AI.II.P.K5aFAA-S-ACS-25 · Nov 2023Knowledge
a. Critical engine
Aerodynamics of OEI operation including: a. Critical engine
Bottom line
The critical engine is the engine whose failure would most adversely affect the airplane’s performance or handling qualities. On twins with each engine rotating in conventional, clockwise rotation as viewed from the pilot's seat, the critical engine will be the left engine. The AFM/POH-published VMC is determined with the critical engine inoperative.
Key numbers
| Number | What it means |
|---|---|
| not more than 5° angle of bank to maintain straight flight at VMC (static determination) | VMC bank |
| within 20 degrees of the original heading after the critical engine is suddenly made inoperative | Heading loss |
| sea level calibrated airspeed, critical engine suddenly made inoperative | VMC speed |
FAA references
- FAA-P-8740-66, Flying Light Twins Safely — FAA-P-8740-66
- AFH ch. 13 (pp. 13-23–13-24) — FAA-H-8083-3C
- PHAK ch. 2 (p. 2-20) — FAA-H-8083-25C (2023)
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