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CO Incident at DEN


blues deville

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The distance the aircraft travelled after leaving the runway, even given the snow-covered ground, is substantial so the speed the a/c had achieved would have been quite high.

That's one HELLUVAN excursion. There's gotta be more to this than a loss of control near V1 ph34r.gif

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That's one HELLUVAN excursion. There's gotta be more to this than a loss of control near V1 ph34r.gif

As I sit in my comfortable chair and put on my football helmet I think, and ponder, and thus come to this conclusion.

Something happened near V1 but the guys in the bird knew they were close to "flying" speed so attempted to get her off the ground............. but realized in a split second, after encountering the lumpy ride on the grass......... that it wasn't going to happen and thus attempted to stop as they careened through the weeds....ergo the long set of tire tracks to point of termination

There..my armchair quarterbacking is complete. laugh.gif

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Finally, the dry “maximum demonstrated” crosswind limit is slightly reduced with winglets to 34kts

That would be for a 90 degree crosswind wouldn't it?

At 50 degrees off runway heading you should be able to accept significantly higher crosswind component.

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mo32a;

That would be for a 90 degree crosswind wouldn't it?

Interesting question.

I would think that the forces of a xwind would act slightly differently at 90deg than they would say, at 50deg for the same xwind component so I would say you're right. In other words, a man carrying a 4x8 sheet of 3/4" plywood in a 34kt wind at 90deg pushing directly against the sheet would struggle differently than a man carrying a similar sheet against a "34kt xwind" component from a 50kt wind that is 45deg to the plywood, assuming both could be found afterwards to report?

The one thought that hasn't been mentioned yet is, while 24kts of xwind is demonstrated and the runway was bare and dry, weathercocking into wind can be a factor in any engine failure and/or reject. Still, all those who fly have done that in the sim and it's seems emminently controllable.

It has also been mentioned that the track on the initial excursion is pretty straight, until the aircraft begins to travel down the gentle slope where it begins to curve further left. Some are mentioning rudder use, dragging wheels, deeper snow on one side and other bits and pieces of etc - I think once off the runway, everyone is along for the ride unless the ground is very flat and there are no obstructions, (YYC 34 Jetsgo excursion).

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I think it has more to do with the cross-wind. It has been reported anywhere from 26kts to 37MPH cross wind. Regardless, it was a "strong" crosswind requiring precise application of cross-wind technique to ensure a safe take-off. This is why our airline limits FO take-off to 15kts of crosswind when the 747 can handle 30kts.

Think about the runway...34R with a wind of 290 at 32kts. This requires several units of aileron all the way to V1. A brief brain fart forgetting opposite rudder will veer the plane to the left. Once it goes, it is very hard to stop. Tendency is to reduce aileron which lifts the left wing. Pilots overreacts with lots of left aileron and the wing slams down striking the pod and the journey through the grass (to the left of the runway) begins.

There may have been a contributing factor such as thrust variation or blown tires but I believe the technique for cross-wind was 80% of the cause....IMO. wink.gif

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Lots of opinion based on nothing so far. There is not even a guarantee that info will be on the recorders.

However, I will say that VMCG is based on fairly light winds. Not that it necessarily has anything to do with this accident.

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handyman;

Way I read it anyway, I think you're exaggerating a lot of factors here.

Remember, it was only a 24kt (approx) xwind component. On it's own, such a xwind isn't a problem for this type or any type I've flown, (haven't flown the 77', 74' or the 73' but have flown everything else).

I don't think the left wing slammed down. The left engine is out in front of the left wing and has "chin" damage, likely from striking the burms or roadway, and there is no winglet damage on the left wingtip.

A momentary weather-cocking/drifting is not difficult to control unless the flight controls are badly mis-handled or not handled at all - with Continental guys I just can't imagine that happening.

Now, anything is possible - just not everything is probable.

(Off topic: Does your airline advocate a lot of into-wind aileron? If not, what do they advocate and why? That in itself is an issue especially if you deploy roll-spoilers. SOP on the 320/330/340 is neutral ailerons.)

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Not arm chairing here… just thinking out loud. wink.gif

I am thinking that this plane never was "rotated" per say.

Interesting to note on the "above view" that Don posted... it seems possible that the reports of "getting airborne for a few seconds" would coincide with the plane leaving the ground when it skipped over the ridge and into the ravine. The view from above looks to me as though the plane was moving at a good rate of speed as it "flew" off the flat terrain and downward. Hence the end of tracks & start of new ones to the final resting point. Perhaps this is why everything (engines/gear) are located relatively close to the final stopping point and the fuse was buckled.

The CVR/FDR data along with the crew's input will eventually tell the story.

Glad no one was killed in what was a wild ride for everyone.

Slim

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handyman;

Way I read it anyway, I think you're exaggerating a lot of factors here.

Remember, it was only a 24kt (approx) xwind component. On it's own, such a xwind isn't a problem for this type or any type I've flown, (haven't flown the 77', 74' or the 73' but have flown everything else).

I don't think the left wing slammed down. The left engine is out in front of the left wing and has "chin" damage, likely from striking the burms or roadway, and there is no winglet damage on the left wingtip.

A momentary weather-cocking/drifting is not difficult to control unless the flight controls are badly mis-handled or not handled at all - with Continental guys I just  can't imagine that happening.

Now, anything is possible - just not everything is probable.

(Off topic: Does your airline advocate a lot of into-wind aileron? If not, what do they advocate and why? That in itself is an issue especially if you deploy roll-spoilers. SOP on the 320/330/340 is neutral ailerons.)

Hi Don,

Most pods will strike before the wing-tips and a pod strike doesn't mean the engine gets ripped off. I have seen where poor handling has caused strikes resulting in control issues which on an accelerating jet with high thrust...exasperates problems.

Our airline uses 1 division of deflection for every 10kts of cross. Convention is, deflection will increase slightly as you approach V1. This is probably to diminish spoiler deflection for some or most of the take-off roll.

If you don't use any ailerons with say a 340...doesn't the wing lift on 30kts of cross? It's probably only 5 or 6 degrees of roll required to pod strike with any weight on the upwind oleo. wink.gif

As for any rotation...I too agree. Everything happened before V1 IMO.

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FROM CNN...more speculation

DENVER, Colorado (CNN) -- A problem with the landing gear, tire or brakes may have caused a Continental Airlines jet to veer off a runway into a 40-foot-deep ravine during its takeoff at Denver International Airport, a source told CNN Monday.

A source tells CNN that it is possible a wheel locked up while the Continental jet took off from Denver.

More than three dozen people were injured in Saturday's accident, most from bruises and broken bones as frightened passengers tried to flee a fire on board. There were no fatalities.

The source said early indications show a problem with the landing gear, tires or brakes could have caused a wheel to lock up.

The National Transportation Safety Board did an "initial readout" of the cockpit voice recorder and flight data recorder recovered from the wreckage Sunday, a government aviation official said.

Robert Sumwalt, a National Transportation Safety Board member leading the investigation team, said Monday at a news conference that both recorders contained "good data" and that the voice recorder was audible.

"Tonight, we should have some overall characterization of what was said in that cockpit," he told reporters.

He would not confirm that a problem with the landing gear, tire or brakes may have caused the accident, saying the investigation was still in its early stages.

Sumwalt also said he could not identify the captain and first officer, nor say whether either was hospitalized or who was actually flying the plane. Neither has been interviewed yet, though federal investigators are arranging for an interview with the first officer. A knowledgeable source told CNN the captain was hospitalized in serious condition.

On Monday investigators were to begin interviewing crew members, pilots and passengers to help determine what caused the accident. From the air, a crack is visible wrapping around the middle part of the plane.

"The captain has not been interviewed at this time," Sumwalt said. "We want to do it as soon as we can but want to be respectful of the captain's mental condition. ... We want to make sure he or she is mentally ready."

When pressed about when that interview would take place, he said, "Everybody wants to get the NTSB interview over with as soon as possible. ... The pilots want to get it over with because it's something you get nervous about."

Preliminary findings may come within a week, Sumwalt said, but a full investigation could take a year.

Gabriel Trejos was about to board Continental Flight 1404, bound for Houston, with his wife and 1-year-old when gate officials announced the plane was experiencing "engine problems," Trejos told CNN affiliate KUSA.

But, "shortly after that, they said everything is fine. There's going to be an on-time flight," Trejos said.

Continental spokeswoman Julie King, however, said she was unaware of any announcement of engine problems on the flight.

The Boeing 737 taxied down the runway at Denver International Airport and accelerated.

It was dark, 6:18 p.m., and the Trejos' baby, leaning against the window, giggled at the lights on the tarmac.

"All of a sudden, it was too much light," said Maria Trejos, who is four months pregnant.

"We felt the plane veer to the left. My husband was holding my son and we felt some bumpiness and I thought it was just turbulence," she said. "I looked to the side and all of a sudden there was this giant fireball behind my husband's head. I have this image of him just grabbing my son's head and just pulling him toward himself and all of a sudden we felt this heat."

She felt a bump, she said. "And it felt like we were airborne for a couple of seconds." Watch Maria and Gabriel Trejos describe the crash »

The plane skidded off the runway, its wheels disintegrating. It slammed into a ravine, its fuel tanks leaking, and caught fire. Luggage fell out of overhead bins that had begun to melt.

Passengers panicked and shoved and stepped over each other. One yelled, "The plane is going to explode!" said Gabriel Trejos, who was clutching his child and feared that the buckling seats would "squash" them both.

The couple fought their way into a line of people scrambling to get out of the back of the plane. Some were trying to get their luggage first.

"I just wanted to get out of there," Gabriel Trejos said.

He noticed that the escape chute in the middle of the plane had fewer people huddled near it. The Trejos dashed for that and escaped.

All 115 people on board survived the crash. Forty people were injured, two critically, authorities said. Bone fractures and bruises were the most common complaint, and there appeared to be no burn victims, fire officials said.

Of the dozens taken to hospitals, five people remained hospitalized late Sunday, Sumwalt said.

In the airport after the ordeal, passengers used terms like "rag doll" to describe how they felt during the nightmare.

"It was incredibly violent," Jeb Tilly told CNN affiliate KPRC. "It was a big left-hand turn and we sort of started bouncing a lot as if we were in a roller coaster, you know, you're kind of getting tossed around in your seat.

"And then there was a lot of silence all of a sudden. We took a big drop and when we hit the ground, that's when the thing really got kind of screwy," Tilly continued. "I think that's when the plane cracked in half at that point and all the overhead baggage compartments broke open and fell down."

At a news conference late Saturday, Patrick Hynes, chief of the airport division of the Denver Fire Department, said crews responding to the scene "had a difficult time narrowing down exactly where the airplane ended up," but found it north of a firehouse.

When they arrived, firefighters found the plane on fire in a ravine about 200 yards from the runway, with its wheels sheared off and fuel tanks leaking, Hynes said.

"They [firefighters] described a surreal scene when they pulled up, heavy fire on the right side of the aircraft, all chutes deployed from both sides of the aircraft, people evacuating and walking up the hillside towards them," he said.

Hynes said the entire right side of the jet was in flames and "a heck of a firefight" followed.

"There was significant extension of fire into the cabin portion," he said. "There's significant fire damage inside with the luggage compartment described as melting and dropping down into the seats."

Hynes said fuel from the aircraft leaked for several hours after the accident.

Has anyone seen any photos of the runway at the point of departure....any black rubber etc that might show brakes locked , a wheel locked up etc???

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Still thinking out loud wink.gif

Once again I refer back to that great "above view" shot Don posted.... it's a .bmp file that I blew up and looked at closely. I am no expert on "witness marks" but it appears to my untrained eye that the plane was rolling on its gear... through the infield until it left the flat terrain. Using the track width as a guide, it appears as though the plane "landed" down the ravine on said gear and very shortly thereafter, the engines also started to show tracks (suggesting possible gear failure at this point of impact) The plane travels along and the left engine, based again on the tracks in the snow, appears to separate from the wing as the plane crossed the road and dug in half way between the road and the stop point.

The question of course is what caused the excursion as the picture only tells some of the story about what happened after they left the runway.

As I said earlier... a wild ride for these people.

Slim

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The photo Don posted kind of tells us a lot. When the plane crossed Whiskey Charlie it was airbourne going over the edge of that taxiway. Having flown into KDEN both as a PIC in our little jet and as a passenger, that stupid ravine has always seemed really deep to me, probably 30 or 40 feet down, and it drops really sharply too, maybe at 35 or 40 degrees of down slope so the 733 must have come down really hard nose first at below V1 or VMCG speed. Kinda like a car going off a cliff that we've seen so often in the movies maybe?

I'm not sure what the KDEN airport designers were considering when they had those ravines built between 34L and 34R but it might have resulted in a lot less damage if the graded areas had been a lot flatter for a runway excursion RTO.

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From CNN..........

DENVER, Colorado (CNN) -- Early indications show no problems with the landing gear, tires or brakes on the Continental Airlines jet that veered off a runway at Denver International Airport in Colorado, despite earlier reports.................

................ "There's no indication from the physical examination on the scene of brake problems at this time," said Robert Sumwalt, a National Transportation Safety Board member leading the investigation team...............The brakes showed no leaks, no locked brakes," Sumwalt told reporters late Monday, adding that the brake pads "looked good."......................

...............He said tire marks indicate that all four main landing gear were inflated. The weather was clear, and no obstacles were on the runway, he said..............

...............Sumwalt said the cockpit voice recorder "shows nothing out of the ordinary" during the preflight operations. He said the recording revealed that 41 seconds after the brakes were released, there were sounds of bumping and rattling. Four seconds later, a crew member called for a rejected takeoff..............

entire article here

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I am thinking the 40ft ravine is a bit of red herring (so to speak). There are a lot of runways out there with hangers and or terminals along side them. 15L, 33R at YYZ for example. That would be ugly.

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handyman;

Most pods will strike before the wing-tips and a pod strike doesn't mean the engine gets ripped off. I have seen where poor handling has caused strikes resulting in control issues which on an accelerating jet with high thrust...exasperates problems.

Yes, I know and understand that, thanks.

Our airline uses 1 division of deflection for every 10kts of cross. Convention is, deflection will increase slightly as you approach V1. This is probably to diminish spoiler deflection for some or most of the take-off roll.

Not sure what "one division of deflection" means. Is that a Boeing term? What amount of aileron deflection brings up the roll spoilers? On the 320 it's about 5deg of sidestick roll command or just touching the edge of what is known as the "iron cross" on the PFD.

If you don't use any ailerons with say a 340...doesn't the wing lift on 30kts of cross? It's probably only 5 or 6 degrees of roll required to pod strike with any weight on the upwind oleo.

From A320/A330/A340 AOMs:

For crosswinds below 20kts:

For crosswind take-offs routine use of into wind aileron is not recommended.

For crosswinds above 20kts:

In strong crosswind conditions, small amounts of lateral control may be used to maintain wings level but care should be taken to avoid using excessive amounts, resulting in excessive spoiler deployment which increases the tendency to turn into wind.

There is no guidance in the Boeing 767 or 777 AOMs regarding crosswind takeoffs and use of ailerons nor does there seem to be a published/demonstrated crosswind limit.

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Yes, I know and understand that, thanks.

I suspect this is in response to my explanation of pods striking prior to wing-tips. I only voiced this in response to your comment which led me to believe you thought otherwise.

I don't think the left wing slammed down. The left engine is out in front of the left wing and has "chin" damage, likely from striking the burms or roadway, and there is no winglet damage on the left wingtip.

Not sure what "one division of deflection" means. Is that a Boeing term? What amount of aileron deflection brings up the roll spoilers? On the 320 it's about 5deg of sidestick roll command or just touching the edge of what is known as the "iron cross" on the PFD.

On the top of the yoke we have an aileron trim indicator which simply shows divisions or units of trim as the yoke wheel moves via the trim mechanism. We use this also for cross-wind deflection adjusting 1 unit per 10 kts of cross. Spoilers will deflect from 2-3 units and 6 units represents approx 47 degrees of wheel movement. So lets assume each division is approx 8 degrees.

For crosswinds above 20kts:

In strong crosswind conditions, small amounts of lateral control may be used to maintain wings level but care should be taken to avoid using excessive amounts, resulting in excessive spoiler deployment which increases the tendency to turn into wind.

Now this really cracks me up....don't the French realize for decades pilots have just used opposite rudder to control the turn? The Airbus guidance leaves me to believe that the corporate policy is for the pilot to watch and just let the machine sort it out. I'm soooo happy I'm a Boeing driver!

There is no guidance in the Boeing 767 or 777 AOMs regarding crosswind takeoffs and use of ailerons nor does there seem to be a published/demonstrated crosswind limit.

Interesting...our 777AOM states 38kts for the 777-300ER and ...

"Limit control wheel input to that required to keep the wings level. Use of excessive control wheel may cause spoilers to rise which has the effect of reducing tail clearance. All of

these factors provide maximum energy to accelerate through gusts while maintaining

tail clearance margins at liftoff. The aircraft is in a sideslip with crossed controls at

this point. A slow, smooth recovery from this sideslip is accomplished after liftoff by

slowly neutralizing the control wheel and rudder pedals."

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A dead heading first officer reentered the aircraft at least three times to aid evacuation.

That the individual actually had to repeatedly reenter the aircraft is cause for concern.

That fact that he/she did speaks volumes about the character of the individual.

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34 kts side component.

Not sure what you mean by that.

Are you indicating that anytime the wind is not right down the runway you have a side component and the aircraft would be limited to 34k winds?

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Not sure what you mean by that.

Are you indicating that anytime the wind is not right down the runway you have a side component and the aircraft would be limited to 34k winds?

34kts of wind at 90 degrees to the aircraft. It's a component of crosswind. Obviously a wind 30 degrees off the nose of the aircraft would require significantly stronger force to affect a cross component of 34kts. Clear? smile.gif

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