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Spanair accident at Madrid

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Spanair accident at Madrid

Old 8th Nov 2008, 16:10
  #2361 (permalink)  
 
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Forget,

The relay schematic in on page 97, post 1935. R2-5 failed in air mode on the ground.
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Old 8th Nov 2008, 16:49
  #2362 (permalink)  
 
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I may not be the most appropiate person to do this summary, but unless someone has time to expand on the topic, this is the "simple" scenario.

-The front landing gear controls many of the ground/air logic through two sensors (right and left wheel).

-Each one of these two sensors "signals" (energizes) a circuit (left or right) depending on their ground/air position. When the wheels have weight and the strut is compressed=on the ground. Or the wheels don't have weight/strut decompressed=front wheels are off the ground. It can happen that a strut is "overinflated" (not properly regulated) and the sensors don't quite reach the closed position (strut is not compressed-down enough) even while on the ground. It could also happen i.e. if the airplane is out-of-balanced overloaded in the back and has no weight in the front. This doesn't seem to have been the case on this flight (read below). Also, the aircraft was almost at maximun takeoff weight, so certainly all wheels were supporting a heavy load.

-Each one of this left&right circuits "signals" (powers) aprox. between half a dozen (right wheel circuit) and a dozen (left wheel circuit) relays.

-Each one of these relays "signals" (powers) between 1 and 4 devices (TOWS and other warnings, heaters, ventilation, lights, cabin pressure, etc).

-Some of these devices receive "power" (signal) from two different relays at the same time from both, right and left wheel circuits. As a result, if the relay that powers it (or the whole circuit for the whole wheel) "fails", it would still work as long as the other wheel's circuit is ok. Those devices are "redundantly" serviced, and therefore would still work correctly even if one relay or one whole circuit (left/right) "fails" (i.e. is disconnected, etc) or one wheel sensor "fails".

-One relay in the left wheel circuit (R2-5) was responsable for both, the TOWS and the RAT probe air intake anti-ice heater. It also powered two other "devices" (AC x-tie/Radio vent), but those two were redundantly serviced from another relay in the other (right) wheel circuit.

-The only circuit servicing the RAT heater and the TOWS was the "left wheel" one. The only relay servicing the RAT and the TOWS was the R2-5. They were NOT redundantly serviced.

-In the same "left wheel" circuit, another relay, R2-12, MAY (someone please confirm) be the one responsable for signaling the Data Flight Recorder the ground/air mode state. The Data flight recorder DID detect and record a change in logic state between ground/air at the appropiate time (shortly after rotation was called). As a result, it is likely that the whole "left wheel" circuit was working (relays R2-308, R2-283, R2-5, R2-125, R2-58, R2-212, R2-3, R2-2, R2-240).

-But since the RAT heater could have only received power if the R2-5 relay thought it was in "flight mode", it was probably malfunctioning (i.e. stuck/blown, electrically shortcutted/opened to the sensor, otherwise malfunctioning). The same fact would've made the TOWS inoperative in all likehood.

-Assuming an R2-5 malfunction, no other systems would've been affected except for the TOWS and the RAT heater.

-The technicians pulled Z29 circuit breaker which only disconnects the RAT probe heater, w/o affecting other systems. They interpreted the MEL allowed for this. That would've "taken care" of the only problem reported by the pilots: "The RAT heater is on while on the ground", by turning it off completely and allowing the a/c to fly since there was no danger of ice formation in such hot weather and destinations.

The technician's actions, while not the smartest in the world, probably complies sufficiently with their jobs requirement. The interpretation to disconnect a "working" (but could be considered "erratic") device as being part of the MEL is up to semantics and interpretation. The only thing the MEL really says is that the airplane can fly with the heater inoperative if the weather and other conditions are met.

Also, nobody had told them anything about a non-working TOWS, that the crew presumably were required to check prior to all this.

Certainly maintenance guys could've put two-and-two together. Although I'm sure "nobody overly pressed them" to do a quick-and-dirty job (i.e. another airplane, transfer busses, gate, personnel, flight plan, etc were all ready for a new plane to be used for that service w/o an overly significant delay), certainly I'm sure they felt that for the comfort and interest of the passengers and the airline it was better just to quickly disconnect such a non-significant "problem" and take care of it later.

Should have not the pilots forgotten to deploy the flaps/slats exactly at that time, nothing would've come of it. I'm sure soon enough (although indeed probably not until another return flight at "night", potentially w/o TOWS unless the crew performed a test), it would've gotten noticed/fixed.

But it had to be on a hot day, with tail wind, with a virtually MAX gross that both issues aligned while a somewhat rookie (2 years, 1000h) copilot was in charge and random stall bad "luck" had them roll right a bit too much, enough to miss the runaway's course making recovery nearly impossible. The nose-up attitude tendency of MD-82 under stall didn't help, I'm sure.

So the short-short version would be: only the TOWS and the heater were "not working". The technicians disconnected only the heater. Nobody (pilots or technicians) noticed the TOWS were also not working, nobody tested them after all this, and nobody made the connection between both conditions being in all likehood closely related.

Last edited by justme69; 8th Nov 2008 at 19:50.
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Old 8th Nov 2008, 17:03
  #2363 (permalink)  
 
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Old 8th Nov 2008, 17:04
  #2364 (permalink)  
 
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Here's a simplifed schematic of R2-5.

[IMG][/IMG]

Last edited by forget; 8th Nov 2008 at 18:28. Reason: Simplifed further.
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Old 8th Nov 2008, 17:06
  #2365 (permalink)  
 
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Old 8th Nov 2008, 18:17
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bubbers44, et al; re “… they forgot the flaps. The warning system didn't work and they crashed. It will happen again if they don't fix it” (#2382).
‘They’ the crew, were operating in conditions where there are opportunities for error, and ‘they’ the crew, are error prone, as are all humans.
Your simplistic view implies blame; although you may not have intended this. This may be a result of oversimplification.

You also refer to those (they) who fix ‘it’; – which ‘it’, the TOCW (the operating conditions) or the human susceptibility to error. Who are these people, what are their responsibilities, and are these responsibilities of similar magnitude as those of the crew? Thus should they proportionally share the burden of this accident?

If the TOCW system had been fixed after previous accidents then this accident might have been avoided. Checks were introduced, but these did not circumvent error. Are they, the people at higher level who decided on checks vs a fix, to be blamed? No, but as with the crew and all of us there is a shared responsibility for safety.

How many Ppruners contributing to this thread knew about the poor working conditions (TOCW problems), how many of us have erroneously failed to select flap (on any aircraft) … how many have reported these issues, and if reported who took action and checked the result?
Not blame (after the event), but responsibility before the event; this isn’t simple.
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Old 8th Nov 2008, 18:31
  #2367 (permalink)  
 
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Lets cut to the chase here .... the crew ****ed up, didn`t set the flaps, presumably paid lip service to formal checklists that should have revealed the error and crashed - end of!
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Old 8th Nov 2008, 19:51
  #2368 (permalink)  
 
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Excellent diagrams, I presume they are relevant to type/mark??

One thing, coil supply is 115AC via CB B 1-23 (anyone got a relay schematic??)

ta.
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Old 8th Nov 2008, 19:53
  #2369 (permalink)  
 
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Safetypee

Love your work but this is a no brainer. As had been said. The crew forgot the flaps. An absolutely vital item in normal procedures. They payed lips service to a checklist designed to catch their previous mistake.

There are standards which need to be maintained in aviation. Finding excuses for gross negligence does not help safety one iota.
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Old 8th Nov 2008, 21:05
  #2370 (permalink)  
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FE Hoppy, bubbers44, Philipat - re:
They payed lips service to a checklist designed to catch their previous mistake.
That the crew screwed up is plainly obvious and tells us nothing new nor does it inform anyone about how to prevent the next human error. If that's all there was to this accident, the thread could have finished on page 1, liberal loads of kapoc notwithstanding. The question begged however, is "Is that all there is to this accident - the crew screwed up, end of story?"

Perhaps I have misunderstood your intent: Do you consider the broad input from those discussing safety factors, safety (preventative) programs, system design features, safety cultures, interpretations of MELs and last of all what crews themselves could have done to prevent this and at least three other accidents of the same cause (plus 55 reported incidents in which the airplane did not crash) all as unnecessary, superfluous and irrelevant to causes and that discussion should have stopped with the above statement of fact?

If so, then how does Philpat's entreaty to "fix - this", a statement with which I'm sure we all agree, get actioned once and for all? Much as we all would like it, crews (pilots/maintenance) can't be just told/implored to "follow SOPs" and that's the end of it. I know from previous posts you don't dismiss investigation or safety programs, so what am I missing?

Last edited by PJ2; 9th Nov 2008 at 17:44.
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Old 8th Nov 2008, 23:03
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B1-23 is shown in the above schematic. It would affect all of the relays, not just R2-5 so it was operating normally. The FDR sensed nose gear oleo extention on take off and would not have let engine power go below flight idle taxiing. They would have noticed that because I had it happen one night when the nose strut was overinflated.
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Old 9th Nov 2008, 00:55
  #2372 (permalink)  
 
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FE hoppy I hope that you agree that a central theme of modern flight safety is that human error cannot be completely eliminated; it can only be minimised or the effects mitigated.
At some point an error will occur. A key aspect of TEM is to ensure that this error is detected (if it cannot be avoided), or does not occur in combination with some other critical feature, or that the outcome is manageable.
I agree that checklists can help, but why only checklists, why not use technology to prevent / detect an error in parallel with the crew. Why not increase normal takeoff speeds so that an inadvertent flapless takeoff might be controlled? These, like most things in aviation, are judgement calls, and are generally in the process of certification – communal experience.

The crew appears to have suffered an error – why; this aspect has yet to be revealed.
Our commercial industry chooses to crew with two pilots, where one might monitor the other. This accident involves one of those rare situations where both pilots suffered simultaneous, or near simultaneous error – there was a safety time span from checklist action until takeoff to detect the error, why were there failures in these aspects?

In this accident it is not up to us to determine if the crew (or others) did all that they could have done in the prevailing circumstances, we should not – we cannot determine negligence. It might be impossible to establish the mental processes which the crew employed; it is difficult to establish intent, knowledge, perception, bias, or belief, etc, which could have affected behaviour from a FDR or CVR.
However, we can at least consider other aspects which could affect the circumstances which might have influenced the crew.
It was not my intent to identify excuses, only the circumstances, which based on current information point towards weaknesses in the TOCW system.

Was it just chance that the crew encountered error provoking circumstances at the same time as the TOCW was at its weakest; if so the danger is that we might ‘blame’ chance, because as has been stated other crews have suffered checklist errors (flaps) without an accident. Chance is not good enough for our industry, thus there is the need to search deeper into the communal experience – the ‘model’ of safety, which like in the financial crash, might be flawed.

Perspectives on Human Error.

Punishing People or Learning from Failure?

Human error: models and management.

Human reliability.
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Old 9th Nov 2008, 04:02
  #2373 (permalink)  
 
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A couple of points.

Nose gear air/ground sense, people have mentioned left wheel and right wheel sensors, is it correct to say, when the the nose oleo extends to a said extension that two sensors(may be 1+2 or L/H+R/H sensors) config the airplane into the air mode and talking of L/H or R/H wheel sensors can confuse people ?

Most MEL's I have seen mention a set of conditions/checks that may be required to allow use of the said MEL item, for the MEL item in question, do MEL's have any conditions/checks(apart from weather) ?

Some comments on hear mention that engineering should of researched more about the pilot's reported defect, should this be the case, then every item in the MEL should have the conditions that engineering should check every possible interconnection before using the MEL, and I guess the conditions should also ask the pilots to do the same !

Always worth remembering, engineers often work alone and do not have another person sitting next to them to talk over any issues, even cabin crew use two staff to check if doors are in auto/man mode, also engineers hours of work and sleep patterns are not well regulated to say the least.

Sounds like lots of learning from this accident, lets hope all the lessons are put in to practice to save lives in the future.

My thoughts with all involved. Joetom.
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Old 9th Nov 2008, 04:04
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I've watched this thread from day one.

now I've seen it all...increase take off speeds to allow for takeoff without flaps/slats.

ok, and now you increase the chance of tire failure.

I am sorry this accident happened. BUT, if you want a safe airline it costs money.

It means a dedication and honor of the highest type. It means that the CEO must create a culture of SAFETY FIRST.

But how can this be when the modern airline CEO doesn't know a trim handle from a suitcase handle. ;0

so, let's quit talking crazy...just do it right.
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Old 9th Nov 2008, 04:35
  #2375 (permalink)  
 
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I sense the outspoken masses would like somebody to blame and this thread closed so we could get on with waiting for the next accident to start another 100+ page thread.

So OK your brief vote is cast. But if history is repeated "those that choose not to participate" can rest assured that their comments have been noted.

For myself, I haven't figured out how to apportion blame, nor what to do while waiting for the next accident. So I shall continue to read this thread for pearls of wisdom.
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Old 9th Nov 2008, 08:21
  #2376 (permalink)  
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We will never agree, SC, but as a professional pilot on a professional pilots' web forum (and I have NO idea what you are), I have to re-arrange your post:-

APPARENT primary cause: Crew failing to select flaps and failing to perform check lists (as yet, as far as I know, unproven - and no-one has stated that the a/c could not have operated satisfactorily with the defect)

Contributing Factors:

Possible technical defect resulting in failure of a warning system - apparently not understood by those who write the maintenance books, nor the engineer or crew.

Possible commercial pressures - the ever present need to operate a company in profit or slide gently down the wall. 'Acceptable accident rate' (defined by 'regulators' in many walks of life) being a 'derivative' of this. If this was a contributor I have no doubt that Spanair will learn the consequences.

I doubt many Spanair pilots - or management - even know what CHIRP is, so you should leave that off your list as irrelevant in this accident. Please define for us a 'defective aircraft'. Are you suggesting the DDM/ADD call-it-what-you-will system be scrapped? As for unions 'criticising an airline'.................

Out of this thread come lessons: pilots must review their operating procedures; manufacturers and airlines need to ensure that maintenance procedures are thorough; it is encumbent on those who can to ensure that this particular 'hole' is plugged. I suppose the 'word I dare not utter' is REGULATION. It is how we get these things achieved that is important.

PJ2 - "If that's all there was to this accident, the thread could have finished on page 1" - I strongly disagree!
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Old 9th Nov 2008, 08:23
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Sense of Urgency

PJ2:

If so, then how does Philpat's entreaty to "fix - this", a statement with which I'm sure we all agree, get actioned once and for all? Much as we all would like it, crews (pilots/maintenance) can't be just told/implored to "follow SOPs" and that's the end of it. I know from previous posts you don't dismiss investigation or safety programs, so what am I missing
Your inputs are always informative, intellegent and pragmatic and I have nothing but respect. I will stand corrected as necessary. I think I actually made my point in the earlier referenced post, but to summarise, the issues I saw were as follows:
  1. It is taking far too long to reach a sensible conclusion, balancing the consequences of being too quick or too slow.
  2. Boeing should ensure that all operators of MD8X aircraft are compliant with TOCW check requirements ahead of EVERY TO in the light of this and several prior incidents. Has this been done and, if not, why not?
  3. Boeing should ensure that the MMEL addresses the relay issues involving the RAT probe. Has this been done and, if not, why not?
I understand that there are legal issues and that these these issues have already, largely, been communicated to lines. However, it still seems to me that the set of circumstances involved would justify repetition for the sake of clarity and the possible saving of lives in future.

Wise (Retired) pilots such as yourself have already concluded that, as good airmanship, a final check of the "Killer items" whilst lining up for TO, whilst not required as an official check, makes very good sense. If I were a pilot I would have learned from this thread that this can save your own life and those of passengers. Why is this not a formal final check? Many lines also now mandate that Flaps be deployed after push back and before taxi commences. Why nor ALL lines?

Those are my only issues and, as I said, I am learning from this and stand ready to be corrected.
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Old 9th Nov 2008, 08:49
  #2378 (permalink)  
 
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latent cause COMMERCIALISM
last events:
-bad troubleshooting
-Crew failing to select flaps and failing to perform check lists
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Old 9th Nov 2008, 09:05
  #2379 (permalink)  
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SC - any chance you can illuminate the 'black hole' that is SC with SOME glimmer of information about what your connection is with this forum and industry?

"Sorry BOAC you need to look further back than just the day before the accident." - actually you need to understand I am primarily looking at the 10 minutes or less before the accident.

"You are obviously BA". - wrong! 0/10 there.

"You are also the classic type who treats symptoms but not causes." - did you mistype that?

"Plug this hole and wait for the next achieves nothing except changes the circumstances of the next hole in the ground." - wrong! You hopefully prevent another similar hole in the ground, so the wait is a long one - a worthy ideal, no?

"Cure the number one single cause, COMMERCIALISM and you are well on your way to a heavy reduction in incidents." - I wait with interest to see your background
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Old 9th Nov 2008, 11:15
  #2380 (permalink)  
 
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Before deregulation,
When airlines were "protected", or state owned ...
Money was never a problem.

Commercialism was not a factor!

But accidents were more frequent at that time.
Plein stupid accidents.
From human error, including pure neglect.

Commercialism is a factor, I fully agree ... it is not the factor, obviously.
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