Definition
Airplanes powered by two engines, typically mounted one on each wing, providing redundancy so the airplane can continue flying if one engine fails.
Plain English
An airplane that has two engines instead of one. If one quits, the other can keep the airplane in the air.
Context Anchor
Seen in multiengine training, airplane performance discussions, emergency procedures, and aircraft checkout materials.
Derivation
Twin' comes from Old English getwinn, meaning 'double' or 'two together.' A twin-engine airplane is simply one with a matched pair of engines.
Why Pilots Care
Twin-engine airplanes provide engine-out redundancy and allow operations in a wider range of conditions, but demand a multi-engine rating and specific emergency procedures.
Intuition Check
Do not assume “twin-engine” means the airplane will always keep climbing after one engine fails. It only means the airplane has two engines; safe performance after an engine failure depends on weight, altitude, weather, and pilot control.
Example Sentence 1
He earned his multi-engine rating in a light twin-engine airplane before moving on to turboprops.
Example Sentence 2
Twin-engine airplanes maintain climb performance after losing one engine on takeoff when operated within weight and speed limits.