Commercial pilot · ACS CA.X.C · lesson pack

One Engine Inoperative by Reference to Instruments

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

An engine failure in instrument conditions doubles the workload: no outside horizon, a yawing airplane, and decisions about altitude, weather and approaches. A pilot who flies attitude and rudder first, then works the flow, keeps control.

1 · Know these cold

•On instruments, the first sign is yaw: the heading turns and the ball (or slip indicator) moves. Hold the attitude and add rudder.(Airplane Flying Handbook (FAA-H-8083-3C), Transition to Multiengine Airplanes; Instrument Flying Handbook (FAA-H-8083-15B))
•The flow, in order: control and attitude; power forward; drag off; identify ("dead foot, dead engine"); verify; feather; secure by the checklist; then troubleshoot.(Airplane Flying Handbook (FAA-H-8083-3C), Transition to Multiengine Airplanes; Commercial Pilot ACS (FAA-S-ACS-7B), CA.X.C.S2, S6)
•Verify by slowly closing the suspected engine's throttle: no change is the confirmation. Manifold pressure, fuel flow and EGT are supporting evidence only.(Airplane Flying Handbook (FAA-H-8083-3C), Transition to Multiengine Airplanes)
•Zero sideslip on instruments: bank about 2-3° toward the operating engine on the attitude indicator, with the ball one-third to one-half out toward it, not centered.(Airplane Flying Handbook (FAA-H-8083-3C), Transition to Multiengine Airplanes; Commercial Pilot ACS (FAA-S-ACS-7B), CA.X.C.S4)
•If you can't hold the yaw or roll with full rudder, reduce power on the operating engine and lower the nose until control returns. Blue line is for performance; VMC is the control limit.(Airplane Flying Handbook (FAA-H-8083-3C), Transition to Multiengine Airplanes)
•Commercial standard: altitude ±100 feet (or minimum sink), airspeed ±10 knots, heading ±10°.(Commercial Pilot ACS (FAA-S-ACS-7B), CA.X.C.S8)
•Decide early: the nearest airport with an approach you can fly on one engine, and tell ATC.(Commercial Pilot ACS (FAA-S-ACS-7B), CA.X.C.S9)

2 · The lesson

Procedures on instruments

Yaw shows as a heading change and a displaced ball; roll follows. Hold the wings with aileron and stop the yaw with rudder.(Instrument Flying Handbook (FAA-H-8083-15B))
Set blue line, then the flow: power forward, drag off, identify (dead foot), verify (close the throttle: no change), feather, secure by the checklist; the engine gauges support, but don't replace, the verify step.(Airplane Flying Handbook (FAA-H-8083-3C), Transition to Multiengine Airplanes)
Then zero sideslip and trim: about 2-3° of bank toward the operating engine on the attitude indicator, the ball one-third to one-half out toward it.(Airplane Flying Handbook (FAA-H-8083-3C), Transition to Multiengine Airplanes)
Turns: a failure in a turn is flown the same way, roll toward wings level or the zero-sideslip bank first. Turn in either direction at standard rate or less, keep the zero-sideslip offset through the turn, and lead the rollout.(Airplane Flying Handbook (FAA-H-8083-3C), Transition to Multiengine Airplanes; Instrument Flying Handbook (FAA-H-8083-15B))
Once secured, troubleshoot by the checklist and judge whether a restart is wise; after a fire, a mechanical failure or an unknown cause, keep it secured.(Airplane Flying Handbook (FAA-H-8083-3C), Transition to Multiengine Airplanes; Your airplane's POH/AFM)
If you can't stop the yaw with full rudder, reduce power on the operating engine and lower the nose; then build back to blue line.(Airplane Flying Handbook (FAA-H-8083-3C), Transition to Multiengine Airplanes)

Performance and fuel

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)
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)
If you can't hold altitude, fly blue line for the least sink and ask ATC for a lower altitude, at or above the minimum en route or vectoring altitude where you can.(Airplane Flying Handbook (FAA-H-8083-3C), Transition to Multiengine Airplanes)
Fuel: crossfeed is an emergency procedure, used only as the POH says, never for takeoff or landing, and never toward a side with a fire or a leak. Plan the diversion at single-engine fuel flow.(Your airplane's POH/AFM)

Low altitude and attention

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)
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))
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))

Want it all on one page, with scenarios? Read the full lesson.

On the flight

ACS standards

Recognize, control, set engine controls, reduce drag, identify, verify, simulate feathering; best engine-inoperative airspeed and trim; checklists; troubleshoot; monitor.(Commercial Pilot ACS (FAA-S-ACS-7B), CA.X.C.S1-S7)
Altitude ±100 feet (or minimum sink), airspeed ±10 knots, heading ±10°; decide on a safe landing and stay within the airplane's limits.(Commercial Pilot ACS (FAA-S-ACS-7B), CA.X.C.S8-S11)

What your instructor is watching for

Your instructor watches for attitude and rudder control on the instruments, the flow in order, a correct verify step, blue line and zero sideslip in straight flight and turns, a clear decision about where to land, and good use of ATC.

3 · Say it out loud

Answer each one out loud, then check yourself and mark how it went.

Remember Recall it
“How do you recognize an engine failure on instruments?”
Understand Explain why
“Why does the attitude indicator matter for zero sideslip?”
Apply Use it on a flight
“In the clouds at 8,000 feet the left engine fails and the airplane won't hold altitude. What do you do?”

4 · Common mistakes

Chasing heading with aileron alone.
Uncoordinated, losing performance.
Instead: Rudder for yaw, small bank toward the good engine.
Verifying on the gauges.
They can mislead; the throttle test doesn't.
Instead: Close the suspected throttle: no change confirms it.
Not telling ATC.
You may need lower altitudes and priority.
Instead: Declare and state your needs.

5 · Quick check

Answer, then reveal. Flag anything you want to see again.

1. What are the tolerances?
2. Which way does the airplane yaw after an engine failure?
3. What speed gives the best single-engine climb or least sink?
4. When may you use crossfeed?
Scenario5. Unable to hold altitude on one engine in IMC. What do you tell ATC?

Trained it? Now prove it: practice one engine inoperative by reference to instruments out loud with our examiner.

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Study aid, not FAA guidance. Sources: Airplane Flying Handbook (FAA-H-8083-3C); Instrument Flying Handbook (FAA-H-8083-15B); Risk Management Handbook (FAA-H-8083-2A); Commercial Pilot ACS (FAA-S-ACS-7B); Your airplane's POH/AFM. Checked against current sources 2026-11-13.