Definition
A system of weights used in the United States and other English-speaking countries for measuring most ordinary goods, including aircraft components and fluids. In this system, one pound equals 16 ounces, and one ounce equals 437.5 grains. It is the standard system used for nearly all aviation weight figures expressed in pounds and ounces.
Plain English
The everyday pound-and-ounce weight system used in the U.S. — the same one used to weigh groceries, baggage, and aircraft loads. One pound is 16 ounces.
Context Anchor
Seen in aircraft weight and balance, loading, baggage, cargo, and equipment weight references.
Derivation
From Old French 'aveir de peis,' meaning 'goods of weight' — that is, goods sold by weight rather than by piece or volume. The term carried into English as the standard system for weighing common goods, which is why it became the default pound used in U.S. aviation.
Why Pilots Care
Aircraft empty weight, fuel quantity, and payload limits are expressed in avoirdupois pounds, directly affecting weight-and-balance computations and legal operating limits.
Intuition Check
Do not treat “avoirdupois” as a special kind of aircraft weight. It simply names the standard 16-ounce pound system used for ordinary weight measurements.
Example Sentence 1
The aircraft's empty weight of 1,650 pounds is expressed in avoirdupois weight, with 16 ounces to the pound.
Example Sentence 2
Maintenance records list the aircraft's basic empty weight using the avoirdupois system.