reaction points. When measuring these distances, it is
necessary that the tape be parallel to aircraft centerline.
Measurements made from the main reaction points are
taken perpendicularly to the chalk line joining these two
points. These measurements may be made quickly by
placing one end of the tape on the point in question and
swinging the other end of the tape across the line in a
small arc. Notice the point at which the tape crosses the
chalk line which shows a shorter distance than any other
along the line. This is the shortest distance between the
line and the point in question and, therefore, is the
perpendicular distance from the point to the line. When
fuselage and wing jack points are used as reaction
points in weighing the aircraft, it is unnecessary to
measure dimension. These points will remain fixed with
respect to the reference datum and their moment arms
may be found in Chart E data. When measuring is
necessary, the required dimensions should be recorded
on DD Form 365-2 as soon as the measurements are
3-5. Aircraft Weighing Area. Procedures outlined
herein are general in nature, since methods of weighing
vary with each type aircraft.
a. Weigh aircraft in closed hangars to avoid
aircraft vibrations which would otherwise be caused by
air currents flowing over lifting surfaces. This vibration
would result in fluctuating scale readings and increase
the possibility of error.
b. Insure that aircraft is thoroughly dry before it is
weighed. Never weigh aircraft immediately after it has
c. Set electronic weighing cells oil their respective
jacks, using proper jack and jack pad adapters. Be sure
that jack adapter is fully threaded into cell assembly. If
a ring-type adapter is used, see that it is centered flush
on ram applying a partial load to it before tightening
Use proper adapters to prevent
jacks from slipping or buckling.
Damage to aircraft or inaccurate
weight readings may result if
Never apply loads to the rim of a
d. Prepare electronic weighing kit for use by
following instructions furnished with kit. Warm up cells
mounted on jacks to be used for jacking.
e. Actuate all jacks simultaneously until weighing
cells are in contact with aircraft jack pads. Continue to
jack aircraft, insuring that aircraft is kept level. When
aircraft is supported at weighing reaction points only,
and is in level position, scale readings may be obtained.
Weight and balance personnel must be alert for possible
errors in scale readings (e.g., side loads or misaligned
jack and cell, etc.). To insure accuracy of results, take
several independent readings (e.g., for beam scales by
upsetting the beams of all scales between readings or
completely unloading the electronic load cells and
rejacking). A minimum of two weighings shall be made.
If the first two weighings are within one quarter of one
percent in weight i.e. (divide the less weight reading by
the greater reading, subtract the results from 1.00 to
obtain the percentage) and 0.1 inch in c.g., additional
weighings are unnecessary. If these constraints are not
met, additional weighings shall be made until they are
satisfied. Enter average weight and c.g. of the two
suitable weighings on aircraft weighing form (DD 365-2).
If variations in scale indications for any reaction point
are greater than that prescribed in the technical manual
covering the kit, reweigh aircraft with another weighing
f. Before final lowering of the aircraft, make
certain that all necessary measurements and scale
readings have been obtained and recorded.
g. Rotary wing aircraft are weighed in the same
manner as conventional aircraft, except that four
reaction points are frequently used instead of three.
When four reaction points are employed, it will be
necessary to use two weighing kits, since each kit
contains only three cell assemblies. If a second kit is
not available, it is permissible to weigh the aircraft using
three reaction points. The cell assemblies will be placed
on the two front jacks and the right rear jack. The left
rear jack is used while raising the aircraft to weighing
position to maintain proper attitude. When the full
aircraft weight is bearing on the jacks, and the aircraft is
level, stop jacking and activate locking devices on the
two front jacks and right rear jack. Slowly lower the left
rear jack/reaction point by ½ inch, at which time the
aircraft's weight can be recorded. Raise the fourth jack
to again bear the weight of the aircraft, then lower all
four jacks simultaneously to return the aircraft to rest on
the hangar floor.
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