Airplane in Percent MAC

A loading schedule is used to document compliance with the certificated weight and balance limitations contained in the manufacturer’s AFM and weight and balance manual. The basic operating weight (BOW) and the operating index are entered into a loading schedule like the one in Figure 1, and the variables for a specific flight are entered as appropriate to determine the loaded weight and CG.

Figure 1. Loading schedule

Use the data in this example:
Basic operating weight: 105,500 lb
Basic operating index (total moment/1,000): 98,837.0
MAC: 180.9 in
LEMAC: 860.5

Figure 2 illustrates passenger, cargo, and fuel loading tables. Using these tables, determine the moment indexes for the passengers (PAX), cargo, and fuel.

Figure 2. Loading schedule for determining weight and CG

The airplane is loaded in this way:
Passengers (nominal weight—170 pounds each)
Forward compartment: 18
Aft compartment: 95

Cargo
Forward hold: 1,500 lb
Aft hold: 2,500 lb

Fuel
Tanks 1 and 3: 10,500 lb each
Tank 2: 28,000 lb

The formula in Figure 3 can be used to determine the location of the CG in inches aft of the datum.

Figure 3. Determining the location of the CG in inches aft of the datum

Determine the distance from the CG to the LEMAC by subtracting the distance between the datum and LEMAC from the distance between the datum and the CG. [Figure 4]

Figure 4. Determining the distance from the CG to the LEMAC

The location of the CG in percent MAC must be known in order to set the stabilizer trim takeoff. [Figure 5]

Figure 5. Determining the location of the CG in percent MAC

RELATED POSTS

• Establishing the Initial Weight of an Aircraft
• Determining the Empty Weight and Empty Weight CG (EWCG)
• Documenting Changes to an Aircraft’s Weight and Balance
• Determining CG Changes Caused by Modifying the Cargo (Part 1)
• Determining CG Changes Caused by Modifying the Cargo (Part 2)
• Determining CG Changes Caused by Modifying the Cargo (Part 3)