Interim safety measures put in place on 220 airliners with an engine flaw are “insufficient” to prevent the risk of a fatal crash, according to the US air safety body.
The National Transportation Safety Board said that passengers could not be sure that the procedures, adopted by airlines flying Boeing 777s with Rolls-Royce engines, would work.
The board’s report will increase the pressure on British Airways to ground 15 of its 777s, the airline’s most profitable aircraft, until the flawed component can be replaced with a redesigned part.
The board said: “Current operational mitigations, which require power reductions, may not prevent additional occurrences at critical flight altitudes.
“Therefore, until the current fuel/oil heat exchangers are replaced by heat exchangers more tolerant to ice accretion, additional failures to achieve commanded thrust could occur and could result in a serious accident and, possibly, injuries and deaths.”
BA, Singapore Airlines, American Airlines and Delta Airlines had all been hoping to continue using the interim safety measures for another 18 months until the modified heat exchanger was ready to be fitted.
Rolls-Royce is under extreme pressure to have the part ready earlier. The language in the board’s report is so stark that the airlines, Boeing and Rolls-Royce would be highly exposed to litigation and damages running potentially to billions of pounds if there were a fatal crash before the new part was fitted.
The last time British Airways had to ground an entire fleet of aircraft was in 2000, when it stopped flying all Concordes after the fatal crash in Paris.
The US National Transportation Safety Board initially highlighted the danger in a report on Thursday. The British Air Accidents Investigation Branch also issued a report on Thursday on the problem but avoided mentioning the continuing risk to passengers.
In January last year, the 152 people on board a BA 777 had a narrow escape when the aircraft lost power in both engines during final approach and crashed on to grass just inside Heathrow’s perimeter fence.
The aircraft’s landing gear was ripped off but only one passenger was seriously hurt, thanks to the skills of John Coward, the co-pilot, and Captain Peter Burkill.
Another 777 with Rolls-Royce engines, operated by Delta Airlines, lost engine power in almost exactly the same way last November after ice blocked the fuel supply.
The pilots managed to take emergency action to correct the failure, known as engine rollback. This incident occurred despite Boeing introducing new safety procedures last September that it claimed had solved the problem.
The US safety board said: “With two of these rollback events occurring within a year, we believe that there is a high probability of something similar happening again.” It said that “the only acceptable solution to this safety vulnerability” was to redesign the flawed component in the engine.
Rolls-Royce is hoping to accelerate the modification programme to begin installation before next winter, when the risk of ice forming in the fuel system is much greater. It declined, however, to set any deadline for removing the flawed components.
“We are working closely with the relevant airworthiness authorities to certify and deliver this modification as soon as possible,” it said in a statement.
British Airways said that it would not be withdrawing any 777s from service. “Absolutely not. That’s not something that’s been suggested in any of the reports,” a spokesman said, adding: “We wouldn’t operate any aircraft if it was unsafe to do so.”
In a separate report on the BA crash, the British Air Accidents Investigation Branch said that more research was needed into why ice accumulated in the fuel supply.
It said that mixing an anti-icing additive into aviation fuel was one possible solution but this “has many drawbacks”, including the need for more regular maintenance.
The problem of ice blockages has grown in recent years with the popularity of ultra-long-haul flights over the poles, meaning that many more aircraft are flying at a high altitude in extremely cold air for several hours.
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