Interactive Aircraft Loading Course

Weight and Balance

Weight and balance is the discipline of placing people, fuel, and baggage in a way that keeps an airplane within its structural limits and center of gravity range. This course shows how each loading decision changes total weight, total moment, and the actual balance point of a typical small, single-engine airplane.

Launch CG Lab Why It Matters

What It Is

Weight is the load. Balance is where that load acts.

Every item in an airplane has both a weight and a location, called an arm, measured from the reference datum. In this module the datum is placed at the tip of the propeller spinner. Multiply each item's weight by its arm and you get moment. Add all the moments together and divide by total weight to find the loaded center of gravity.

  • Weight tells you how much mass the airplane must carry.
  • Moment tells you how strongly that mass pulls the CG forward or aft.
  • Center of gravity tells you where the aircraft will balance in flight.

Why It Matters

CG location changes stability, control feel, and stall behavior.

A forward CG usually increases stability but may require more tail-down force, longer takeoff runs, and higher stall speed. An aft CG can reduce pitch stability, make stalls harder to recover from, and leave the pilot with less elevator authority when it matters most. Safe loading means staying within both maximum weight and the approved CG envelope.

  • Too heavy stresses performance, climb, and landing distance.
  • Too far forward can make rotation and flare difficult.
  • Too far aft can make the airplane less stable and less recoverable.

Interactive CG Lab

Load the airplane and watch the balance point move

Adjust fuel, passengers, and cargo. The airplane outline uses the propeller spinner tip as the zero-inch datum, and the live CG symbol shifts as weight and moment change.

40 gal usable at 6 lb/gal

180 lb at the front-seat station

150 lb at the front-seat station

80 lb at the rear-seat station

30 lb in the baggage compartment

Within envelope Weight normal

Start by noting how fuel and front-seat loading keep the CG relatively forward, then add rear weight and baggage to watch the balance point move aft.

0 total weight (lb)
0 total moment (lb-in)
0 loaded CG arm (in)

Aircraft Side View

Reference datum at spinner tip

The live CG symbol shows where the airplane balances along the fuselage.

Weight and balance airplane loading diagram A side-view outline of a small single-engine airplane with the datum at the propeller spinner and a moving CG symbol. Datum 0 in Spinner tip CG

Balance Envelope

Weight versus CG arm

The same CG symbol is plotted against a representative single-engine loading envelope.

Weight and balance envelope chart A chart showing acceptable CG range by total weight with a moving CG symbol. 72 78 84 90 1,500 1,800 2,100 2,400 2,550 CG Arm (inches aft of datum) Weight (lb)

Moment Breakdown

See where the math comes from

Station Arm (in) Weight (lb) Moment (lb-in)
Empty airplane 78.0 1,660 129,480
Fuel 48.0 0 0
Pilot 84.5 0 0
Front passenger 84.5 0 0
Rear passengers 118.1 0 0
Baggage / cargo 142.8 0 0
Total 0 0 0

1. Datum gives every number meaning

The same item can produce a very different moment depending on how far it sits from the spinner-tip datum.

2. Rear loading moves CG quickly

Baggage and rear-seat loading often have a larger aft effect than pilots expect because their arms are much longer.

3. Fuel can move the balance too

Fuel is not just weight. Because it has its own arm, burning or adding fuel shifts both total weight and total moment.

4. Use the POH for the actual airplane

This lab uses representative numbers for training. Real-world go/no-go decisions must use the aircraft's approved data.