Icing Hazards Surface on Boeing's Newest 747 Jet: WSJ

By  Andy Pasztor

The Wall Street Journal

Oct. 16, 2013 8:02 p.m. ET

Years after aviation-safety experts thought they had eliminated the danger of airliner engines abruptly shutting down from internal ice accumulation, the same airborne hazard is showing up on a new generation of Boeing Co. jumbo jets.

The Chicago plane maker and General Electric Co., whose engines are installed on the biggest and newest Boeing 747 model, are now working together on fixes to prevent ice buildup that can prompt the giant airliner's engines to temporarily malfunction or even stop working while cruising roughly 7 miles, or 41,000 feet, above the earth.

A GE spokesman said there are proposed software changes—which still need to be tested and then approved by the Federal Aviation Administration—designed to detect the presence of ice crystals in the atmosphere and eject the tiny particles before they form a coating deep inside engines that can melt or break into chunks.

In extreme cases, the accumulation of ice inside an engine could cause damage to turbine blades or sudden dousing of the ignition system, though there haven't been any reported accidents.

The problems underscore difficulties regulators and industry officials face in resolving some persistent engine-safety issues. The reliability of jet engines has improved exponentially over the last few decades, contributing to steadily lower accident rates across the U.S. and other regions. Some older GE designs, for instance, have racked up outstanding safety records of one airborne engine shutdown per every million flight hours.

Still, challenges with the GEnx-2B engines on extra-long 747 aircraft—known as 747-8s—highlight complex and nagging icing hazards that once again are forcing industry leaders and an international research team to scramble for answers. Before the partial government shutdown, according to industry officials, the FAA was moving toward mandating modifications to the 747-8's computerized engine controls and making plans to warn pilots about susceptibility to internal engine icing while flying over storm-prone regions at roughly 40,000 feet.

Previously, experts believed such icing occurred primarily below 25,000 feet. From the mid-1990s to the end of 2011, the FAA and various engine manufacturers investigated ice-crystal buildups affecting more than 100 big jets around the world, including at least 14 instances of dual-engine shutdowns, called "flameouts." Starting in 2007, the industry successfully rolled out various modifications to counter those hazards.

The latest engine problems, however, caught GE, Boeing and the FAA by surprise, partly because they cropped up on a different engine model at significantly higher altitudes than anticipated, according to industry officials. Moreover, the recent incidents often occurred in clear air without clouds or signs of nearby storms.

Since the spring GE has investigated four 747-8 freighters with icing-related engine problems, including a Russian AirBridge Cargo plane that had two engines surge and a third engine dramatically lose thrust July 31 while flying at 41,000 feet over China. Russian investigators said three of its four engines suffered damage, but the plane landed safely.

Boeing's 747-8 passenger version, dubbed the Intercontinental, is the world's longest commercial aircraft and can carry more than 460 passengers in three classes. Customers for the 747-8 include Deutsche Lufthansa AG  and Cathay Pacific Airways Ltd.

On Wednesday, a GE spokesman said all of the 747-8 incidents occurred around "unique convective weather systems" such as unusually large thunderstorms reaching high altitudes. Only the AirBridge Cargo incident, which intensified industry concern, "resulted in engine damage," according to GE.

Airlines have been "experiencing a growing number of ice-crystal" incidents, according to the GE statement, reflecting more long-range jets crossing over tropical regions of the world. Engine flameouts and thrust reductions, typically happen quickly, with virtually no warning, according to safety experts.

Boeing said it is "working closely" with GE "on the software solution." The FAA didn't have any immediate comment.

Such icing emergencies remain rare. "I'm not alarmed by an event that we are learning from," said Mark Rosenker, former vice chairman of the National Transportation Safety Board, adding that experts "continue to look at any type of incident to get as close to 100% engine reliability as possible."

A different category of icing hazard has dogged some of Boeing's widely-used 777 widebody jets since 2008, when ice blocked the fuel-system plumbing of a British Airways PLC jet powered by Rolls-Royce engines that ended up crashing on final approach to London's Heathrow Airport. After extensive investigation and ground tests, experts determined the accident stemmed from a type of icing that didn't occur inside engines.

Separately, over the years Boeing has dealt with a string of potentially dangerous overheating incidents and chronic structural damage to parts called thrust reversers attached to Boeing 777 engines manufactured by Rolls-Royce PLC. Used to help jets slow down after landing, 18 of the devices have suffered fractures or failures of their inner walls over the past 10 years, according to a Boeing spokeswoman. Since 2005, she said the company has "communicated extensively" with 777 operators and issued nonbinding recommendations to check or replace the suspect parts, but "we're unable to confirm how many inspections or modifications have taken place."

But the thrust-reverser issue may be coming to a head. In August, as part of a report on a Royal Brunei Airlines 777 that lost part of its reverser after takeoff from London, British accident investigators said Boeing told them the FAA "may mandate inner wall replacement on all Rolls-Royce powered Boeing 777 aircraft."

An FAA spokeswoman didn't have an immediate response, and a spokesman for Rolls-Royce declined to comment. 

Source:  http://online.wsj.com