Definition
The highest power setting an engine is approved to use during all phases of flight other than takeoff. It is below the takeoff power rating and may be sustained for longer periods, though typically still time-limited or subject to specific operating conditions defined by the manufacturer.
Plain English
It is the strongest the engine is allowed to run when it is not taking off. Takeoff power is higher, but you can only use that for a short time. Maximum Except Takeoff is the next step down, and you can use it for longer.
Context Anchor
Seen in engine operating limits, performance charts, and aircraft or engine manual power-setting instructions.
Derivation
The name describes itself plainly: the maximum power allowed except during takeoff. The phrasing comes from how engine manufacturers list power ratings — takeoff is treated separately because it is the briefest and most demanding setting, so everything else is grouped under one ceiling below it.
Why Pilots Care
Keeps the engine within safe temperature and stress limits for longevity while still allowing the extra power needed only for takeoff.
Intuition Check
Do not read this as “maximum power for takeoff.” It means the maximum approved power except for the separate takeoff power rating.
Example Sentence 1
After lift-off and reaching a safe altitude, the pilot reduced power from takeoff setting to Maximum Except Takeoff for the climb.
Example Sentence 2
The performance chart shows the maximum except takeoff manifold pressure available at 5,000 feet.