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Air Asia Indonesia Lost Contact from Surabaya to Singapore

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Air Asia Indonesia Lost Contact from Surabaya to Singapore

Old 19th Jan 2015, 14:52
  #2181 (permalink)  
 
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I do wonder if the situation with ECAM can sometimes be likened to having a padlock in front of you, ie the actual problem that's occurring, and you're handed a bunch of keys and have to try each in turn before you get to the correct one.
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Old 19th Jan 2015, 15:11
  #2182 (permalink)  
 
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5:Spurious warnings, cautions and whatnots are far more common that real ones.
If we are talking about stall warnings, this does not seem to be the case, not in AB anyway. The 767 and 737 had their problems it seems. ATSB, at least mandates reporting of All stall warnings. http://www.atsb.gov.au/publications/2012/ar-2012-172.aspx

6:Spurious alarming data is not immediately distinguishable from actual alarming data.

It can by definition not be distinguishable,
otherwise it would not be alarming. Unfortunately non useful reactions are 1) panic or 2) ignore it 3) decide it is "spurious" - in any order.

Useful reactions one assumes are part of the type training of pilots.
c) actually taking the aircraft by the scruff of the neck and putting it roughly where it should be has become a HUGE decision accompanied by much trepidation.
should this not be AAA* priority 1 rather than c? - though possibly inserting a "gently" or "carefully" somewhere? The Quantas A380 exploding engine crew seem to have done it right, others less so.

8:Spurious protection triggers can expose passengers to random dumb designer mistakes. (Too trusting of sensors without appreciating the "what if" hypothetical scenarios. Which happen from time to time)
I am far from convinced that there are many "spurious protection triggers" or "dumb designer mistakes". No, I am not a pilot, but I have been intimately involved in real time safety critical software design, realisation and testing. The overwhelming majority of the work is actually involved in the "what ifs". Unfortunately in some situations there is just not enough information for the software to continue reliably. Why the Bus can not default to sensible neutral values of thrust and pitch (and trim maybe) before dumping it on the pilots I do not know, I have only worked on environmental software for AC not FBW.
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Old 19th Jan 2015, 16:07
  #2183 (permalink)  
 
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DrPhillipa
Why the Bus can not default to sensible neutral values of thrust and pitch (and trim maybe) before dumping it on the pilots I do not know
So many posters know diddly-squat about A320 FCS.... if you don't know why post?
It does not "dump" on the pilots... In alternate law thrust is locked at current value until PF takes over manually, pitch law remains (with auto-trim) the same (1g stick free so no pitch change if you leave it alone), except you lose protections in the event of high speed, high alpha, and big pitch excursions, roll law degrades to direct control of ailerons and spoilers.
If it goes to direct law then you have direct control of elevators as well, and must use manual pitch trim.
In all laws the a/c remains completely controllable by flying attitude.
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Old 19th Jan 2015, 16:20
  #2184 (permalink)  
 
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Post AF447

An A330 driver was telling me of the new sim exercise at high altitude with sensors gone u/s.

As per current drill, he switched off the automatics and set pitch and thrust manually.

The instructor then had him restore autothrust. A/T decided there was an overspeed, reduced thrust and things went downhill from there.

During the AF447 discussion, I was wondering when AB would flight test a high altitude stall as it could provide important information to the investigation.

With drone technology, the tests could be flown from the ground.

Last edited by RatherBeFlying; 20th Jan 2015 at 00:07.
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Old 19th Jan 2015, 16:34
  #2185 (permalink)  
 
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Quote/...

Post AF447
During the AF447 discussion, I was wondering when AB would flight test a high altitude stall as it could provide important information to the investigation.

With drone technology, the tests could be flown from the ground.

.../unquote.


The Concorde prototypes had a crew escape hatch CONCORDE SST : Duxford Internal Pictures


Possibilities....
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Old 19th Jan 2015, 16:46
  #2186 (permalink)  
 
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I am far from convinced that there are many "spurious protection triggers" or "dumb designer mistakes". No, I am not a pilot, but I have been intimately involved in real time safety critical software design, realisation and testing.
And yet, out in the real world, physics and reality stubbornly come up with scenarios and combinations that you had not though about.

I am a pilot and I can testify to the thousands of spurious faults and messages an A320 comes up with. Most of the time Ctrl/Alt/Delete does the job. Sometimes sadly there is no time for that sort of thing. A humble attitude and a very heavy dose of realism is an essential attribute of any engineer dealing with safety critical systems
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Old 19th Jan 2015, 17:05
  #2187 (permalink)  
 
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TyroPicard:
So many posters know diddly-squat about A320 FCS.... if you don't know why post?
In order to ask questions and learn. And your answer was quite informative, thanks.
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Old 19th Jan 2015, 17:35
  #2188 (permalink)  
 
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c) actually taking the aircraft by the scruff of the neck and putting it roughly where it should be has become a HUGE decision accompanied by much trepidation.
should this not be AAA* priority 1 rather than c? - though possibly inserting a "gently" or "carefully" somewhere? The Quantas A380 exploding engine crew seem to have done it right, others less so.
We are discussing the problems associated with automation not behaving as intended. You need to realise that all is not well, then what you might do to rectify it and after that take action, otherwise you’re just doing random stuff.

On two recent flights I’ve observed otherwise competent pilots watching the speed rapidly bleed off due to a high-rate altitude capture. At that point, no FMC or MCP skills are going to help, you’re in a pre-programmed trajectory. It’s AP out and I had to hint several times as many people are reluctant/uncomfortable/unhappy doing this at altitude.

If nasty things start happening up near the top of the flight envelope, e.g. you are rapidly approaching the definition of a “jet upset”, gently and carefully could be your undoing as it may take pitch/roll attitudes and control deflections that you’ve never used before outside the simulator (and maybe not even in there) in order to recover. See AF447. The QF A380 was a fine example of CRM and technical skills saving the day but they were not fighting the aeroplane for control.

(In the above quote “roughly” was meant as “approximately” rather than crudely or violently.)
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Old 19th Jan 2015, 18:14
  #2189 (permalink)  
 
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" In fact the most important step in spin recovery for the F18A was to disconnect the FBW computers and go to direct electrical link. "

Of course, the point was, that the pilots of most airliners are far enough from the center of gravity, where, in a spin, it is more like the infamous "G machine" centrifuge, astronauts trained in, than an F18A. The pilots of the larger airliner, can not take control because the G's keep their hands pinned. Although I think it's a good idea worth looking into, maybe an automation cure is worse than the disease. Instead of automation to get out of flat spin, maybe more training, to not get there in the first place, is a better use of resources. Maybe some resources to both. Doesn't always need to be either/or.
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Old 19th Jan 2015, 18:22
  #2190 (permalink)  
 
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Ian and Machinbird
I don't know how applicable would be to the AF A330 scenario, but back during the original 777 flight testing, there was a story going around (from normally reputable sources) that an FAA pilot had inadvertently gotten a 777 into a deep stall at high altitude. The Boeing pilot promptly took over and was able to recover the airplane but the resultant altitude loss was "well over 10k". I can't personally vouch for the accuracy of the story (friend of a friend type stuff) - and assuming it did indeed happen it was kept pretty quiet (no news reports that I'm aware of).

BTW, again, not sure how applicable to how Brand A does things, but Boeing routinely does stall testing of its new aircraft, although not extreme deep stall scenario. Back in the late 1980's I was onboard for many hours of stall testing on a 767. Granted, fairly benign stalls (hold altitude, let the speed drop until the wing stalls and let it fall out of the stall and recover). Also, "windup turns" - used to test inlets at high airflow/high AOA (perform a constant altitude turn with engines set to the desired power, then keep pulling the turn tighter until the aircraft stalls and falls out of the turn). Such testing was always done in daylight in clear air - and during one preflight I recall a request that the flight test pilot "avoid" using the rudder when recovering from the stall, as large rudder swings could slice off the trailing cone which would end the test day. The pilot rather roughly responded that he was going to do whatever he felt necessary to recover the airplane
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Old 19th Jan 2015, 19:00
  #2191 (permalink)  
 
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May I ask two questions:-
1. Why are we discussing spins when no one knows whether the Air Asia aircraft ever got into a spin?
2. How many large commercial jet aircraft have ever got into a spin?
It seems to me that the discussion is taking a wrong turn.
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Old 19th Jan 2015, 19:19
  #2192 (permalink)  
 
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The closest analogue might be a Russian airliner (Tu-154M) that got caught in a massive thunderstorm over Ukraine in 2006.

After large pitch oscillations due to the severe turbulence, the aircraft climbed beyond its service ceiling before entering a flat spin -- plunging 37,000ft into the ground. All 170 aboard perished.
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Old 19th Jan 2015, 19:55
  #2193 (permalink)  
 
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Deep Stalls

I was always under the impression that entering a deep stall, where elevator authority is lost because airflow over the HS is in a "shadow" created by the wings, occurred mostly in high tail designs. Am I wrong?
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Old 19th Jan 2015, 19:58
  #2194 (permalink)  
 
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Since the discussion on stall/spin is continuing, it would be useful to know if there is an answer to the following question. For the A320 is it known if there have been any tests, including wind tunnel tests during the design phase, that might indicate if the aircraft can be put into a deep stall condition, which in this case would be due to the THS itself stalled so that there is no longer elevator control effectiveness (since with a non-T-tail the mainplane would be unlikely to be able to shield the THS from normal airflow). In this case would this likely be unrecoverable even with significant height loss, or might there be unusual recovery techniques such as using thrust to provide airflow over the THS or possibly attempt to bank using residual aileron action, and then apply rudder to push the nose down enough to regain airflow across the mainplane?

This will likely stretch the limits of knowledge in an area beyond the normal flight envelope but it would be interesting to know if there is any knowledge of this extreme flight condition.

There is video of stall tests in flight for the 737 such as at https://www.youtube.com/watch?v=a4V8W31YwTQ, and presumably analogous tests for the regime as the stall begins were also conducted by Airbus for each of the type it designed and built? There is also a nice lecture given jointly by Boeing and Airbus about stall testing at:

https://www.youtube.com/watch?v=HVt6LiDbLos

Last edited by mcloaked; 19th Jan 2015 at 20:26. Reason: Later found a useful link to a relevant video.
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Old 19th Jan 2015, 20:17
  #2195 (permalink)  
 
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Originally Posted by Bergerie1
May I ask two questions:-
1. Why are we discussing spins when no one knows whether the Air Asia aircraft ever got into a spin?
2. How many large commercial jet aircraft have ever got into a spin?
It seems to me that the discussion is taking a wrong turn.
1 The answer to #1 is that it appears to fit the impact conditions very well. See http://www.pprune.org/rumours-news/553569-air-asia-indonesia-lost-contact-surabaya-singapore-109.html#post8830502 At this point, it is just a theory until confirmed or denied by the accident investigation.
2. If it has wings, it can depart into a spin. Ask yourself what would happen to your twin underwing engine jet if it pitched up for some inappropriate reason and then compressor stalled one engine at an inopportune time due to the high transient AOA.
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Old 19th Jan 2015, 20:20
  #2196 (permalink)  
 
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I know what will happen to at least 95% of posts on this thread when FDR readout is available.
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Old 19th Jan 2015, 20:42
  #2197 (permalink)  
 
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Originally Posted by AM
The Concorde prototypes had a crew escape hatch
I'm not sure what your point is, but all the Airbus prototypes I've been on have had crew escape hatches. They would be used in case something went very badly during any of the many stall tests that were done.
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Old 19th Jan 2015, 20:50
  #2198 (permalink)  
 
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Thcrozier, while this definition is not universal, this is the way I think of stalls:
Stall - When the airflow separates causing the wing to loose lift. Most stalls can be readily recovered with a simple nose-down command, although the details can be tricky since one wing will often stall first resulting a sudden roll.
Deep stall - extreme stall where the nose is not allowed to drop and most forward speed is lost - forward speed is similar to the descent speed (e.g. Air France A330). Deep stalls take a long time to recover from since there is initially little airflow over the tail to provide a nose down command.
Unrecoverable stall - stall where the spoiled flow from the stalled wing effectively blanks the tail, completely preventing the necessary nose down command to recover - quite common in 'T' tail aircraft.


OK465 - I don't know how the FAA pilot would have done that, but my suspicion is that he was trying something that he wasn't supposed to and/or hadn't been briefed (that's happened before, where I do have first hand knowledge, when the FAA pilot performed a maneuver he'd been specifically told not to perform - tends to result in rather strained relations between Boeing and the Feds - and would also be consistent with it being kept 'quiet').
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Old 19th Jan 2015, 21:12
  #2199 (permalink)  
 
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@Volume

Interesting that they look at all the previous flights, is there some pre-existing malfunction suspected? Do they need to calibrate some models?
Why would one think that the investigators would not analyse previous flight data? For the purpose of a full investigation this must be done... simple as that. They're not "expecting" anything per se...
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Old 19th Jan 2015, 22:21
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all this talk of stalls...

just remember for those of you who haven't heard of the many types of stall...if you can't get the nose down...

you might try rolling into a steep bank and this may cause the nose to come down eventually. this was taught many years ago when concepts like deep stall came out.


I would like to think that most planes certified will likely NOT get into the hairiest of stalls without some coaxing from either a very good test pilot or an odd sort of computer scenario.

I imagine , right now, that at least a dozen people in indonesia have a really good idea of what happened ...and what didn't happen...we might hear something in 10 days or so...just a guess
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