The ultimate test of whether or not there is a problem with an airplane’s weight and balance is when it is loaded and ready to fly. The only real importance of an airplane’s empty weight and empty weight center of gravity is how it affects the loaded weight and balance of the airplane, since an airplane doesn’t fly when it is empty. The pilot in command is responsible for the weight and balance of the loaded airplane, and he or she makes the final decision on whether or not the airplane is safe to fly.

As an example of an airplane being loaded for flight, the Piper Seneca twin will be used. The Type Certificate Data Sheet for this airplane was shown earlier in this chapter, and its center of gravity range and CG envelope were also shown.

The information from the Type Certificate Data Sheet that pertains to this example loading is as follows:

CG Range (Gear Extended)

S/N 34-7250215 through 34-7450220:
(+87.9″) to (+94.6″) at 4,200 lb
(+82.0″) to (+94.6″) at 3,400 lb
(+80.7″) to (+94.6″) at 2,780 lb
Straight line variation between points given.
−32 in‑lb moment change due to gear retracting landing gear

Empty Weight CG Range

None

Maximum Weight

S/N 34-7250215 through 34-7450220:
4,200 lb—Takeoff
4,000 lb—Landing

No. of Seats

7 (2 at +85.5″, 3 at +118.1″,
2 at +155.7″)

Maximum Baggage

200 lb (100 lb at +22.5, 100 lb at +178.7)

Fuel Capacity

98 gal (2 wing tanks) at (+93.6″) (93 gal usable). See NOTE 1 for data on system fuel.

• Airplane Serial Number: 34-7250816
• Airplane Empty Weight: 2,650 lb
• Airplane Empty Weight CG: +86.8″

For today’s flight, the following useful load items will be included:

• 1 pilot at 180 lb at an arm of +85.5″
• 1 passenger at 160 lb at an arm of +118.1″
• 1 passenger at 210 lb at an arm of +118.1″
• 1 passenger at 190 lb at an arm of +118.1″
• 1 passenger at 205 lb at an arm of +155.7″
• 50 lb of baggage at +22.5″
• 100 lb of baggage at +178.7″
• 80 gal of fuel at +93.6″

To calculate the loaded weight and CG of this airplane, a four column chart will be used, as shown in Figure 4-22.

Figure 4-22. Center of gravity calculation for Piper Seneca.

Based on the information in the Type Certificate Data Sheet, the maximum takeoff weight of this airplane is 4,200 lb, and the aft-most CG limit is +94.6″. The loaded airplane in the chart above is 25 lb too heavy, and the CG is 1.82″ too far aft. To make the airplane safe to fly, the load needs to be reduced by 25 lb and some of the load needs to be shifted forward. For example, the baggage can be reduced by 25 lb, and a full 100 lb of it can be placed in the more forward compartment. One passenger can be moved to the forward seat next to the pilot, and the aft-most passenger
can then be moved forward. If these changes are made, the four column calculation will be as shown in Figure 4-23.

Figure 4-23. Center of gravity calculation for Piper Seneca with weights shifted.

With the changes made, the loaded weight is now at the maximum allowable of 4,200 lb, and the CG has moved forward 4.41″. The airplane is now safe to fly.