Introduction
There are many factors in the safe and efficient operation of
aircraft, including proper weight and balance control. The
weight and balance system commonly employed among
aircraft consists of three equally important elements: the
weighing of the aircraft, the maintaining of the weight and
balance records, and the proper loading of the aircraft. An
inaccuracy in any one of these elements defeats the purpose
of the system. The final loading calculations are meaningless
if either the aircraft has been improperly weighed or the
records contain an error.
Improper loading decreases the effic ency and performance of
an aircraft from the standpoint of altitude, maneuverability,
rate of climb, and speed. It may even be the cause of failure
to complete the flight or, for that matter, failure to start the
flight. Because of abnormal stresses placed upon the structure
of an improperly loaded aircraft, or because of changed fly ng
characteristics of the aircraft, loss of life and destruction of
valuable equipment may result.
Weight and Balance
Control
Chapter 1
Aircraft can perform safely and achieve their designed
efficiency only when they are operated and maintained in the
way their designers intended. This safety and efficiency is
determined to a large degree by holding the aircraft’s weight
and balance parameters within the limits specified for its design.
The remainder of this handbook describes how this is done.
Responsibility for Weight and Balance
Control
The responsibility for proper weight and balance control
begins with the engineers and designers and extends to the
technicians who maintain the aircraft and the pilots who
operate them. Modern aircraft are engineered utilizing state-
of-the-art technology and materials to achieve maximum
reliability and performance for the intended category. As
much care and expertise must be exercised in operating
and maintaining these efficient aircraft as was taken in their
design and manufacturing:
1. The designers of an aircraft set the maximum weight
based on the amount of lift the wings or rotors can
provide under the operational conditions for which
the aircraft is designed. The structural strength of the
aircraft also limits the maximum weight the aircraft
can safely carry. The designers carefully determine
the ideal center of gravity (CG) and calculate the
maximum allowable deviation from this specific
location.
2. The manufacturer provides the aircraft operator with
the empty weight of the aircraft and the location of its
empty weight center of gravity (EWCG) at the time
the certified aircraft leaves the factory. Amateur-built
aircraft must have this information determined and
available at the time of certification
3. The FAA-certificated mechanic or repairman who
maintains the aircraft keeps the weight and balance
records current, recording any changes that have been
made because of repairs or alterations.
4. The pilot in command (PIC) has the responsibility
prior to every flight to know the maximum allowable
weight of the aircraft and its CG limits. This allows
the pilot to determine during the preflight inspection
that the aircraft is loaded so that the CG is within the
allowable limits.
Terminology
Pilots and FAA-certificated mechanics or repairmen must
ensure they understand the terms as they relate to the
aircraft in question. For small aircraft terminology, use
the information found in sources associated with Civil
Air Regulation (CAR) 3 certification or General Aviation
Manufacturers Association (GAMA) Specification No. 1
for part 23 aircraft or part 27 for rotorcraft. For terminology
applied to large part 25 aircraft, information can be found
in Advisory Circular (AC) 120-27, Aircraft Weight and
Balance Control. The glossary contains the most current
terms and defin tions. Current regulations are available from
the Superintendent of Documents; U.S. Government Printing
Office; Washington, DC 20402. They are also located on the
FAA website at www.faa.gov. Earlier regulations may be
available in libraries or in the Federal Register.
Weight Control
Weight is a major factor in airplane construction and
operation, and it demands respect from all pilots and
particular diligence by all maintenance personnel. Excessive
weight reduces the efficiency of an aircraft and the available
safety margin if an emergency condition should arise.
When an aircraft is designed, it is made as light as the
required structural strength allows, and the wings or rotors are
designed to support the maximum allowable 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. In accordance with Title 14 of the Code
of Federal Regulations (14 CFR) part 23, the structure of a
normal category airplane must be strong enough to sustain
a load factor of 3.8 times its weight. Every pound of weight
added to a normal category aircraft requires that the structure
be strong enough to support 3.8 pounds. An aircraft operated
in the utility category must sustain a load factor of 4.4 times
its weight, 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 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, when all seats
are occupied, the baggage compartment is full, and all fuel
tanks are full, the aircraft is grossly overloaded. This type
of design requires the pilot to give great consideration to
the requirements of each specific flight. 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.
Overloading an aircraft can create a variety of problems:
• The aircraft needs a higher takeoff speed, which results
in a longer takeoff run.
• Both the rate and angle of climb are reduced.
• The service ceiling is lowered.
• The cruising speed is reduced.
• The cruising range is shortened.
• Maneuverability is decreased.
• A longer landing roll is required because the landing
speed is higher.
• Excessive loads are 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 if 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 may 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. Some helicopters 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 is
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
are noted by a placard, usually on the instrument panel, and
they should be strictly followed.
As an aircraft ages, its weight usually increases due to debris
and dirt collecting in hard-to-reach locations and moisture
absorbed in the cabin insulation. This increase in weight is
normally small, but it can be determined only by accurately
weighing the aircraft.
Changes of fixed equipment may have a major effect upon
the weight of the aircraft. Many aircraft are overloaded by
the installation of extra radios or instruments. Fortunately,
the replacement of older, heavy electronic equipment with
newer, lighter types results in a weight reduction. This
weight change, however helpful, can cause the CG to shift,
which must be computed and annotated in the weight and
balance record.
Repairs and alterations are the major sources of weight
changes. It is the responsibility of the FAA-certificate
mechanic or repairman making any repair or alteration to
know the weight and location of a change, to compute the
CG, record the new empty weight and EWCG in the aircraft
weight and balance record, and update the equipment lists.
If the newly calculated EWCG should happen to fall outside
the EWCG range, it is necessary to perform an adverse-
loading check. This requires a forward and rearward
adverse-loading check and a maximum weight check.
These weight and balance extreme conditions represent the
maximum forward and rearward CG position for the aircraft.
An adverse-loading check is a deliberate attempt to load an
aircraft in a manner that creates the most critical balance
condition and still remains within the design CG limits of the
aircraft. If any of the checks fall outside the loaded CG range,