Aircraft Powerplant

• Aircraft weight and balance control

  The primary purpose is safety, the secondary purpose is to aid efficiency during flight
• Overloading of the aircraft is not the only concern, the distribution of the weight is important also
• The aircraft has CG limits, and any loading that places the CG outside the established limits seriously impairs controllability of the aircraft
• Reasons for aircraft becoming heavier as they become older

  • Repair
  • Alteration
  • Replacement of aircraft parts
  • Modification
• Repair and alteration


  Major sources of weight change
• Responsibilities of the A&P FAA-certificated mechanic or repairman when an aircraft has undergone extensive repair or major alteration

  1. Establish by computation that the authorized weight and CG limits are not exceeded

  2. Record the new empty weight center of gravity (EWCG) data in the current approved aircraft flight manual or issued operating limitations
• When an aircraft has undergone extensive repair or major alteration, it should be reweighed and a new weight and balance record started
• Types of weighing scales used for aircraft

  • Mechanical platform scale
  • Electronic/Load cell scale
• Mechanical platform scale


  • Low profile, easy to handle, safe, and reliable
• Electronic/Load cell scale


  • Reliable means to weigh aircraft, typically cheaper than the platform type
  • Allows the aircraft to be set up and weighed in its level flight attitude
• Using load cell scales to weigh aircraft

  1. Aircraft is placed on jacks with electronic load cells between the jack and the jack pad

  2. Aircraft is raised on the jacks until the wheels or skids are off the floor and the aircraft is in a level flight attitude

  3. The weight measured by each load cell is indicated on the control panel
• All scales for aviation use, manual or electronic, must be protected when stored or shipped, and they must be checked periodically for accuracy
• The maximum recognized period between calibration checks is 12 months, but this period may be reduced by an airworthiness authority dependent on the conditions of use
• Tare


  The extra weight absorbed by the scale in addition to the weight of the aircraft, such as jacks, wheel chocks, or ground locks
• Preparing an aircraft for weighing

  1. Inspect and set scales to zero

  2. Locate scales in the same environment they will be used and allow them to come up to temperature

  3. Weigh the aircraft inside a hangar

  4. Ensure the aircraft is clean inside and out

  5. Ensure all required equipment is properly installed and no extra equipment is installed

  6. Ensure all required permanent ballasts are properly secured and all temporary ballasts are removed
• Standard weights


  Established weights for numerous items involved in weight and balance computations, should not be used if actual weights are available
• Draining the fuel before weighing


  1. Drain fuel from the tanks as specified by the manufacturer, or until the fuel quantity gauges read empty when the aircraft is in level-flight attitude

  2. Any fuel remaining in the system is considered residual or unusable fuel and is part of the aircraft empty weight
• Aircraft weight and balance control

  The primary purpose is safety, the secondary purpose is to aid efficiency during flight
• Draining the oil before weighing


  1. For aircraft certificated under CAR part 3, the empty weight does not include the engine lubricating oil, so it must be drained or its weight subtracted

  2. For aircraft certificated under 14 CFR parts 23 and 25, the full oil is included in the empty weight
• Overloading of the aircraft is not the only concern, the distribution of the weight is important also
• The aircraft has CG limits, and any loading that places the CG outside the established limits seriously impairs controllability of the aircraft
• Reasons for aircraft becoming heavier as they become older

  • Repair
  • Alteration
  • Replacement of aircraft parts
  • Modification
• Preparing other fluids before weighing

  1. The hydraulic fluid reservoir and all other reservoirs containing fluids required for normal operation should be full

  2. Fluids not considered part of the empty weight are potable water, lavatory precharge water, and water for injection into the engines
• Responsibilities of the A&P FAA-certificated mechanic or repairman when an aircraft has undergone extensive repair or major alteration

  1. Establish by computation that the authorized weight and CG limits are not exceeded

  2. Record the new empty weight center of gravity (EWCG) data in the current approved aircraft flight manual or issued operating limitations
• Configuring the aircraft for weighing


  1. Consult the aircraft service manual regarding position of the landing gear shock struts and the control surfaces

  2. For helicopters, the main rotor must be in its correct position
• Mechanical platform scale


  Weighing scale mostly used for small aircraft, low profile, easy to handle, safe, and reliable
• Electronic/Load cell scale


  Weighing scale mostly used for Helicopter/Narrow/Large transport aircraft, reliable means to weigh aircraft and are typically cheaper than the platform type
• Jacking the aircraft for weighing

  1. Use care when raising the aircraft on jacks, especially with spring steel landing gear

  2. Install stress panels or plates before using wing jacks

  3. Raise the jacks simultaneously and keep the safety collars screwed down against the jack cylinder
• Using load cell scales to weigh aircraft

  1. The aircraft is placed on jacks with electronic load cells placed between the jack and the jack pad

  2. The aircraft is raised on the jacks until the wheels or skids are off the floor and the aircraft is in a level flight attitude

  3. The weight measured by each load cell is indicated on the control panel
• Leveling the aircraft for weighing

  1. The aircraft must be in its level flight attitude, determined by information in the TCDS

  2. Lateral level is not specified for all light aircraft, but provisions are normally made on helicopters for determining both longitudinal and lateral level

  3. Leveling is normally done by adjusting the air pressure in the nosewheel shock strut when weighing from the wheels
• All scales for aviation use, manual or electronic, must be protected when stored or shipped, and they must be checked periodically for accuracy
• Tare


  The extra weight absorbed by the scale in addition to the weight of the aircraft, such as jacks, wheel chocks, or ground locks
• Safety precautions when jacking aircraft

  • Stress plates must be installed under the jack pads if specified by the manufacturer
  • If anyone is required to be in the aircraft, there must be no movement
  • The jacks must be straight under the jack pads before beginning to raise the aircraft
  • All jacks must be raised simultaneously and the safety devices engaged to prevent the aircraft tipping
• Preparing an aircraft for weighing

  1. Inspect and set scales to zero

  2. Weigh the aircraft inside a hangar

  3. Ensure the aircraft is clean and all required equipment is properly installed

  4. Remove any temporary ballasts
• Types of aircraft jacks

  • Axle jacks
  • Tripod jacks
• Standard weights


  Established weights for numerous items involved in weight and balance computations, should not be used if actual weights are available
• Axle jacks


  • Portable, self-contained hydraulic jacks used for tire repair, brake service, and other maintenance involving the landing gear
• Draining the fuel before weighing

  1. Drain fuel from the tanks until the fuel quantity gauges read empty when the aircraft is in level-flight attitude

  2. Any fuel remaining in the system is considered residual or unusable fuel and is part of the aircraft empty weight
• Tripod jacks


  • Portable, self-contained hydraulic jacks used for raising the nose, wing or tail of an aircraft, can be used to lift the entire aircraft
• Draining the oil before weighing

  1. For aircraft certificated under CAR part 3, the empty weight does not include the engine lubricating oil, so it must be drained or its weight subtracted

  2. For aircraft certificated under 14 CFR parts 23 and 25, the full oil is included in the empty weight