Definition
In a multi-engine aircraft, the technique of using unequal power settings between the left and right engines to produce a yawing moment, typically used for fine heading control or to compensate for an asymmetric condition.
Plain English
On an aircraft with more than one engine, you set one engine's power slightly higher than the other so the aircraft yaws (turns its nose) toward the side with less power. It is a way to make small heading corrections using the throttles instead of the rudder.
Context Anchor
Seen in multiengine instrument flying and trim discussions, especially when managing yaw or reducing the need for constant rudder pressure.
Derivation
"Differential" comes from Latin differentia, meaning "a difference." Here it simply means the two engines are set at different power levels rather than matched. That difference is what produces the yaw.
Why Pilots Care
It reduces rudder deflection and pilot workload while maintaining precise heading control, especially useful in engine-out or instrument conditions.
Analogy
Think of a rowboat with one oar pulling slightly harder than the other -- the boat naturally turns toward the weaker side. Engines work the same way.
Intuition Check
Do not read “power control” here as electrical control or throttle use in general. In this term, “power” means engine thrust, and “differential” means the thrust is different from one side of the airplane to the other.
Example Sentence 1
She used differential power control to nudge the heading two degrees right without touching the rudder.
Example Sentence 2
In IMC, small differential power adjustments helped hold the localizer without constant rudder pressure.