An Etihad flight incident in May, in which the European safety regulator says an engine temporarily "stagnated", has spurred modifications to some Airbus aircraft to prevent the build up of ice. Airbus A330s and A340s using Rolls-Royce engines must replace oil-cooler devices with a newer design that is less susceptible to ice build-up during long-haul flights, particularly over water or polar regions, the European Aviation Safety Agency (EASA) said last week.
Earlier, the European and US safety regulators issued similar directives for Boeing aircraft which use Rolls-Royce engines following incidents involving flights by British Airways and Delta Air Lines. Etihad's Flight 313 in May was approaching Manchester Airport when air traffic control requested a go-around due to a runway being obstructed by a vehicle. "Both engines initially responded correctly; however, after the initial acceleration engine number one stagnated and the corresponding engine stall warning was displayed in the cockpit," the EASA said in its report. Etihad pilots acted appropriately to the engine stall, responding immediately to regain control of the aircraft, it said. "As per procedure, the crew throttled back the engine, which recovered."
An Etihad spokeswoman said the incident culminated in a "rapid recovery and safe, uneventful landing", and added that "along with other affected airlines, we are making the minor modifications required over the next six months". "We report all such events as a matter of course to the relevant authorities and manufacturers," she said.† After investigating the Etihad incident, EASA said ice blocking was a possible cause of the incident.
Airlines have until January 2011 to make all the required fixes. The long lead time indicates that ice build-up is extremely rare, the trade press has reported. There have been two other recent incidents of ice build-up within fuel systems, both involving Boeing 777 aircraft. In November last year, a Delta Air Lines flight from Shanghai to Atlanta suffered an "uncommanded rollback", or loss of thrust, in one engine while the aircraft was in cruising mode. The problem was cleared after pilots took measures including descending to 31,000 feet. The cause of the rollback has not been determined.
In January of last year, a British Airways flight crashed as it approached Heathrow Airport in London. The Air Accidents Investigation Branch of the UK determined that "an uncommanded reduction in thrust occurred on both engines as a result of reduced fuel flows". No one was killed in the crash. The investigation revealed that, "under certain conditions, over a long period of low fuel temperatures, ice may accumulate in the main tanks and/or in the associated engine fuel feed systems".