Airasia Plane Missing?

[DEFCON]

Even though we can’t yet appreciate the Captain’s rationale for leaving his seat, it is probably fair to assume his actions represent an extraordinary attempt by the human component of the flight control equation to wrestle control of the aircraft back from ‘Hal’.

[Don Hudson]

Hi Rich;

The FCOM indicates that the loss of both FACs results in Pitch Alternate, Roll Direct, Yaw Mechanical.

I can't imagine the circumstances either Rich...I would think at the minimum, a diversion to the nearest suitable would be required if things are that bad.

[Woody Pusher]

Rich Pullman said:-

Generally speaking, there's a reason why some CBs aren't within reach when strapped in.

Rich,

I noted from Don Hudson's comments - "The FACs cannot be reset in the air using the four CBs, (two on the overhead for FAC 1, two on the rear cockpit bulkhead for FAC 2)", that if FAC-1 was reset, FAC-2 would assume control. Which means that a very deliberate action needs to be taken to disable FAC-2, and probably the very reason that FAC-2 CBs are located on the rear bulkhead.

I interpret the reset PBs on the overhead to be inter-latched; meaning that only one can be reset at any time, and the remaining FAC takes over.

[anonymous]

I interpret the reset PBs on the overhead to be inter-latched; meaning that only one can be reset at any time, and the remaining FAC takes over.

Wrong...both FACS can be turned off at the same time...

As far as CBs deliberately being out of reach ... That may be a side effect of the limited real estate overhead the pilots. I'm not an Airbus engineer but the overhead CB panel has CBs for primary systems...there's just not enough room for every CB ... So the remaining Cbs are on the back panel

[Don Hudson]

Anonymous - it's a small point but I know that there were discussions among Airbus engineers at the design stage (Design Progress Group) to place CBs beyond convenient reach.

The switches are push-on, push-off and are independent; the FACs can both be turned off at the same time but we never do two such things at once...and the FCOM cautions that these things should be done one-at-a-time.

[Mitch Cronin]

I wonder if he may have been trying to force one FAC to take over from the other 'faulty" one?

The history of the snag and his prior experience with it could have led him to this sort of a fix-it thought....?

Maybe he even saw that done on the ground?

...and maybe I'm in left field?

It sure would be interesting to know exactly what they were looking at!

[Mitch Cronin]

BTW.. Conehead?, Anyone?... Which boxes have an [for e.g.]A system breaker ov'hd and a B system breaker behind - for box 1, and the same but reversed for box 2? Was that not the FACs? ...or was that ELACs or SECs????

("box"=mitch's quick slang for magical computer-like gadgets in tin boxes that "DO Things" and usually have stupid TLA's! *)

* - three letter acronym.

[Don Hudson]

Mitch - re, "forcing FAC 2" etc., good question.

In imagining what happened, I keep having to remind myself of Sidney Dekker's, (Field Guide to Understanding Human Error) comment, "What we think should have happened does not explain people's behaviour" and the known fact that what people did at the time made sense to them.

This doesn't prevent knowledgable speculation - that's the interesting part of the puzzle, asking the question, What behaviour fits all the known facts when we don't know what we don't know?, etc.

In response to your question regarding CBs, each FAC has two CBs - the two for FAC1 are on the overhead, the two for FAC 2 are on the bulkhead. For ATAs "Auto Flight" and "Flight Controls" boxes, all box 1's CBs are on the overhead, all box 2's are on the bulkhead. The following may help further understanding but also increases the puzzle as to why the CBs were pulled.

The aircraft has two flight augmentation computers (FACs) that perform four main functions:

• Yaw function
– Yaw damping and turn coordination
– Rudder trim
– Rudder travel limitation
• Flight envelope function
– PFD speed scale management
. Minimum/maximum speed computation
. Maneuvering speed computation
– Alpha-floor protection
• Low-Energy Warning function
• Windshear detection function

In performing these functions the FAC uses independent channels :
- Yaw damper
- Rudder trim
- Rudder travel limit
- Flight envelope

Each FAC interfaces with the elevator aileron computers (ELACs) when the APs are disengaged, or with the FMGS when at least one AP is engaged.

Both FACs engage automatically at power-up.

The pilot can disengage or reset each FAC (in case of failure) by means of a pushbutton on the flight control overhead panel.

When a FAC is disengaged (FAC pushbutton set off) but still valid, the flight envelope function of the FAC remains active.

If both FACs are valid, FAC1 controls the yaw damper, turn coordination, rudder trim, and rudder travel limit, and FAC2 is in standby.

FAC1 keeps the aircraft within the flight envelope through FD1 ; FAC2 performs this function through FD2.

If a failure is detected on any channel of FAC1, FAC2 takes over the corresponding channel.

Rich re memory...in sympathy man...in sympathy!

[Boney]

A silly question. Is the disengaging and/or resetting of the FAC via the pushbutton on the flight control overhead panel done via the QRH?

I ask as the resetting of cb's, as per TC advisory, are discouraged unless it is required for "safety". If in fact they were dealing with a know fault, why not just stay in your seat and "fly the airplane first" until at least one is in stable flight and/or out of harm's way vis~a~vis clear of CB's.

Thanks.

[boestar]

Generally the CB are located where they are due to the bus that is powering the system. FAC 1 would certainly be fed by a different bus that FAC2 or there would really be no point in having 2. A single bus failure would bring the aircraft down. Not a good design philosophy.

My suspicion would be that this is the reason they are located where they are.

it is almost NEVER a good practice to shut offf two of anything in flight (or on the ground in some cases) unless there are 3 of whatever you are turning off.

[Don Hudson]

Boney;

To provide a general answer, these days airliners are machines that are truly flown & operated "by the book". In normal ops there is almost no latitude to wander away from the FCOM procedures.

In the past, (40 years ago), it was a far looser arrangement but these days "by the book" is a mandatory process for operational as well as legal reasons because one cannot know all there is to know about one's airplane anymore. There is a congenial balance between need-to-know, nice-to-know and making-it-up-as-one-goes. The latter was common fourty years ago, and sometimes even necessary; not nearly as much so today, although a pilot is still a pilot and may do what he-she thinks is needed to preserve life and property.

From the moment I joined the airline, CB resets were done only once - if the thing popped again, it was prohibited to reset it a second time. That's still the case today for some systems - fuel pumps for example, on the 'bus.

That generality set, any non-normal process is done either from the QRH or the FCOM in Supplementary Procedures. Any switching of the flight control computers is a non-normal process. A recycling of each FAC pb on the overhead, using the QRH, isn't a problem. But from what I understand about these things the boxes themselves will have gone through a lot of internal processes/tests prior to announcing that they need help by a recycling of the pb or a reset through pulling the breaker, the point being, if they're "asking for help" and the airplane isn't performing properly, that's the time to land asap.

By design, it is highly unusual to actually be required to get out of the seat to deal with an abnormality on one's aircraft. If one has to get out of one's seat, one should be diverting to the nearest suitable, period. So what was the emergency and why wasn't it declared when requesting higher...? I hope we'll know.

That's why, as others have said here, this story must have much more to it than we're currently being told. One cannot be doing just trouble-shooting work while navigating towards/around TRWs, especially when asking/demanding higher and/or headings for diversion around, etc, and one cannot be taking some serious and unusual actions without first making a decision to divert to an alternate or turn back.

[Boney]

Thanks Don. We are all awaiting the report so that we can all learn.

Cheers.

[DEFCON]

Hi Rich

If I may offer a guess in answer to your question.

The time / location charts posted by Woody seem to indicate the aircraft passed through some rough air between 23:16:33 and 23:16:52.

At 23:17:43 the plot shows the aircraft had reached the apogee of its zoom climb and was starting down; a 51 second window.

Available information suggests the FO was the PF.

The media has reported that one of the FAC’s had been causing problems for about a week.

Assume something dramatic occurred at 23:16:52. No matter the cause of the event, the aircraft entered a zoom climb. The crew appears to have been powerless to stop it.

Right, or wrong, the Captain, seemed to believe one, or maybe both of the FAC’s were somehow at fault and immediately took steps to rectify the problem.

Did the Captain believe the FO was capable of handling the aircraft properly; I can’t say for certain?

Knowing instinctively that the time to save his ship was extremely short, the Captain may have concluded the best course of action in the circumstance demanded immediate intervention versus assuming control of a non-responsive aircraft from the PF all while trying to pass on the instructions he felt were necessary to their regaining control?

Edited to remove the reference to the Captain leaving his seat in response to a correction to the published information.

[boestar]

Newer systems, Mostly on Biz Jets, Use SSPC (Solid State Power Controllers) in lieu of Circuit breakers. The benefit here is that when one trips, you get a certain number of resets and are then locked out. The number of resets is set by the manufacturer. This prevents the multiple reset issue that has caused failures and fires in the past. Its a good system and ALL pilot resetable Circuits are withing reach of the pilot AND the copilot without turning around.

[boestar]

Do we KNOW what the consequences of switching off BOTH FACs in flight? I know in the past there have been instances with autoflight systems that, when switched off, caused unusual flight path departure (so to speak). Do the FACs actually alter the positions of the flight controls to maintain stability in flight? If so, is it not possible that when the FACs were cycled off that the aircraft Flight controls returned to a neutral state or some other configuration causing the sudden departure?

[Don Hudson]

"Snowballs to Avalanches"...

If this story is true, this puts another take again on what happened in the cockpit and may not be the fault of Indonesian authorities this time but of the media who may have misunderstood a translation of the phrase "leaving the seat". I've reset CBs on the A320 and one has to loosen the seatbelt to reach the CB panel which is behind the overhead panel, but one doesn't need to get out of the seat to do so.

boestar;

The FCOM says that the ELACs take information from the FACs to control flight. It's my impression that the FACs, by themselves, do not move the control surfaces.

[boestar]

Don:

Whether directly or indirectly through the ELACs. Is the scenario still possible or whould the aircraft "default" to a stable state?

[mo32a]

Does anyone else besides me find it a little scary that experienced pilots have no idea what happens to their airplane when they turn something on or off?

[boestar]

Mo.. Thats what I am trying to figure out. Does ANYONE know what happens if we shut stuff off?

I am sure there is a flight software engineer that might have a clue somewhere.

[Don Hudson]

mo32a, boestar,

The information is there in the FCOM. Whether it's "on the test" or whether included in training or not, It comes down to knowing your airplane, period.

Slightly off-topic but germane to the discussion on competency and automation, as we move towards an "SMS and Audit-driven" world, there is a phenomenon developing, the boundaries of which are slowly coming into view, regarding the old-fashioned notion of "excellence" as opposed to the notion of "metrics" and "achieving the standard as set out in the documents" - the first notion has to do with professionalism, the second with bureacratic "accuracies" - to me this kind of thinking where one can measure and count "standards" till the cows come home but the notion of "professionalism" and "excellence" while instantly recognizable by those who know their stuff is not conveniently countable and therefore one cannot be made "a-countable".

This is at the seat of what I believe to be an endemic degradation of these old-fashioned notions in favour of mere counting. While this is the subject of some other thread, we're seeing this kind of mundane bueaucratic stupidity in educational standards as well, as we move towards clinically-"safe" society in layers of audited documents shield those responsible for "The Standard". These notions swirl around one another but at their various centers, they represent "automation" in the societal and bureaucratic sense. It is rather dehumanizing in the wrong areas, the results of which may show that one "met the standard" but still crashed...

For me anyway, it is not always necessary to understand what happens if or when one takes actions which are prohibited in the FCOM. The "knowing" in this case is clearly, "don't do it", not "what happens if we do it anyway?"

Also, there is a stated difference between "disengaging them" and "shutting them off"..one is benign by design, the other is "dangerous".

Anyway,...

With the FACs either disengaged by using the FAC switches on the overhead panel, the LOC-through-untoward-computer-behaviour scenario is highly unlikely. With the FACs turned OFF by pulling all four CBs, the results are not described in the FCOM but I believe that the airplane would again be stable, (no untoward/unexpected control surface movement).

With FACs either disengaged, the airplane reverts to Alternate Law in pitch, Direct Law in roll. So the airplane would be flyable like a B737 but a bit more sensitive particularly in roll, but not uncontrollable. We can bet that the sim experiments have already begun.

Messing with the ELACs and SECs is a different thing entirely - I think loss-of-control could result from pulling these computers' CBs.

First, it is interesting to note that the ELACs and the SECs are in ATA27, Flight Controls but the FACs are in ATA22, Auto Flight - they are envelope/speed/yaw control "generators", which supply information to the flight control computers.

For CB resets of ELAC and SEC flight controls computers, the FCOM (Supplementary procedures) states:

ELAC Elevator Aileron Computer - In-Flight Procedure

WARNING
C/B reset of ELACs are prohibited in flight. However, resetting of ELACs is permitted via the appropriate P/B switches (only one at a time).

WARNING
For the ELAC only, DO NOT ATTEMPT A RESET in case of uncommanded maneuvers.

PROCEDURE: Appropriate ELAC P/B SWITCH (one at a time) OFF, then ON.
– ELAC P/B 1 or 2 ...........................................OFF then ON
RESET P/B AFTER: 1s POWER UP TEST DURATION: 8s

and,

SEC Spoiler Elevator Computer - In-Flight Procedure

WARNING
C/B reset of SECs are prohibited in flight. However, resetting of SECs is permitted via the
appropriate P/B switches (only one at a time).

PROCEDURE : Appropriate SEC P/B SWITCH (one at a time) OFF, then ON.
– SEC P/B 1 or 2 or 3 .......................................................................................................OFF then ON
RESET P/B AFTER: 1s POWER UP TEST DURATION: 8s

[Mitch Cronin]

Not just you. ....That bit of scariness began creeping into the scene with the first tales of FBW technology. Airbus made it sound as if they were saying "well of course we don't want them to know everything"... They even began intentionally hiding things during certain phases of flight.

The battle of Pilots vs Boffins has been ongoing and seems to end only when the Boffins create their own win by just designing out the pilot.

[Mitch Cronin]

...sorry, my last was a response to Mo32a...

[Mitch Cronin]

Don... that envelope protection etc... I think includes the sort of thing the old monkey-motion engineers would call speed dampening, or some such... (sorry words aren't here right now?) You know... cntrl surface travel limits over such a speed etc... ? Loss of both FACs =loss of same? Yes?

Sorry mate... really bad way to ask a simple question... But I'll bet you get it?

If so... , and a control input was being maintained at some, diminished-due-airspeed angle, and then someone pulled the cb's and that 'diminish' command went away.... could explain very sudden change in attitude. ....maybe...

[boestar]

Mitch you make a good point. If the FAC is actually what is taking the flight conditions and limiting control surface deflection based on that data then it is definately possible that the removal of that piece from the equation could definitely result in a larger scale deflection and possible loss of control.

For example a rudder limiter. Faster you go the shorter the travel. Simple enough but what if there is a removal of that speed parameter? Does the rudder suddenly go full deflection with a full rudder input? That would most certainly be a bad thing. Same for aileron or elevator. A small deflection suddenly becomes large at cruise and you could easily depart from flight mode to brick mode.

[Guest]

Now they say there is no evidence that the Captain left his seat..........................

(Reuters) - Indonesian air crash investigators said on Monday they had not so far found evidence that the pilot of an AirAsia jet had left his seat, or that power to an automated control system was shut off, shortly before the aircraft plunged into the sea.

Two sources familiar with the investigation had told Reuters that Captain Iriyanto was out of his seat carrying out the unusual procedure of pulling the circuit-breaker on a flight computer when his co-pilot apparently lost control of the Airbus A320.

AirAsia flight QZ8501 vanished from radar screens on Dec. 28, less than half-way into a two-hour flight from Indonesia's second-biggest city of Surabaya to Singapore. All 162 people on board were killed.

"Up until today, there is no indication yet that the captain left his seat as reported by Reuters," Ertata Lananggalih, an investigator with the National Transportation Safety Committee (NTSC), told Reuters at the team's office in Jakarta, referring to the story published on Saturday.

People familiar with the investigation had earlier told Reuters that investigators were examining maintenance records of one of the plane's automated systems, the Flight Augmentation Computer (FAC), and how the pilots may have reacted to any outage.

Bloomberg News reported on Friday that the pilots of the crashed plane had tried to reset the FAC during the flight, and had then pulled a circuit-breaker to cut power to the device.

People familiar with the matter told Reuters it was the Indonesian captain who took this step, rather than his less experienced French co-pilot, Remy Plesel, who was flying the plane.

CIRCUIT BREAKER

NTSC investigators disputed on Monday that the circuit breaker was pulled.

"Up until today, there is no indication or evidence yet that the circuit breaker was pulled," Lananggalih said.

The NTSC declined to elaborate further, saying the accident was still under investigation.

However, a document prepared by the investigation team and reviewed by Reuters indicated the FAC system and the cockpit circuit breakers were among the issues of interest to the probe.

The schedule document listed more than 30 items for discussion. Along with more general points such as "wreckage recovery" and "maintenance review", it included the entry "FAC engagement and failure understanding" and another entry related to pulling "CB", a common abbreviation for circuit-breakers.

"This is .. just inventory. It is to make the investigation easier. There are maybe 40 or 35 things that have to be discussed," said Tatang Kurniadi, chief of the NTSC, when asked about the list.

"It is not just circuit breakers. This is the first plan...it could change again because of developments. This was prepared in the first week of the investigation."

The checklist made no mention of pilot seats or movements in the cockpit.

Investigators have said it was too early to say whether the accident involved pilot error or a mechanical fault.

AirAsia declined comment. The airline said previously it would not comment while the crash, its first ever fatal accident, was under investigation by the NTSC.

Indonesia has released some factual details of the circumstances of the crash, but has not made public the preliminary accident report it submitted to the International Civil Aviation Organization last week.

Although more is becoming known about the chain of events, people familiar with the investigation warned against making assumptions on the accident's cause, which needed more analysis.

Safety experts say air crashes are most often caused by a chain of events, each of which is necessary but not sufficient to explain the underlying causes of the accident.

http://www.reuters.com/article/2015/02/02/us-indonesia-airplane-idUSKBN0L61NG20150202?feedType=RSS&feedName=worldNews

(Additional reporting by Kanupriya Kapoor in Jakarta; Editing by Alex Richardson)