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Author Topic: AirAsia 8501 Crash Report Blames Computer Failure, Pilot Response  (Read 12778 times)

Offline joeyb747

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"The main flight control computer on the Airbus A320 had a cracked joint that caused it to malfunction repeatedly — including four times during the flight, and 23 times the previous year — Indonesia's National Transportation Safety Committee concluded in a report."

Also,

"The midair emergency unfolded over two-and-a-half minutes, the report said, suggesting passengers were aware of a serious problem. In its final moments, the plane rolled 104 degrees to the left before plummeting at a rate of up to 20,000 feet per minute.

The flight had been normal until warning messages prompted the pilots to pull a circuit breaker in an effort to reset the computer, against the advice of the plane's operating manual.

"Subsequent flight crew action resulted in inability to control the aircraft ... causing the aircraft to depart from the normal flight envelope and enter a prolonged stall condition that was beyond the capability of the flight crew to recover," the report said."


PDF copy of the report is linked in the story below...

http://www.nbcnews.com/storyline/airasia-plane-crash/airasia-crash-report-blames-computer-failure-pilot-response-n471831
« Last Edit: December 01, 2015, 10:42:05 AM by joeyb747 »



Offline joeyb747

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Re: AirAsia 8501 Crash Report Blames Computer Failure, Pilot Response
« Reply #1 on: December 01, 2015, 10:41:18 AM »
"Contributing factors:

The cracking of a solder joint of both channel A and B resulted in loss of electrical continuity and led to RTLU (rudder travel limiter unit) failure. The existing maintenance data analysis led to unresolved repetitive faults occurring with shorter intervals. The same fault occurred 4 times during the flight.

The flight crew action to the first 3 faults in accordance with the ECAM messages. Following the fourth fault, the FDR recorded different signatures that were similar to the FAC CB‟s being reset resulting in electrical interruption to the FAC‟s.

The electrical interruption to the FAC caused the autopilot to disengage and the flight control logic to change from Normal Law to Alternate Law, the rudder deflecting 2° to the left resulting the aircraft rolling up to 54° angle of bank.

Subsequent flight crew action leading to inability to control the aircraft in the Alternate Law resulted in the aircraft departing from the normal flight envelope and entering prolonged stall condition that was beyond the capability of the flight crew to recover."


From:

http://avherald.com/h?article=47f6abc7/0028&opt=0


Offline joeyb747

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Re: AirAsia 8501 Crash Report Blames Computer Failure, Pilot Response
« Reply #2 on: December 01, 2015, 10:51:42 AM »
Normal Law vs Alterrnate Law was discussed in detail regarding Air France 477. After the pitot tube iced over, and the computer lost that parameter of data, it switched to ALTERNATE LAW. In NORMAL LAW on Airbus equipment, the crew CAN NOT push the airplane outside it's limits. It reaches bank, climb, or decent limit and holds at that point, regardless of control input. The crew CAN NOT stall the airplane in normal law. In ALTERNATE LAW however, those protections are removed, and it is possible to over-stress and stall the airframe.

Check this out:

http://www.airbusdriver.net/airbus_fltlaws.htm 

Offline InterpreDemon

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Re: AirAsia 8501 Crash Report Blames Computer Failure, Pilot Response
« Reply #3 on: December 01, 2015, 09:17:19 PM »
I have worked with electronics all my life, and the cold solder joint gremlin is as old as electronics themselves.

That's why I prefer "cable law" to either normal or alternate law. Reading the transcript of the AF447 CVR, the flight crew debating this law and that law like barristers before the Bar as they managed to hold the aircraft in a continuous stall for three and a half minutes from cruise altitude to "sound of impact", or seeing that Asiana crew "point and click" their auto-throttles to a short landing and snap their tail off on a bright CAVU day in SFO, does not give one confidence in the basic or CRM training of non-US crews.

On the other hand, Sullenberger dealt with a double engine failure by first flying the plane, second making sound decisions and third exercising good CRM. I have to think that even he was very aware of the fact he was flying by wire since, contrary to procedure, the first thing he did was fire up the APU, a task that was supposed to be further down the checklist. He knew that without electricity there is inevitable lawlessness.

I have always been uncomfortable in any fly-by-wire aircraft when not wearing a parachute, which is why the DC-9/MD-80 with it's direct cable, servo tab flight controls, not to mention the smooth, quiet ride up front, was my favorite airliner of all time.

Offline joeyb747

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Re: AirAsia 8501 Crash Report Blames Computer Failure, Pilot Response
« Reply #4 on: December 02, 2015, 07:27:05 AM »
Well said sir.