Skip to main content

Weight and Balance

Objectives​

Motivations​

Timings​

Format​

Elements​

Weight and Balance Concepts​

  • Basic torque
    • Moment = weight * radius (arm)
    • Moments are additive, we can sum them to determine total pitching moment
  • Definitions
    • Datum: Fixed reference point to measure from, in the POH
    • Station: Area where item can be loaded (front seat, back seat, fuel tanks)
    • Arm: Distance from datum to the item
    • Moment: Item arm * item weight
    • Center of Gravity: Location of new C.G. = Total moments / total weights
    • Loading Envelope: Graph of acceptable weight and CG ranges
  • Types of weights
    • Basic empty weight
      • The standard empty weight plus the weight of optional and special equipment that have been installed
      • Includes all oil, fluids, and unusable fuel
    • Standard empty weight
      • All oil, fluids, and unusable fuel
      • This is the weight of the aircraft as it comes from the factory, with standard equipment installed
      • This is not normally used for weight and balance calculations
    • Licensed empty weight
      • Similar to standard empty weight for aircraft built before GAMA standardization of standard empty weight
    • Max ramp weight: weight for taxi but not flight
    • Zero fuel weight: maximum authorized weight minus usable fuel
  • Common fluids
    • Fuel: 6 lbs / gallon
  • Example documents
    • NW Airtech W&B Amendment: Empty weight, empty arm
    • Loading arrangements diagram (POH pg. 110)
    • Sample loading problem worksheet (POH pg. 112)
    • Loading Graph (POH pg. 114)
    • CoG Moment Envelope (POH pg. 115)
    • CoG Limits (POH pg. 116)

Weight and Balance Sample Problem​

  • N2017E Problem A
    • Setup
      • Fuel: 50 gallons of 100LL
      • Pilot: 160lbs
      • Co-pilot: 180lbs
      • Rear passenger: 120lbs
      • Expected fuel burn during the flight: 40 gallons
    • What is the takeoff and landing weight?
    • What happens if we move our 180 passenger to the rear seats?
    • What happens if we add a forth passenger to the copilot seat who weighs 200?
    • Double checking our work in ForeFlight

Effects of CG and Weight​

  • Over maximum weight
    • Longer takeoff roll
    • Longer landing roll
    • Slower rate of climb
    • Structural compromise
    • Potential damage on landing
  • Loading fore/aft CG
    • Not enough elevator authority in slow or fast flight
    • CG Aft:
      • Less stable
      • Faster cruise speed
      • Limited forward elevator, may inhibit stall recovery
    • CG forward:
      • More stable
      • Slower
      • More elevator
      • Limited after elevator authority, may prevent adequate landing flare

References​