Weight & Balance

Importance of Aircraft Weight and Balance Control

• Safety Considerations:

  • Ensures aircraft and occupants fly safely when loaded.

  • Essential for all operation levels, from aerobatics to normal flight.

• Mechanical Responsibility:

  • Mechanics play a crucial role in maintaining proper weight and balance control.

FAA Regulations on Aircraft Weight

• Private Aircraft vs. Commercial Operators:

  • FAA does not require periodic reweighing for private aircraft.

  • Commercial operators are required to reweigh periodically.

• Alterations:

  • No requirement to reweigh private aircraft after alterations.

  • New weight and balance calculated mathematically unless specific circumstances arise.

Calculating Weight Changes in Aging Aircraft

• Common Sources of Weight Change:

  • Repairs and alterations (e.g., heavier battery replacements).

  • Installation of lighter components (e.g., new avionics).

• Minor Weight Changes:

  • Accumulation of grime, moisture, or additional hardware may slightly alter weight.

Understanding Empty Weight and Operating Weight

• Empty Weight Definition:

  • Includes all fixed equipment installed (e.g., radios, avionics).

  • Fuel Consideration:

    • Unusable fuel included because it cannot be drained.

• Oil Inclusion:

  • Depends on FAA certification standards; newer planes include oil in empty weight since March 1, 1978.

Defining Useful Load

• Components of Useful Load:

  • Crew, fuel, passengers, and cargo.

• Calculating Useful Load:

  • Difference between maximum allowable gross weight and empty weight.

  • Total weights (empty weight + useful load) must not exceed maximum weight limits.

Weight Considerations in Aircraft Operations

• Maximum Takeoff Weight:

  • Determined by manufacturer, found in specifications or type certificate data sheets.

• Zero Fuel Weight:

  • Maximum weight without fuel; critical in large aircraft for structural stress calculations.

Datum and Arm Measurements

• Datum Line:

  • An imaginary line from which horizontal measurements for balance are taken.

  • Usually placed forward of the nose for accuracy in calculations.

• Arm Measurements:

  • Horizontal distance of an object from the datum, always in inches.

• Fuselage Station Numbers:

  • Identify arm distances used for locating aircraft parts.

Moments and Center of Gravity

• Calculating Moments:

  • Moment = Weight x Arm.

• Center of Gravity Definition:

  • Point where nose-heavy and tail-heavy moments are equal.

• Average Moment Arm:

  • Average location of all weights in the aircraft; determined to ensure balance during flight.

Balancing Load Adjustments

• Center of Gravity Adjustments:

  • Removing weight from behind the CG moves it forward.

  • Importance of CG location for aircraft handling and safety.

Leveling Aircraft for Weight Calculation

• Methods of Leveling:

  • Spirit levels, plumb bob, or inclinometer to determine level attitude for weighing.

• FAA Guidelines:

  • Use level indicators specified for each aircraft type.

Reweighing Aircraft

• Reasons for Reweighing:

  • Loss of weight and balance records or inaccuracies due to equipment changes.

• Pre-Weighing Preparations:

  • Removal of non-essential items and draining of fuel except for unusable fuel.

Tare Weight Considerations

• Determining Empty Weight:

  • Tare weight (e.g., chocks) must be subtracted from scale readings to find net aircraft weight.

Scenario Calculations Examples

• Center of Gravity and Weight Computation:

  • Given weights and arms, calculate total weight and moments to find average CG.

• Impact of Changes on CG:

  • Removal of items or modification of weight affecting CG placement and balance.

Theoretical Concepts in Weight and Balance

• Lever Principle:

  • Concept of balance similar to a lever on a fulcrum (CG as the fulcrum).

• Each weight's moment must balance:

  • Calculate moments based on the weight and their distances from the CG.

Importance of Accurate Weight and Balance Checks in Helicopters

• Helicopter Restrictions:

  • Center of gravity range is more critical due to the effects on cyclic pitch control.