PDF Handbook FAA H-8083-1A Weight and Balance - 3 MB
The FAA Weight and Balance Handbook (H-8083-1A) is a fundamental resource for pilots, aviation maintenance technicians, and flight engineers.
This official publication provides the principles and methods for aircraft weight and balance control.
Understanding these concepts is critical for ensuring flight safety and efficiency.
This handbook is an essential study guide for certification and a vital reference for daily operations.
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Aircraft Weight and Balance Handbook FAA-H-8083-1A
8083-1A Cover.indd 1
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Figure 2-13. Placement of weight B to cause the board to balance
Figure 2-10. Moving the CG of a board by shifting the weights. This about its center.
is the original configuration.
Basic Weight and Balance Equation
This equation can be rearranged to find the distance a
weight must be shifted to give a desired change in the CG
Figure 2-11. Shifting the CG of a board by moving one of the location:
weights. This is the original condition of the board.
To shift weight B so the board will balance about its
center, 50 inches from the CG of weight A, first determine
the arm of weight B that will produce a moment that
causes the total moment of all three weights around this This equation can also be rearranged to find the amount of
desired balance point to be zero. The combined moment of weight to shift to move the CG to a desired location:
weights A and C around this new balance point, is 5,000
in-lb, so the moment of weight B will have to be -5,000 lb-
in in order for the board to balance. [Figure 2-12]
It can also be rearranged to find the amount the CG is
moved when a given amount of weight is shifted:
Finally, this equation can be rearranged to find the total
Figure 2-12. Determining the combined moment of weights A and C. weight that would allow shifting a given amount of weight
to move the CG a given distance:
Determine the arm of weight B by dividing its moment,
-5,000 lb-in, by its weight of 200 pounds. Its arm is -25
inches.
Solution by Formula
This same problem can also be solved by using this basic
equation:
To balance the board at its center, weight B will have to be Rearrange this formula to determine the distance weight B
placed so its CG is 25 inches to the left of the center of the must be shifted:
board, as in Figure 2-13.
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Figure 4-3. Blank weight and balance worksheet.
Figure 4-4. Completed weight and balance worksheet.
When planning the flight, fill in the blanks in the
worksheet with the specific data for the flight. [Figure 4-4]
Pilot..............................................120 lbs
Front seat passenger.....................180 lbs
Rear seat passenger......................175 lbs
Fuel 88 gal...................................528 lbs
Baggage A...................................100 lbs
Baggage B......................................50 lbs
Determine the moment of each item by multiplying its
weight by its arm. Then determine the total weight and the
sum of the moments. Divide the total moment by the total
weight to determine the CG in inches from the datum. The
total weight is 3,027 pounds and the CG is 43.54 inches aft
of the datum.
To determine that the airplane is properly loaded for this
flight, use the CG limits envelope in Figure 4-5 (which
is typical of those found in the POH/AFM). Draw a line
vertically upward from the CG of 43.54 inches, and one
horizontally to the right from the loaded weight of 3,027
pounds. These lines cross inside the envelope, which
shows the airplane is properly loaded for takeoff, but 77
pounds overweight for landing.
Figure 4-5. Center of gravity limits chart from a typical POH.
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Computations Using Weight and Moment Indexes
If the weight and balance data uses moment indexes
rather than arms and moments, this same alteration can be Figure 5-5. Typical notation in a TCDS when an aircraft has an
empty-weight CG range.
computed using a chart like the one shown on Figure 5-4.
Subtract the weight and moment indexes of all the If the TCDS list an empty-weight CG range, and after the
removed equipment from the empty weight and moment alteration is completed the EWCG falls within this range,
index of the airplane. Add the weight and moment indexes then there is no need to compute a fore and aft check for
of all equipment installed and determine the total weight adverse loading.
and the total moment index. To determine the position of
the new CG in inches aft of the datum, multiply the total But if the TCDS lists the EWCG range as βNoneβ (and
moment index by 100 to get the moment, and divide this most of them do), a check must be made to determine
by the total weight to get the new CG. whether or not it is possible by any combination of legal
loading to cause the aircraft CG to move outside of either
Empty-Weight CG Range its forward or aft limits.
The fuel tanks, seats, and baggage compartments of Adverse-Loaded CG Checks
some aircraft are so located that changes in the fuel or
occupant load have a very limited effect on the balance Many modern aircraft have multiple rows of seats and
of the aircraft. Aircraft of such a configuration show an often more than one baggage compartment. After any
EWCG range in the TCDS. [Figure 5-5] If the EWCG is repair or alteration that changes the weight and balance,
located within this range, it is impossible to legally load the A&P mechanic or repairman must ensure that no
the aircraft so that its loaded CG will fall outside of its legal condition of loading can move the CG outside of its
allowable range. allowable limits. To determine this, adverse-loaded CG
checks must be performed and the results noted in the
weight and balance revision sheet.
Figure 5-4. Weight and moment index changes caused by a typical alteration.
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Determining the Loaded CG of the Airplane in Percent Determine the distance from the CG to the LEMAC by
MAC subtracting the distance between the datum and LEMAC
The basic operating weight (BOW) and the operating index from the distance between the datum and the CG:
are entered into a loading schedule like the one in Figure
7-1 and the variables for the specific flight are entered as
are appropriate to determine the loaded weight and CG.
Use the data in this example:
Basic operating Weight........................... 105,500 lbs.
The location of the CG in percent of MAC must be known
Basic operating index (total moment/1,000). .. 98,837.0
in order to set the stabilizer trim takeoff. Use this formula:
MAC.............................................................. 180.9 in
LEMAC............................................................. 860.5
On Board Aircraft Weighing System
Some large transport airplanes have an on board aircraft
weighing system (OBAWS) that, when the aircraft is on
the ground, gives the flightcrew a continuous indication of
the aircraft total weight and the location of the CG in %
MAC.
The system consists of strain-sensing transducers in each
Figure 7-1. Loading tables. main wheel and nose wheel axle, a weight and balance
computer, and indicators that show the gross weight, the
Use Figure 7-2 to determine the moment indexes for the CG location in percent of MAC, and an indicator of the
passengers (PAX), cargo, and fuel. ground attitude of the aircraft.
The airplane is loaded in this way: The strain sensors measure the amount each axle deflects
and sends this data into the computer, where signals from
Passengers (nominal weight 170 pounds each)
all of the transducers and the ground attitude sensor are
Forward compartment........................... 18
integrated. The results are displayed on the indicators for
Aft compartment................................... 95
the flightcrew.
Cargo
Forward hold.............................. 1,500 lbs
Aft hold...................................... 2,500 lbs
Fuel
Tank 1 & 3...................... 10,500 lbs each
Tank 2...................................... 28,000 lbs
Determine the location of the CG in inches aft of the
datum by using this formula:
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Figure 7-7. Determining the loaded weight and CG of a Beech 1900 in the passenger configuration.
Figure 7-8. Weights and moments - occupants.
Figure 7-9. Weights and moments - baggage.
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Nose Wheel Airplane with Datum Behind the Main Tail Wheel Airplane with Datum Behind the Main
Wheels Wheels.
The datum (D) is 75 inches behind the main-wheel The datum (D) is 80 inches behind the main-wheel
weighing points, the weight of the nose wheel (F) is weighing points, the weight of the tail wheel (R) is 67
340 pounds, and the distance between main wheels and pounds, and the distance between main wheels and tail
nose wheel (L) is 78 inches. The total weight (W) of the wheel (L) is 222 inches. The total weight (W) of the
airplane is 2,006 pounds. Refer to Figure 3-6 on page 3-5. airplane is 1,218 pounds. Refer to Figure 3-8 on page 3-6.
Use this formula:
Use this formula:
1. Determine the CG in inches from the main wheels:
1. Determine the CG in inches from the main wheels:
(340)(x)(78)(Γ·)(2006)(=) 13.2
2. Determine the CG in inches from the datum: (67)(x)(222)(Γ·)(1218)(=) 12.2
(75)(+)(13.2)(=) 88.2 2. Determine the CG in inches from the datum:
The minus sign before the parenthesis in the formula (80)(+/-)(+)(12.2)(=) -67.8
means the answer is negative. The CG is 88.2 inches The CG is 67.8 inches ahead of the datum.
ahead of the datum (-88.2).
Tail Wheel Airplane with Datum Ahead of the Main
Determining CG, Given Weights and Arms
Wheels Some weight and balance problems involve weights and
arms to determine the moments. Divide the total moment
The datum (D) is 7.5 inches ahead of the main-wheel
by the total weight to determine the CG. Figure 8-5
weighing points, the weight of the tail wheel (R) is 67
contains the specifications for determining the CG using
pounds, and the distance between main wheels and tail
weights and arms.
wheel (L) is 222 inches. The total weight (W) of the
airplane is 1,218 pounds. Refer to Figure 3-7 on page 3-6.
Determine the CG by using the data in Figure 8-5 and
following these steps:
Use this formula:
1. Determine the total weight and record this number:
(830)(+)(836)(+)(340)(=)(2006)
1. Determine the CG in inches from the main wheels.
2. Determine the moment of each weighing point and
(67)(x)(222)(Γ·)(1218)(=) 12.2
record them:
2. Determine the CG in inches from the datum:
(830)(x)(128)(=)106240
(7.5)(+)(12.2)(=) 19.7 (836)(x)(128)(=) 107008
(340)(x)(50)(=) 17000
The CG is 19.7 inches behind the datum.
Figure 8-5. Specifications for determining the CG of an airplane
using weight and arm.
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