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Balance refers to the location of the CG along the longitudinal axis of the aircraft.
This factor is of primary importance to safety of flight. There are forward and aft
limit beyond which the CG should not be located for flight. These limits are established
by the aircraft design engineers to ensure proper predictable aircraft control about
the horizontal, vertical, and lateral axes. The operational weight and balance limits
for each aircraft are contained in the Pilot's Operating Handbook or flight manual.
This information may also be obtained from the FAA Aircraft Specification or Type
Certificate Data Sheets, which are available at most aircraft maintenance facilities.
The weight and balance information for each aircraft must be amended when repairs or
alterations have been made that effect a change in the aircraft empty weight or CG
location (reference 14 CFR 43.5(a)(4) and 91.31 (b)). To ensure aircraft
controllability during flight, the aircraft must be loaded within the design weight
and CG limits.
A forward CG limit is specified to ensure that sufficient elevator deflection is
available at minimum speed as for landing. The aft CG limit is the most critical during
flight maneuvers or operation of the aircraft. Aircraft stability decreases as the CG
moves aft, and the ability of the aircraft to right itself after maneuvering will be
correspondingly decreased. The aircraft will be highly unstable in gusting or turbulent
air, making attitude and directional control extremely difficult.
If, after the aircraft is loaded, the CG does not fall within the allowable limits,
it is essential to shift loads before flight is attempted. The actual location of the CG
is determined by a number of factors under control of the pilot:
- Placement of baggage and cargo.
- Assignment of seats to passengers according to each individual's weight.
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Fuel load. Selective use of fuel from various tank locations during flight may
aid in maintaining safe balance conditions.
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