CO Incident at DEN

[mo32a]

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?

Exactly what I stated in my first post.

I thought CC had a contrary viewpoint, which is why I questioned it.

OTOH he didn't answer the question, so maybe he does have a different thought.

[Guest rattler]

More, talking about the speeds.

DATE:23/12/08

SOURCE:Air Transport Intelligence

Continental 737 crash: Pilot called for rejected take-off

By David Kaminski-Morrow

Cockpit voice-recorder evidence shows one of the pilots of the Continental Airlines Boeing 737-500 involved in the runway excursion accident at Denver called for a rejected take-off.

The US National Transportation Safety Board says the call came just four seconds after the recorder picked up a "bumping and rattling sound" as the jet accelerated down runway 34R on 20 December.

During a briefing on the accident a spokesman for the NTSB stated that the CVR showed "nothing out of the ordinary" during pre-flight checks and taxi-out for the service to Houston. The NTSB has also reportedly said there is no evidence of any problems with the CFM International CFM56 engines, thrust reversers, brakes or flaps.

Twenty-eight seconds after the brakes were released, says the spokesman, one of the pilots stated that take-off power was set. But 41s after release, a "bumping and rattling" began, and the call to reject take-off came at 45s.

There was no debris on the runway, which was bare and dry. Main landing-gear tyre marks started 1,900ft from the runway 34R threshold and nose-gear marks began 100ft further on.

The jet then began to veer off the centreline, says the spokesman, exiting the runway at 2,650ft from the threshold. It travelled into a grassy area before crossing taxiway WC and striking a berm.

As a result of the inertia from the impact, and the profile of the terrain, the aircraft "slightly became airborne". From the point at which it left the runway, the 737 travelled around 2,000ft before coming to rest.

The rattling sound continued to the end of the cockpit-voice recording, at 51s. The spokesman indicates that the recording was ended by the triggering of a deceleration 'g-switch', probably from the aircraft's impact with the ground after it struck the berm.

Information from the flight-data recorder information is "very good", he adds, and shows that the jet reached a maximum speed of 119kt. At the point where the flight-data recording ceased - again, possibly due to the ground impact - the aircraft was moving at 89kt.Despite the aircraft's suffering severe structural damage and a fire around the right rear fuselage, none of the 115 occupants was killed, although dozens were taken to hospital with varying degrees of injury

[handyman]

More, talking about the speeds.

OK, I'm now curious how a nose wheel made skid marks! I'm starting to think nose-wheel shimmy resulting in linkage failure castoring over and causing the skid-marks. It took a further 650' for the aircraft to depart the runway so unless someone tried to use the nose-wheel steering at speed, failure of the nose-wheel must have caused the skid.

[handyman]

So did the nose gear scissors fail?

[Moon The Loon]

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..............

Nobody's picked up on this??

What were they thinking? Or maybe they'd had previous experience in an MD80 in Calgary???

[Guest woxof]

I'm not sure what your point is?

[Guest rattler]

DATE:07/01/09

SOURCE:Air Transport Intelligence

No obvious culprit in Continental 737 excursion at Denver: NTSB

By John Croft

New NSTB information on the runway excursion by a Continental 737-500 departing the Denver International Airport the night of 20 December reveals no obvious failure mechanism that would have caused aircraft to depart the left side of the runway.

Of the 115 occupants on the aircraft, 34 were transported to hospitals and five were admitted after the aircraft crossed a snow-covered grassy drainage basin area and crossed a taxiway and a service road before coming to rest 2,300ft from the point where it left the runway. Despite a post-crash fire on the right side of the aircraft, no passengers or crew were killed.

Pilots of Flight 1404, departing Denver for Houston, told NTSB investigators that "all appeared normal until the aircraft began to deviate from the centreline" on the 1818h departure on Runway 34R. Winds were recorded from 290 degrees at 24kt with gusts to 32kt, presenting a left crosswind condition for the departure.

The captain further told investigators that the airplane "suddenly diverged" to the left and "attempts to correct the deviation with the rudder were unsuccessful." The pilot also stated that he "briefly attempted to return the aircraft to the centreline" using the tiller mechanism.

While the cockpit voice recorder (CVR) had revealed that the pilots called for a rejected takeoff after "bumping and rattling" sounds were heard, further analysis of the flight data recorder and correlation with the CVR show that the rejected takeoff occurred after the aircraft left the side of the runway, says the NTSB. The bumping sounds occurred after the aircraft left the runway as well.

A preliminary examination of the aircraft's rudder system revealed no abnormalities, the board states, and the main landing gear and brakes, which had separated from the aircraft during the accident sequence, were found to be in "good" condition by visual inspection. There were no signs of hydraulic leaking or flat spots on the tires, investigators explain.

Data from the aircraft's flight data recorder (FDR) show no evidence of pre-impact malfunctions with either engine. But power on the number one engine was reduced before power reduction of the second engine in the accident sequence. Examination of the number one engine indicated the power reduction was consistent with ingestion of snow and earth as the 737-500 departed the runway.

The board's findings show both engines were commanded into reverse thrust following the rejected takeoff.

[DEFCON]

Contaminated surfaces?

[Guest rattler]

Contaminated surfaces?

Not a pilot but would contaminated surfaces caused the veer? Maybe just extreme weather cocking caused by the winglets????? I sure hope there is a wind tunnel recreation of the event.

[DEFCON]

"Not a pilot but would contaminated surfaces caused the veer?"

Yes, it's possible.

"Maybe just extreme weather cocking caused by the winglets?????"

I don't have any first hand experience with the B73's winglets, but I think that scenario is unlikely.

I know little of this crash, but some degree of surface contamination on one horizontal stab and or one side of the vertical could have produced an upset on airflow at rotation leaving the rudder ineffective? The pilots would have believed something was terribly wrong, rejected the T/O and been left with little to guide the ship?

[Guest woxof]

No doubt the NTSB will be closely examining peak wind gusts and pilot inputs to the flight controls. As well as the wind given to the aircraft by ATC. And perhaps X-wind certification of the aircraft with winglets.

Keep in mind that the weather given by ATC to pilots in Canada is "Mean Wind", that is the average wind over the last two minutes. How this affects the accuracy of gusts, I am not sure. As well, I am not sure if ATC in the U.S. gives Mean wind or Now wind. Sometimes you do seem to get a huge single gust when a front comes through.