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Spanair accident at Madrid

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Spanair accident at Madrid

Old 24th Sep 2008, 07:22
  #1981 (permalink)  
 
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Question Stall recovery technique in swept wing jets

A question from a lowly PPL: is using ailerons an accepted technique to counteract roll when a swept wing stalls?

I vividly remember my instructor insisting on not using ailerons but to use rudder input to counteract roll when stalled. Aileron input could make matters worse and introduce additional aerodynamic effects leading to an increased roll rate and eventually spin entry.

The Northwest accident report mentions substancial loss of lift because of aileron (and linked to this: spoiler) use during recovey. I am NOT suggesting this technique was used in the Madrid disaster!

I apologise in advance to the Sky Gods I might have offended by this post. Please remember I'm only a weekend Warrior (or should that be warrior?)

Johan
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Old 24th Sep 2008, 08:28
  #1982 (permalink)  
 
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Wind shear technique

I'm afraid the crew did'nt recognise their stall condition ... They had no training to handle that.

But maybe they had received extensive training against "negative" windshear on initial climb. That happens when an airplane, shortly after take off enters a layer of considerable tailwind. That can happen on a calm morning, and not only in a stormy day.

The training emphasize keeping the aircraft in the stick shaker zone - "hanging on" - NOT lowering the nose ... Of course, airline pilots (most of them ...) let the yaw damper handle the rudder, and try keeping the wings level only with the stick.

Not lowering the nose is actually a key point when entering a negative wind shear during an approach. (so as not touching gear & flaps). But I disagree with this recommandation during climb ...

If that training is not properly put into perspective, it quicly becomes a (bad) habit for reacting to a stick shaker / stall condition.
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Old 24th Sep 2008, 08:54
  #1983 (permalink)  
 
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Kilo, what you say is correct about using rudder. Using aileron will further aggravate the stall on the wing and therefore wing drop. As bis says I think this is done in light aircraft for training, getting you well into the stall rather than recovering at the first sign.
In a modern jet we just un-stall the aircraft as discussed previously on here. Put the nose down etc.

With a large fin on the tail I don't think applying boot full’s of rudder at this point is a recognised technique! One aircraft accident was caused when the handling pilot used rudder to pick up a wing that had dropped due to wake turbulence. Oscillation occurred and the rudder came off! On a jet we have a lot of power avail and if you do stall it (you should be warned well before) you should be able to recover quickly....

In this case, if the aircraft only ever got to 40ft they must have only been a few seconds into the air. If the wing stalled and fell rapidly to strike the ground at the tip I wonder if they really had any time to think about using rudder, aileron or will power to get the wing back up! As Bis said they won't have had the time to recognise the situation as a stall.
Instinct will have probably kicked in and they will have probably used aileron to attempt to stop the roll. As we do on many TO's out of a blustery MAD!!
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Old 24th Sep 2008, 09:30
  #1984 (permalink)  
 
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Wind shear/Bis47 post 2013

Can you please expand and clarify tthe current recommendations ( from your company ?) in some detail
Im not clear on those recommendations themselves, and which items you disagree with and why..
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Old 24th Sep 2008, 15:43
  #1985 (permalink)  
 
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El Mundo, citing first-hand access to the aircraft's maintenance log, wrote that in the days before the crash, there has been alarms and inspections regarding slats and flaps; and two events of overheated RAT probe on the day before the crash.
Original in Spanish: El sistema de despegue falló dos días antes de la tragedia
Automated English translation

Is this for real? If yes, it possible to sort out what the flat/slats alarms reported are about? And/or, is a reliable transcript of the maintenance log available?
The problems EL Mundo refers to are concerning the AUTOSLAT system, that is completely indipendent from "normal" slats/flaps extension
The TLB have only one entries saying "autoslat fail light on"
The emergency checklist says that in flight you should be aware that Slats can go directly to "Land" position (instead on takeoff, just mid-extension) when selecting any position
Nothing else
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Old 24th Sep 2008, 15:44
  #1986 (permalink)  
 
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El Mundo, citing first-hand access to the aircraft's maintenance log, wrote that in the days before the crash, there has been alarms and inspections regarding slats and flaps; and two events of overheated RAT probe on the day before the crash.
This has been discussed before in the thread.

It seems the MD-82 has a known "problem" that the autoslat failure lamp turns on sometimes when the flaps are set. You just put them back and set them again. It's not a "real" problem, just a glitch with the autoslat warning that happens once in a blue moon.

Autoslats are not used during take off.

I have no idea how the system works exactly , but I remember the explanations by those who do making sense and they all agreed the "failure" wasn't related to the accident. Just a coincidence. If someone cares to explain exactly what the autoslat fail warning light indicates (and how or why it can be on while setting flaps 15 upon landing), we will all appreciate it.

I don't have access to the maintenance logs. But here is a picture of the page describing failures as reported to the judge:

http://img133.imageshack.us/img133/6...anair13bw3.jpg

In short, it says:

Day 1) Right reverser, acummulator low caution light on. Action taken: right reverser deactivated, valve blocked in DUMP position, C/B out, no leaks found, accumulator 1000 psi.

Day 18) Autoslats fail when slats extended -- Action, system reset, everything fine, failure doesn't show up again during their testing.
Pilots: During landing, autoslat light turns on again when flaps 15 was selected -- Action, several tests done (PSU, Stall warning computer, etc)
Report back from pilot: "Autoslat light not on again ever since" - Service replies: THX

Day 19) During line up, on 3 occasions, RAT temperature reaches 90º ... EPR drops to 1 30 same as sequence L36" -- Maintenance in Barcelona runs tests as AMM 34 18.00 ???

Low tire pressure on main wheel 4º -- Maintenance action in Barcelona: replaced tire 4.

So, basically, the RAT probe heater was pbbly intermitently (or permanently, who knows) turning on while on the ground also on the 19th, the day before the accident, but nobody quite caught the failure, it seems.

As we know, the airplane made another flight w/o incidents on the same morning with the same pilots. Theoretically, on that occassion, the crew was suppossed to have run a TOWS check before takeoff. I don't think the CVR contains that flight, as it only records 40 min and since they did one RTG right before they were about to TO in Madrid, they were taxing and stuff for like an hour on their second flight of the day (the one where the accident happened).

Most of this has been discussed before in the thread wayyyy back.

Last edited by justme69; 24th Sep 2008 at 15:55.
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Old 24th Sep 2008, 17:48
  #1987 (permalink)  
 
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Bis47 Wind shear technique

The training emphasize keeping the aircraft in the stick shaker zone - "hanging on" - NOT lowering the nose ... Of course, airline pilots (most of them ...) let the yaw damper handle the rudder, and try keeping the wings level only with the stick.
Bis, that is not quite correct. Training should be to keep one just out of the stick shaker zone or as Mr Boeing used to say "nibbling the stick shaker". The problem is that once in the the shaker zone, the pilot has no idea of just how far he is in or how close to actual stall he now is and a sudden change in relative airflow can easily take one straight past that critical angle with possibly little or no chance of recovery in such circumstances.
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Old 25th Sep 2008, 01:05
  #1988 (permalink)  
 
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In this video you can see how to check the alarms.
http://es.youtube.com/watch?v=MpQejVs3ryc
And here, after minute 3.15 you can see a check on the way to the runway to test the alarm and the flaps.
http://es.youtube.com/watch?v=4EJKQnTmGs4

Last edited by agusaleale; 25th Sep 2008 at 01:23.
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Old 25th Sep 2008, 01:40
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Unfortunately with no TOWS that check would have also had no take off warning on their check if the flaps were up. The check for TOWS should be done prior to flap extension to get the warning. When the captain advanced the thrust levers to test configuration if R2-5 had failed in the air position the TOWS would be silent just as it was for the crash even if the flaps were up.
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Old 25th Sep 2008, 01:59
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Since the RAT temp previous to this flight climbed to 90C on a couple of occasions before this incident on the ground it sounds like a bad receptical for R2-5 making the relay fail to air mode intermittently might have caused the problem. Probably a little corrosion causing a bad contact for the relay coil that energizes the relay. These are the hardest problems to diagnose because they go away when the contacts are making contact.
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Old 25th Sep 2008, 03:59
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A TOCWS that needs manually checking every take-off by simulating a bad take-off config, won't self test easily and quickly, nor is designed to be particularly fault-tolerant is to me, plain and simply, in dire need of some re-engineering in today's more hurried and busy cockpits - the reasoning that these are fairly new aircraft but entitled to inherit 'legacy' systems from fairly old designs... is starting not to cut the mustard anymore!

In short.. I think quite a few eyes have been opened by this very tragic accident. I really do hope a Public Court of Inquiry does an extremely thorough job into itemising every salient issue here....and fairly briskly!
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Old 25th Sep 2008, 04:06
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In fact, can someone answer this question please...?

Are the racks of relays and CBs changed entirely 'on condition' throughout the aircraft's life, or are they 'lifed' and the whole rackfull changed based on flying hours, flights or a given time from installation/ manufacture date?
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Old 25th Sep 2008, 09:49
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Most LRUs (Line Replacable Units) are "on condition". It is rare for any easily replaced component to be anything else. Emergency equipment springs to mind as an exception. More major components like undercarrige legs and engines tend to be lifed, although the modern engine is slowly tending towards O/C with an ultimate life.
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Old 25th Sep 2008, 10:49
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Didn't Recognize A Stall?!!!!

Bis 47:
I'm afraid the crew did'nt recognise their stall condition ... They had no training to handle that.
If they didn't recognize a stall, just who taught them to fly? Dagwood Bumstead? As I've said before, apparently they jerked the plane into the air based on a configuration they hadn't selected. Aviate, navigate, communicate. They didn't do the first one.
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Old 25th Sep 2008, 10:59
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For those interested in the rescue, survability or impact of the terrain angle of the accident, there is a video showing the site after most of the cleanup was done.

You can see it here:

Interstitial - Noticia

Clean-up of the area had been temporarily suspended as the judge agreed to a requirement by Spanair to send some expert to inspect the site. It will continue tomorrow.

Last edited by justme69; 25th Sep 2008 at 19:08.
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Old 25th Sep 2008, 18:22
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life time of relays

As been said before generally all small ctrl relays are all "on condition" as lifetime limit. However all the big power ctrl relays and line contactors are life timed with flight hours or/and elapsed time. These are the only relays that are so called serialized that meens with seraial number on and can be tracked down in maintenace computersystems for installation time and ammount of flight hours accumulated. All other relays are so called consumable sparepart with no serial number and no tracking of accumulated time and therfore changed only when they fail. This is a general rule for most aircraft types.

Regards

wings 1011
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Old 25th Sep 2008, 22:24
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"On condition", means that items which are not normally energised in flight are tested at intervals, such as flotation switches on helicopters equipped with floats which initiate automatic inflation of the floats during ditching. Items such as relays and switches which are energised during flight are said to be "tested" on every flight and would not normally be replaced until they fail. They are normally sealed units as there is less chance of any corrosion affecting the contacts. Being sealed they cannot be inspected, replacing them all during a major aircraft check could be counter productive as there is no guarantee that a new unit is more reliable, if it's not broke don't try to fix it.
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Old 25th Sep 2008, 23:37
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Originally Posted by captplaystation View Post
Telefonica's gone, replaced with "Drive to your next disaster location with PEUGEOT", strange how companies don't monitor when and in relation to what, their ads will be used. Can't think of a positive spin on that at all, maybe some advertising whizz-kid could explain the logic.
Not claiming to be either advertising or a whizz-kid, but I suspect this is down to ad selection by automated keyword matching. The ads will be sourced from a large pool (likely provided by a third party agency) and will be matched to the page based on the other page content - the idea being to display "relevant" ads.

These sort of keyword matching algorithms can't yet do much about context let alone assess "sensitivity" when choosing an ad, so sometimes you get ads that no resonable person would have matched to the content. This is already leading to complaints, see eg.

ASA: Publishers must vet AdSense ads ? The Register

I don't see this changing though - replacing with a manual process won't be feasible, and the automated matching will always be (more) flawed.
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Old 26th Sep 2008, 19:52
  #1999 (permalink)  
 
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Some speculations about R2-5, inspired by the new information about previous RAT heater problems.

From a systems reliability point of view the fact that the four relay contacts control totally different functions implies that a fault indication affecting any of those functions may have side effects on the other functions. This implies that, for example, any fault tracing instruction of the RAT heater system should include a test that can discover if the R2-5 relay has either failed completely, which may have been the case here, or only in the RAT heater circuit.

More generally, I wonder if the electrical fault isolation procedures are generally designed only top-down (i.e. if a system does not work, which components to suspect) or also bottom-up (i.e. if a component fails, which systems are affected). For this particular case, it seems both methods should be used.
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Old 26th Sep 2008, 21:20
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I agree. It seems since the RAT heater can only get power if R2-5 is in air mode disconnecting the RAT heater only removed the symptom, not the cause which affected a crucial TOWS system to fail in air mode also.
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