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• Only the pilot and minimum fuel if they are ahead of the aft CG limit.
5– 7
Ballast
It is possible to load most modern airplanes so the center of
gravity shifts outside of the allowable limits. Placards and
loading instructions in the Weight and Balance Data inform
the pilot of the restrictions that will prevent such a shift from
occurring. A typical placard in the baggage compartment of
an airplane might read:
When the CG of an aircraft falls outside of the limits, it can
usually be brought back by using ballast.
Temporary Ballast
Temporary ballast, in the form of lead bars or heavy canvas
bags of sand or lead shot, is often carried in the baggage
compartments to adjust the balance for certain flight
conditions. The bags are marked “Ballast XX Pounds —
Removal Requires Weight and Balance Check.” Temporary
ballast must be secured so it cannot shift its location in flight,
and the structural limits of the baggage compartment must
not be exceeded. All temporary ballast must be removed
before the aircraft is weighed.
Permanent Ballast
If a repair or alteration causes the aircraft CG to fall outside
of its limits, permanent ballast can be installed. Usually,
permanent ballast is made of blocks of lead painted red and
marked “Permanent Ballast — Do Not Remove.” It should
be attached to the structure so that it does not interfere with
any control action, and attached rigidly enough that it cannot
be dislodged by any flight maneuvers or rough landing.
Ballast: A weight installed or carried
in an aircraft to move the center of
gravity to a location within its
allowable limits.
Two things must first be known to determine the amount of
ballast needed to bring the CG within limits: the amount the
CG is out of limits, and the distance between the location of
the ballast and the limit that is affected.
If an airplane with an empty weight of 1,876 pounds has
been altered so its EWCG is +32.2, and the CG range for
weights up to 2,250 pounds is +33.0 to +46.0, permanent
ballast must be installed to move the EWCG from + 32.2
to +33.0. There is a bulkhead at fuselage station 228 strong
enough to support the ballast.
To determine the amount of ballast needed, use this formula:
When rear row of seats is occupied, 120 pounds of baggage
or ballast must be carried in forward baggage
compartment. For additional loading instructions, see
Weight and Balance Data.
A block of lead weighing 7.7 pounds attached to the bulkhead
at fuselage station 228, will move the EWCG back to its
proper forward limit of +33. This block should be painted red
and marked “Permanent Ballast — Do Not Remove.”
Temporary Ballast Formula
The CG of a loaded airplane can be moved into its allowable range
by shifting passengers or cargo, or by adding temporary ballast.
To determine the amount of temporary ballast needed, use this
formula:
5– 8
6– 1
Chapter 6
Weight and Balance Control—
Large Aircraft
Loading schedule: A method and
procedure used to show that an
aircraft is properly loaded and will
not exceed approved weight and
balance limitations during operation.
Takeoff weight: The weight of an
aircraft just before lift-off. It is the
ramp weight less the fuel burned
during start, taxi, and ground run.
Landing weight: The takeoff weight
of an aircraft less the fuel burned
and/or dumped en route.
Empty weight: The weight of the
airframe, engines, all permanently
installed equipment, and unusable
fuel. 14 CFR, Part 25 includes full
oil and CAR 4B requires the oil to
be drained.
Fleet weight: The average weight of
aircraft of the same model and
configuration that have the same
equipment installed.
Weight and balance control for large aircraft consists of
the following:
• Establishing and monitoring the empty weight and
EWCG of the aircraft either individually, or as part of a
fleet. This includes both the initial weighing and the
required periodic reweighing of the aircraft.
• Maintaining a loading schedule that allows the aircraft
to be loaded in such a way that the weight and balance
remain within the approved limits. Provisions are made
to track the weight and CG changes as occupants and
cargo are loaded or deplaned, and as the CG is shifted by
moving cargo from one bin to another. The cargo loading
schedule takes into consideration the floor loading limits
so the structure will not be damaged by an overweight
cargo pallet.
　
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