Jet's first trouble sign was veer on runway
Engines operated normally until plane left tarmac
By Kevin Flynn, Rocky Mountain News (Contact)
Published January 7, 2009 at 3:09 p.m.
Photo by Linda McConnell © special to The Rocky
NTSB chief investigator Bill English stands by the burned wreckage of Continental Flight 1404 is placed in an enclosed area of Continental hangar in Commerce City, Colo, Monday January 5, 2009. The NTSB still has no answers as to the cause of the flight but all passenger survived with only minor injuries.
The engines on Continental Flight 1404 were operating normally until the Boeing 737 left the runway at Denver International Airport in the Dec. 20 accident that injured 38 people.
An update released Wednesday by the National Transportation Safety Board, which includes information from the first interviews with the pilot and co-pilot, found that the first sign the flight crew had that there was any trouble was the actual veering of the plane to the left of the runway.
While witnesses reported that there were "bumping and rattling sounds" that might have preceded that, investigators have matched noises on the cockpit voice recorder with the information on the flight data recorder to determine that the noises came after the plane went off the left side of the runway at the airport.
One curious finding is that the flight crew called for the aborted takeoff seven seconds after the plane had begun to slide across the snow.
The plane careened down an embankment. over a perpendicular taxiway and an airport service road, losing its left engine along the way, before stopping near an airport fire station.
The plane traveled 2,300 feet after leaving Runway 34R. Reports had a direct crosswind from the west at 27 mph, and gusts were reported up to 32 mph.
Planes usually take off in the prevailing wind direction, which is from the north at DIA. Indeed, the NTSB reported that flights were operating in a northerly direction for landings and departures.
The NTSB isn't expected to determine a cause of the accident for at least a year. While the new report doesn't rule out engine trouble, reports so far indicate the only damages to the engines were from the impact with the ground off the runway.
The right engine, which sucked in snow and dirt, caught fire as a result of the crash and the right rear portion of the plane was severely burned.
According to the interview with the pilot, who was in control of the plane during the takeoff, "all appeared normal until the aircraft began to deviate from the runway centerline," the NTSB update reads.
"The captain noted that the airplane suddenly diverged to the left, and attempts to correct the deviation with the rudder were unsuccessful. He stated that he briefly attempted to return the aircraft to the centerline by using the tiller to manipulate the steering of the nose gear but was unable to keep the aircraft on the runway."
The plane reached a top speed of 119 knots (about 135 mph).
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January 7, 2009
3:28 p.m.
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AC writes:
So what made it veer off the runway? Wind? That's frightening.
January 7, 2009
3:33 p.m.
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ofcourse writes:
This all could have gone very bad.
Kudo's and thanks to those who helped get everyone off the plane.
January 7, 2009
4:04 p.m.
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vendari01 writes:
I gather that a sudden and strong cross-wind gust at the wrong moment, say just as the aircraft was about to rotate, could cause it to veer. Since aircraft usually take off into the wind, this is rarely a problem. Aircraft just make lousy off-road vehicles.
January 7, 2009
4:30 p.m.
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bph writes:
The 737 can takeoff in a 30 kt crosswind. Don't blame it on the wind.
January 7, 2009
4:41 p.m.
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temurlan writes:
It sounds like something went wrong with the controls for the steering. Wind would roll the plane over not steer it in a different direction. At least that's my thought.
January 7, 2009
5:02 p.m.
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psyclone writes:
bph - I heard that the winds were coming from the west at 31-35kts at the time of the crash. Have you heard otherwise? Is there somewhere this info can be obtained?
Personally, I've come into DIA from the North gate on a 777 with a last-minute runway change proposed by approach due to crosswinds. All the 737 pilots in front of us took the change to land into the wind but our pilot did a masterful job landing with a strong crosswind. Granted, a 777 is a beast and much more technologically advanced than the 737, but I was surprised, listening to ATC, at how apprehensive the 737 pilots were. Maybe it was just good customer service on their part!
January 7, 2009
5:46 p.m.
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AC writes:
Yeah, I'm thinkin' crosswind, maybe a big gust. The plane wasn't near rotation, but was less than 2,000 feet down the line.
January 7, 2009
6:04 p.m.
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saveourplanet writes:
All your expert thoughts about the wind being the cause are well thought out - except that the aircraft deviated into the wind.
January 7, 2009
10:51 p.m.
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b727plumber writes:
saveourplanet,
That's because the aircraft will weathervane into the wind. In this case, with a strong wind from the left, the aircraft will yaw to the left.
January 8, 2009
6:33 a.m.
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TallPaul writes:
One theory I heard from a pilot friend was that as the pilots tried to fight the strong cross wind with the plane trying to weathervane into the wind, they lowered the left wing, as the crosswind would try to flip the plane over (clockwise flip on a left-to-right crosswind). This model plane has only 2 1/2 foot clearance between the engine and the runway, so they touched the left engine to the ground as they dipped the left wing, momentarily killing the left engine, further weathervaning the plane to the left. If true, the records should show the left engine sputtering or dying. I haven't heard that yet in any reports.
January 8, 2009
8:20 a.m.
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B300 writes:
I dont think they have a clue? Probably human error. Why dont they just wait until they THINK they know happened and then make a report? Or maybe this has to do with the insueing law suits?
January 8, 2009
8:21 a.m.
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SockRayBlue writes:
My thoughts...........
The crosswind caused a compressor stall on the windward (left) engine. Much like blowing air across a bottle top. The left engine lost power and the right engine caused the craft to yaw to the left into the wind.
Then again it could be along the lines of TallPaul's posting.
January 8, 2009
8:26 a.m.
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INC writes:
A term not used since DIA was finished...
Microburst...
explains it. Obviously enough to push that plane enough off of the runway to drop the landing gear into the dirt. the rest is physics of friction.
January 8, 2009
9:46 a.m.
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joggle writes:
I don't think so SockRayBlue. 30 knot gusts are not that strong for a 737. Unless there was a rudder failure I would have to guess human error was involved (which is, in fact, the cause of the majority of accidents).
January 8, 2009
9:48 a.m.
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Dub writes:
There are reports that a prairie dog was crossing the runway, and the pilot, being from Boulder, tried to avoid running it over and lost control. Fortunately the PD escaped with minor injuries,and was treated and dismissed.
January 8, 2009
11:01 a.m.
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AC writes:
Tallpaul and B300, the story says the engines were both operating normally until after the plane left the runway; that means there was no stall or sputtering while on the runway.
January 8, 2009
12:16 p.m.
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lwt5150 writes:
A yaw as described above could have been caused by a sudden, intense crosswind that may have stalled the windward engine and yawed the plane into the gust.
The fact that they say that both engines were operating normally is a bit perplexing, unless they had a compressor stall after they left the runway. Plus, no affect from the pilot activating the rudder adds to the mystery. This is a 737 after all, and maybe a very close look at the rudder will yield some clues (Pittsburgh and Colorado Springs crashes).
I've flown into Denver on United and listened to ATC in thunderstorms. They are VERY wary of microbursts at ATC, and the 737's in front of us were eager to pattern until the weather moved on.
Maybe a problem with the gear on the left side of the plane: a tire lockup or a problem in the hydraulics on the gear. Maybe the engine ingested goose as it rotated?
January 8, 2009
12:55 p.m.
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RomBrew writes:
When they built that airport you couldn't have put it in a more weather active area. Since I was a kid we would drive out there and watch lightning, tornados, etc. Pena and his crew were morons for suggesting it. It is a miracle nothing worse has happened at DIA sooner. Although odds are something catastrophic will someday take place.
BTW thank heavens the prarie dog was unhurt.
January 8, 2009
1:43 p.m.
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dwood writes:
I think I'll just wait until the NTSB releases their findings. Wind, goose, hydraulics, prairie dog, steering controls, human error, did I miss any? The analysis done just by looking at pictures is amazing. I'm going with sun spots, it should fit with the rest of these "theories".
January 8, 2009
9:02 p.m.
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AC writes:
RomBrew writes: "When they built that airport you couldn't have put it in a more weather active area. Since I was a kid we would drive out there and watch lightning, tornados, etc. Pena and his crew were morons for suggesting it. It is a miracle nothing worse has happened at DIA sooner. Although odds are something catastrophic will someday take place."
Are you for real?
"An active weather area?" You mean there's more weather over there than over here?
You never got over that 1989 vote, I guess. But your claim is a debunked urban myth. I watched the 1987 tornado in Park Hill and the once that closed Stapleton when it went up RW 35L. "Active weather area" indeed!