If you get a tremendous upset you'll revert to a form of alternate law to aid in recovery (yaw damper available in that case). The loss of both FACs will also revert the aircraft into alternate law (sans yaw damper)... that's how people in sim world put the aircraft into alternate law for stall demos and such.

The aircraft is extremely stable, so you really don't notice the loss of the yaw damper. I've had it in alternate via turning off both FACs in the real thing, and subsequently in direct when dropping the landing gear. The aircraft is twitchier due to the direct control of the ailerons in alternate law, but pitch control is the normal feel. Direct law is noticeably twitchy due to the direct control of all surfaces.

 

Sorry but this is starting to look pretty much like AF447 with the exception that the start of the event was caused by failure of both FACs (as opposed to pitot probe icing)...................


AirAsia Co-Pilot Was Likely at Helm Before Crash - WSJ



Investigators looking into the fatal crash of AirAsia Flight 8501 believe the co-pilot was at the controls before the jet went into a dangerously fast climb, two people familiar with the probe said.

Indonesian authorities, these people said, are delving into what factors may have surprised or confused the first officer—who was much less experienced than the captain—and caused the nose of the Airbus A320 to point upward at an unusually steep angle while the plane’s computerized stall-protection systems either malfunctioned or were disengaged.

The Airbus A320 lost forward airspeed during its rapid climb, stalled and then crashed into the water below.

After spending more than two weeks analyzing twin black-box recorders, investigators believe First Officer Rémi-Emmanuel Plesel, a French national born in the Caribbean territory of Martinique, was flying the aircraft as it maneuvered to avoid a storm cell on Dec. 28 en route to Singapore from Surabaya, Indonesia. Turbulence or updrafts are suspected of contributing to the plane’s dramatic climb, but investigators continue to examine the interaction of pilot commands and computer-controlled flight systems during the climb and subsequent descent.

Repeated automated stall warnings were captured on the cockpit-voice recorder as the co-pilot and captain struggled unsuccessfully to regain control of the jet, investigators have said.

Investigators, safety experts and AirAsia officials have stressed that it is too early to draw definitive conclusions, and they have declined to discuss specific findings so far. In addition, the focus of the probe could shift as more black-box data is assessed. The country’s National Transportation Safety Committee, which is heading up the investigation, has filed a preliminary accident report with the International Civil Aviation Organization as required. But on Tuesday, the Indonesian agency’s chief told The Wall Street Journal the report would contain no analysis, and no data from the jet’s black boxes. It isn’t clear whether the report or any of its contents would be made public soon.

Nonetheless, some specifics about the crash are available. Based on data previously released by Indonesian authorities, the jetliner climbed more than 5,000 feet in less than 30 seconds—several times faster than any jetliner is supposed to ascend. It changed directions twice during that period, before it started to descend quickly. The jet changed its heading at least twice more and went into a spiral.

All 162 people on board were killed in the crash. At least 70 bodies have been recovered from the Java Sea.

The flight-data recorder, according to the two people familiar with the probe, indicates the first officer’s control stick pulled the plane’s nose up. But it isn’t clear when those commands occurred in the sequence of events, or why they were initiated.

Mr. Plesel, who left a job as an engineer at Total SA to fulfill a childhood dream of becoming an airline pilot, had about 2,200 flight hours over roughly three years flying for AirAsia. Captain Iriyanto, a former fighter pilot, had nearly 10 times that many total hours in his logbook, including more than 6,000 flying A320s for the Indonesian arm of the fast-growing budget carrier.

Airbus planes have computerized protection systems designed to avoid an aerodynamic stall, a condition in which an aircraft’s wings lose lift because forward speed is too low or the wings are pointing upward too steeply. But under extreme circumstances, such as multiple failures or disconnection of redundant flight-control computers, the stall-protection system becomes inoperative. That is apparently what happened to Flight 8501, though questions remain about the primary and contributing factors.

From the beginning, investigators have been looking into operation of the plane’s computerized controls, including information provided by speed sensors, air-data computers and other components. They have said icing of speed sensors, a phenomenon that contributed to numerous fatal airliner crashes and serious incidents over the years, doesn’t appear to have been a factor this time. Investigators also have effectively ruled out a midair explosion, decompression, sabotage or deferred maintenance items as probable causes.

 

Pilots Disabled Critical Computers Moments Before AirAsia Crash - Bloomberg Business

 

Pulled the circuit breakers? I find that one hard to believe in a supposedly chaotic cockpit in the middle of the night. If they did indeed push or pull anything it would have been to turn two of the ADRs off. I find that one hard to believe as well and even if they experienced unreliable speed indications, there is a procedure for that event. Fascinating and tragic at the same time.

 

Yeah that is incredible. Remember in the SilkAir 185 disaster 20 years ago, where the "pop" of the circuit breaker on CAM was controversial, and the decay of bus voltage was used to determine intentional disconnect versus overload condition caused it to disconnect. In that case the NTSB indicated almost certainly pilot suicide, while the Indonesian investigation said it was "inconclusive." Probably a similar analysis going on right now.

I hope that the government releases raw data for independent analysis in addition to recordings, both domestically and abroad, as a matter of policy, for this type of reason. Analysis aimed at getting to the truth is much better than a single governmental or private agency's opinion and potentially biased or self-interested views.

 

It sounds like the media screwing up what "disabling" means. I've seen the CB comments but in other articles they are saying the pilots "shut down" or "turned off" the computers. My best guess is pushing both FACs to the off position to de-energize that computer.

 

No CBs just 2 push buttons on the overhead.

 

http://www.theguardian.com/world/201...ontrol-reports

CA pulled FAC CB's and right after that jet went into ascent and stalled. Another article said CA tried to regain control over next three minutes flight was recorded before aircraft impacted water.


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Approaching a severe thunderstorm at nearly the A-320 coffin corner, CA gets out of seat to pull FAC C/B's?

If I remember my days on the line working the A-320, a FAC reset with C/B took a couple of minutes. That would seem like a lifetime under the conditions they were flying.

During that time they would lose all of:

Rudder trim, Rudder limiter, Yaw damper, Flight envelope and speed computations, and Wind shear detection.

If he did pull the C/B, that would be highly unusual. I don't know of any FOM (or QRH) that would have any pilot doing C/B resets in flight of a FAC, ELAC, or SEC. Anybody?

That FDR data will be interesting.

 

FL320 is not coffin corner for an A320. And correct most abnormal/QRH procedures would just direct you to de-energize the flight control computer to the OFF position. Not pull a CB.