Definition
VSSE is the minimum speed, established by the manufacturer for a multiengine airplane, at which one engine may be intentionally rendered inoperative for training or demonstration purposes. It is shown on the airspeed indicator as a published figure (not a colored marking) and is set above VMC to provide a safety margin against loss of directional control during deliberate engine cuts.
Plain English
It's the slowest speed at which an instructor or pilot is allowed to deliberately shut down or simulate failure of one engine in a twin. Below this speed, intentionally killing an engine is considered unsafe because the airplane is too close to losing controllability.
Context Anchor
Seen in multiengine airplane training, especially before an instructor simulates an engine failure after takeoff or during climb practice.
Derivation
The 'V' comes from the French vitesse, meaning 'speed' — the standard prefix used for all aviation V-speeds. 'SSE' stands for 'Safe Single-Engine.' Knowing this helps the speed sit naturally alongside other V-speeds like VMC and VYSE.
Why Pilots Care
Using VSSE after an engine failure gives a reliable margin that prevents loss of directional control and supports safe climb or return to the airport.
Intuition Check
VSSE is not the speed where an airplane is guaranteed to climb on one engine. It is the minimum speed for intentionally starting a one-engine-inoperative training exercise.
Example Sentence 1
The instructor waited until the airplane accelerated through VSSE before pulling the right throttle to simulate an engine failure.
Example Sentence 2
Before the checkride the instructor had the student demonstrate maintaining VSSE during a simulated engine failure on takeoff.