On triple sevens and ice crystals

[Mitch Cronin]

Purloined from elsewhere:

From The TimesMarch 13, 2009

Airliners to keep flying despite safety warning

High probability of more engine failures, says watchdog

The 152 people on board a BA 777 had a narrow escape in January last year

Ben Webster, Transport Correspondent

UK and US take very different perspectives | Jet a success with airlines cutting costs | Rolls-Royce engines: two incidents in a year | How ice crystals blocked the flow of fuel

Dozens of aircraft using Heathrow have a potentially fatal engine flaw that means there is a “high probability” of a repeat of the failure that caused last year’s British Airways crash, according to the American air safety watchdog.

Rolls-Royce, which makes the engines, is working on a safety modification but the Boeing 777s will remain in service with the flaw for another 18 months.

Until the change is made, more than 220 Boeing 777s with Rolls-Royce engines, including 15 operated by BA, will continue to be vulnerable to ice in the fuel supply causing a loss of power in the engines.

The US National Transportation Safety Board highlighted the danger in a report yesterday. The British Air Accident Investigation Branch also issued a report yesterday on the problem but avoided mentioning the continuing risk to passengers.

The 152 people on board a BA 777 had a narrow escape in January last year 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 by the impact but only one passenger was seriously injured.

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. The second incident occurred despite Boeing introducing new safety procedures last September that it claimed had solved the problem.

The US safety board said yesterday: “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 admitted that the component, the fuel/oil heat exchanger, was flawed but said that the replacement part had to be tested and certified and would not be ready for installation for up to 12 more months.

Other airlines operating 777s with Rolls-Royce engines include Singapore Airlines and American Airlines.

The board recommended that airlines should be compelled to fit the new part within six months of it being available for installation, meaning that 777s could continue flying with the flaw until August next year.

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.”

The spokesman said that BA, in common with all operators of 777s with Rolls-Royce engines, had taken a number of actions to reduce the risk of ice building up in the fuel supply, including ordering pilots to accelerate at certain points on long flights through cold air to increase fuel supply.

The board said that the precautions, while reducing the risk of engine power loss, could be a dangerous distraction for pilots and carried their own risks. “They add complexity to flight crew operations. Because the recovery procedure requires a descent, the aircraft may be exposed to other risks such as rising terrain or hazardous weather, or the inability to achieve maximum thrust during a critical phase of flight, such as during a missed approach,” it said.

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: “This is a major scientific challenge, possibly taking several years to complete, so the regulatory authorities are urged to jointly initiate such research.”

The AAIB said that mixing an antiicing 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.

Wow! Not sure I'd ever have thought I'd be glad to have the GE's problems. At least they're usually limited to one engine at a time.