Definition
The short delay between the pilot moving the power lever forward and the engine actually producing the increased thrust or power being commanded. In turbocharged and turbine engines, this delay is more noticeable because the engine must spool up before full output is delivered.
Plain English
When you push the throttle forward, the engine doesn't respond instantly — there's a small pause before the extra power shows up.
Context Anchor
Encountered when operating turbine-powered airplanes, especially during approaches, landings, missed approaches, and any situation where the pilot may need power quickly.
Derivation
"Lag" comes from an old word meaning to fall behind or be slow to follow. Here it describes how the engine's response falls behind the pilot's input.
Why Pilots Care
Anticipating power lag prevents insufficient climb performance or unintended airspeed changes during critical maneuvers.
Analogy
It is like pressing the accelerator in a heavy truck and waiting a moment before the truck actually starts pulling harder. The command happens first; the response follows shortly after.
Intuition Check
Power lag does not mean the engine is weak or failing. It means there is a normal delay between requesting power and receiving it.
Example Sentence 1
On the go-around, the pilot advanced the throttle early, knowing power lag would delay the climb response by a couple of seconds.
Example Sentence 2
Reducing throttle for descent requires allowing extra time for power lag so the aircraft does not lose altitude unexpectedly.