Probe into emergency landing at London Heathrow after power anomalies on Evergreen freighter finds no clues.

An investigation into the emergency diversion of an Evergreen International Airlines Boeing 747-100 freighter to London Heathrow, UK has so far failed to determine why one of the aircraft's engines flamed out and the other three, according to the pilots, did not respond correctly to the power levers.

The UK Air Accident Investigation Branch confirms it is investigating the event, including why the aircraft (N481EV) was not diverted to London Stansted airport instead of Heathrow's runway 27R, the approach to which takes it over the centre of the city.

The event occurred on 24 April as the 34-year old aircraft was en route to New York JFK from Germany, says Evergreen. The No 4 engine flamed out while the aircraft was cruising at 36,000ft (11,000m), and the crew descended and attempted to relight the engine without success.

Evergreen director of quality, safety and internal evaluation Vern Berry says the pilots have reported they noticed that power-lever position for the operating engines was producing less power than expected. He adds: "With one engine inoperative and the remaining engines acting unusually [the crew] decided, after consultation with dispatch and maintenance control, to divert to the nearest suitable airport."

The aircraft captain declared an emergency and informed air traffic control that he intended to land at London Heathrow. The 747 executed a series of high-bank 'S' turns to reduce airspeed and altitude while making a visual approach, but the aircraft was "fully stabilised" at 1,000ft and the subsequent touchdown was uneventful, says Evergreen.

Fuel filters and the engine electronic display were replaced at Heathrow. But Berry says: "Subsequent investigation into the reason for the flame-out revealed no erroneous readings or evidence of fuel contamination. Operation of all engines to maximum power after the event and in [subsequent] operation have not repeated the flame-out or the low-power condition noted by the crew. All engines are currently operating normally."


Source: Flight International