What happened
On December 24, 2001, an Embraer 145LR, registration HB-JAD, operated by Crossair, departed Basel Airport for Hamburg. During the initial climb, the crew received a "PIT TRIM 1 INOP" warning on the EICAS. The primary stabilizer trim system had become jammed and was unresponsive.
As the aircraft continued to climb, the autopilot was engaged, but the trim position remained fixed. Eventually, the autopilot disconnected, leaving the aircraft in a state that was difficult to control manually. The crew had to apply significant nose-down pressure to maintain a proper flight attitude. To assist with speed reduction and control, the crew extended the landing gear. After declaring a Mayday and requesting an immediate return to Basel, the crew successfully utilized the backup trim system, which restored controllability. The aircraft landed safely without any injuries to the crew or the four passengers on board.
The investigation
The investigation examined flight data recorder (DFDR) and cockpit voice recorder (CVR) data, alongside maintenance and operational records. Investigators focused on the aerodynamic limits of the trim system and the flight parameters during the takeoff roll and rotation. The investigation also reviewed the aircraft's weight and the crew's response to the malfunction.
Findings
- The primary cause of the incident was the jamming of the horizontal stabilizer trim due to the aircraft exceeding aerodynamic limits.
- The system limits were exceeded because the aircraft's rotation was too slow, and the aircraft was operating at a low takeoff mass (only 4 passengers and 47 kg of baggage).
- The aircraft's speed exceeded the recommended limit of 160 KIAS for the first trim application, reaching 173 KIAS during the rotation phase.
- The crew did not respond effectively to the initial trim failure.
Safety action
Following the incident, the aircraft manufacturer, Embraer, issued an operational bulletin limiting the initial climb speed to 160 KIAS before the first trim application. Embraer also implemented several hardware and software improvements, including increasing the power supply to the trim motors, strengthening the stabilizer actuator clutch, and enhancing the reliability of the control unit and switches. Additionally, the operator updated its standard operating procedures to include specific callouts and standardized rotation techniques to prevent similar occurrences.