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arm of each item is included on the list, and all equipment
installed when the aircraft left the factory is checked.
When an aircraft mechanic or repairman adds or removes
any item on the equipment list, he or she must change
the weight and balance record to indicate the new empty
weight and EWCG, and the equipment list is revised to
show which equipment is actually installed. Figure 2-22
is an excerpt from a comprehensive equipment list that
includes all of the items of equipment approved for this
particular model of aircraft. The POH for each individual
aircraft includes an aircraft specific equipment list of
the items from this master list. When any item is added
to or removed from the aircraft, its weight and arm are
determined in the equipment list and used to update the
weight and balance record.
The POH/AFM also contains CG moment envelopes and
loading graphs. Examples of the use of these handy graphs
are given in chapter 4.
Figure 2-21. Typical weight and balance data for 14 CFR part 23 airplane.
2–12
Figure 2-22. Excerpt from a typical comprehensive equipment list.
2–13
Figure 2-22. Excerpt from a typical comprehensive equipment list (continued).
2–14
3–
3 Chapter Weighing the Aircraft and Determining
the Empty Weight Center of Gravity
Chapter 2 explained the theory of weight and balance
and gave examples of the way the center of gravity could
be found for a board loaded with several weights. In this
chapter, the practical aspects of weighing an airplane and
locating its center of gravity are discussed. Formulas are
introduced that allow the CG location to be measured in
inches from various datum locations and in percentage of
the mean aerodynamic chord.
Requirements
Weight and balance is of such vital importance that each
mechanic or repairman maintaining an aircraft must be
fully aware of his or her responsibility to provide the pilot
with current and accurate 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 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. The A&P mechanic or the
repairman responsible for the work must provide the pilot
with current and accurate aircraft weight information and
where the new EWCG is located.
Equipment for Weighing
There are two basic types of scales used to weigh aircraft:
scales on which the aircraft is rolled so that the weight is
taken at the wheels, and electronic load cells type where a
pressure sensitive cell are 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.
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 or skids 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. [Figure 3-27]
Mechanical scales should be protected when they are not
in use, and they must be periodically checked for accuracy
by measuring a known weight. Electronic scales normally
have a built-in calibration that allows them to be accurately
zeroed before any load is applied.
Figure 3-1. Low profile mechanical platform scales are used to
weigh some aircraft. One scale is placed under each wheel.
3–
Figure 3-2. Electronic load cell scale. A load cell is placed at each
jack point.
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
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Aircraft Weight and Balance Handbook(13)
