Definition
A rapid forward movement of the throttle or power lever from a low setting to a high setting, used during turbine engine testing or certification to evaluate how quickly and reliably the engine can spool up without stalling, surging, or flaming out.
Plain English
Slamming the throttle from low power to high power as fast as it will go, to see how the engine handles a sudden demand for full thrust.
Context Anchor
Seen in turbine engine operation, maintenance checks, and discussions of how quickly an engine can respond when power is needed.
Derivation
Jam here means to push or shove something quickly and forcefully into position, as in jamming a lever forward. Acceleration refers to the engine's increase in speed and power. Together they describe an abrupt, forced power increase rather than a smooth one.
Why Pilots Care
Can produce detonation, power surges, or engine damage if repeated during critical phases of flight.
Grounding Statement
Picture advancing the power lever quickly on a turbine aircraft and expecting the engine to build power smoothly without lag or distress.
Intuition Check
Do not read “jam” here as a blockage or a stuck engine. In “jam acceleration,” it means the power lever is moved rapidly to demand a quick engine response.
Example Sentence 1
During certification testing, the engine must tolerate a jam acceleration from idle to takeoff power without surging.
Example Sentence 2
Smooth throttle movement prevents jam acceleration and keeps the mixture from becoming overly rich.