Introduction
This chapter discusses general guidelines and procedures for
weighing large fixed-wing aircraft exceeding a takeoff weight
of 12,500 pounds. Several examples of center of gravity (CG)
determination for various operational aspects of these aircraft
are also included. Persons seeking approval for a weight and
balance control program for aircraft operated under Title
14 of the Code of Federal Regulations (14 CFR) part 91,
subpart K, 121, 125, or 135 should consult with the Flight
Standards District Office (FSDO) or Certificate Management
Office (CMO) that has jurisdiction in their area. Additional
information on weight and balance for large aircraft can be
found in Federal Aviation Administration (FAA) Advisory
Circular (AC) 120-27, Aircraft Weight and Balance Control,
FAA Type Certificate Data Sheets (TCDS), and the aircraft
flight and maintenance manuals for specific aircraf
Weight and Balance Control—
Commuter Category and
Large Aircraft
Chapter 9
Figure 9-1. Determining the distance of CG.
Distance CG to LEMAC Datum to CG – Datum to LEMAC
CG
Distance weight is shifted
=
Figure 9-2. Determining the EWCG in percent MAC.
EWCG in % MAC CG in inches from LEMAC × 100
MAC=
Establishing the Initial Weight of an
Aircraft
Prior to being placed into service, each aircraft is weighed
and the empty weight and CG location established. New
aircraft are normally weighed at the factory and are eligible
to be placed into operation without reweighing if the weight
and balance records were adjusted for alterations and
modifications to the aircraft, such as interior reconfigurations
An aircraft transferred from one operator that has an approved
weight and balance program to another operator with an
approved program does not need to be weighed prior to use by
the receiving operator unless more than 36 calendar months
have elapsed since the last individual or fleet weighing, or
unless some other modification to the aircraft warrants that
the aircraft be weighed. Aircraft transferred, purchased, or
leased from an operator without an approved weight and
balance program, and that have not been modified or have
been minimally modified, can be placed into service without
being reweighed if the last weighing was accomplished by an
acceptable method (for example, manufacturer’s instructions
or AC 43.13-2, Acceptable Methods, Techniques, and
Practices—Aircraft Alterations) within the last 12 calendar
months and a weight and balance change record was
maintained by the operator. It is potentially unsafe to fail to
reweigh an aircraft after it has been modified
When weighing large aircraft, compliance with the relevant
manuals, operations specifications, or management
specification is required to ensure that weight and balance
requirements specified in the Aircraft Flight Manual (AFM)
are met in accordance with approved limits. This provides
information to the flight crew that allows the maximum
payload to be carried safely.
The aircraft should be weighed in still air or an enclosed
building after the aircraft has been cleaned. Ensure that the
aircraft is in a configuration for weighing with regard to
flight controls, unusable fuel, ballast, oil and other operating
fluids, and equipment as required by the controlling weight
and balance procedure.
Large aircraft are not usually raised off the floor on jacks
for weighing; they are weighed on ramp-type scales. The
scales must be properly calibrated, zeroed, and used in
accordance with the manufacturer’s instructions. Each scale
should be periodically checked for accuracy as recommended
in the manufacturer’s calibration schedule, either by the
manufacturer or by a recognized facility, such as a civil
department of weights and measures. If no manufacturer’s
schedule is available, the period between calibrations should
not exceed 12 months.
Determining the Empty Weight and
Empty Weight CG (EWCG)
When the aircraft is properly prepared for weighing, roll it
onto the scales, and level it. The weights are measured at
three weighing points: the two main wheel points and the
nosewheel point. The empty weight and empty weight CG
(EWCG) are determined by using the following steps with
the results recorded in the weight and balance record for use
in all future weight and balance computations.
1. Determine the moment index of each of the main-
wheel points by multiplying the net weight (scale
reading minus tare weight), in pounds, at these points
by the distance from the datum, in inches. Divide these
numbers by the appropriate reduction factor.
2. Determine the moment index of the nosewheel
weighing point by multiplying its net weight, in
pounds, by its distance from the datum, in inches.
Divide this by the reduction factor.
3. Determine the total weight by adding the net weight of
the three weighing points and the total moment index
by adding the moment indexes of each point.
4. Divide the total moment index by the total weight and
multiply the result by the reduction factor. This gives
the CG in inches from the datum.
5. Determine the distance of the CG behind the leading
edge of the mean aerodynamic chord (LEMAC)
by subtracting the distance between the datum and
LEMAC from the distance between the datum and
the CG. [Figure 9-1]
6. Determine the EWCG in percentage of MAC (percent
MAC) by using the formula in Figure 9-2.
Figure 9-3. Incremental weight changes that should be recorded in a weight and balance change record.
In the weight change record of a—
Large cabin aircraft
Medium cabin aircraft
Small cabin aircraft
An operator should record any weight changes of—
± 10 lb or greater
± 5 lb or greater
± 1 lb or greater
Figure 9-4. Loading schedule.
Item Weight (lb) Moment/1,000
92,837
1,781
16,602
1,020
2,915
10,451
10,451
25,589
161,646
BOW
Passengers Fwd station
Passengers Aft station
Fwd cargo
Aft cargo
Fuel tank 1
Fuel tank 3
Fuel tank 2
105,500
3,060
16,150
1,500
2,500
10,500
10,500
28,000
177,710
Documenting Changes to an Aircraft’s
Weight and Balance
The weight and balance system should include methods by
which a complete, current, and continuous record of the
weight and CG of each aircraft is maintained, such as a log,
ledger, or other equivalent electronic means. Alterations and
changes affecting the weight and/or balance of the aircraft
should be recorded in this log. Changes in the weight or
location of weight in or on the aircraft should be recorded
whenever the weight change is at or exceeds the weights
listed in Figure 9-3.
Determining the Loaded CG of the
Airplane in Percent MAC
A loading schedule is used to document compliance with the
certificated weight and balance limitations contained in the
manufacturer’s AFM and weight and balance manual. The
basic operating weight (BOW) and the operating index are
entered into a loading schedule like the one in Figure 9-4, and
the variables for a specific flight are entered as appropriate
to determine the loaded weight and CG.
Use the data in this example:
Basic operating weight ..................................105,500 lb
Basic operating index (total moment/1,000) .... 98,837.0
MAC ..................................................................180.9 in
LEMAC ................................................................. 860.5
Figure 9-5 illustrates passenger, cargo, and fuel loading
tables. Using these tables, determine the moment indexes
for the passengers (PAX), cargo, and fuel.
The airplane is loaded in this way:
Passengers (nominal weight—170 pounds each)
Forward compartment ................................................. 18
Aft compartment ......................................................... 95
Cargo
Forward hold ......................................................1,500 lb
Aft hold ..............................................................2,500 lb
Fuel
Tanks 1 and 3 ...........................................10,500 lb each
Tank 2 ..............................................................28,000 lb
The formula in Figure 9-6 can be used to determine the
location of the CG in inches aft of the datum.
Figure 9-5. Loading schedule for determining weight and CG.
# of passengers Weight (lb) Moment/1,000
Forward compartment centroid—582.0
Aft compartment centroid—1,028.0
5 850 495
10 1,700 989
15 2,550 1,484
20 3,400 1,979
25 4,250 2,473
29 4,930 2,869
10 1,700 1,748
20 3,400 3,495
30 5,100 5,243
40 6,800 6,990
50 8,500 8,738
60 10,200 10,486
70 11,900 12,233
80 13,600 13,980
90 15,300 15,728
100 17,000 17,476
110 18,700 19,223
120 20,400 20,971
133 22,610 23,243
Weight (lb) Forward hold arm—680.0 Aft hold arm—1,166.0
6,000 6,966
5,000 3,400 5,830
4,000 2,720 4,664
3,000 2,040 3,498
2,000 1,360 2,332
1,000 680 1,166
900 612 1,049
800 544 933
700 476 816
600 408 700
500 340 583
400 272 466
300 204 350
200 136 233
100 68 117
Fuel Loading Table
Weight (lb) Arm Moment/1,000
8,500 992.1 8,433
9,000 993.0 8,937
9,500 993.9 9,442
10,000 994.7 9,947
10,500 995.4 10,451
11,000 996.1 10,957
11,500 996.8 11,463
12,000 997.5 11,970
Weight (lb) Arm Moment/1,000
8,500 917.5 7,799
9,000 917.2 8,255
9,500 917.0 8,711
10,000 916.8 9,168
10,500 916.6 9,624
11,000 916.5 10,082
11,500 916.3 10.537
12,000 916.1 10,993
Weight (lb) Arm Moment/1,000
22,500 914.5 20,576
23,000 914.5 21,034
23,500 914.4 21,488
24.000 914.3 21,943
24,500 914.3 22,400
25,000 914.2 22,855
25,500 914.2 23,312
26,000 914.1 23,767
26,500 914.1 24,244
27,000 914.0 24,678
27,500 913.9 25,132
28,000 913.9 25,589
28,500 913.8 26,043
29,000 913.7 26,497
29,500 913.7 26,954
30,000 913.6 27,408
Full capacity **(see note at lower left)
Tanks 1 and 3 (each) Tank 2 (3 cells)
Passenger Loading Table Cargo Loading Table
Moment/1,000
18,500 915.1 16,929
19,000 915.0 17,385
19,500 914.9 17,841
20,000 914.9 18,298
20,500 914.8 18,753
21,000 914.7 19,209
21,500 914.6 19,664
22,000 914.6 20,121
** Note:
Computations for Tank 2 weights for
12,500 lb to 18,000 lb have been
purposely omitted.
Full capacity
Figure 9-6. Determining the location of the CG in inches aft of
the datum.
( )CG inches aft of datum = × 1,000Total moment index
Total weight
( )= × 1,000161,646
177,710
= 909.6 inches
Figure 9-7. Determining the distance from the CG to the LEMAC.
Distance CG to LEMAC = Datum to CG – Datum to LEMAC
= 49.1 inches
= 909.6 – 860.5
Figure 9-8. Determining the location of the CG in percent MAC.
( )CG % MAC = × 100Distance CG to LEMAC
MAC
( )= × 10049.1
180.9
= 27.1%
Determine the distance from the CG to the LEMAC by
subtracting the distance between the datum and LEMAC from
the distance between the datum and the CG. [Figure 9-7]
The location of the CG in percent MAC must be known in
order to set the stabilizer trim takeoff. [Figure 9-8]
Operational Empty Weight (OEW)
Operational empty weight (OEW) is the basic empty weight
or fl et empty weight plus operational items. The operator has
two choices for maintaining OEW. The loading schedule may
be utilized to compute the operational weight and balance of
an individual aircraft, or the operator may choose to establish
fleet empty weights for a fleet or group of aircraf
Reestablishing the OEW
The OEW and CG position of each aircraft should be
reestablished at the reweighing. In addition, it should be
reestablished through calculation whenever the cumulative
change to the weight and balance log is more than plus or
minus one-half of 1 percent (0.5 percent) of the maximum
landing weight, or whenever the cumulative change in the
CG position exceeds one-half of 1 percent (0.5 percent) of the
MAC. In the case of rotorcraft and aircraft that do not have a
MAC-based CG envelope (e.g., canard equipped airplane),
whenever the cumulative change in the CG position exceeds
one-half of 1 percent (0.5 percent) of the total CG range, the
weight and balance should be reestablished.
When reestablishing the aircraft OEW between reweighing
periods, the weight changes may be computed provided the
weight and CG location of the modifications are known;
otherwise, the aircraft must be reweighed.
Fleet Operating Empty Weights (FOEW)
An operator may choose to use one weight for a fleet or group
of aircraft if the weight and CG of each aircraft is within the
limits stated above for establishment of OEW. When the
cumulative changes to an aircraft weight and balance log
exceed the weight or CG limits for the established fleet weight,
the empty weight for that aircraft should be reestablished.
This may be done by moving the aircraft to another group, or
reestablishing new fleet operating empty weights (FOEWs)
Onboard Aircraft Weighing System
Some large transport airplanes have an onboard aircraft
weighing system (OBAWS) that, when the aircraft is on the
ground, gives the flight crew a continuous indication of the
aircraft total weight and the location of the CG in percent
MAC. Procedures are required to ensure the onboard weight
and balance system equipment is periodically calibrated in
accordance with the manufacturer’s instructions.
An operator may use an onboard weight and balance
system to measure an aircraft’s weight and balance as a
primary means to dispatch an aircraft, provided the FAA
has certified the system and approved the system for use in
an operator’s weight and balance control program. As part
of the approval process, the onboard weight and balance
system must maintain its certificated accuracy. The accuracy
demonstration test is provided in the maintenance manual
portion of the Supplemental Type Certificate (STC) or type
certificate of the onboard weight and balance system.
The system consists of strain-sensing transducers in each
main wheel and nosewheel axle, a weight and balance
computer, and indicators that show the gross weight, the
CG location in percent MAC, and an indicator of the ground
attitude of the aircraft.
The strain sensors measure the amount each axle defl cts and
sends this data into the computer, where signals from all of
the transducers and the ground attitude sensor are integrated.
The results are displayed on the indicators for the flight crew.
Using an onboard weight and balance system does not relieve
an operator from the requirement to complete and maintain
a load manifest.