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Re: Engine icing & flameout at 38,000 feet/cruise
Posted By: Phil Bunch (pool-70-105-228-65.port.east.verizon.net)
In Response To: Re: Engine icing & flameout at 38,000 feet/cruise (Jeroen Dorrestein)
Date: 7 APR 2008 - 23:35z
Engine Problems Spur Safety Efforts
By ANDY PASZTOR
April 6, 2008 10:01 p.m.Popular models of passenger jets have been buffeted by a variety of engine problems in recent years, hastening industry officials and regulators to seek safety fixes in an area that had been relatively problem free.
The problems range from old-fashioned manufacturing defects to subtle computer-control glitches to design shortcomings that allow engine damage from internal ice accumulation before takeoff. Such difficulties generally escape the attention of average passengers.
But because they involve nearly every major engine builder and jetliner manufacturer, efforts to find answers have focused industry attention on the sometimes arcane vulnerabilities of engines. The result, according to many safety experts, is that engine-related issues have reappeared as one of the top safety challenges facing commercial aviation world-wide.
The overall reliability of today's advanced jet turbines continues to improve, with some engine families boasting fewer than four instances per million hours of operation in which pilots shut down engines to prevent further damage from a malfunction. Yet there has been a flurry of safety questions in the past few years, even as U.S. and foreign carriers fly increasingly longer routes over oceans and remote polar regions devoid of emergency landing strips.
In October 2004, a Pinnacle Airlines regional jet without passengers crashed in Missouri, killing the two pilots aboard, after both General Electric Co. engines locked up. The cockpit crew lost control of the aircraft at an unusually high altitude, and failed to follow proper procedures to restart the engines. Two years later, however, crash investigators questioned the adequacy of those procedures and urged regulators to conduct new tests to ensure reliable restarts during such unexpected maneuvers. At the time, a GE spokesman said the high-altitude "flameout" created "a scenario that's new for everybody."
In June 2006 at Los Angeles International Airport, American Airlines mechanics tested a different GE engine on a Boeing 767 that had experienced a minor problem. Parked inside the hangar, however, the engine exploded violently. Turbine blades broke apart with a terrific bang, sending shrapnel through the plane's fuselage, puncturing fuel tanks and hurling large metal chunks nearly half a mile. The plane was severely damaged by fire, but a similar engine disintegration in flight easily could have cause a crash, according to federal crash investigators. The company and the Federal Aviation Administration quickly agreed on more-frequent inspections for certain engines, particularly those with the most flight hours. Since then, inspections have been ratcheted up.
Engine makers and government safety watchdogs on both sides of the Atlantic have issued a string of recommendations and directives to reduce the chances of ice damage to engines while aircraft are still on the ground. For various Boeing aircraft such as the 757, the original 767 and the extended range version of the 767, pilots say onboard ice-detectors or automatic anti-ice systems don't work reliably on the ground. Earlier this year, U.S. regulators said larger Boeing 777s equipped with engines built by Rolls-Royce PLC also had anti-ice shortcomings during ground operations.
When taxiing these and other jetliner models for long distances around airports, or when remaining in place with engines idling for extended periods, pilots have been told to vary power settings in dense fog, mist or other icy conditions. Such steps are intended to prevent buildup of internal ice that can break off and smash into swiftly turning turbine blades.
Despite years of investigations, airborne icing hazards seemingly remain the most elusive. Five months after an accumulation of ice crystals temporarily shut down three of the four engines on a Philippine Airlines 747 approaching Manila, General Electric is now mulling additional software fixes. A Philippine Airbus A330, powered by a different version General Electric engine with slightly different software modifications, flew a shorter route through the same storm around the same time, according to the company. But the engines on that plane didn't experience any disruptions.
Write to Andy Pasztor at andy.pasztor@wsj.com1
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