Definition
In a multi-engine aircraft, the technique of advancing one engine's throttle more than the other to produce asymmetric thrust, used to help steer the aircraft on the ground or counteract a tendency to swerve during the takeoff roll.
Plain English
Pushing one engine's power lever forward more than the other so the airplane turns or stays straight, instead of relying only on the rudder or nosewheel steering.
Context Anchor
Seen in multiengine instrument takeoff procedures, where the pilot may have little outside visual reference and must keep the airplane tracking straight after power is applied.
Derivation
Differential' comes from the Latin 'differentia,' meaning a difference between things. Here it simply means the two throttles are set differently from each other, rather than moved together as a matched pair.
Why Pilots Care
Gives pilots an extra way to control heading at low speeds when the rudder is less effective or during engine-out situations.
Analogy
Like turning a rowboat by pulling harder on one oar than the other.
Grounding Statement
On a takeoff roll, more power on one side of the airplane can make the nose swing away from that side.
Intuition Check
Differential throttle does not mean a separate special throttle control. It means using the existing engine throttles unevenly to create or correct a turning tendency.
Example Sentence 1
During the instrument takeoff roll, the pilot used a touch of differential throttle to keep the aircraft aligned with the centerline until the rudder became effective.
Example Sentence 2
After an engine failure on takeoff, the pilot applied differential throttle to help keep the nose straight until airspeed increased.