Spanair accident at Madrid
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el,
You are not using the MEL to work the aircraft. You are deferring a problem in accordance with the MEL. If you are pulling a C.B. for the RAT heater, you are carrying out a maintenance action to deactivate a system. The reason you are deferring fixing an item can be for many reasons and the most common are time and spares availability.
As has been discussed before, the aircraft appears not to have been in the air mode on the ground, but has had a relay with contacts in the incorrect sense . Relays fail in many ways, so the TOWS may have been working, but just the RAT probe heater contacts of R2-5 failed. This appears to be a reoccurring problem, so maybe it should have been found on previous TOWS tests, but it was not.
You are not using the MEL to work the aircraft. You are deferring a problem in accordance with the MEL. If you are pulling a C.B. for the RAT heater, you are carrying out a maintenance action to deactivate a system. The reason you are deferring fixing an item can be for many reasons and the most common are time and spares availability.
As has been discussed before, the aircraft appears not to have been in the air mode on the ground, but has had a relay with contacts in the incorrect sense . Relays fail in many ways, so the TOWS may have been working, but just the RAT probe heater contacts of R2-5 failed. This appears to be a reoccurring problem, so maybe it should have been found on previous TOWS tests, but it was not.
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Please point out where this has ever been said
The query seems to me whether the reason the RAT Heater was heating was examined i.e. investigate the cause of the problem, or whether just the symptom was addressed i.e. not work out why the RAT Heater was incorrectly heating, just stop it doing so.
Whilst I am sure some Spanish judge will state the Engineer should have "thought more deeply", and the 20:20 hindsight pPrune judges as well, my personal opinion is that "curing the symptom" is what 90% of engineers would have done, especially given the time pressure. That is how MELs are used today - you might not like, and I don't
The immediate solution is to amend the MEL for the RAT Heater (and other systems) to prevent pulling those CBs without specific other fault finding.
But longer term, I think MEL philosophy needs to be addressed. These are supposed to concern "faulty / defective" items i.e. not working. Items working correctly but at the wrong time, or intermittently, can cause additional problems, or mask the real problem, and the MEL IMHO should not be the first port of call
NoD
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Would this accident have occured with a fully functioning TOWS but RAT heater CB pulled?
The answer is NO it wouldn't.
The answer is NO it wouldn't.
Posts above show occasions where TOWS have been ignored.2 systems seem to have "failed". One was deployment of Flaps. One was TOWS. One is critical, one is supplementary...
If the Flaps don't get deployed, we have a major system / SOP failure. TOWS is a supplementary system designed to "trap" the first failure, and usually would do. However, we cannot rely on it doing so, nor blame the TOWS for the accident. Even if the TOWS had been tested, it might have had a failure mode that allowed it to say it passed, and/or failed later on.
The recommendations of the inquiry, need IMHO, to 90%+ concentrate on stopping an aircraft getting to a takeoff roll without Flaps deployed. If an aircraft starts rolling, then aborts due no Flaps + TOWS - that is not the safety system working "correctly". It just a **** lucky near accident
NoD
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Here we go again. Lets get the facts right. NO CB WAS PULLED WHICH AFFECTED THE TOWS
Please point out where this has ever been said
AFAIK only 1 CB got pulled - the one for the RAT Heater, and the RAT Heater alone... so I for one believe it has been said repeatedly.
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Just for clarification, there have been several accidents of this type where slightly different reasons have led to similar consecuences.
-There have been cases where a perfectly serviceable TOWS was disconnected by a "human" pulling a c/b (MAP case in Lanzarote).
-There have been cases where a (electrically) "working" TOWS has not been activated due to a bad switch in the thrust handles (727's like in Delta Dallas accident or 737 in DCA incident). In those cases, a theoretical "lighted indicator" that would've signaled the TOWS was powered on the ground would've given the false sense of security that the TOWS was working, when it actually wasn't for practical purposes.
Even worse, in Dallas case, the switch was determined to work "some times", perhaps once every 2 or 3 actuations, so checking the TOWS would've only LIKELY, but not for sure, have detected the malfunction. Neither an "operating" lighted TOWS indicator nor a test are 100% effective measures to know the TOWS won't fail when it's needed. The most effective measure given current designs is the test shortly before each takeoff, though, as it would most likely catch an inop TOWS on time. The pilots are not going to be staring at a lighted TOWS indicator to see if it's on while they take off. And having it "on" doesn't mean the TOWS will work if the switch in the handle is broken or if the loudspeaker is blown, i.e. Only chance of catching it is to test it and pray it doesn't fail from that time until the time it's needed.
(Incidently, in Dallas Delta accident, i.e., the crew answered the checklist FLAPS/SLATS as the correct "15/15/Green light" while the FDR and the CVR showed no indications that they ever moved the handle nor did they really had appropiate time to have done it as they moved to the next item in a like less than a second. So paying "lip service" to checklists is a long known fact.)
-There have been cases where the TOWS failed for undetermined reasons (Northwest in Detroit).
-There have been cases where (probably) the TOWS failed due to part of the ground/air logic circuit failure (Spanair).
-There have been cases where the TOWS worked just fine but the crew failed to take appropiate action (LAPA).
-There have been cases of accidents with victims where it wasn't clearly reported why or if the TOWS failed (Lufthansa in Nairobi or India Air in Hyderabad).
But the short story is: quite a few airplanes have tried to take off with incorrect configurations, when procedures, training and aircraft indicators (flaps/slats panel indicators) should've made it clear that this wasn't a good idea. Most of them have been "saved" by the TOWS. Of the rest, most have crashed and some have saved the day one way or another (quick command of flaps, reducing angle of attack and flying ground effect, aerodynamics conditions allowing for clean takeoff with little performance penalties, etc).
But we come back to quite common even nowadays scenarios of landings with gear retracted (forgotten, usually on small private planes, but even recently in small and even some large airliners), spoilers in the wrong setting, or similar events. They range from simple oversights to configuration alarms being turned off by the crew while dealing with another malfunction that made them distracted.
A 100% reliable TOWS is not "impossible", but it's probably not "worth the time and effort". Such a design and expense is probably better use on other, more vital systems. But a much better design is certainly possible, one that is close to 100% effective and today's technology should make it more than cheap enough to be considered. So why not?
But the main reason for these accidents, crew failure to perform vital actions for which they were trained and under not overly-stressful circunstances (well rested, before a takeoff, plenty of time to double check on 20 minutes long taxiing... some of you would simplify it as "pilots simply screwed up"), will not really be solved, only "masked" by the more effective TOWS.
-There have been cases where a perfectly serviceable TOWS was disconnected by a "human" pulling a c/b (MAP case in Lanzarote).
-There have been cases where a (electrically) "working" TOWS has not been activated due to a bad switch in the thrust handles (727's like in Delta Dallas accident or 737 in DCA incident). In those cases, a theoretical "lighted indicator" that would've signaled the TOWS was powered on the ground would've given the false sense of security that the TOWS was working, when it actually wasn't for practical purposes.
Even worse, in Dallas case, the switch was determined to work "some times", perhaps once every 2 or 3 actuations, so checking the TOWS would've only LIKELY, but not for sure, have detected the malfunction. Neither an "operating" lighted TOWS indicator nor a test are 100% effective measures to know the TOWS won't fail when it's needed. The most effective measure given current designs is the test shortly before each takeoff, though, as it would most likely catch an inop TOWS on time. The pilots are not going to be staring at a lighted TOWS indicator to see if it's on while they take off. And having it "on" doesn't mean the TOWS will work if the switch in the handle is broken or if the loudspeaker is blown, i.e. Only chance of catching it is to test it and pray it doesn't fail from that time until the time it's needed.
(Incidently, in Dallas Delta accident, i.e., the crew answered the checklist FLAPS/SLATS as the correct "15/15/Green light" while the FDR and the CVR showed no indications that they ever moved the handle nor did they really had appropiate time to have done it as they moved to the next item in a like less than a second. So paying "lip service" to checklists is a long known fact.)
-There have been cases where the TOWS failed for undetermined reasons (Northwest in Detroit).
-There have been cases where (probably) the TOWS failed due to part of the ground/air logic circuit failure (Spanair).
-There have been cases where the TOWS worked just fine but the crew failed to take appropiate action (LAPA).
-There have been cases of accidents with victims where it wasn't clearly reported why or if the TOWS failed (Lufthansa in Nairobi or India Air in Hyderabad).
But the short story is: quite a few airplanes have tried to take off with incorrect configurations, when procedures, training and aircraft indicators (flaps/slats panel indicators) should've made it clear that this wasn't a good idea. Most of them have been "saved" by the TOWS. Of the rest, most have crashed and some have saved the day one way or another (quick command of flaps, reducing angle of attack and flying ground effect, aerodynamics conditions allowing for clean takeoff with little performance penalties, etc).
But we come back to quite common even nowadays scenarios of landings with gear retracted (forgotten, usually on small private planes, but even recently in small and even some large airliners), spoilers in the wrong setting, or similar events. They range from simple oversights to configuration alarms being turned off by the crew while dealing with another malfunction that made them distracted.
A 100% reliable TOWS is not "impossible", but it's probably not "worth the time and effort". Such a design and expense is probably better use on other, more vital systems. But a much better design is certainly possible, one that is close to 100% effective and today's technology should make it more than cheap enough to be considered. So why not?
But the main reason for these accidents, crew failure to perform vital actions for which they were trained and under not overly-stressful circunstances (well rested, before a takeoff, plenty of time to double check on 20 minutes long taxiing... some of you would simplify it as "pilots simply screwed up"), will not really be solved, only "masked" by the more effective TOWS.
Last edited by justme69; 10th Nov 2008 at 19:13.
It was determined by the regulators that the system should be checked prior to each flight. However that gets in the way of making a profit so some operators drop it down to first flight of the day only.
Do you have anything other than supposition to support this?
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The TOWS check takes 10 seconds. Usually during push back. It would not slow down operations at all. Yes, the TOWS would not be required if pilots did their checklsts properly. I always thought if I really did the checklist nothing should be a problem. Just responding to the checklist is another matter that is easy to fall in to. We get bored and keep repeating the same checklists and sometimes just say the words. That is where the problem lies. Saying the response then looking at the actual position. Usually you realise the mistake but the checklist reader may assume what you said was true if he did not verify. Humans are prone to get complacent when doing the same thing over and over.
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Originally Posted by NigelOnDraft
2 systems seem to have "failed". One was deployment of Flaps. One was TOWS. One is critical, one is supplementary...
1) The flap system has NOT FAILED. evidence so far suggests that pilots have NOT set flaps.
2) The TOWS system HAS FAILED. Due to R2-5 malfunction,
3) Maintenance has FAILED to detect and address (2).
Regarding the comment about 90% of engineers would have done (3) same as in Madrid. I have a problem in believing so, but if it's true that makes me happy that I'm not a Pilot and I don't fly that often after all.
All the rest I agree with you.
Last edited by el #; 10th Nov 2008 at 07:15.
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el #
Agreed, but I did clarify it with:
Re the Engineers, I am afraid that is my observation, with quite a few years of Airline Ops, a good number as Capt - and increasingly so. Defect in book (e.g. an ECAM Message), ECAM Message in MEL cross refers to MEL procedure, MEL actioned PDQ, or if "No Maint Actions required" then Flt Crew expected to accept it under ACF.
It is the MEL sections, under the above scenario, that are supposed to "trap" insidious deeper problems...
I am not saying that the Spanish / Spanair / MD-80 philosophy is the same since I work under a different authority / airline / type(s). But I am saying that from my experience, the apparent chain of events as far as the RAT Heater / Engineering actions went, is much as I would expect, and certainly not enough as far as those individuals were concerned to have been e.g. negligent enough to carry any responsibility in law.
NoD
1) The flap system has NOT FAILED. evidence so far suggests that pilots have NOT set flaps.
If the Flaps don't get deployed, we have a major system / SOP failure.
It is the MEL sections, under the above scenario, that are supposed to "trap" insidious deeper problems...
I am not saying that the Spanish / Spanair / MD-80 philosophy is the same since I work under a different authority / airline / type(s). But I am saying that from my experience, the apparent chain of events as far as the RAT Heater / Engineering actions went, is much as I would expect, and certainly not enough as far as those individuals were concerned to have been e.g. negligent enough to carry any responsibility in law.
NoD
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Blubbers44 posted :-
Once upon a time I thought I had engaged and involved four other people in a calculation - fortunately one with a non-fatal outcome - when it turned out to be incorrect I remonstrated at length only to be told - "Oh, we heard what you said but we didn't bother to actually work it out because we thought YOU knew what you were doing!"
Just responding to the checklist is another matter that is easy to fall in to. We get bored and keep repeating the same checklists and sometimes just say the words. That is where the problem lies. Saying the response then looking at the actual position. Usually you realise the mistake but the checklist reader may assume what you said was true if he did not verify. Humans are prone to get complacent when doing the same thing over and over.
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forget said:
Purely from logic perspective - the conclusions (a) that MEL writers did not consider why RAT might heat on ground and (b) that the MEL was poorly written is not justified by your argument you present, unless the MEL actually contemplates the scenario of the RAT heat operating when air/ground logic dictates that it should NOT be operating. If the MEL merely states that flight is permitted with RAT heat inoperative (for whatever reason) in certain circumstances (no icing forecast), then the MEL did the job it was designed to do. Of course it is possible to argue that it should do more - but that's another issue.
When the MD-80 RAT Heat MEL was written up it allowed flight with no forecast icing conditions. Simple, and no problem so far. Pull the RAT Heater circuit breaker and off you go. Crucially, what wasn’t considered by the MEL writers was why the RAT might Heat on Ground. A failure of Relay R2-5 (Flight Mode) would do it – which would also disable the TOWS. So, pull the RAT Heat circuit breaker, RAT Heat problem fixed, TOWS is now inop with NO indication of failure. And I defy any line engineer, no matter how smart, to raise his hand and say “Hold on guys, RAT Heat on, I bet R2-5s failed and we can’t just pull the RAT breaker because the TOWS might also be inop”. That’s down to the MEL actions and, from what I’ve seen in this case, they ain’t up to the job.
This accident has been waiting to happen from the day the aircraft left Long Beach. Very poor TOWS/Flight/Ground logic design, and very poorly written MEL.
This accident has been waiting to happen from the day the aircraft left Long Beach. Very poor TOWS/Flight/Ground logic design, and very poorly written MEL.
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communication on the internet forum is imprecise...
yikes
we are pilots talking to pilots...sometimes we are cryptic, it is our way.
we use one word that covers many in radio work.
we chat on this forum as if we were in the ''ready room'' talking things over with our fellows.
I don't always agree with Nigel, but I wouldn't point at his posts as imprecise.
when we don't understand, we should ask questions...say again
Someone indicated that when the airlines were regulated we had more plane crashes...true. But we have more safety gadgets now, more experience and we shouldn't be repeating accidents from 20 years ago.
30 years ago the US airline industry was deregulated. IF it had remained regulated, adding new safety gadgets to the cost of a ticket, things might even have been safer.
cryptically yours
sevenstrokeroll
yikes
we are pilots talking to pilots...sometimes we are cryptic, it is our way.
we use one word that covers many in radio work.
we chat on this forum as if we were in the ''ready room'' talking things over with our fellows.
I don't always agree with Nigel, but I wouldn't point at his posts as imprecise.
when we don't understand, we should ask questions...say again
Someone indicated that when the airlines were regulated we had more plane crashes...true. But we have more safety gadgets now, more experience and we shouldn't be repeating accidents from 20 years ago.
30 years ago the US airline industry was deregulated. IF it had remained regulated, adding new safety gadgets to the cost of a ticket, things might even have been safer.
cryptically yours
sevenstrokeroll
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imagine
imagine if another plane had been right behind the doomed flight? imagine if one of the pilots behind the doomed plane noticed that the flaps/slats were not extended.
imagine if that pilot didn't radio a warning prior to taking the runway?
imagine if that pilot DID radio a warning?
WE are our brother's keeper. Keep your eyes open for the problems of others...and after you check their plane out for problems...CHECK YOUR OWN PLANE ONE MORE TIME. (or like count basie, ''april in paris'' one more once)
imagine if that pilot didn't radio a warning prior to taking the runway?
imagine if that pilot DID radio a warning?
WE are our brother's keeper. Keep your eyes open for the problems of others...and after you check their plane out for problems...CHECK YOUR OWN PLANE ONE MORE TIME. (or like count basie, ''april in paris'' one more once)
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MEL precision...
You may fly with RAT probe heat INOP.
The RAT heat is on on the ground, when it should be off.
The fault is not in the RAT heat, it is in the system that auto-controls it, so a different MEL item may apply. But the RAT heat is not INOP.
Simple, innit.
You may fly with RAT probe heat INOP.
The RAT heat is on on the ground, when it should be off.
The fault is not in the RAT heat, it is in the system that auto-controls it, so a different MEL item may apply. But the RAT heat is not INOP.
Simple, innit.
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Defect. "One nav light inop on left wing tip"
Action. "Crew will not accept MEL, so new bulb fitted, still inop"
Aircraft N/stopped and crew and passengers to hotels.
Working party on route to troubleshoot and fix inop nav light.
This appears to be the way some see things going.
One point has crossed my mind, this MEL item may of been used many many times in the past for the same said pilot reported defect, when defect was fixed by changing a relay, did no alarm bells get sounded !
Action. "Crew will not accept MEL, so new bulb fitted, still inop"
Aircraft N/stopped and crew and passengers to hotels.
Working party on route to troubleshoot and fix inop nav light.
This appears to be the way some see things going.
One point has crossed my mind, this MEL item may of been used many many times in the past for the same said pilot reported defect, when defect was fixed by changing a relay, did no alarm bells get sounded !
Per Ardua ad Astraeus
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It is indeed a sobering thought, NoD, that if the crew HAD tested the TOWS as per the apparent manufacturer's rec., before the return to stand, things could well have been different.
It is indeed a sobering thought, ..., that if the crew HAD tested the TOWS as per the apparent manufacturer's rec., before the return to stand, things could well have been different.
Should it be in the takeoff checklist right before the crew call out green green for the flaps/slats. If not is there a chance that someday a crew does the check on taxi out then aborts the takeoff for any reason goes back to the stand and some maintainence function mistakenly disables the TOWS.
It's not easy to pick out the best solution without data and analysis of the Pro and Cons
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whenever mx does work in the cockpit, we have to do an ''originating' checklist...meaning first flight of the day.
whenever I got into the cockpit, I checked that the engines were not running and then I moved the throttles, got the warning and pulled them back.
it takes less time than it takes to type.
whenever I got into the cockpit, I checked that the engines were not running and then I moved the throttles, got the warning and pulled them back.
it takes less time than it takes to type.