What happened
On 10 February 2011, a Fairchild Metro III, registration EC-ITP, was performing an international scheduled passenger service from Belfast City Airport to Cork Airport. During the approach to Runway 17, which was under Low Visibility Procedures, the aircraft attempted a missed approach after descending below the decision height. During this maneuver, the aircraft experienced a sudden roll to the left followed by a rapid roll to the right, causing the right wingtip to strike the runway. The aircraft subsequently flipped into a fully inverted position and slid off the runway into soft ground. The accident resulted in 6 fatalities, 4 serious injuries, and 2 minor injuries.
The investigation
Investigators examined the wreckage, engines, and flight recorders to reconstruct the final moments of the flight. While the aircraft's technical logs showed no recent defects, analysis of the Flight Data Recorder (FDR) revealed a long-standing torque mismatch between the two engines. Although the propellers and engines were found to be operating at high power during the impact, laboratory testing of the engine control components revealed a critical hardware flaw.
Specifically, investigators found an anomaly in the PT2/TT2 sensor for the No. 2 engine. The sensor's bellows were shorter than required by the manufacturer, leading to a leak. This defect caused the sensor to report a temperature significantly lower than the actual temperature, which directly influenced how fuel was delivered to the engine.
Findings
- The primary contributing factor was a defective PT2/TT2 sensor on the No. 2 engine, which provided an incorrect, colder temperature signal to the fuel control unit.
- This erroneous signal caused incorrect fuel scheduling, resulting in a faster torque response and higher torque for a given power lever angle on the No. 2 engine compared to the No. 1 engine.
- FDR data indicated that approximately eight seconds before impact, the No. 1 engine torque dropped to a negative value, while the No. 2 engine torque remained at zero or higher.
- Calculations suggest that both power levers were moved below the flight idle position between eight and six seconds before the crash, before being rapidly advanced to high power just before impact.
- The stall warning horn was recorded by the Cockpit Voice Recorder during the final seven seconds of the flight.