If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below. |
|
|
Thread Tools | Display Modes |
#1
|
|||
|
|||
Jet's skid marks raise puzzling questions
http://www.theglobeandmail.com/servl...tory/National/
Jet's skid marks raise puzzling questions By PAUL KORING Saturday, August 6, 2005 Updated at 2:03 AM EDT From Saturday's Globe and Mail The long skid marks raise troubling questions about whether the crew should have aborted the landing, whether they made and then abandoned an attempt to take off again, and whether the Airbus A340's sophisticated anti-skid system was working properly in the wild and wet conditions. Investigators have confirmed that the aircraft “landed long” — that is, touched down much farther down the runway than it should have — and was still travelling at about 150 kilometres an hour when it ran off the end of the 2.4-km runway. Investigators also confirmed yesterday that a treasure trove of data from the flight recorders and cockpit conversations survived the fiery aftermath of the accident and has been successfully extracted from the so-called black boxes in France. “I'm very happy to report we have good, solid data,” said Réal Levasseur, lead investigator for the Transportation Safety Board probe. He said that will “allow us to . . . start removing wreckage from the site much earlier than we would have anticipated.” Investigators are using more than 650 data parameters; most were measured several times a second, including the positions of individual switches, airspeed, altitude and the control inputs from the crew. The team will be able to minutely reconstruct the flight of the aircraft, which arrived in the middle of a thunderstorm after a transatlantic journey from Paris. Investigators also completed their interrogation yesterday of the unidentified Air France co-pilot who was flying the landing. The captain remains in hospital with unspecified back injuries and has yet to be interviewed. “The co-pilot was very frank in his discussions with us,” Mr. Levasseur said. Although it may be months before the investigation is complete, the flight and cockpit recorders should quickly provide answers to crucial questions about whether the Air France pilots were considering aborting the landing and briefly advanced the throttles to initiate a “go-round” after landing halfway down the runway. A go-round, usually initiated before touchdown, is the prescribed procedure for aborting an unstable landing or one that would put the aircraft down in the wrong place on the runway. Pilots are trained to apply power, climb away, contact air-traffic control and seek a return to the landing pattern rather than continue with an unstable approach and landing. If the Air France crew even momentarily began a go-round by advancing the throttles after landing, it would have cancelled out the preprogrammed automatic braking that pilots usually dial into the Airbus's sophisticated flight management computers before landing. And if the go-round decision itself was then reversed or countermanded by the Air France captain, the flight crew would then be faced with braking manually using the foot pedals. According to Mr. Levasseur, an initial examination of the ill-fated aircraft's tires showed no evidence of aquaplaning. That occurs when the tires slide on a thin film of water. With no evidence of aquaplaning, and of anything so far that indicates something amiss with the aircraft, investigators will focus on the flight crew's decisions, performance, training and whether they followed the best procedures. The crash, from which all 309 people on board scrambled to safety before fire engulfed the fuselage, was the first serious accident involving the long-range, four-engined, wide-body A340. The long skid marks on runway 24L puzzled several aviation experts. Three experts, all with extensive experience with the systems on the A340, offered conflicting theories as to whether the skid marks could have been made with the aircraft's sophisticated anti-skid braking system, assuming that system was operating properly. Normally, anti-skid systems (just like those on modern cars) prevent wheels from locking up on hard braking, releasing just enough pressure to keep the wheels turning, which provides the maximum possible deceleration. Locked-up wheels that skid actually lengthen braking distances. One expert suggested the skid marks would on closer examination turn out to be a staccato series of marks, left by a functional anti-skid system. Another suggested that the TSB investigators may have mistaken the marks, believing a skid that long would have shredded the tires, even in the wet conditions. At least one set of main landing wheels, with tires apparently intact, is visible in photographs of the burned-out wreck. Finally, another expert suggested the crew may have disengaged the anti-lock system — although he offered no explanation as to why they would — either by flipping a switch in front of the co-pilot or engaging the parking brake that applies maximum force to all the aircraft's brakes. All three experts agreed that unless there was some sort of catastrophic series of multiple failures that rendered the main braking computer and at least two layers of backups inoperable, then the automatic anti-skid braking system would be available to the pilots unless they disengaged it. |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Insurance fails to pay up. | Miss L. Toe | Air travel | 49 | November 10th, 2004 08:47 AM |
Insurance fails to pay up. | Miss L. Toe | Europe | 57 | November 10th, 2004 08:47 AM |
Taiwan's New SARS Case Raise Questions | Mighty Land | Asia | 3 | December 21st, 2003 08:20 PM |