Weight and Balance Calculations for The Multiengine Airplane

The weight and balance concept for a multiengine plane is more complex than that of the single engine airplane due to several loading areas, including nose and aft baggage compartments, or varied fuel tanks and numerous seating options. Weight and balance thus must be adressed by the pilot before any flight. A standardized terminology in the domain is the 'basic empty weight.' Basic empty weight equals standard empty weight (weight of the standard airplane, full hydraulic fluid, unuseable fuel, and full oil) plus optional equipment (weight of all equipment installed beyond standard). A difference between that concept and more ancient terminologies is that it includes the weight of full oil, which was not included before

The multiengine airplane is where most pilots encounter the term 'zero fuel weight.' Zero fuel weight is the maximum allowable weight of the airplane and payload, assuming there is no useable fuel on board. If a zero fuel weight limitation is published for a plane in the AFM/POH, then all weight in excess of that figure must consist of useable fuel. The purpose of a zero fuel weight is to limit load forces on the wing spars with heavy fuselage loads

Let's now check some calculations in terms of weight and balance as a multiengine airplane is having numeric values associated with the following data:

• Basic empty weight
• Zero fuel weight
• Maximum takeoff weight (at the beginning of the takeoff roll -to allow for the fuel needed for taxi and runup)
• Maximum useable fuel

Here are the usual calculations used

• Useful load (maximum combination of useable fuel, passengers, baggage, and cargo that the airplane is capable of carrying) is calculated like Maximum takeoff weight minus Basic empty weight
• Payload (maximum combination of passengers, baggage, and cargo that the airplane is capable of carrying. A zero fuel weight, if published, is the limiting weight) is calculated like Zero fuel weight minus Basic empty weight
• Fuel capacity at maximum payload (assuming maximum payload, the only weight permitted in excess of the zero fuel weight must consist of useable fuel) is Maximum takeoff weight minus Zero fuel weight, which gives fuel allowed in lb
• Payload allowed at maximum fuel capacity is calculated like Maximum takeoff weight minus Weight with max. fuel (which is Basic empty weight plus Maximum useable fuel)
• Maximum landing weight (when published) is a limitation of weight at landing. This requires preflight planning of fuel burn to ensure that the airplane weight upon arrival at destination will be at or below the maximum landing weight

In terms of balance at last, the flight characteristics of the multiengine airplane will vary significantly with shifts of the center of gravity (CG) within the approved envelope. At forward CGs, the airplane will be more stable, with a slightly higher stalling speed, a slightly slower cruising speed, and favorable stall characteristics. At aft CGs, the airplane will be less stable, with a slightly lower stalling speed, a slightly faster cruising speed, and less desirable stall characteristics. Some multiengine airplanes may require ballast to remain within CG limits under certain loading conditions (like most passengers seated aft hence a ballast in the nose baggage compartment, or a a student and instructor aboard only with a ballast in the aft baggage compartment). The pilot always must direct the seating of passengers and placement of baggage and cargo to achieve a center of gravity within the approved envelope