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information for the actual weight of the aircraft and the
location of the center of gravity. The pilot in command has
the responsibility to know the weight of the load, CG,
maximum allowable gross weight, and CG limits of
the aircraft.
The weight and balance report must include an equipment
list showing weights and moment arms of all required and
optional items of equipment included in the certificated
empty weight.
When an aircraft has undergone extensive repair or major
alteration, it should be reweighed and a new weight and
balance record started.
Equipment for Weighing
There are two basic types of scales used to weigh aircraft:
scales on which the aircraft is rolled so the weight is taken
from the wheels, and electronic load cells placed between the
aircraft jack and the jack pads on the aircraft.
Some aircraft are weighed with mechanical scales of the low
profile type similar to those shown in Figure 3-1.
Large aircraft, including heavy transports, are weighed by
rolling them onto weighing platforms with electronic
weighing cells that accurately measure the force applied by
the weight of the aircraft. [Figure 3-2]
Electronic load cells are used when the aircraft is weighed
by raising it on jacks. The cells are placed between the jack
and the jack pad on the aircraft, and the aircraft is raised on
the jacks until the wheels are off the floor and the aircraft is
in a level flight attitude. The weight measured by each load
cell is indicated on the control panel.
Mechanical scales should be protected when they are not
in use, and they must be periodically checked for accuracy
by measuring a known weight and noting any errors detected.
Electronic load cells normally have a built-in calibration that
allows them to be accurately zeroed before any load
is applied.
Who’s responsible?
AMTs must provide the pilot with current and accurate aircraft weight
information and where its EWCG is located.
The pilot in command has the responsibility to know the weight of the
load, CG, maximum allowable gross weight, and CG limits of
the aircraft.
Load cell: A component in an
electronic weighing system placed
between the jack and the jack pad on
the aircraft. The load cell contains
strain gauges whose resistance
changes with the weight on the cell.
3–2
Bilge area: The lowest part of an
aircraft structure in which water and
contaminants collect.
Figure 3-1. Low profile platform scales are used to weigh some aircraft. One scale is placed under each wheel. (Photo courtesy
General Electrodynamics Corp.)
Figure 3-2. Weighing platforms accurately measure the weight of
large aircraft without having to raise the aircraft off the ground.
(Photo courtesy General Electrodynamics Corp.)
Specific Gravity
Both the heat energy available and the weight of the fuel are
determined by its specific gravity (s.g.), and this in turn is affected by
its temperature. Cold fuel has a higher s.g. and therefore weighs more
per gallon than warm fuel, and since the heat energy content is
measured in Btu or Calories per pound or kilogram, cold fuel has more
heat energy per gallon than warm fuel.
Preparation for Weighing
The major considerations in preparing an aircraft for weighing
are discussed below.
Weigh Clean Aircraft Inside Hangar
The aircraft should be weighed inside a hangar where wind
cannot blow over the surface and cause fluctuating or false
scale readings.
The aircraft should be clean inside and out, with special
attention paid to the bilge area to be sure no water or debris
is trapped there, and the outside of the aircraft should be as
free as possible of all mud and dirt.
Equipment List
All of the required equipment must be properly installed, and
there should be no equipment installed that is not included
in the equipment list. If such equipment is installed, the
weight and balance record must be corrected to indicate it.
3–3
Ballast
All required permanent ballast must be properly secured
in place and all temporary ballast must be removed.
Draining the Fuel
Drain fuel from the tanks in the manner specified by the
aircraft manufacturer. If there are no specific instructions,
drain the fuel until the fuel quantity gauges read empty when
the aircraft is in level flight attitude. Any fuel remaining in
the system is called residual, or unusable fuel and is part of
the aircraft empty weight.
If it is not feasible to drain the fuel, the tanks can be topped
off to be sure of the quantity they contain and the aircraft
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