Mirage probe puts spotlight on Dassault's flight computer's behaviour

On February 1, two experienced Indian Air Force (IAF) pilots died when their newly upgraded Mirage 2000-I fighter crashed while taking-off in Bengaluru. A Court of Inquiry (CoI) investigating the accident is now confronting the worrying possibility of a glitch in the Mirage 2000’s flight computer that kicks in without warning, causing the aircraft to behave unpredictably.

IAF flight records examined by the CoI have revealed at least four such incidents in the past. In each of these, a flying Mirage 2000 has, suddenly and without command from the pilot, jerked its nose towards the ground. Then, as spontaneously, the nose was jerked upwards. Each time, the aircraft has continued this up-and-down jerking — termed “pitch oscillations” — for several seconds before resuming normal flight.

Members of the CoI from the IAF, Hindustan Aeronautics (HAL), the National Aeronautics Laboratory (NAL) and the Aeronautical Development Agency (ADA) are veering round to the belief that such an incident caused the February 1 crash.
In three recorded incidents, the “pitch oscillations” took place at high altitudes, giving the aircraft time to correct itself. However, on February 1, the ill-fated Mirage 2000-I’s flight computer jerked the fighter’s nose down just after it lifted off the runway. With the aircraft barely five metres off the runway, it had no time, or altitude to correct itself. In a fraction of a second, the nose slammed onto the runway, the front undercarriage (nose wheel) sheered off, and the aircraft careened across the runway, fatally out of control.

In facing “pitch oscillations” when their aircraft was five metres above the ground, the two pilots who died were unluckier than several predecessors whose aircraft misbehaved at higher altitudes. An incident recorded in 1989 recounts that Mirage 2000, aircraft number KF138, experienced “sudden and momentary pitch oscillations... (for) a few seconds” at an altitude of 4,500 feet some 16 minutes after take-off. The oscillations exerted a violent force of “+10.5g to -6g” (“g” indicates the force of gravity) on the pilots and caused the cockpit’s red and amber warning lights to glow.
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