Weight & Balance Flashcards
Reference Datum
- The imaginary vertical plane from which all horizontal distances are measured
- Set by the manufacturer
“Station” when referred to for weight and balance
- The location on the a/c fuselage given in terms of the distance from the reference datum
Arm
- The horizontal distance (usually in inches) from the reference datum to the CG of an item
- “Arms” in front of the reference datum are negative, and behind are positive
- If reference datum is ahead of the nose, all arms are positive
Moment
- A force that cause an object to rotate
- Weight of an item x Arm = Moment (expressed in poud-inches)
CG Limits
- The extreme forward/aft CG location within which the plane maybe operated at any given weight
Usable Fuel
The fuel available for flight planning
Unusable Fuel
- Fuel in the tanks that can’t be safely used in flight or drain on the ground
Basic Empty Weight
- Weight of the airplane, unusable fuel, undrainable oil & full fluids plus optional equipment
Payload
- The weight of the occupants, cargo & baggage
Useful load
The difference between takeoff weight, or ramp weight, and basic weight
Airworthiness documents for an aircraft.
Airworthiness Certificate
Registration Certificate
Radio License (international flying)
Operators Manual
Weight and Balance sheet
Supplemental Type Certificate
Placards
Max Takeoff Weight
Max weight approved for starting takeoff roll
Max Landing Weight
Max weight approved for landing touchdown
AvGas Weight / gallon
6lbs per gallon
Jet Fuel Weight/ gallon
7lbs
Oil Weight / gallon
7.5
Water Weight / gallon
8.35
How to calculate Moment
Weight x Arm = Moment
Center of Gravity Equation
Total Moment / Total Weight = CG
First Step to Determining Weight and Balance
- Begin w/ empty weight and make a list of everything that will be loaded in the plane (people, bags, fuel, weight of each item)
What happens to moment when weight is shifted aft?
- You increase moment
How can you increase moment without adding more weight?
- Shifting weight aft
If the weight has been moved forward of the reference datum, how would you calculate the new CG?
- Calculate the new moment by multiplying the weight of the item moved and the new arm location (which is forward of the reference datum
- Subtract (because it’s forward of the reference datum) the new moment from the total moment
- Divide the new moments by the total weight to get the new CG
What is the formula for calculating how much weight is needed to be shifted foward?
- Find how many inches weight needs to be moved
- Find difference in arm length between new location weight to be moved to
- New Arm Length / Dist. needed to Move
- Divide the total weight by the product from step 3 to get the amount of lbs needed to move
How to calculate adding mass to a/c
Mass Change = Change of CG
_____________ ______________________
New Total Mass Distance Between Mass & CG
Service Ceiling
Where climb rate is 100’/ minute
Where can I find the W&B chart for my aircraft?
Located in the back of the POH
What happens when the CG is moved further aft of an aircraft?
- The aircraft is less stable, meaning the ability to recover from disturbances during flight would require more effort from the pilot
- There’s less downforce on the elevator and the aircraft has a nose up attitude
When there’s less downforce on the elevators, this means?
- The aircraft is less stable
What is a stable aircraft?
The ability for an airplane to recover from an inflight disturbance with minimal pilot input
Where can I find the limits for CG fore and aft limitations?
- In the Type Certificate Data Sheet (TCDS)
- Aircraft specification and AFM
- POH
