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Compressor Stall in 747 (Long)
Posted By: Matthew Sheil (203-206-128-223.perm.iinet.net.au)
Date: 22 JUN 2007 - 00:32z
Hi Guys,
Just been talking with Hardy on this to program my sim for compressor stall motion. :-)
Thought you might be interestedBy WILLIAM M. CARLEY
Staff Reporter of THE WALL STREET JOURNALAs the United Airlines jumbo jet lifted off from San Francisco International
Airport one night last summer, one of its four engines lost power. Because of
poor flying techniques, the co-pilot who was at the controls slowed and nearly
stalled and crashed the plane."Push [the nose] down" to pick up speed, shouted two extra pilots sitting in the
rear of the cockpit. The co-pilot did, but now the jet was off course and
heading toward San Bruno Mountain northwest of the airport. The jet's
ground-proximity warning sounded, and the extra pilots shouted, "Pull up, pull
up!"Carrying 307 passengers and crew, the
plane cleared the hill by only 100 feet.
The jet also barely missed apartments and
houses with hundreds of sleeping
residents. A crash of the jet, which was
heavily loaded with fuel, would have been
one of the worst aviation accidents in
history.
The captain finally took control and flew
over the ocean, dumping fuel before
returning safely to the airport. But the incident -- just now being publicly
disclosed -- has rocked the world's biggest airline and spurred the Federal
Aviation Administration to force changes in United's pilot-training techniques.
The jumbo's low flight also has alarmed local residents, with one man declaring
in a call recorded by an airport hotline: "I thought the damn thing was coming in
on my roof."United, a unit of UAL Corp., based near Chicago, acknowledges the incident
and says that it has spurred the carrier to take a series of steps, ranging from a
safety audit of all its 9,500 pilots to a major shakeup in its pilot training.
Edmund Soliday, vice president for safety, says the airline hasn't lost a plane
because of poor piloting for 20 years, "and we are taking this incident very
seriously." He says the airline aims to improve its margin of safety "so we won't
have to look at a hole in the ground someday."In Washington, Nicholas Lacey, who as FAA director of flight standards is the
agency's top official on piloting issues, says United's close call "didn't result in a
tragedy -- but it was a near-tragedy." Mr. Lacey adds that for a variety of
reasons, "complacency might have set in" among some United pilots.The agency is now pushing United hard to improve skills of its pilots, especially
its 747-400 co-pilots, or to ground some of them. One FAA mandate that was
to become effective this month would have grounded so many United co-pilots
that it would "severely hamper" the airline's international operation, according to
a letter to United pilots from the Air Line Pilots Association. (The union
represents the carrier's pilots.) That FAA proposal has been modified, and
United says international flights won't be cut, but the agency is still pressing for
pilot improvements.Additional United close calls in recent months -- also never publicly disclosed
-- have broadened the concern beyond the 747-400 crews. "In the past
months, we have had several operational incidents," airline jargon for close
calls, W.J. Carter, chief of United's Honolulu-based pilots, wrote in a Feb. 23
internal memo to his flight crews. "Major accidents historically are preceded by
a series of these seemingly unrelated incidents. This disturbing trend is cause for
concern," the memo continued.United has set up a special one-hour safety seminar which all its pilots must
attend by May 10. If they don't, they will be dropped from the flying schedule
without pay. According to the union's letter to United pilots, "This is as close as
an airline can come to a military 'stand down,' " when military flyers are
temporarily grounded because of safety concerns.United officials declined to discuss details of the incidents because they were
disclosed to management by pilots under a confidential safety-reporting system.
But many safety analysts say that United, which had no legal obligation to
publicly disclose some of the close calls, should be commended for alerting its
pilots. "They have treated this [San Francisco] incident like an accident to raise
safety awareness among their pilots, and for that I give them kudos," says the
FAA's Mr. Lacey.Despite the close calls, United emphasizes its safety record is excellent, with
nearly 6.2 million flights without a crash since a United 737 went down in
Colorado Springs in 1991. Safety analysts agree that United's record is strong.
United has been a leader in many safety measures, including teaching pilots in
simulators how to escape wind shears, beginning in the 1980s, and installing
better ground-proximity warning systems in jets in recent years.The close call in San Francisco, safety analysts say, raises issues that have been
worrisome for years. Airplanes are designed to take off and climb safely even if
an engine fails. In the San Francisco episode, why didn't the United co-pilot fly
the plane properly? There is "no doubt we had a pilot proficiency problem,"
concedes United's Mr. Soliday.One factor in pilot proficiency is the enormous increase in long-range flying in
recent years. The jet in the close call was a Boeing 747-400, designed to fly
nonstop trips such as New York to Tokyo. The jumbo routinely makes
14-hour flights. Concerned about pilot fatigue, Boeing designed the cockpit for
as many as four crew members: a captain and co-pilot who handle flying duties,
and two extra pilots sitting behind (dubbed "bunkies" because they can rest in
bunks) who relieve the others during the flight.But because these flights and rest periods required between them are so
time-consuming, pilots make only a few trips each month. And with four pilots
aboard, chances of practicing takeoffs and landings -- the most critical phases
of flight -- are few.At United, says a spokesman, captains of 747-400s average only three
takeoffs and landings a month. Co-pilots, because there are three of them
aboard each flight, get even less practice, averaging just one takeoff and landing
a month. Because of scheduling complexities and vacations, some co-pilots
don't make a takeoff and landing for months.The problem isn't unique to United. Boeing has sold nearly 450 of the
747-400s to 30 airlines around the world, including British Airways, Japan
Airlines and Northwest Airlines. Nor is the issue confined to Boeing planes; the
Airbus Industrie A340 makes similar long flights, many with four pilots in the
cockpit.How many jets at other carriers may have had narrow escapes similar to
United's isn't known. Because of limitations and loopholes in FAA and National
Transportation Safety Board databases, many close calls escape public notice.
But David Simmon, a former United pilot who is now a safety consultant, says
long-range flying "is known to cause proficiency problems due to the limited
number of takeoffs and landings shared among a four-person crew." The issue,
he adds, "is an ongoing industry problem."Another factor in the San Francisco close call may be complacency. The latest
generation of jets, including the 747-400, are so highly automated and reliable
that pilots may simply get bored. "On these long flights, it's very hard to keep
the pilots on the edge of their seats," says Cecil Ewell, chief pilot and vice
president for flight at American Airlines. "Hardly anything ever goes wrong,"
says the FAA's Mr. Lacey.The answer to these concerns was supposed to be simulators, where pilots can
drill regularly and practice emergency moves. But the simulators can't replicate
everything, and still can't replicate critical moments in United's close call. There
are also questions about how well simulators are used for training. Asks Mr.
Simmon, the consultant: "Is some simulator training perfunctory?"Such problems may have played a role last June 28 as United Flight 863
prepared for takeoff at San Francisco International. FAA documents and tapes
of air-traffic controllers obtained by The Wall Street Journal under the Freedom
of Information Act, as well as interviews with pilots familiar with the incident,
show the takeoff wasn't going to be routine.Bound for Sydney, Australia, the jet weighed almost 450,000 pounds and was
carrying nearly an additional 400,000 pounds of fuel for the long flight -- weight
that would reduce its ability to climb. And as the jet revved its engines at 11:39
p.m., ocean fog had crept in, obscuring much of the San Francisco area --
including the hills northwest of the airport."United 863 ... , runway 28 right, cleared for takeoff," the San Francisco tower
controller radioed to the plane.For reasons that remain unexplained, the co-pilot at the controls had even less
real-world practice than usual. He had made a takeoff and landing in a real
747-400 the previous week, but that was his first in nearly a year. (FAA rules
call for three takeoffs and landings within 90 days, but all can be done in a
simulator.)Just as the jet lifted off from the runway heading northwest, the right inboard
engine malfunctioned for unknown reasons, triggering so-called compressor
stalls in the engine. These stalls produce enormous backfires, with fire and
smoke exploding out the rear of the engine and violently shaking the whole
plane."It's bang, bang, bang and shudder, shudder, shudder," says the FAA's Mr.
Lacey.The shaking was so violent that the pilots couldn't read their instruments at first,
and frantically guessed at the cause. "Maybe it's a [blown] tire," one of the extra
co-pilots shouted. But then the co-pilot at the controls read an instrument
showing problems in the right inboard engine, and it was shut down.With two engines at full power on the left wing and only one now operating on
the right, the left engines began pushing the plane into a right turn. To counter
that, pilots say, the co-pilot should have just used the rudder on the tail. But he
mistakenly turned his control wheel to the left. That extended ailerons, control
panels on the rear of the wings which would tend to make the jet bank to the
left. But the co-pilot's action also extended spoilers, panels on top of the wing
that increase drag and cut the jet's ability to climb.Unable to climb much, but with its nose still up, the heavy jet began to slow
down, so much that the dreaded "stick-shaker" warning began. In this warning,
the pilot's control column literally shakes, signaling the plane is going so slow
that it's beginning to stall and is about to crash."Push down, push down" the nose to gain speed, the extra co-pilots yelled. The
co-pilot did, but now there was another danger ahead. Off course because of
the right turn, the jet was headed towards San Bruno mountain, a broad lump
that rises to 1,576 feet a few miles northwest of the airport. Densely populated
areas lap at the mountain's base. The crew couldn't see the mountain. It was
bathed in dense fog.Suddenly the plane's ground proximity warning sounded, an automatic voice
calling, "terrain, terrain, pull up, pull up." The two extra co-pilots echoed the
warning, screaming "Pull up!"Heavy with fuel, spoilers extended and still in a skidding right turn which further
increased drag, the jet could barely climb. But the co-pilot pulled the nose up
anyway. The jet cleared the top of the mountain by about 100 feet, according
to both airline and FAA officials. It was so close to the ground that air
controllers' radar lost contact with the plane, sparking fears in the tower that
Flight 863 had crashed.San Francisco controller Cynthia Grimm immediately called a controller at
another FAA radar post. "Hi, is United 863 -- oh, there he is" on the radar
scope, she exclaimed. "He scared me, we lost radar" contact.Lurching over South San Francisco, then Daly City and San Francisco, the jet
was so low it terrified residents. At the airport, a telephone hot line recorded a
deluge of complaints. "People were running out of their houses for fear the
plane was going to crash," a South San Francisco resident said, according to
call transcripts. The identities of callers are kept confidential. The jet set off car
alarms, "it shook the whole house, we thought it was going to take out the
neighborhood," said another caller.In Daly City, "I thought I was going to have to go under the couch," one man
said. And a San Francisco woman said her daughter's nearby home was
shaken "like it was an earthquake."As the jet headed out to sea to dump fuel for an emergency landing, the FAA
was already securing tapes of the air controller conversations. United officials
retrieved the jet's flight-data recorder, which saves items such as speed, altitude
and engine performance, and began their own inquiry.FAA and United officials were shocked at what they found: The crew had
violated fundamental flying rules, such as maintaining minimum air speed. "They
didn't do the basics," says the FAA's Mr. Lacey.The FAA, United and its pilots' union have taken a series of remedial steps,
some short-term "quick fixes," as one United pilot puts it. They have also
launched studies which in the next year or so may lead to other changes in
United's operations.One of the more controversial moves was made in December by James
Edwards, the FAA's principal operations inspector overseeing United's pilots.
He ruled that by this month, every 747-400 co-pilot had to have made three
takeoffs and landings in a real plane within 90 days or be effectively banned
from the cockpit. That would have grounded so many co-pilots that United
would have been forced to cancel some of its overseas flights, including as
many as 30% of its Pacific flights, according to a pilots' union estimate.But the FAA and United have hammered out a compromise. Within 90 days of
a flight, a co-pilot now must have made at least one takeoff and landing in a real
jet, plus two in a simulator. Co-pilots who haven't met the requirement must
make their next flight with a "check captain." Check captains are highly
experienced management pilots who check other pilots."The bottom line," states the Feb. 3 union letter to all United pilots, "is the FAA,
after reviewing our aircraft landing records and other items, has determined that
the simulator cannot nor was it ever intended to be the sole method" for
keeping pilots' landing skills up to date.United has taken other short-term steps. It has retrained the crew of Flight 863.
Using data from the recorder and with other pilots playing the role of the crew,
the airline made a video portraying the close call in one of its simulators at its
Denver training base. The shaking of the real airplane, however, was so severe
it couldn't be duplicated in the simulator. United is now trying to improve its
simulators.The carrier is showing the video to all its pilots, and re-emphasizing certain
flying rules. One rule: the rudder (not ailerons) must be used to maintain
direction when an engine fails on takeoff.In addition, United has increased the frequency of recurrent training for all its
747-400 pilots. Instead of getting recurrent training -- which involves days of
extensive simulator and classroom work -- once a year, 747-400 crews are
now getting it twice a year.United has spent $2.5 million on remedial measures, and "before we're through
we may be up to $5 million," says Mr. Soliday.United and the pilots' union also have set up a joint committee composed of 10
747-400 captains and co-pilots to study possible changes in how the jet should
be manned. At Northwest Airlines, for example, a 747-400 cockpit features a
captain and co-pilot at the controls, and a second captain and co-pilot in the
seats behind who provide relief on long flights. At United, there is only one
captain and three co-pilots, called first officers. Captains are generally more
experienced than first officers.William Brashear, a United 747-400 captain and pilots' union official, says the
Northwest system will be one of the approaches studied. But he says that at
United, all the co-pilots are trained and rated as captains anyway, and lack only
seniority to get the captain's title.In the meantime, says Mr. Brashear, United and its pilots "are working just as
hard as we can to make this airline as safe as possible."-------
end of article
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