Quiz: 6 Questions To See How Much You Know About Weight and Balance

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It's an essential part of your preflight planning...

1) You and a friend are going flying in your Cessna 172R tomorrow morning, so you crunch some numbers to see if you will be within limits for the flight.

Basic Empty Weight: 1,678.0lbs (Arm: 39.54in)(Moment: 66,354.31)
Pilot: 180 lbs (Arm: 37in)
Front Passenger: 155 lbs (Arm: 37in)
Baggage: 0 lbs (Arm: 95in)
Fuel: 53 gallons (Arm: 48in)

Your Cessna's C.G. at the current weight is 38.8in-47.3in. What is the current weight, moment and C.G.? Is it within range?

Multiplying all the weights by the arm will give you a moment. Remember to multiply the fuel in gallons by 6 (1 gallon of 100LL is 6lbs). Add the weights, and you'll get 2,331 lbs. Add the moments. Divide the moment by the weight and you will get a C.G. of 40.3.

Multiplying all the weights by the arm will give you a moment. Remember to multiply the fuel in gallons by 6 (1 gallon of 100LL is 6lbs). Add the weights, and you'll get 2,331 lbs. Add the moments. Divide the moment by the weight and you will get a C.G. of 40.3.
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2) You're looking in your aircraft's POH at the weight and balance chapter. What is an arm, and why are some negative?

The arm is a measured distance from the reference datum. In most aircraft, like the Cessna 172, the reference datum is the firewall. Any weight located aft of the reference datum (passengers and baggage for example in a C172) will be positive. Any weight located forward (such as the engine) will be negative.

The arm is a measured distance from the reference datum. In most aircraft, like the Cessna 172, the reference datum is the firewall. Any weight located aft of the reference datum (passengers and baggage for example in a C172) will be positive. Any weight located forward (such as the engine) will be negative.
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3) Why is it important to calculate weight and balance not only for takeoff but for landing as well?

Since you burn fuel in flight, the C.G. can be significantly different on landing than it was for takeoff. Most aircraft have wing-mounted tanks, so the C.G. change typically moves forward as fuel is burned.

Since you burn fuel in flight, the C.G. can be significantly different on landing than it was for takeoff. Most aircraft have wing-mounted tanks, so the C.G. change typically moves forward as fuel is burned.
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4) What is the Zero Fuel Weight (ZFW)?

The Zero Fuel Weight is the weight of the aircraft, cargo and passengers excluding useable fuel. The gross weight of the aircraft minus the ZFW can give you the amount of useable fuel (in pounds) that you can carry onboard and still be at or below the max ramp weight.

The Zero Fuel Weight is the weight of the aircraft, cargo and passengers excluding useable fuel. The gross weight of the aircraft minus the ZFW can give you the amount of useable fuel (in pounds) that you can carry onboard and still be at or below the max ramp weight.
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5) What is the difference between the Standard Empty Weight and the Basic Empty Weight?

Basic Empty Weight is Standard Empty Weight plus optional equipment.

Basic Empty Weight is Standard Empty Weight plus optional equipment.
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6) How much does one gallon of 100LL weigh? How much does one gallon of Jet A weigh?

One gallon of 100LL weighs 6 lbs and one gallon of Jet-A is 6.7 lbs.

One gallon of 100LL weighs 6 lbs and one gallon of Jet-A is 6.7 lbs.
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