The Dutch Safety Board has detected a pattern of aircraft autopilot systems misinterpreting radio signals given by airport instrument landing system (ILS), which has led to minor incidents so far, but could lead to disaster if not addressed. And just like computer programmers trying to reproduce bugs to be able to identify a problem, the Dutch Safety Board ordered test flights and were able to reproduce the dangerous conditions that were unknown to the international aviation community until now.
On May 31, 2013 a Boeing 737-800 landing at Eindhoven airport was given instructions to land, and as usual, upon approach it switched on the autopilot for ILS landings, which uses radio signals: one type of signal says ‘pitch up’ and another says ‘pitch down’. Due to the steeper than usual approach of the Boeing, the autopilot went ‘pitch up’ instead of ‘pitch down’, while the plane already had the brakes on, the landing gear out and was decreasing its speed, a recipe for stalling the plane. The pilots took control of the plane, did a go-around, and safely landed the aircraft with the autopilot off.
In this case and other similar incidents elsewhere with different planes, the crew had a limited response time to disconnect the autopilot and recover the aircraft, a potentially dangerous situation according to the Dutch Safety Board. About 1,500 to 2,000 major runways worldwide use an ILS, while planes all around the world use an autopilot system that has this glitch.
Someone’s fear of flying just got real, but not mine though, I love flying.
If you want real details, watch this English-language video: