J-Class
7th Apr 2008, 22:20
Airline Regulators Grapple
With Engine-Shutdown Peril
Investigators Find
New Icing Threat;
FAA Proposes Rules
By ANDY PASZTOR
April 7, 2008; Page A1
******************
UNRAVELING A MYSTERY
• The Problem: Engines on commercial jetliners have been shutting down suddenly, but temporarily, in midflight.
• The Response: After discovering a new kind of icing, airlines and regulators come up with suggestions for minimizing the problem, but the shutdowns persist.
• What's Next: On Monday, the FAA will propose new flight procedures to address the problem further.Modern jet engines long were thought to be impervious to internal icing. But airlines, regulators and weather scientists now think otherwise, and have been scrambling to figure out how to handle the hazard. Despite some progress, the shutdowns keep happening.
***************
As a Qatar Airways flight dodged thunderstorms on approach to Shanghai in 2006, it encountered a problem that, until recently, was considered virtually impossible: nearly four miles above the earth, both engines of the big Airbus A330 shut down at the same time.
The engines quickly restarted and the pilots managed a safe landing. But the incident, along with similar ones before it, set off alarm bells throughout the industry because of the cause: ice inside the engines.
On Monday, the Federal Aviation Administration will propose new safety rules that are expected to apply eventually to about 1,200 widebody jetliners world-wide, including Boeing 747 jumbo jets. Pilots of those planes will be required to turn on engine anti-ice systems more frequently during descents, to reduce the chances of sudden shutdowns and to increase the likelihood that engines that quit will restart.
In recent weeks, the U.S. aviation-safety system -- effectively a partnership between the FAA and the airlines themselves -- has been shaken by revelations of lax oversight of Southwest Airlines Co. The coordinated response to the baffling engine-shutdown problem shows another side to the system: when airlines and regulators openly share information, they can tackle tough technical problems.
Here's what they've figured out about the engine shutdowns: At high altitude near intense storms, moisture turns into tiny ice crystals that can be sucked inside an engine. At first, the crystals melt. But sometimes the water freezes again on metal surfaces. Eventually, accumulating ice can either break into chunks that damage turbine blades, or melt and douse the ignition system.
The odds of both of a plane's engines shutting down at once were supposed to be about one in a billion. Since 2002, however, internal ice has been blamed for at least 14 instances of dual-engine shutdowns, called "flameouts," and several times that many single-engine outages. Investigators now believe that since the mid-1990s, so-called crystalline icing has prompted dramatic power drops or midair engine stoppages in more than 100 jets. So far, the flameouts haven't been blamed for any crashes, because the engines on big commercial jets have always managed to restart.
"If people had said just a few years ago that ice could build up within jet engines at high altitudes, we would have dismissed them," says Jim Hookey, a senior investigator at the U.S. National Transportation Safety Board, or NTSB. "As it turns out, this problem existed for a long time. The industry just never had enough knowledge before about the atmosphere or the threat from ice crystals."
By examining the dual-engine flameouts in relation to storm patterns, Mr. Hookey and other investigators began unraveling the icing mystery. Powerful thunderstorms, particularly over the Pacific Ocean in the spring and summer, can spawn smaller-than-normal ice particles, they say. These particles, which cannot be detected by pilots or weather radar, are swept into jet engines, leading to the problem.
Some experts contend that climate change is resulting in larger storms containing more ice particles -- a possible explanation for the frequency of the problem in recent years. Another possible factor is increasing traffic. Passenger flights over the Pacific, where more than two-thirds of the shutdowns have occurred, have risen more than fivefold so far in this decade, making it more likely that jets will encounter ice crystals.
Array of Engines
Flameouts have occurred on engines made by General Electric Co. and United Technologies Corp.'s Pratt & Whitney unit. A wide array of jets have been affected, including some built by Boeing Co. and European rival Airbus, and various regional and business jet models.
Rick Kennedy, a spokesman for GE's engine unit, says the company has invested heavily in both ground and flight testing, and "has made significant progress addressing these challenges across different aircraft models." But it's hard to replicate flameouts, he says, because "industry knowledge of these elusive atmospheric conditions is limited."
A Pratt & Whitney spokeswoman said the company has "worked closely with the NTSB throughout the investigations" and also is working with the FAA and other companies.
Although GE and others have made adjustments to their engines, the problem persists. Last November, GE says, three of the four revamped GE engines on a Philippine Airlines Boeing 747 experienced brief stoppages while descending toward Manila.
Given the millions of flight hours logged by long-range jets each year, in-flight engine shutdowns are a rarity. And when the engines do shut down, they typically fire back up and return to normal within 60 to 90 seconds. Passengers usually aren't aware anything has gone wrong.
Ice Studies
Even after years of studying icing, the airline industry still doesn't understand all the ways it can affect jet engines. In January, after a long flight over the arctic, a British Airways PLC jetliner crash-landed close to London's Heathrow Airport. Investigators and safety experts don't believe ice built up inside the engines. But many of them think that unusually frigid outside temperatures during the flight helped cause ice, slush or some kind of contaminant to build up in the Boeing 777's fuel system, starving both Rolls-Royce engines of fuel. With minimal power on final approach, the plane slammed down 300 yards short of the runway. All 152 people on board survived. Rolls-Royce PLC won't comment on the crash investigation.
Icing incidents of various kinds are forcing a re-examination of engine dependability in adverse weather. Seasoned aviators long have understood the hazards ice can pose. When ice builds up on wings or other external airplane parts, it can impair a jet's ability to gain lift. Anti-icing systems -- which range from spraying the wings with chemicals before takeoff to heating portions of the skin during flight -- long ago solved that problem.
As modern jet engines evolved, they became so dependable that they were considered nearly infallible. Engines routinely stayed in service for 20 or 25 years, often without experiencing a problem significant enough to warrant removal from aircraft. Pilots could go through an entire career without a single engine emergency, let alone two quitting at the same time. "For practical purposes, the likelihood of that was considered zero," says Richard Healing, a former member of the NTSB.
Foolproof Safeguards
As a result, twin-engine airliners have been permitted to fly practically any polar or over-water route, regularly traveling up to five hours away from the nearest emergency landing strip. Commercial pilots grew comfortable flying through increasingly rough conditions. Although torrential rain and hail were known to shut down engines, the industry came to see icing safeguards as foolproof.
Those assumptions began to crumble in July 2004, when the first documented dual-engine icing event on a U.S. business jet sparked concern inside the NTSB. Over the next two years, Mr. Hookey, one of the board's propulsion experts, became concerned about shutdowns on two more Beechjets, a workhorse corporate and charter aircraft built by Raytheon Co. Flight-recorder readouts revealed neither mechanical breakdowns nor obvious pilot errors.
Two Loud Pops
In late 2005, a Beechjet flown by a charter firm had lost both engines suddenly while cruising below 38,000 feet, without passengers, in bad weather near northern Florida. Mr. Hookey took the unusual step of interrogating the pilots, who reported hearing two loud pops, about 10 seconds apart, before the flameouts.
As the plane descended rapidly, the pilots tried unsuccessfully three times to restart the engines. Donning oxygen masks and relying on instruments powered by backup electricity, the pilots threaded the airplane through menacing clouds to glide to a safe landing in Jacksonville. (Such maneuvers, which have been pulled off even in regular commercial jets, are considered extraordinary piloting feats.) The captain's account, recalls Mr. Hookey, "really tipped us off that it may be an environmental condition."
Within six months, both the NTSB and FAA were pursuing icing as an explanation. Comparing different engine incidents one day, Mr. Hookey wondered if they somehow were linked to big storm systems. To test his suspicion, he juxtaposed radar tracks of the aircraft with weather-satellite data for the same times. Each aircraft, he realized, had been flying in violent weather conditions.
Mr. Hookey urged engine makers to more closely evaluate weather data and to analyze engine-performance data in more detail. He prodded the NTSB to issue its first public warning indicating that ice ingestion could shut down engines without warning. During a May 2006 meeting of U.S. and Canadian investigators in Montreal, FAA officials argued that the cause of the problem appeared to be the behavior of ice crystals under certain conditions -- not fuel characteristics or specific engine designs, as previously thought.
In a nine-page recommendation letter to the FAA that summer, the NTSB explained how ice crystals can accumulate inside engines, despite interior temperatures way above freezing. Initially, the particles melt in the hot engine air, the board indicated. But as more ice is sucked in, some of those particles stick to the wet surfaces, cooling them. Eventually, enough ice builds up to create a hazard. Pilots have no clues, visual or otherwise, because the ice particles ordinarily don't stick to the outside of the engines, according to the NTSB.
Remaining Skeptical
Some in the industry, citing nearly two decades of reliable Beechjet performance, were skeptical of the explanation. But as the safety board and FAA officials dug into records of earlier engine problems on commuter jets and a small airliner, they discovered new complexities to icing within engines. New studies by GE and Pratt & Whitney, the maker of Beechjet engines, buttressed the NTSB's conclusion.
Calling the risk unacceptable, the safety board issued recommendations urging greater pilot awareness and fast-track development of devices to detect internal icing. Many in the industry, trained to believe that ice couldn't stick to interior metal surfaces at the bitter-cold temperatures at high altitude, remained skeptical of the icing theory.
Meanwhile, engineers and technicians at GE's icing-simulation facility in Peebles, Ohio, had begun to investigate the spate of twin-engine flameouts involving Boeing 747, 767 and other widebody jet models that use GE's popular CF-6 engines. Before 2003, GE had fixed a similar but simpler problem -- lower-altitude icing stoppages -- by tweaking digital engine controls. But that fix wouldn't work for the latest flameouts, which occurred above 25,000 feet, where weather conditions and engine behavior can be different.
The Qatar Airways incident in 2006 had involved a version of the CF-6. It was the fifth such incidence involving GE's premier engine family in about three years. The first challenge for the engine maker was to figure out how to mimic unusual atmospheric conditions so it could study how the high-altitude ice crystals interfere with engine performance. "It took about a year to get it right," recalls Mr. Kennedy, the GE spokesman.
Taking Action
GE eventually released three rounds of safety bulletins covering more than 1,350 widebody aircraft. Engine-control software was revised to increase the flow of "bleed air" -- heated air that is vented out of the engine. The idea was to suck the ice chunks out before they caused problems. GE also recommended that when pilots are flying under conditions known to produce ice crystals, they should boost power to the engines to help get rid of the ice.
Rolls-Royce also took action to lower icing risk, making minor modifications to engine designs and suggesting new procedures for pilots, according to industry officials. A spokesman for Rolls-Royce didn't have any comment.
In October 2006, the FAA weighed in, issuing a special safety bulletin about the CF-6 engines. Describing ice crystals "as a serious potential environmental threat," the bulletin called on pilots to "especially avoid flying over strong" storm systems and to "maintain vigilance for recognizing a potential ice crystal encounter."
After working further with engine makers and other industry players, by August 2007 the FAA directed airlines to install revised software on a wide range of GE-powered aircraft to reduce the icing risk. In addition, the FAA has tightened standards for newly designed engines so they will be less susceptible to icing.
GE is mulling additional fixes for existing engines. Industry officials say Rolls-Royce has told airline customers it is voluntarily modifying some turbine-blade designs, partly so they will better withstand potential problems from shedding ice.
Investigators continue struggling to understand why various engine designs react differently to extreme weather conditions. "We still don't have a really good scientific explanation," says Fran Fravara, the FAA's point man in this area.
Write to Andy Pasztor at [email protected]
With Engine-Shutdown Peril
Investigators Find
New Icing Threat;
FAA Proposes Rules
By ANDY PASZTOR
April 7, 2008; Page A1
******************
UNRAVELING A MYSTERY
• The Problem: Engines on commercial jetliners have been shutting down suddenly, but temporarily, in midflight.
• The Response: After discovering a new kind of icing, airlines and regulators come up with suggestions for minimizing the problem, but the shutdowns persist.
• What's Next: On Monday, the FAA will propose new flight procedures to address the problem further.Modern jet engines long were thought to be impervious to internal icing. But airlines, regulators and weather scientists now think otherwise, and have been scrambling to figure out how to handle the hazard. Despite some progress, the shutdowns keep happening.
***************
As a Qatar Airways flight dodged thunderstorms on approach to Shanghai in 2006, it encountered a problem that, until recently, was considered virtually impossible: nearly four miles above the earth, both engines of the big Airbus A330 shut down at the same time.
The engines quickly restarted and the pilots managed a safe landing. But the incident, along with similar ones before it, set off alarm bells throughout the industry because of the cause: ice inside the engines.
On Monday, the Federal Aviation Administration will propose new safety rules that are expected to apply eventually to about 1,200 widebody jetliners world-wide, including Boeing 747 jumbo jets. Pilots of those planes will be required to turn on engine anti-ice systems more frequently during descents, to reduce the chances of sudden shutdowns and to increase the likelihood that engines that quit will restart.
In recent weeks, the U.S. aviation-safety system -- effectively a partnership between the FAA and the airlines themselves -- has been shaken by revelations of lax oversight of Southwest Airlines Co. The coordinated response to the baffling engine-shutdown problem shows another side to the system: when airlines and regulators openly share information, they can tackle tough technical problems.
Here's what they've figured out about the engine shutdowns: At high altitude near intense storms, moisture turns into tiny ice crystals that can be sucked inside an engine. At first, the crystals melt. But sometimes the water freezes again on metal surfaces. Eventually, accumulating ice can either break into chunks that damage turbine blades, or melt and douse the ignition system.
The odds of both of a plane's engines shutting down at once were supposed to be about one in a billion. Since 2002, however, internal ice has been blamed for at least 14 instances of dual-engine shutdowns, called "flameouts," and several times that many single-engine outages. Investigators now believe that since the mid-1990s, so-called crystalline icing has prompted dramatic power drops or midair engine stoppages in more than 100 jets. So far, the flameouts haven't been blamed for any crashes, because the engines on big commercial jets have always managed to restart.
"If people had said just a few years ago that ice could build up within jet engines at high altitudes, we would have dismissed them," says Jim Hookey, a senior investigator at the U.S. National Transportation Safety Board, or NTSB. "As it turns out, this problem existed for a long time. The industry just never had enough knowledge before about the atmosphere or the threat from ice crystals."
By examining the dual-engine flameouts in relation to storm patterns, Mr. Hookey and other investigators began unraveling the icing mystery. Powerful thunderstorms, particularly over the Pacific Ocean in the spring and summer, can spawn smaller-than-normal ice particles, they say. These particles, which cannot be detected by pilots or weather radar, are swept into jet engines, leading to the problem.
Some experts contend that climate change is resulting in larger storms containing more ice particles -- a possible explanation for the frequency of the problem in recent years. Another possible factor is increasing traffic. Passenger flights over the Pacific, where more than two-thirds of the shutdowns have occurred, have risen more than fivefold so far in this decade, making it more likely that jets will encounter ice crystals.
Array of Engines
Flameouts have occurred on engines made by General Electric Co. and United Technologies Corp.'s Pratt & Whitney unit. A wide array of jets have been affected, including some built by Boeing Co. and European rival Airbus, and various regional and business jet models.
Rick Kennedy, a spokesman for GE's engine unit, says the company has invested heavily in both ground and flight testing, and "has made significant progress addressing these challenges across different aircraft models." But it's hard to replicate flameouts, he says, because "industry knowledge of these elusive atmospheric conditions is limited."
A Pratt & Whitney spokeswoman said the company has "worked closely with the NTSB throughout the investigations" and also is working with the FAA and other companies.
Although GE and others have made adjustments to their engines, the problem persists. Last November, GE says, three of the four revamped GE engines on a Philippine Airlines Boeing 747 experienced brief stoppages while descending toward Manila.
Given the millions of flight hours logged by long-range jets each year, in-flight engine shutdowns are a rarity. And when the engines do shut down, they typically fire back up and return to normal within 60 to 90 seconds. Passengers usually aren't aware anything has gone wrong.
Ice Studies
Even after years of studying icing, the airline industry still doesn't understand all the ways it can affect jet engines. In January, after a long flight over the arctic, a British Airways PLC jetliner crash-landed close to London's Heathrow Airport. Investigators and safety experts don't believe ice built up inside the engines. But many of them think that unusually frigid outside temperatures during the flight helped cause ice, slush or some kind of contaminant to build up in the Boeing 777's fuel system, starving both Rolls-Royce engines of fuel. With minimal power on final approach, the plane slammed down 300 yards short of the runway. All 152 people on board survived. Rolls-Royce PLC won't comment on the crash investigation.
Icing incidents of various kinds are forcing a re-examination of engine dependability in adverse weather. Seasoned aviators long have understood the hazards ice can pose. When ice builds up on wings or other external airplane parts, it can impair a jet's ability to gain lift. Anti-icing systems -- which range from spraying the wings with chemicals before takeoff to heating portions of the skin during flight -- long ago solved that problem.
As modern jet engines evolved, they became so dependable that they were considered nearly infallible. Engines routinely stayed in service for 20 or 25 years, often without experiencing a problem significant enough to warrant removal from aircraft. Pilots could go through an entire career without a single engine emergency, let alone two quitting at the same time. "For practical purposes, the likelihood of that was considered zero," says Richard Healing, a former member of the NTSB.
Foolproof Safeguards
As a result, twin-engine airliners have been permitted to fly practically any polar or over-water route, regularly traveling up to five hours away from the nearest emergency landing strip. Commercial pilots grew comfortable flying through increasingly rough conditions. Although torrential rain and hail were known to shut down engines, the industry came to see icing safeguards as foolproof.
Those assumptions began to crumble in July 2004, when the first documented dual-engine icing event on a U.S. business jet sparked concern inside the NTSB. Over the next two years, Mr. Hookey, one of the board's propulsion experts, became concerned about shutdowns on two more Beechjets, a workhorse corporate and charter aircraft built by Raytheon Co. Flight-recorder readouts revealed neither mechanical breakdowns nor obvious pilot errors.
Two Loud Pops
In late 2005, a Beechjet flown by a charter firm had lost both engines suddenly while cruising below 38,000 feet, without passengers, in bad weather near northern Florida. Mr. Hookey took the unusual step of interrogating the pilots, who reported hearing two loud pops, about 10 seconds apart, before the flameouts.
As the plane descended rapidly, the pilots tried unsuccessfully three times to restart the engines. Donning oxygen masks and relying on instruments powered by backup electricity, the pilots threaded the airplane through menacing clouds to glide to a safe landing in Jacksonville. (Such maneuvers, which have been pulled off even in regular commercial jets, are considered extraordinary piloting feats.) The captain's account, recalls Mr. Hookey, "really tipped us off that it may be an environmental condition."
Within six months, both the NTSB and FAA were pursuing icing as an explanation. Comparing different engine incidents one day, Mr. Hookey wondered if they somehow were linked to big storm systems. To test his suspicion, he juxtaposed radar tracks of the aircraft with weather-satellite data for the same times. Each aircraft, he realized, had been flying in violent weather conditions.
Mr. Hookey urged engine makers to more closely evaluate weather data and to analyze engine-performance data in more detail. He prodded the NTSB to issue its first public warning indicating that ice ingestion could shut down engines without warning. During a May 2006 meeting of U.S. and Canadian investigators in Montreal, FAA officials argued that the cause of the problem appeared to be the behavior of ice crystals under certain conditions -- not fuel characteristics or specific engine designs, as previously thought.
In a nine-page recommendation letter to the FAA that summer, the NTSB explained how ice crystals can accumulate inside engines, despite interior temperatures way above freezing. Initially, the particles melt in the hot engine air, the board indicated. But as more ice is sucked in, some of those particles stick to the wet surfaces, cooling them. Eventually, enough ice builds up to create a hazard. Pilots have no clues, visual or otherwise, because the ice particles ordinarily don't stick to the outside of the engines, according to the NTSB.
Remaining Skeptical
Some in the industry, citing nearly two decades of reliable Beechjet performance, were skeptical of the explanation. But as the safety board and FAA officials dug into records of earlier engine problems on commuter jets and a small airliner, they discovered new complexities to icing within engines. New studies by GE and Pratt & Whitney, the maker of Beechjet engines, buttressed the NTSB's conclusion.
Calling the risk unacceptable, the safety board issued recommendations urging greater pilot awareness and fast-track development of devices to detect internal icing. Many in the industry, trained to believe that ice couldn't stick to interior metal surfaces at the bitter-cold temperatures at high altitude, remained skeptical of the icing theory.
Meanwhile, engineers and technicians at GE's icing-simulation facility in Peebles, Ohio, had begun to investigate the spate of twin-engine flameouts involving Boeing 747, 767 and other widebody jet models that use GE's popular CF-6 engines. Before 2003, GE had fixed a similar but simpler problem -- lower-altitude icing stoppages -- by tweaking digital engine controls. But that fix wouldn't work for the latest flameouts, which occurred above 25,000 feet, where weather conditions and engine behavior can be different.
The Qatar Airways incident in 2006 had involved a version of the CF-6. It was the fifth such incidence involving GE's premier engine family in about three years. The first challenge for the engine maker was to figure out how to mimic unusual atmospheric conditions so it could study how the high-altitude ice crystals interfere with engine performance. "It took about a year to get it right," recalls Mr. Kennedy, the GE spokesman.
Taking Action
GE eventually released three rounds of safety bulletins covering more than 1,350 widebody aircraft. Engine-control software was revised to increase the flow of "bleed air" -- heated air that is vented out of the engine. The idea was to suck the ice chunks out before they caused problems. GE also recommended that when pilots are flying under conditions known to produce ice crystals, they should boost power to the engines to help get rid of the ice.
Rolls-Royce also took action to lower icing risk, making minor modifications to engine designs and suggesting new procedures for pilots, according to industry officials. A spokesman for Rolls-Royce didn't have any comment.
In October 2006, the FAA weighed in, issuing a special safety bulletin about the CF-6 engines. Describing ice crystals "as a serious potential environmental threat," the bulletin called on pilots to "especially avoid flying over strong" storm systems and to "maintain vigilance for recognizing a potential ice crystal encounter."
After working further with engine makers and other industry players, by August 2007 the FAA directed airlines to install revised software on a wide range of GE-powered aircraft to reduce the icing risk. In addition, the FAA has tightened standards for newly designed engines so they will be less susceptible to icing.
GE is mulling additional fixes for existing engines. Industry officials say Rolls-Royce has told airline customers it is voluntarily modifying some turbine-blade designs, partly so they will better withstand potential problems from shedding ice.
Investigators continue struggling to understand why various engine designs react differently to extreme weather conditions. "We still don't have a really good scientific explanation," says Fran Fravara, the FAA's point man in this area.
Write to Andy Pasztor at [email protected]