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Pilot's Handbook of Aeronautical Knowledge
Aerodynamics of Flight
Weight and Balance

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Pilot's Handbook of Aeronautical Knowledge



Table of Contents

Chapter 1, Introduction To Flying
Chapter 2, Aircraft Structure
Chapter 3, Principles of Flight
Chapter 4, Aerodynamics of Flight
Chapter 5, Flight Controls
Chapter 6, Aircraft Systems
Chapter 7, Flight Instruments
Chapter 8, Flight Manuals and Other Documents
Chapter 9, Weight and Balance
Chapter 10, Aircraft Performance
Chapter 11, Weather Theory
Chapter 12, Aviation Weather Services
Chapter 13, Airport Operation
Chapter 14, Airspace
Chapter 15, Navigation
Chapter 16, Aeromedical Factors
Chapter 17, Aeronautical Decision Making




Weight and Balance
The aircraft's weight and balance data is important
information for a pilot that must be frequently reevaluated.
Although the aircraft was weighed during the certification
process, this data is not valid indefinitely. Equipment changes
or modifications affect the weight and balance data. Too often
pilots reduce the aircraft weight and balance into a "rule of
thumb" such as: "If I have three passengers, I can load only
100 gallons of fuel; four passengers, 70 gallons."

Weight and balance computations should be part of every
preflight briefing Never assume three passengers are always
of equal weight. Instead, do a full computation of all items
to be loaded on the aircraft, including baggage, as well as
the pilot and passenger. It is recommended that all bags be
weighed to make a precise computation of how the aircraft
CG is positioned.

The importance of the CG was stressed in the discussion
of stability, controllability, and performance. Unequal load
distribution causes accidents. A competent pilot understands
and respects the effects of CG on an aircraft.

Weight and balance are critical components in the utilization
of an aircraft to its fullest potential. The pilot must know
how much fuel can be loaded onto the aircraft without
violating CG limits, as well as weight limits to conduct
long or short flights with or without a full complement of
allowable passengers. For example, an aircraft has four seats
and can carry 60 gallons of fuel. How many passengers can
the aircraft safely carry? Can all those seats be occupied at
all times with the varying fuel loads? Four people who each
weigh 150 pounds leads to a different weight and balance
computation than four people who each weigh 200 pounds.
The second scenario loads an additional 200 pounds onto the
aircraft and is equal to about 30 gallons of fuel.

The additional weight may or may not place the CG outside
of the CG envelope, but the maximum gross weight could
be exceeded. The excess weight can overstress the aircraft
and degrade the performance.

Aircraft are certificated for weight and balance for two
principal reasons:

1. The effect of the weight on the aircraft's primary
structure and its performance characteristics
2. The effect of the location of this weight on flight
characteristics, particularly in stall and spin recovery
and stability

Aircraft, such as balloons and weight-shift control, do not
require weight and balance computations because the load
is suspended below the lifting mechanism. The CG range
in these types of aircraft is such that it is difficult to exceed
loading limits. For example, the rear seat position and fuel
of a weight-shift control aircraft are as close as possible to
the hang point with the aircraft in a suspended attitude. Thus,
load variations have little effect on the CG. This also holds
true for the balloon basket or gondola. While it is difficult
to exceed CG limits in these aircraft, pilots should never
overload an aircraft because overloading causes structural
damage and failures. Weight and balance computations are
not required, but pilots should calculate weight and remain
within the manufacturer's established limit.