Weight and Balance
Commercial Ground School AVF 221
Weight and Balance
WEIGHT AND BALANCE HANDBOOK
Aircraft Weight and Balance Handbook
FAA 8083-1A
You’ll need to download a copy and it can be found here:
https://www.faa.gov/regulations_policies/handbooks_manuals/aircraft/
THE WEIGHT AND BALANCE SYSTEM
3 elements:
Weighing of the aircraft
Weight and balance records
Proper loading
Maximum weight a plane can carry is dependent on
Amount of lift the wings will generate
Structural strength of the airframe
TERMS
Reference datum- imaginary vertical plane from which all horizontal distances are measured
If all numbers are positive, the datum must be out in front of (or at) the nose of the airplane
Station- a designated location on the fuselage measured from the reference datum
TERMS
Empty weight- the weight of the aircraft with all the necessary equipment installed does not include people or baggage
Basic empty weight- the weight of the aircraft with all equipment, oil and unusable fuel does not include people or baggage
Licensed empty weight- old term before GAMA, same as Basic Empty Weight
TERMS
Max ramp weight- max weight of aircraft for taxi operations (it includes start taxi and runup fuel)
Max takeoff weight- max weight approved for the start of the takeoff run
TERMS
Useful load- weight of the pilots, pax, bags, useable fuel and drainable oil.
difference between take off weight and basic empty weight
Payload- weight of the occupants, cargo and baggage
Zero fuel weight- weight exclusive of usable fuel, useful for calculations when fuel is a variable
TERMS
Tare- weight of chocks, blocks, stands ect used when weighing an aircraft
Arm- the horizontal distance from the reference datum, may also be referred to as an index unit
Moment- the force exerted by a weight using an arm usually measured in in/lbs or foot/lbs
TERMS
Center of gravity- the point at which an airplane would balance if suspended from that point, the mass center of the aircraft.
Expressed in inches or %MAC
EFFECTS OF WEIGHT
Aircraft are designed for multi-role missions in mind
Few general aviation aircraft can take a full load of fuel and full load of passengers
The pilot must choose between hauling a lot of people or having a long range
The pilot must also understand weight effects on takeoff
High density altitude may limit those options even further
High drag takeoff such as grass or standing water
EFFECTS OF WEIGHT
More weight means:
Higher takeoff speed
Longer takeoff roll
Rate of climb decreased
Angle of climb decreased
Overheating in the climb
Added wear on the engine
Service ceiling lower
Cruising speed less
Higher fuel burn
Range is less
Maneuverability decreased
Longer landing roll
Excessive loads on structure
STABILITY AND CONTROL
The CG must be in front of the center of lift for positive stability to exist (exception is canard design)
This produces the nose down force
This in turn is offset by the tail down force
This is what gives us positive longitudinal stability
STABILITY AND CONTROL
Lateral balance is usually upset by uneven fuel loading
The Buttock Line is the dividing line between equal parts left and right
This will cause the aileron to be deflected downward on the heavy side causing drag
This in turn will cause a yaw which must be corrected with rudder
Very inefficient set up for cruise flight
If the aircraft has sweptback wings, the CG will shift
If outboard fuel is used first, CG will shift forward
If inboard fuel is used first, CG will shift aft
STABILITY AND CONTROL
Forward CG problems:
Difficult or impossible to flare
Excessive nose wheel heaviness
Heavy control forces
Excessive nose up trim
Higher stall speed
Rearward CG problems:
Decreased longitudinal stability
Extreme control difficulty
Violent stall characteristics
Very light control forces
Easy to overstress the airframe
Lower stall speed
STABILITY AND CONTROL
The forward limit is restricted to allow for sufficient elevator/stabilator control in the flare
The aft limit is restricted to prevent over rotation, stall and spin recovery – the most critical maneuver or operation
TYPE CERTIFICATE DATA SHEET
The FAA keeps pertinent specifications for all aircraft on the Type Certificate Data Sheet
When an 100hr or annual is done it is the mechanics responsibility to make sure the aircraft adheres to them
This includes all weight and balance data generic to that model of aircraft
As the aircraft is modified over its existence, the mechanics keep a running record of all modifications and apply that information to the keep the weight and balance sheet accurate
WEIGHING THE AIRCRAFT
When weighing an airplane it must be leveled before draining the fluids
Somewhere on the airplane there is a designated level point
The Bonanza has 2 screws that are removed and a level is attached
On the C-23, the level is placed on the baggage compartment floor
On the B-19, they remove the back seat and place the level there
If the airplane has slats or flaps these must be in the proper position as indicated on the TCDS
Hydraulic reservoirs should be full, drinking and washing reservoirs should be empty
This assures the same starting condition for the weigh in
WEIGHING THE AIRCRAFT
This all must be accomplished on a clean aircraft
Must be done inside a closed hanger
Aircraft under CAR part 3 needs the engine oil drained (old timers)
AKA Licensed Empty Weight or just Empty Weight (before GAMA)
Aircraft under part 23 or 25 keep the engine oil
This is the Basic Empty Weight (after GAMA)
An IA or certified repair station must make the sign off after a major alteration or repair changes the weight and balance
Aircraft with 20 or more seats or over 6,000lbs and multi’s under part 135 are required to be weighed every 36 calendar months
PROPER PAPERWORK
Note the word supersedes
Date, signature, number
Adverse Load check
This is done to ensure that any legal loading does not cause the plane to be out of limits
For example the Bonanza has a load limit of 270lbs in the baggage compartment
COMPUTING WEIGHT AND BALANCE
Graph method
COMPUTING WEIGHT AND BALANCE
The CG envelope
COMPUTING W&B
COMPUTING W&B
COMPUTING W&B
LARGE AIRCRAFT
Typically larger or jet aircraft use limits that reference the CG to the Leading Edge MAC or LEMAC
Horizontal stabilizer trim is figured using a table given in %MAC or ANU (airplane nose up)
Cargo pallet loads must be calculated and referenced to floor load limitations on a pounds per square foot basis
COMMUTER CATEGORY
DENSITY VARIATION OF FUEL
LOAD MANIFEST