Single-Engine Inoperative

Single-Engine Inoperative (SEI) is the critical flight condition where one engine of a multi-engine aircraft has failed or been shut down, requiring the aircraft to operate on the remaining engine(s).

• V-speeds for SEI: V1 (decision speed), V2 (takeoff safety speed with one engine out), VMCA (minimum control speed air)
• Performance: Climb gradient is significantly reduced — must meet minimum gradient requirements (2.4% for two-engine aircraft at takeoff)
• Drift down: The aircraft may not be able to maintain altitude and must drift down to a lower level
• Asymmetric thrust: The operating engine creates a yawing moment that must be controlled with rudder
• Critical engine: On some aircraft (typically propeller), one engine failure is more adverse than the other
• All airline pilots are extensively trained in engine-out procedures in the simulator