A serious incident with aircraft 9H-MFX of the model Embraer E-550 in connection with take-off from Bromma airport, Stockholm

Summary

Shortly after take-off from Runway 12 at Stockholm/Bromma Airport, the pilots received a warning of a Flight Control System failure, and the aircraft experienced an increased pitch rapidly to an angle beyond what the crew expected. The pilot attempted to counteract the pitch movement using the control stick but noted that the stick had limited authority. The pilot then used the manual pitch trim to decrease the angle of the horizontal stabiliser and stop the continued climb. The crew issued a Mayday call over the radio, and the air traffic controller directed them for an approach and landing at the departure airport after the full functionality of the Flight Control System had been restored.

The aircraft's unexpected upward pitch movement was caused by a failure in both flight control computers after rotation. The Flight Control System degraded to a simpler control mode, called Direct Mode, which resulted in the stabiliser ceasing auto-trimming, leaving the aircraft at an untrimmed condition for the prevailing airspeed.

The operator, Flexjet, has been exposed to two similar events within a short timeframe. After the previous incident at Paris-Le Bourget, Flexjet implemented specific measures to mitigate the effects should a similar situation occur again.

During system testing conducted by the manufacturers, the fault was successfully recreated. The identification of the system's behaviour provided the basis for modifying the Flight Control System to reduce the risk of such failures.

SHK assesses that the measures taken by the manufacturer are sufficient to address similar incidents in the future.

During the investigation, it emerged that several similar occurrences had taken place with­out being reported to the Safety Investigation Authorities (SIA) in the countries where the events occurred. SHK considers this to represent a systemic issue but assesses that EASA's[1] taken and planned safety actions will effectively improve the process so that safety reports reach the appropriate SIA in a timely manner to enable an efficient investigation.

Causes of the Serious Incident

The aircraft's rapid and unexpected upward pitch movement immediately after lift-off was caused by a fault causing both Flight Control Computers to reset. This caused the system to downgrade to a simpler control mode, which also resulted in the stabiliser angle not auto­matically adjusting for the increasing airspeed.

The extremely out-of-trim condition required the pilot to apply almost full stick inputs to regain the commanded pitch attitude and forcing a manual re-trim of the aircraft.

Safety recommendations

None.

Given the measures already taken by EASA, Flexjet and Embraer, SHK refrains from issuing further safety recommendations.

[1] EASA – The European Union Aviation Safety Agency.