Engine Failure during Takeoff

WHAT IF ENGINE FAILS DURING TAKEOFF

On 29th March 2018, a Swearingen SA-227 DC  was hit by a bird during the takeoff run, the crew decided to abort the takeoff but this decision caused runway overrun which caused severe damage to the aircraft and minor injuries to some passengers. So why was the decision of the crew to abort the takeoff not correct? The concept of whether or not to abort the takeoff in case of an engine failure would be discussed in this article.

 Swearingen SA227-DC Metro 23

Introduction to different takeoff speeds:

To understand the behavior of an aircraft if its engine fails during takeoff, we should initially look at different speeds involved during takeoff of an aircraft. There are three speeds which play an important role during the takeoff roll, these are V1, Vr, and V2. The speed definition remains the same for all airplanes, no matter whether it is a twin-engine Cessna or a Boeing 747. V1 is the speed at which the pilot either aborts the takeoff and stays on the ground or continues to takeoff and lift off even if he loses an engine. V1 is also called the takeoff decision speed, as below V1 the takeoff must be aborted and above V1 takeoff must not be aborted. Vr is the speed at which pilot begins to apply the pitch up control. The speed at which the main gear of the aircraft is lifted is called liftoff speed. V2 is the takeoff safety speed at which the aircraft could safely climb with one engine inoperative.

Calculating the value of V1:

The value of V1 is mainly dependent upon accelerate Stop and accelerate Go distances. Accelerate Stop distance is the total distance required to stop the plane on the runway in a case of engine failure after gaining the certain speed using idle thrust, brakes, and spoilers. Accelerate Go distance is the total distance aircraft required to continue the take-off at 50 ft in a case of engine failure after gaining the certain speed. Accelerate Stop and Go distances are calculated using the speed, weight, and environmental conditions. In some aircraft, the crew sends the departure information to ACAR (Aircraft communications addressing and reporting system) which returns the values of different aircraft takeoff speeds including V1, based on different runway settings. Some operators use paper charts and FMS (Flight management system) to calculate V1.

Taking the decision to takeoff or abort it:

If the engine fails before V1 the pilot should immediately abort the takeoff and apply all necessary matters to bring the aircraft to a stop. Full reverse thrust can’t be added to calculate the braking capacity of an aircraft because, in case of an engine failure, one of the reversers would be inoperative. V1 needs to be calculated prior to every takeoff taking into account: runway length, aircraft weight, wing flaps setting, runway surface contamination, engine thrust, environmental factors and even the aircraft brakes because it is the fundamental step to make the go or no-go decision as it assures that if an engine fails prior to it, there would be enough runway leftover to come to a complete stop.

Even when there is a serious malfunction after V1, the pilot must commit to takeoff. Otherwise, a takeoff abort will lead to a runway overrun and could severely damage the aircraft. The pilot must take the corrective measure for the malfunction occurred after V1 in the air and then land the aircraft. The height of the aircraft above the end of the runway is known as screen height.

The steps which are to be followed if an engine fails are: the pilot needs to maintain the speed of V2 in order to leave the runway at a screen height of 35 feet or higher and maintain the climb rate at V2 to be clear of obstacles and he should be able to maintain that speed and climb rate until reaching “one engine out acceleration altitude” where he would then increase the speed of aircraft and retract the slats and flaps and continue with the emergency procedures. So this is what could be the possible decisions if an aircraft engine fails at a particular speed.