What Happens When an Airplane Engine Fails: A Pilot’s Perspective

Engine failure in a multi-engine aircraft is a rare event. However, it can still happen. And it is one of the most common failures practiced during pilot training and checks. Each license check involves one engine failure on takeoff, one precision single-engine approach and one non-precision approach, and a go-around.

What happens when an engine fails

Most multi-engine aircraft in use today have engines hung from the wings. The engines are placed at a certain horizontal distance from the aircraft’s center of gravity (CG). This distance is known as arm length. The thrust generated by the engines acts through the CG which behaves like the pivot of a seesaw.

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Under normal conditions, both engines generate the same amount of thrust. However, when one engine fails, there is a thrust imbalance because the dead engine no longer produces thrust while the working engine continues to do so. The moment generated by the energized engine yaws the aircraft toward the inoperative engine. This yaw must be stopped to ensure the aircraft does not enter a spiral dive.

To counter unwanted yaw of the engine during operation, a force must be generated in the yaw axis. It comes from the tail or the vertical stabilizer. Pilots can vary the force generated by the tail using the rudder attached to it. So when an engine fails, pilots use their feet and press the rudder pedal to deflect steering until yaw is controlled. If the engine fails on the right side, the left rudder is applied and if it is on the left side, the right rudder should be applied.


In a twin-engine aircraft, the loss of one engine results in a 50% reduction in total power or thrust. Even if, in terms of performance, an engine failure leads to a loss of 70% of performance. Indeed, an engine failure leads to drag due to the deviation of the control surfaces (rudder and sometimes ailerons and spoilers) and due to skidding.

Engine failure on takeoff

During takeoff, the aircraft flies at low speed and high thrust. A combination that gives the least control efficiency. For this reason, pilots must be precise with flight controls. During takeoff, there is a decision speed called V1. It is the speed beyond which the takeoff must be continued even if a failure such as an engine failure were to occur because, beyond this speed, the aircraft may not be able to stop safely. security. Below this speed, the takeoff must be aborted.


Precision piloting is required to get the most out of the aircraft during an engine failure on takeoff. Photo: Getty Images

When an engine fails on takeoff, the pilot flying must apply firm pressure on the rudder to control drift to the dead engine. Failure to do so close to the ground can result in loss of control. In most aircraft, engine failure also results in roll tendencies. This must be countered by proper roll controls.

In most aircraft, the use of rudder inputs cannot cause the aircraft to skid because the force on the vertical stabilizer can drag the aircraft sideways in the air. This causes additional drag. So, to eliminate skidding, about 5 degrees of roll control can be applied to the powered motor. This stops skidding and reduces the rudder deflection needed to counter yaw. These two elements help to reduce drag and increase aircraft performance.

Once at a safe altitude with the aircraft under full control, engine failure procedures and checklists can be attempted. The important thing is not to rush things. Engine failure is not something a well-trained pilot should worry about. The rush of things led to catastrophic results such as the crash of TransAsia Airways Flight 235.

Engine failure during cruise

At high altitude, the air is less dense, and therefore less dense. The engines are running near their maximum rpm to generate the required amount of thrust. When an engine fails at these altitudes, the thrust from the remaining engine can longer balance the drag force, causing the aircraft to lose speed. If altitude is maintained, the aircraft may lose speed to the point where loss of control becomes highly probable.

Thus, at high altitude, when an engine fails, the aircraft must be brought into descent to an altitude where the engine’s remaining thrust can balance the drag. This altitude is known as the One Engine Inoperative (OEI) ceiling. This ceiling depends mainly on the weight of the aircraft. The heavier the aircraft, the lower the OEI ceiling will be. For a typical airliner, the OEI ceiling is between 20,000 and 25,000 feet.

At high altitude, the air is less dense. Thus, the impact of an engine failure on the aircraft is much greater. Photo: Vincenzo Pace | Single flight.

There are two main strategies when dealing with the descent of an engine failure event. In the first strategy, the aircraft is put on a descending trajectory with a stable windmill speed. This allows pilots to attempt a restart. Below this reel speed, the motor may struggle to gain enough spin.

The standard A320 strategy. Photo: Airbus A320 FCTM

In the second strategy, the aircraft speed is reduced to what is called a minimum drag speed called VMD. This is the speed at which the least amount of drag acts on the aircraft. When descending at this speed, the aircraft coasts down to the ceiling of the OEI at a slower rate. This strategy is useful if the engine fails in a high terrain environment where a faster descent may result in impact with the terrain. This is also known as drift down as the aircraft drifts slowly towards the OEI ceiling.


The A320 obstacle strategy. Photo: Airbus A320 FCTM

Once at the OEI ceiling, the aircraft can navigate at the best OEI ceiling speed.

Engine failure during approach and landing

The actions of the pilot during an engine failure during the final approach to landing can be two. The first is to simply continue the approach with the remaining engine. The other is to do a go-around, sort through procedures and checklists, and come in for a single-engine approach and landing.

The best option is to continue landing, if an engine fails on final approach. Photo: Airbus.

From a personal point of view, I would say that it is best to continue the approach if the aircraft is configured for landing. The flight can be performed by the pilot flying, while the engine securing process can be performed by the pilot not flying. In most airliners, an engine failure does not cause significant system losses due to redundancy. Thus, the flight characteristics of the aircraft are hardly affected. Therefore, continuing the landing is probably the safest option.

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