a
high speed for long distances. Agricultural aircraft must
carry large loads short distances and be extremely
maneuverable. Trainers and private aircraft must be
lightweight, low cost, simple, and safe to operate.
All aircraft regardless of their function have two characteristics
in common: all are sensitive to weight, and the
center of gravity of the aircraft must be maintained within a
specified range.
Maximum weight: The maximum
authorized weight of the aircraft and
all of its equipment as specified in the
Type Certificate Data Sheets (TCDS)
for the aircraft.
Center of gravity (CG): The point at
which an airplane would balance if
suspended. Its distance from the
reference datum is found by dividing
the total moment by the total weight
of the airplane.
Empty weight: The weight of the
airframe, engines, and all items of
operating equipment that have fixed
locations and are permanently installed
in the aircraft.
Empty-weight center of gravity
(EWCG): The center of gravity of an
aircraft, when the aircraft contains
only the items specified in the aircraft
empty weight.
1–2
Weight Control
Weight is a major factor in airplane construction and
operation, and it demands respect from all pilots and
particular diligence by all AMTs. Excessive weight reduces
the efficiency of an aircraft and the safety margin
available if an emergency condition should arise.
When an aircraft is designed, it is made as light as the
required structural strength will allow, and the wings
or rotors are designed to support the maximum allowable
gross weight. When the weight of an aircraft is increased,
the wings or rotors must produce additional lift and the
structure must support not only the additional static loads,
but also the dynamic loads imposed by flight maneuvers.
For example, the wings of a 3,000-pound airplane must
support 3,000 pounds in level flight, but when the airplane
is turned smoothly and sharply using a bank angle of 60°,
the dynamic load requires the wings to support twice this,
or 6,000 pounds.
Severe uncoordinated maneuvers or flight into turbulence
can impose dynamic loads on the structure great enough to
cause failure. The structure of a 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 operating 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
　
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