"Investigators: Pilots Aborted Takeoff" (shades of US Air 5050?)

[DemoTex]

Federal investigators said late Monday that an unusual rattling sound can be heard on the cockpit recorder of a Continental Airlines flight shortly before it veered off a runway after an aborted takeoff Saturday, injuring more than three dozen people.

National Transportation Safety Board officials said the jet's pilots aborted takeoff at high speed in a bid to keep from hurtling off the side of a runway at Denver International Airport last Saturday. But the plane became uncontrollable anyway and within seconds slammed into a snowy ravine.

Robert Sumwalt, the NTSB member on site who is serving as spokesman for the federal and industry crash teams, told a press briefing late Monday that an interview with the plane's copilot revealed that the jet began drifting off the center of the strip as it reached about 103 m.p.h. Board officials estimate the aircraft reached a maximum speed of more than 135 m.p.h. before veering off the runway, sliding across a field and ending in the ravine with its left engine and main landing gear sheared off. (Bold and underline mine)

(More ..)

http://online.wsj.com/article/SB123001946569629719.html

The Continental 1404 crash at Denver International (KDIA) is beginning to sound a lot like the US Air 5050 crash at New York's LaGardia (KLGA) in 1989. I was involved with the US Air 5050 accident investigation and the investigation of another near-disaster involving Boeing 737-300/400 rudder trim. The Continental 737 at KDIA appears to have had serious directional control problems on the runway, just like US Air 5050 had on KLGA's runway 31 that September night in New York. Rudder trim? Nosewheel steering? Rudder actuator (like US Air 427 at KPIT in 1994)?


USAir 5050 in the water off end of runway 31 at NYC's LaGardia.

[yardwork]

1. Interesting. Can you translate that for people with no understanding of the terminology?

It's good to have the perspective of an expert, and I'm interested in learning more, but I don't understand a lot of what you just wrote.

[MindPilot]

2. Is rudder trim even a factor at speeds below rotation?

The path off the runway appears to be a fairly clean arc, I'm guessing that if it were a rudder problem, the a/c would tend to oscillate as the pilot attempted to counter the rudder with the nosewheel steering resulting in a much more uneven path.

There appears to be a piece of debris near the point where the a/c leaves the runway. I wonder if a nose wheel tire blew or perhaps some other gear failure.

[DemoTex]

3. Tire/gear failure was 1st on my mind too ..

But NTSB vice-chairman Robert Sumwalt seems to have ruled those out.

US Air 5050 began the takeoff roll with fully deflected rudder trim. Without going into the sorry story of how it (the rudder trim) got that way, how it was missed during checklists, or why a brand-new first officer on his first-ever revenue flight was allowed to perform his first-ever takeoff with paying passengers on board on the proverbial dark and stormy night, suffice it to say that the captain (when he finally realized the f/o was drifting off the runway centerline and assumed control of the aircraft himself) was able to keep the 737-400 within the width of the runway. However, because he (the captain) did not "believe" in auto-brakes and because his decision to reject the takeoff was delayed, the jet ran off the end of runway 31.

A decision to reject a takeoff does not come easy. A rejected takeoff is fraught with peril. A high-speed reject (above V1) is done only as the lesser of other disastrous consequences (mainly, the perception that the aircraft cannot be safely flown). Perception is a highly subjective concept at 150 mph.

The arc does suggest that whatever the problem was, aircraft steering (rudder, nose-wheel steering, differential braking, etc) was minimally effective. If it was a flight control problem the DFDR (digital flight data recorder) will tell the tale .. and soon. Rudder trim alone would not have resulted in that much of an excursion from the runway centerline, unless there were other factors at work (including pilot incapacitation).

The USAir 5050 rudder-trim accident is a case study in error chain management. Or mismanagement as the case was that night in 1989.