Engine Failure of an Aircraft with Custom Propulsion

This example shows the flight of a Hawker Siddeley HS-121 Trident 3B, which has two turbofan engines mounted on the rear fuselage and one turbofan engine and one booster turbojet engine mounted on the vertical tail. A logical switch simulates the left engine failure mid-flight. The smaller booster engine is set to start producing thrust when a given threshold value of the throttle demand is exceeded. For modeling this kind of propulsion configuration, a custom propulsion model was created for the Trident 3B.

The first plot shows how all remaining engines go full throttle as the left engine fails at 35 min and yet the aircraft is not able to provide enough thrust to sustain the given velocity at the cruise altitude, resulting in deceleration.

The second plot shows how the autopilot starts applying both ailerons and rudder to compensate for the generated yaw moment due to differential thrust right after the left engine fails. Later during the simulation as the aircraft has descended and decelerated such that it sustains a steady level flight with the remaining engines, it can be also seen from the plot below that both the ailerons and rudder are still being deflected and the aircraft is flying with a small roll angle to be able fly straight forward.