In a twin-engine aircraft, what is the significance of engine-out climb gradient and how is it calculated?

• A. It ensures acceptable climb with one engine inoperative; calculated by comparing net power/thrust available with required climb gradient and altitude
• B. It is the maximum rate of climb with all engines
• C. It is calculated by subtracting the best rate of climb from the required gradient
• D. It is not used in IFR flight planning

Answer: (A)

Engine-out climb gradient is about what a twin can do if one engine fails during takeoff or initial climb. It sets the minimum climb performance with one engine inoperative to ensure you can still clear obstacles on the departure.

The reason this is the best answer is that it directly describes the purpose and the method of assessment: you compare the power or thrust available with one engine inoperative (as influenced by weight, altitude, temperature, configuration) to the required climb gradient for the departure and the altitude you’re at. If the available OEI climb gradient meets or exceeds the required gradient, the aircraft can safely meet obstacle clearance under that one-engine-inoperative condition; if not, it doesn’t.

In practice, climb gradient is often expressed as a percentage or feet per nautical mile, and the calculation links the actual OEI performance (net thrust/power available) to the required gradient at the given altitude. This is why engine-out climb performance is a key consideration in IFR departure planning and certification.