Definition
A unit of force in the foot-pound-second (FPS) system, defined as the force required to accelerate a mass of one pound at a rate of one foot per second per second. One poundal equals approximately 0.0311 pound-force.
Plain English
A small unit of force. It's how much push you need to make a one-pound object speed up by one foot per second every second.
Context Anchor
Seen mainly in older aviation, physics, and engineering references that discuss force, mass, acceleration, or aircraft structural loads.
Derivation
From 'pound' plus the suffix '-al', coined in the late 1800s to give the pound-mass system its own unit of force, parallel to how the dyne serves the gram-centimeter system. The name signals it is a pound-based force unit.
Why Pilots Care
Most pilots will not use poundals directly, but understanding the unit helps when reading older aerodynamics texts or engineering references where force, mass, and acceleration are kept strictly separate.
Intuition Check
Do not read “poundal” as just another word for “pound.” A poundal is a unit of force, and it is only about one thirty-second of a pound-force.
Example Sentence 1
In the FPS system, a force of ten poundals applied to a five-pound mass produces an acceleration of two feet per second squared.
Example Sentence 2
Converting the measured force from poundals gave the correct acceleration value for the calculation.