One Engine Inoperative: What Happens

Losing an engine on a twin is not a loss of half the performance — it is an asymmetric load that has to be flown against, and under the wrong combination of conditions it may not climb at all. This lesson is what happens and how you know which engine has stopped.

At a glance

• Yaw and roll gotowards the dead engine
• Directional controlmainly rudder, with additional aileron input
• Identification mnemonicdead foot — dead engine
• Critical enginethe left-hand engine, in the pilot's view

What the aeroplane does

One engine inoperative means an asymmetric loss of thrust producing uncommanded yaw and roll towards the dead engine with coordinated controls. Directional control is maintained mainly by rudder, with additional aileron input.

WARNING — In certain combinations of airplane weight, configuration, ambient conditions, speed and pilot skill, negative climb performance may result on one engine. The sudden application of power during one-engine-inoperative operation makes control of the airplane more difficult.

Both halves of that warning matter. The first says the aeroplane may descend however well you fly it; the second says the instinctive response — pushing the good engine up quickly — makes the aeroplane harder to hold.

Identifying the failed engine

The mnemonic is dead foot — dead engine. Once directional control is re-established the pilot feels control force on the foot pushing the rudder pedal on the side of the operative engine, while the foot on the failed side feels no force. The engine instruments further help analyse the situation.

NOTE — With respect to handling and performance the left-hand engine, in the pilot's view, is considered the critical engine.

Abnormal engine behaviour

The abnormal engine behaviour drill is a single step: apply full power. If the abnormal behaviour is sustained, the one-engine-inoperative procedures are used.

Check yourself

• Which way do yaw and roll go when an engine fails, and which control answers them first?

• What does the dead foot — dead engine mnemonic tell you, and when can you use it?

• Which is the critical engine on this type?

• What does the warning say about the sudden application of power?

• What is the whole of the abnormal engine behaviour drill?

Study aid — always fly your aircraft's current AFM/POH.