Definition
The highest altitude at which a multi-engine airplane, with one engine inoperative and the remaining engine(s) operating at maximum continuous power, can still maintain a steady climb of 50 feet per minute in a clean configuration at the best single-engine rate-of-climb speed (Vyse).
Plain English
The highest altitude a twin-engine airplane can still slowly climb after losing one engine. Above this altitude, with one engine out, the airplane can no longer gain height — it will only hold altitude or descend.
Context Anchor
Seen in multiengine airplane performance charts, especially when planning whether the airplane can climb after an engine failure.
Derivation
‘Service’ here doesn’t mean ‘maintenance.’ It comes from the older aviation use of ‘service ceiling’ — the altitude at which the airplane can still perform useful service, defined as a small but steady climb rate (50 fpm). ‘Single engine’ specifies that this is measured with one engine failed.
Why Pilots Care
It sets the practical upper limit for safe flight over mountains or obstacles if an engine fails.
Grounding Statement
At the single engine service ceiling, the airplane is still climbing, but only very slowly: 50 feet in one minute.
Intuition Check
Do not read “ceiling” as the absolute highest altitude the airplane can ever reach on one engine. Here it means the practical one-engine climb limit where only 50 feet per minute of climb remains.
Example Sentence 1
Before crossing the ridge, the pilot checked the single engine service ceiling and confirmed it was above the minimum en route altitude.
Example Sentence 2
With an 8,500-foot single engine service ceiling, the flight stayed below that altitude when terrain required an engine-out escape path.