What happened
On 29 November 2003, an Airbus A320-232, registration G-EUUI, was operating a scheduled passenger service from London Heathrow to Edinburgh. Upon reaching a cruising altitude of 28,000 feet, the crew and passengers experienced loud bangs and significant vibrations throughout the airframe. The flight crew identified that the No 2 engine had experienced a surge, with engine parameters fluctuating before returning to normal. A passenger also reported seeing an orange flash near the right engine.
Following advice from the operator, the crew decided to return to Heathrow. During the return leg, the No 2 engine surged again. As the aircraft approached Birmingham, a series of further surges occurred on the right engine, accompanied by an ignition message on the ECAM. The crew, believing that the No 1 engine was also surging, declared a MAYDAY and diverted to Birmingham Airport. The aircraft landed safely without further incident, and there were no fatalities or injuries among the 7 crew members or 92 passengers on board.
The investigation
The AAIB investigation focused on the cause of the engine instability and the adequacy of the crew's response. Investigators examined the engine's Electronic Engine Control (EEC) and found that the No 2 engine's P2T2 probe was providing inaccurate temperature data. Specifically, the probe was reading a temperature significantly lower than the aircraft's actual total air temperature.
Further examination of the P2 and T2 probe revealed cracks in the temperature sensing elements, which had allowed moisture to enter the unit and cause erroneous readings. This faulty data caused the EEC to incorrectly adjust the compressor inlet guide vanes, reducing the engine's surge margin during power changes. The investigation also reviewed the airline's Quick Reference Handbook (QRH) and found that certain critical guidance material from the manufacturer's manual had been omitted, which could have assisted the crew in identifying the surge earlier.