WEIGHT AND BALANCE
Weight and Balance Effects of Operating at High Total Weights
● Weight - is just another word for the • Higher takeoff speed
force of gravity. It is a force that acts
at all times on all objects near Earth. • Longer takeoff run
● Mass - is the quantity of matter in a • Reduced rate and angle of climb
physical body. • Lower maximum altitude
● Balance - refers to the location of the • Shorter range
Center of Gravity (CG) of an airplane
and is important to airplane stability • Reduced cruising speed
and safety in flight.
• Reduced maneuverability
● Center of gravity (CG) - is the
• Higher stalling speed
imaginary point where the aircraft
would balance if suspended. • Higher approach and landing speed
Importance of Balance • Longer landing roll
Weight and balance have a direct effect on • Excessive weight on the nose wheel or
the stability and performance of the aircraft. tail wheel
● If a plane is too heavy, it may never
get off the ground.
● If it's out of balance, it may be
uncontrollable when it does take
flight.
● Obviously, neither of these scenarios
will produce a desired outcome.
Center of gravity (CG) - which is the imaginary
point where the aircraft would balance if
suspended. CG shifts within the CG limits.
CG limits - also called the CG envelope or
range, the CG limits are established by the
manufacturer. It is the forward and aft center
of gravity locations within which the aircraft
must be operated at a given weight.
Reference Datum - The center of gravity limits
usually are specified in inches from a
reference datum. This is an imaginary vertical
plane from which all horizontal distances are
measured for balance purposes.
By: Engr. Kyla Mae M. San Jose
Strike Wing Aviation Training Center
Private Pilot Course
WEIGHT AND BALANCE
Terms describing the empty Airplane ● Maximum ramp weight - which is the
maximum allowed for ground
● Basic empty weight - includes the
operations, such as taxiing.
weight of the standard airplane,
optional equipment, unusable fuel, ● Maximum Takeoff Weight - is the
and full operating fluids including full maximum weight at which the pilot is
engine oil. allowed to attempt to take off, due to
structural or other limits.
● The unusable fuel - is the small
amount of fuel in the tanks that ● Maximum landing weight -
cannot be safely used in flight or determined by the manufacturer and
drained on the ground. is based on the amount of stress the
aircraft's structure can withstand
● Licensed empty weight - which is
during landing.
similar to basic empty weight except
that it does not include full engine oil. ● Usable fuel - The fuel available during
Instead, it only counts the weight of flight that is safe to use.
undrainable oil.
You can obtain basic empty weight by simply
Principles of Weight and Balance
adding the weight of the oil to the licensed
empty weight.
Terms describing the loaded Airplane
● Ramp weight - is the term used to
describe the airplane loaded for flight
prior to engine start.
● Takeoff Weight - subtracting the fuel
burned during engine start, runup,
and taxi, yields takeoff weight, it is
also the weight of the airplane just
before you release the brakes to
begin the takeoff roll. ● Arm - the name for a distance from
the datum. On airplanes, the
● Landing Weight - is the takeoff weight distances are generally measured in
minus the fuel burned enroute. inches, and by tradition, distances aft
● Useful load - BEW minus Ramp of the datum are positive numbers
Weight or Takeoff Weight, it includes and forward of the datum are
the weight of the flight crew and negative.
usable fuel, as well as any passengers, ● Moment - a weight that is created on
baggage, and cargo. the end of an Arm.
● Payload - is the term used for the Note: When the weight in pounds and the arm
weight of only the passengers, in inches are multiplied together, the resulting
baggage, and cargo. moment is expressed in pound-inches.
“Weight(lb) x Arm(in.) = Moment (lb-in.)”
By: Engr. Kyla Mae M. San Jose
Strike Wing Aviation Training Center
Private Pilot Course
WEIGHT AND BALANCE
Computational Method
Aircraft Allowances:
Maximum gross weight..............2,100 pounds
CG range.....................................78–150 inches
Given:
Weight of front seat occupants......340 pounds
Weight of rear seat occupants......350 pounds
Fulcrum pivot - the point on which a lever Fuel..................................................75 gallons
rests or is supported and on which it pivots.
Weight of baggage in area 1............80 pounds
Methods of determining Total Weight and
CG
1. Computational Method
2. Table Method
3. Graph Method
By: Engr. Kyla Mae M. San Jose
Strike Wing Aviation Training Center
Private Pilot Course
WEIGHT AND BALANCE
A moment divided by a constant such
as 100, 1,000, or 10,000. The purpose
of using a moment index is to simplify
weight and balance computations of
aircraft where heavy items and long
arms result in large, unmanageable
numbers.
By: Engr. Kyla Mae M. San Jose
Strike Wing Aviation Training Center
Private Pilot Course
WEIGHT AND BALANCE
Graph Method Example
Given:
Front seat occupants..................340 pounds
Rear seat occupants....................300 pounds
Fuel................................................40 gallons
Baggage area 1 .............................20 pounds
By: Engr. Kyla Mae M. San Jose
Strike Wing Aviation Training Center
Private Pilot Course
WEIGHT AND BALANCE
By: Engr. Kyla Mae M. San Jose
Strike Wing Aviation Training Center
Private Pilot Course
WEIGHT AND BALANCE
Weight Shift Formula
By: Engr. Kyla Mae M. San Jose
Strike Wing Aviation Training Center
Private Pilot Course
WEIGHT AND BALANCE
Sample Problems
1. An Aircraft with an empty weight of 2,100 3. As weighed, the total empty weight
pounds and an empty weight CG + 32.5 was of an aircraft is 5,862 pounds with a
altered as follows: moment of 885,957. However, when
the aircraft was weighed, 20 pounds
1. Two 18-pound passenger seats locate
of hydraulic fluid are in the tank
at +73 were removed.
located at +101. What is the empty
2. Structural modifications were made at
weight CG of the aircraft?
+77 increasing weight by 17 pounds.
3. A seat and safety belt weighing 25
pounds were installed at +74.5;
4. Radio equipment weighting 35
pounds was installed at + 95
What is the new empty weight CG?
• When weighing an aircraft to find its
empty weight, a full reservoir of
hydraulic fluid is included, but the
potable water is not part of the
required equipment.
• When the water is computed out of
the empty weight, the new empty
weight to be 56,842 pounds and the
new empty-weight CG is located at
the fuselage station 151.365.
2. Aircraft as loaded weighs 4,954 pounds at
4. Two boxes which weigh 10 pounds
a CG of +30.5 inches. The CG range is +32.0
and 5 pounds are placed in an
inches to + 42.1 incase. Find the minimum
airplane so that their distance aft
weight the ballast necessary to bring the CG
from CG are 4 feet and 2 feet
within CG range. The ballast is is +162 inches.
respectively. How far forward of the
CG should the third box, weighing 20
pounds, be placed so that the CG will
not be changed?
Note: In order to not change the CG of the aircraft, it is necessary the moment of the 20-pound weight be the
same but have the opposite sign as the combined moments of the 10-pound box and the 5-pound box.
moment of the 10LB is 40 pound/feet
moment of the 5LB box is 10 pound/feet
Total positive moment is 50 pound/feet
Divide the required moment by the weight, the 20LB box will have to be placed 2.5 feet ahead of the CG.
By: Engr. Kyla Mae M. San Jose
Strike Wing Aviation Training Center
Private Pilot Course
WEIGHT AND BALANCE
5. An aircraft with an empty weight of 7. An aircraft had an empty weight of
1,800 pounds and and empty weight 2,886 pounds with a moment of
CG of +31.5 was altered as follows: 101,673.78 before several alterations
were made. The alterations included:
1. two 15-pound passenger seats
1. Removing two passenger seats
located at +72 were removed;
(15 pounds each) at +71
2. structural modifications increasing 2. Installing a cabinet (97 pounds) at
the weight 14 pounds were made at +71
+76; 3. Installing radio equipment (30
pounds) at +94
3. a seat and safety belt weighting 20 4. The alterations caused the new
pounds were installed at +73.5 empty weight CG to move.
4. radio equipment weight 30 pounds
was installed at +30.
What is the new empty weight CG?
The alterations shown here will change the 1.62 inches aft of the original empty weight
empty weight to 1,834 pounds and empty- CG
weight CG will move the fuselage station
31.61 The alterations shown here will change the
empty weight to 3,003 pounds and the empty-
weight CG will move to fuselage station 36.85
6. If a 40-pound generator applies Before alterations the EWCG was at +35.23
+1400 inches -pounds to a reference
axis the generator is located? The New EWCG of +36.85 is 1.62 inches aft of
the original EWCG.
The distance from the axis is found by
dividing the moment but the weight.
1,400 divided by 40 = 35
since the moment is positive, the arm
will always be positive. The generator
is located +35 inches from the axis
By: Engr. Kyla Mae M. San Jose
Strike Wing Aviation Training Center
Private Pilot Course
WEIGHT AND BALANCE
8. What is the empty weight CG off the 9. When an empty aircraft is weight,
aircraft described below? the combined net weight at the main
gears is 3,540 pounds with an arm of
Datum is forward of the 195.5 inches. At the nose gear, the
net weight is 2,322pounds with an
main gear center point...............................30.24 inches
arm of 83.5 inches. The datum line is
Actual distance between tail gear forward of the nose of the aircraft.
Why is the empty CG of the aircraft?
and main gear center points.....................360.26 inches
Net weight at right main gear...................9,980 pounds
Net weight at left main gear.....................9,770 pounds
New weight at tail gear.............................1,970 pounds
These items were in the aircraft when weighed:
1. lavatory water tank full (34 pounds at +352) 10. An aircraft with an empty weight of
1,500 pounds and an empty weight
2. Hydraulic fluid (22 pounds at -8) CG of +28.4 was altered as follows:
3. Removable ballast (142 pounds at +380) 1. two 12-pound seats located at
+68.5 were removed
2. a seat and safety belt weighting
30 pounds were installed at +70.5
3. radio equipment weighting 25
pounds was installed at +85
What is the new empty weight CG?
The empty weight of this aircraft is
1,559 pounds and its empty-weight
CG is located at fuselage station 30.30
By: Engr. Kyla Mae M. San Jose
Strike Wing Aviation Training Center
Private Pilot Course
WEIGHT AND BALANCE
11. The following alteration was
performed on an aircraft:
A model B engine weighting 175
pounds was replaced by a Model D
engine weighing 185 pounds at a -
62.00 station. The aircraft weight and
balance records show the previous
empty weight to neb 998 pounds and
empty weight CG of 13.48 inches.
What is the new empty weight CG?
12. Find the empty weight Cg location for
the following tricycle-gear aircraft.
Each main wheel weighs 753 pounds,
nose wheel weighs 22 pounds,
distance between nose wheel and
main wheels is 87.5 inches, nose
wheel location is +9.875 inches from
datum, with 1 gallon of hydraulic
fluid at -21.0 inches included in the
weight scale.
By: Engr. Kyla Mae M. San Jose
Strike Wing Aviation Training Center
Private Pilot Course
