Definition
In a multi-engine airplane with one engine inoperative, the airspeed that produces the greatest gain in altitude per unit of time. It is published in the Pilot's Operating Handbook and is commonly designated VYSE. It assumes the critical engine failed, the propeller on the failed engine is feathered or in the position specified by the manufacturer, and the airplane is configured per the manufacturer's procedure.
Plain English
The speed that gives you the most height gained per minute when flying a twin with one engine out. It's the speed you aim for to climb away from the ground as quickly as possible on the remaining engine.
Context Anchor
Seen in multiengine airplane limitations, performance data, and airspeed discussions; it is commonly associated with the blue marking on the airspeed indicator when that marking is installed.
Why Pilots Care
Flying this speed after an engine failure gives the best chance of clearing obstacles and reaching a safe altitude before the remaining engine overheats or fuel is exhausted.
Intuition Check
Do not read “single-engine” here as “an airplane that has only one engine.” In this context, it means a multiengine airplane being flown with one engine failed or not producing power.
Example Sentence 1
After securing the failed engine, the pilot pitched for the single-engine best rate of climb speed and held the blue line all the way to a safe altitude.
Example Sentence 2
The checklist calls for establishing single-engine best rate of climb speed before attempting to troubleshoot the failed engine.