Tuesday, February 24, 2009

Air Asia Emergency Landing Kuching Airport


Hantu Laut

A very sketchy report of one of Air Asia flights into Kuching Airport yesterday that had the nose wheel locked at 90-degree angle forcing the pilot to land under emergency condition with fire streaming from its nose wheel.The pilot managed to bring the plane to a stop safely.No one was hurt in the incident.

Before you jump to conclusion and start blaming the airline let's get the facts correct first.This is not the first such incident happened to the undercarriage of Airbus air crafts.Records show that Airbus had a number of such incidents before.

A Canadian study issued last year documented 67 incidents of nose-landing-gear failures on Airbus 319, 320 and 321 aircraft worldwide since 1989.None has caused any serious damage or injury to passengers.One recent case was JetBlue Flight 292 from Burbank to JFK International New York that made a forced landing at Los Angeles Airport.



Apparently, the locking of the nose wheel at 90-degree is a design fault.

Most landing gears were made by Messier-Dowty.





The JetBlue story:


Today, shortly after takeoff from the Bob Hope Burbank airport, a JetBlue A-320 was unable to retract its nose gear. The pilot informed ATC and the plane was vectored over to the Long Beach airport where it did a low flyby, so JetBlue maintenance personnel could look at the problem. They were able to confirm that the nose gear had rotated to a position of about 90 degrees out of line to where it should have been. That is why the gear could not be retracted into the wheel well.

The intended destination of the flight was New York Kennedy. Obviously it could never fly that far with the landing gear extended, so the pilot had no choice but to fly in the Los Angeles Area for about 3 hours to burn off the weight of the major portion of fuel on board (there is no ability to dump fuel, on the A-320). He had to do that to reduce the weight of the airplane so that it could be landed at the slowest possible speed.

To reduce the risk of the nose gear structure breaking loose, which would lead to more damage to the aircraft and increase the risk of fire, it would also be necessary to land without putting anymore weight on the nose wheel structure than absolutely necessary, and to delay its actually touching the runway for as long as possible. I presume the pilot located passengers and their carryon bags as far aft as was feasible, so that when the plane touched down, the center of gravity being further aft helped to accomplished that objective.

To keep the nose gear from touching the pavement for as long as possible after the main gear contacts the runway, the pilot on some planes (like Boeing or Douglas airliners) might employ a non-standard technique of trimming the horizontal stabilizer towards the nose up position, during the actual landing flare, until it will go no further. Then, as the nose began to drop, he would hold it off even longer with the elevators, until they too were pulled back to the full nose up position.

That is a very difficult maneuver however, especially since pilots are not given simulator time to practice it. The danger lies in the pilot running out of any pitch control at all, before he has gently lowered the nose gear to the runway. If he does run out of pitch control prematurely, the nose gear may impact with too much downward force, and that would significantly increase the risk of its breaking off and causing additional damage to the plane.

Captain Scott Burke proved to have the required skills; no one could have improved on that performance. He stopped right on the center line of that 12,000 foot runway (25L-----which was not an "auxiliary" runway, as one Sacramento TV News station claimed), with plenty of room to spare. Best of all, the nose gear did not break loose.

I believe this is at least the seventh case of this type of accident (there may be even more than that), where the nose gear rotates to a position of 90 degrees, from where it should be, when the gear is down for takeoff and landing (this kind of problem could never happen on a Boeing airliner-----only the French come up with designs like that).

On Feb. 16, 1999 an America West A-320-231, attempted to land at Columbus, Ohio (CMH), total of 31 on board. Same kinds of ECAM warnings, when the landing gear was lowered. That plane was finally forced to land with the nose gear rotated 90 degrees out of line. Same result as this JetBlue plane, which landed safely at LAX today, except they evacuated down the emergency slides at CMH, because the pilot could see smoke curling up from underneath and he couldn't get the tower to answer his query----if any fire could be seen.

Prior to that AWA emergency landing at CMH, the French had issued a service bulletin on the problem. However, no ADs had yet been issued by either the French DGAC or the American FAA, so compliance was advisable, but not mandatory. America West Airlines did not choose to heed that bulletin, and the emergency landing was the result.

Analysis of the previous cases revealed "...external hydraulic O-ring seals on the steering control module's selector valve were extruded (distorted out of the seal's groove). A small offset was found in the steering control valve."

Airbus further found that the problem would not be detectable by normal visual inspection procedures. It appears that though the problem is rather rare, it does have to do with that particular design of the steering control module. Quoting Airbus: Read more......

2 comments:

kittykat46 said...

It is a known design issue (Airbus will not admit to the word "flaw") in the A320.

Under some circumstances the front wheel will come down but fail to lock in the front-back alignment, remainding at 90 degrees to the aircraft body.

Airbus insists that there is no need for a redesign and retrofitting because the failure will not happen if maintenance is done strictly according to procedure.

If Airbus is right, it implies Air Asia's maintenance is questionable.

DeePo said...

i wonder is MAS used the same airbus? now AA freak me out