Definition
A condition in a multiengine airplane in which the thrust produced on one side of the aircraft is greater than the thrust produced on the other, creating a yawing and rolling tendency toward the side with less thrust. It most commonly occurs when one engine fails or is producing reduced power while the other engine continues to produce full or higher power.
Plain English
When one engine is pushing harder than the other, the airplane wants to swing and roll toward the weaker side. The pilot has to use rudder and aileron to keep it flying straight.
Context Anchor
Encountered in multiengine training, especially when discussing engine failure, takeoff performance, and control of the airplane after one engine loses power.
Derivation
From Greek 'a-' meaning 'not' and 'symmetria' meaning 'balanced proportion.' Asymmetrical simply means 'not balanced.' Thrust here is the forward force from the engines. Together: unbalanced forward force — one side pushing more than the other.
Why Pilots Care
Unmanaged asymmetrical thrust produces strong yaw that can quickly lead to loss of directional control if not countered with immediate rudder and proper aircraft configuration.
Analogy
It is like rowing a boat with one oar pulling harder than the other. The boat does not just slow down; it turns toward the weaker side.
Grounding Statement
Picture one engine still pulling strongly while the other is weak or failed: the airplane is being pulled unevenly, so the nose wants to swing.
Intuition Check
Do not think of asymmetrical thrust as just “less power.” The key point is uneven power from side to side, which creates a turning force.
Example Sentence 1
When the right engine failed shortly after takeoff, the asymmetrical thrust caused the airplane to yaw sharply to the right until the pilot applied left rudder.
Example Sentence 2
During the engine-out drill the pilot reduced power on the operating engine to simulate asymmetrical thrust and practiced maintaining heading with rudder and aileron.