Commercial pilot · ACS CA.X.A
Maneuvering with One Engine Inoperative
At altitude, an engine failure is flown the same way every time: control, blue line, the flow, then a calm decision about a restart and where to land.
This lesson is written for multi-engine land or multi-engine sea. You picked single-engine land: speeds, altitudes and procedures differ, so follow your POH/AFM and your instructor.
Why this one matters
At altitude an engine failure gives you time, but not a normal airplane: many light twins can't climb on one engine, and some can't hold altitude. The errors come from rushing, feathering the wrong engine, mismanaging fuel, or restarting an engine that should stay shut down. A practiced, single flow and a plan to divert to the nearest suitable airport make it routine.
Can’t miss
- •Losing one engine costs half the power but 80-90% of the climb performance. Many light twins can't climb on one engine, and some can't hold altitude, at gross weight on a hot day or at a high field.(Airplane Flying Handbook (FAA-H-8083-3C), Transition to Multiengine Airplanes)
- •One flow: control and blue line; power forward; drag off; identify; verify; feather promptly; secure by the checklist. Then troubleshoot and, if it's safe, restart by the checklist.(Airplane Flying Handbook (FAA-H-8083-3C), Transition to Multiengine Airplanes; Commercial Pilot ACS (FAA-S-ACS-7B), CA.X.A.S1-S6)
- •Above the absolute ceiling the airplane drifts down at VYSE and levels off at the absolute ceiling; plan the route and airport with terrain in mind.(Airplane Flying Handbook (FAA-H-8083-3C), Transition to Multiengine Airplanes)
- •Don't restart after a fire, a mechanical failure, oil loss or a fuel leak, or with no known cause. A propeller unfeathered for a restart that fails may not feather again, and windmilling it adds heavy drag.(Airplane Flying Handbook (FAA-H-8083-3C), Transition to Multiengine Airplanes; Your airplane's POH/AFM)
- •Zero sideslip, the least drag on one engine: bank about 2-3° toward the operating engine with the ball one-third to one-half out toward it, and rudder to hold heading. A centered ball with the wings level is a sideslip that costs climb and raises VMC.(Airplane Flying Handbook (FAA-H-8083-3C), Transition to Multiengine Airplanes)
- •Training: no intentional failure below VSSE; the real feather, secure and restart only at a safe altitude, near an airport you could land at if the restart fails, completed no lower than 3,000 feet AGL (or the manufacturer's higher altitude).(Airplane Flying Handbook (FAA-H-8083-3C), Transition to Multiengine Airplanes; Commercial Pilot ACS (FAA-S-ACS-7B), Appendix 2)
- •Commercial standard: altitude ±100 feet (or minimum sink), airspeed ±10 knots, headings ±10°.(Commercial Pilot ACS (FAA-S-ACS-7B), CA.X.A.S7)
What you should know
VMC and speeds K1 · K2
- Published VMC (the red line) is the slowest speed at which you can keep control with the critical engine suddenly inoperative, then hold straight flight with no more than 5° of bank. It is set under fixed conditions: sea-level standard day; maximum takeoff power on the operating engine; the critical engine windmilling with its propeller control in the takeoff position; the most unfavorable weight (the lightest) and the most unfavorable (aft) center of gravity; gear up; wing and cowl flaps and trim in the takeoff position; out of ground effect; no more than 5° of bank toward the operating engine; heading held within 20° with no more than 150 pounds of rudder force.(14 CFR 23.149 (now 23.2135); Airplane Flying Handbook (FAA-H-8083-3C), Transition to Multiengine Airplanes)
- Your real VMC differs whenever the conditions do. It goes up with a windmilling propeller (feathering lowers it), an aft CG, lighter weight, more power on the operating engine, and less bank toward it. It goes down with less power (a normally aspirated engine at altitude; a turbocharged one only above its critical altitude), gear extended (keel effect), and ground effect.(Airplane Flying Handbook (FAA-H-8083-3C), Transition to Multiengine Airplanes)
- Bank matters most: VMC rises more than 3 knots for each degree of bank less than 5°, and with the wings level control can be lost almost 20 knots above the published red line. Up to 5° toward the operating engine is the certification number, not the way you fly.(Airplane Flying Handbook (FAA-H-8083-3C), Transition to Multiengine Airplanes)
- The critical engine is the one whose failure is hardest to control: on twins with both propellers turning clockwise (seen from behind), the left, because of P-factor, accelerated slipstream, spiraling slipstream and torque. Twins with counter-rotating propellers (a Seminole or a Duchess) have no critical engine.(Airplane Flying Handbook (FAA-H-8083-3C), Transition to Multiengine Airplanes)
- VMC (red line): minimum control speed. VYSE (blue line): best rate of climb, or least loss, on one engine. VXSE: best angle on one engine. VSSE: safe single-engine speed, the slowest at which an engine may be intentionally failed in training.(Airplane Flying Handbook (FAA-H-8083-3C), Transition to Multiengine Airplanes)
Feathering, securing, restarting K3 · K4 · K5
- The airborne flow, as the POH gives it: control first (rudder, bank toward the operating engine), pitch for blue line; mixtures, propellers, throttles forward; gear and flaps up once you are committed to fly; identify ("dead foot, dead engine"); verify; feather; then secure by the checklist.(Airplane Flying Handbook (FAA-H-8083-3C), Transition to Multiengine Airplanes; Your airplane's POH/AFM)
- Verify by slowly closing the throttle of the engine you identified: no change in yaw or sound confirms it. If the yaw gets worse or the airplane loses power, that is the good engine: advance it at once and identify again. An engine still making useful power can be left running until you have altitude and speed.(Airplane Flying Handbook (FAA-H-8083-3C), Transition to Multiengine Airplanes)
- Feather promptly once verified: most light twins can't feather once the propeller has slowed below a minimum RPM (the anti-feather lock). At altitude, a quick look for an obvious cause (fuel selector, mixture, fuel pump) is fine if it doesn't delay the flow.(Airplane Flying Handbook (FAA-H-8083-3C), Transition to Multiengine Airplanes)
- A feathered propeller is turned edge-on to the wind and stops, cutting its drag sharply.(Airplane Flying Handbook (FAA-H-8083-3C), Transition to Multiengine Airplanes)
- Secure the dead engine by the checklist (mixture idle cutoff, fuel off, magnetos and alternator off, cowl flap closed), then monitor the operating engine's temperatures and the electrical load on its single alternator.(Your airplane's POH/AFM)
- Zero sideslip, the least drag on one engine: bank about 2-3° toward the operating engine with the ball one-third to one-half out toward it, and rudder to hold heading. A centered ball with the wings level is a sideslip that costs climb and raises VMC.(Airplane Flying Handbook (FAA-H-8083-3C), Transition to Multiengine Airplanes)
- Restart only when the cause is known and safe (for example, fuel starvation now corrected), by the POH restart checklist: fuel on, mixture set, magnetos on, propeller forward, starter or accumulator; warm the engine at low power before using it.(Your airplane's POH/AFM)
Flying on one R1 · R2 · R3 · R4 · R5
- Single-engine service ceiling: where the airplane climbs only 50 feet per minute at VYSE. Absolute ceiling: where it can't climb at all. Above the absolute ceiling it drifts down at VYSE and levels off there; between the two it still climbs, just slowly.(Airplane Flying Handbook (FAA-H-8083-3C), Transition to Multiengine Airplanes)
- Fuel: protect the operating engine's supply first. Use crossfeed only exactly as the POH directs, and never toward a side with a fire or a leak.(Your airplane's POH/AFM)
- Turn in either direction at blue line or above, keeping zero sideslip; turns toward the dead engine are acceptable.(Airplane Flying Handbook (FAA-H-8083-3C), Transition to Multiengine Airplanes)
- Monitor the operating engine within its limits, manage its cowl flap, and shed electrical load to suit one alternator.(Your airplane's POH/AFM)
- Tell ATC: declare an emergency when warranted, state that you are on one engine, and ask for the vectors, altitudes and runway you need.(Aeronautical Information Manual (AIM))
- Divert to the nearest suitable airport.(Airplane Flying Handbook (FAA-H-8083-3C), Transition to Multiengine Airplanes)
- Hold blue line; don't let the airspeed decay trying to climb. VXSE is used only to clear an obstacle after takeoff, then accelerate to VYSE. The hard floor with asymmetric power is VMC (VSSE for intentional failures); a stall there can roll into a spin.(Airplane Flying Handbook (FAA-H-8083-3C), Transition to Multiengine Airplanes)
- Clear the area, and keep scanning for traffic while you handle the failure.(AC 90-48, Pilots' Role in Collision Avoidance)
- A failure is loud and startling. Fly the airplane first (control, then airspeed), then work the flow and checklists in order, and divide attention between the failure, the flight path and traffic.(Risk Management Handbook (FAA-H-8083-2A))
On the flight
ACS standards
- Recognize the failure, use the memory items, identify, verify and feather; secure the engine; determine the cause; restart per the POH.(Commercial Pilot ACS (FAA-S-ACS-7B), CA.X.A.S1-S6)
- Altitude ±100 feet (or minimum sink), airspeed ±10 knots, headings ±10°; checklists.(Commercial Pilot ACS (FAA-S-ACS-7B), CA.X.A.S7-S8)
What your instructor is watching for
Your instructor watches for control first, a methodical identify and verify, a prompt feather, zero sideslip in straight flight and turns, sound restart judgment, accurate single-engine flying, and a proper restart.
Scenarios
Decide what you would do first, then see the worked answer.
The failed engine's fuel gauge reads empty, the other tank half full, and there's no sign of fire or a leak.
What do you do? See the worked answer
Protect the operating engine's fuel first. If the POH allows crossfeed to the failed engine and the cause is clearly fuel starvation, a restart by the checklist is reasonable; otherwise keep it secured and divert.
Your airplane's POH/AFM
The left engine stops with a bang and oil streaks across the cowling.
Do you try a restart? See the worked answer
No: a mechanical failure with oil loss. Keep it feathered and secured and divert.
Airplane Flying Handbook (FAA-H-8083-3C), Transition to Multiengine Airplanes
At 9,000 feet over mountains; the single-engine absolute ceiling is 6,000.
What do you plan? See the worked answer
A drift-down at VYSE to about 6,000 feet: pick a route and airport that keep you clear of terrain, and tell ATC.
Airplane Flying Handbook (FAA-H-8083-3C), Transition to Multiengine Airplanes
Common mistakes
Skipping the verify step.
Feathering the good engine.
Instead: Always verify.
Troubleshooting before feathering.
Drag and a propeller that may no longer feather.
Instead: Feather and secure, then troubleshoot.
Restarting without knowing the cause.
It may be on fire or failed, and may not feather again.
Instead: Restart only for a known, safe cause.
Now train it
Say it out loud, hear it asked, and take the quick check in this lesson’s practice pack. It tracks your shaky spots.
Got it?
When it feels solid, practice maneuvering with one engine inoperative out loud with our examiner.
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Go to the source (free)
Teaching this? The instructor lesson plan →
Sources
- Airplane Flying Handbook (FAA-H-8083-3C): Transition to Multiengine Airplanes
- Instrument Flying Handbook (FAA-H-8083-15B)
- Risk Management Handbook (FAA-H-8083-2A)
- Commercial Pilot ACS (FAA-S-ACS-7B): Areas IX and X (multiengine)
- Your airplane's POH/AFM: Emergency Procedures; Performance
- FAA-P-8740-66, Flying Light Twins Safely
Study aid, not FAA guidance. Regulations change; check the current text at eCFR and the ACS. Checked against current sources 2026-11-13.