Regulators to Issue New Rules For 777s With Rolls-Royce Engines

(By ANDY PASZTOR)

U.S. and European air-safety regulators, concerned about potentially dangerous ice buildups in the fuel systems of certain long-distance jetliners, are about to issue new operating rules for around 220 Boeing 777 aircraft, according to people familiar with the matter.

The mandatory safety directives apply only to planes with engines manufactured by Rolls-Royce PLC, which account for about one third of the roughly 730 Boeing 777 fleet world-wide, these people said. But under prodding from British safety officials, according to these people, Boeing will analyze whether similar precautionary measures should be extended to the rest of its Boeing 777 line. The rules are expected to be released in the next few days, perhaps as early as Thursday.

In January, a British Airways PLC Boeing 777 crashed about 1,000 feet short of its intended runway at London's Heathrow Airport. All 152 aboard survived. But the accident -- believed to be the first of its kind involving a Boeing 777 – has attracted attention and concern throughout the global aviation community. Investigators suspect that the plane's fuel system became plugged from ice or slush that formed during a flight from China.

The directives call for pilots to vary the engine-throttle settings during long flights when airborne temperatures are unusually low, these people said, and particularly revving up engines momentarily before starting a descent toward an airport The aim is to boost power as a way prevent internal ice accumulation from plugging up fuel systems, which could make engines unresponsive to pilot commands during critical maneuvers such as landing approaches.

The safety directives follow voluntary operational changes Boeing has developed over the past few months and intends to distribute to American Airlines, Delta Air Lines, Singapore Airlines, Cathay Pacific, Emirates and other carriers operating Rolls-Royce powered Boeing 777s.

As part of the latest report updating the Heathrow crash investigation slated for release Thursday, Great Britain's Air Accidents Investigation Branch, or AAIB, is expected to call for more study about the general hazards of slushy fuel in Boeing 777s. Much of the focus is on aircraft following long polar or oceanic routes -- which can entail hours of flight in cruise requiring minimal changes in speed or engine power. Under the new procedures, periodic altitude changes will be done using greater engine thrust than normal. If pilots suspect a fuel-system blockage related to formation of slush or ice, they will be instructed to first pull back the throttles to idle as a technique to help the system clear itself.

British Airways, Boeing Co., the AAIB and the U.S. National Transportation Safety Board, which also is participating in the investigation, didn't have any comment. A spokesman for Roll-Royce couldn't be reached for comment. Alison Duquette, a spokeswoman for the U.S. Federal Aviation Administration said, "We are closely monitoring the situation and will take whatever action is necessary" to ensure safety.

The Jan. 17 crash had already prompted some airlines to reassess procedures to prevent ice formation in fuel systems. But until now, airlines using Boeing 777s hadn't received any official word about the advantages of making periodic adjustment to engine settings.

The precautionary rules, among other things, are less tied to specific temperature thresholds than previous procedures. Carriers normally monitor outside air temperatures and keep track of fuel temperatures. If those inside temperatures creep too low, pilots currently have the option to descend to warmer air, or they can speed up to increase the heat generated by air friction against the plane's skin.

The safety directives are expected to be interim steps, while Boeing and Rolls-Royce mull possible changes in the design of the oil cooler, which is where investigators believe the blockage most likely occurred in the British Airways crash.

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Fonte: Flight Safety Information 04/09/2008.