Emerging evidence from the recent crash in Ethiopia suggests that malfunctioning automatic control systems overwhelmed the crew and doomed the flight. Based on my analysis, it appears that the Ethiopian Airlines crew followed the standard procedures found in the Boeing 737 pilots operating handbook and flight crew operations manual.
A typical flight starts with manual control of the plane. The pilot and co-pilot will personally steer the aircraft onto the taxiway, configure the flaps for takeoff, actively control the aircraft as it accelerates down the runway, and smoothly pull back on the control yoke to lift the plane off the ground and into flight. The flight’s altitude and speed data, transmitted from the plane in real time and made available to the public by FlightRadar24.com, shows that happened normally as Ethiopian Airlines Flight 302 left the runway.
Everything appears to have gone as usual on the initial climb away from the takeoff, too. Normally, the pilot will retract the landing gear and maintain a relatively steady speed as the aircraft climbs. The plane might accelerate slightly until it’s going fast enough that the flaps – extended to increase lift at lower speeds – can be safely retracted, letting the wings themselves generate the necessary lift. This process usually takes place in the first minute after takeoff. Once the aircraft has climbed to 1,000 feet above the ground, the pilot will engage the autopilot system.
That’s the point at which the computer takes over – and where, my analysis of the data suggests, things went wrong for Ethiopian Airlines Flight 302. A modern autopilot system gives the computer command of the engine throttles, rudder, elevators and ailerons – basically full control over the aircraft.
Simulating the expected flight
Using modeling tools developed by my research team, I recreated a hypothetical flight profile to simulate the Ethiopian Airlines 737 departure based on the handbook procedure for an identical plane carrying a similar amount of weight. The simulation timing, key speeds and altitudes all follow my best estimate of the procedure that a trained pilot would be expected to follow.
Comparing this data to the actual flight data, I was able to see where the ideal predicted performance differs from the actual motions of the lost flight. My simulation closely matches the actual speeds of the aircraft on its takeoff roll, and recreates its first few miles of airborne flight. The pilot let the aircraft accelerate gently during initial climb, which isn’t specifically called for or prohibited in the official manual.
The flight paths between a typical flight and the actual course sharply diverge only after the aircraft reached an altitude of 1,000 feet above the runway.