Spanair accident at Madrid
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RAT/RAM AIR TEMP probe
someone mentioned how the RAT probe couldn't be the possible cause for this crash.
at this time, we still don't know exactly what was wrong or done to rectify the RAT probe issuse (if it was the rat probe).
But.
There is a scenario in which the RAT probe gets heated (as an anti ice measure) on the ground when it is not supposed to be heated.
The system detecting whether the plane is on the ground (known by different names, squat switch, ground shift mechanism, weight on wheel) can be fooled and the plane "thinks" its in the air and starts to heat the probe. It usually means a circuit breaker has been pulled or otherwise not properly set.
I've seen this happen while on the ground. You get erroneous readings of temp.
BUT HERE IS THE RUB...if the Mechanic disabled the current to the RAT PROBE HEATER and did not recognize the problem with GROUND SHIFT MECHANISM...
YOU MIGHT LOSE THE TAKEOFF CONFIGURATION WARNING!!!!! THIS WOULD ALLOW YOU TO ATTEMPT TAKEOFF WITHOUT SLATS/FLAPS!!!! IF THE PILOT FORGOT,there would be no warning.
THIS MIGHT be a viable scenario!!!
OTHERS with MD*80 experience (mine is on the 9) please check and report!!!
at this time, we still don't know exactly what was wrong or done to rectify the RAT probe issuse (if it was the rat probe).
But.
There is a scenario in which the RAT probe gets heated (as an anti ice measure) on the ground when it is not supposed to be heated.
The system detecting whether the plane is on the ground (known by different names, squat switch, ground shift mechanism, weight on wheel) can be fooled and the plane "thinks" its in the air and starts to heat the probe. It usually means a circuit breaker has been pulled or otherwise not properly set.
I've seen this happen while on the ground. You get erroneous readings of temp.
BUT HERE IS THE RUB...if the Mechanic disabled the current to the RAT PROBE HEATER and did not recognize the problem with GROUND SHIFT MECHANISM...
YOU MIGHT LOSE THE TAKEOFF CONFIGURATION WARNING!!!!! THIS WOULD ALLOW YOU TO ATTEMPT TAKEOFF WITHOUT SLATS/FLAPS!!!! IF THE PILOT FORGOT,there would be no warning.
THIS MIGHT be a viable scenario!!!
OTHERS with MD*80 experience (mine is on the 9) please check and report!!!
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What about load sheet trim? is it easy to load this MD tail heavy? or indeed accidentaly overload the aircraft.
I have often wondered about the local effects of hot tarmac on performance calculations. ie OAT is +30, but runway temperature is nearer +40 (this is often commented on in F1)
Is the NTSB investigating as well as the Spannish? When can we expect 1st report of findings?
I have often wondered about the local effects of hot tarmac on performance calculations. ie OAT is +30, but runway temperature is nearer +40 (this is often commented on in F1)
Is the NTSB investigating as well as the Spannish? When can we expect 1st report of findings?
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F14, spanish minister of transport will report in a commission public audience next friday.
However, since the investigation is under judiciary secret, she may not reveal or even known certain facts or preliminary findings. It will be more likely an examination of the background safety situation in general. Be assured that Spanair and everyone involved with their fleet is being scrutinized now.
I think that eventually the public pressure will mount enough that more information will have to be released one way or another (think "sources close to investigation").
However, since the investigation is under judiciary secret, she may not reveal or even known certain facts or preliminary findings. It will be more likely an examination of the background safety situation in general. Be assured that Spanair and everyone involved with their fleet is being scrutinized now.
I think that eventually the public pressure will mount enough that more information will have to be released one way or another (think "sources close to investigation").
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sevenstrokeroll,
I think you might be right. I'm no systems expert but a non-functional
RAT probe to me looks as if could cause ALOT of problems.
Attached below text is from MD80. The schematics is from B717, I'm unsure
if the system is identical on the two types but I assume they atleast are
similar.
XPM
I think you might be right. I'm no systems expert but a non-functional
RAT probe to me looks as if could cause ALOT of problems.
Attached below text is from MD80. The schematics is from B717, I'm unsure
if the system is identical on the two types but I assume they atleast are
similar.
XPM
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[sevenstrokeroll] BUT HERE IS THE RUB...if the Mechanic disabled the current to the RAT PROBE HEATER and did not recognize the problem with GROUND SHIFT MECHANISM...
YOU MIGHT LOSE THE TAKEOFF CONFIGURATION WARNING!!!!! THIS WOULD ALLOW YOU TO ATTEMPT TAKEOFF WITHOUT SLATS/FLAPS!!!! IF THE PILOT FORGOT,there would be no warning.
THIS MIGHT be a viable scenario!!!
YOU MIGHT LOSE THE TAKEOFF CONFIGURATION WARNING!!!!! THIS WOULD ALLOW YOU TO ATTEMPT TAKEOFF WITHOUT SLATS/FLAPS!!!! IF THE PILOT FORGOT,there would be no warning.
THIS MIGHT be a viable scenario!!!
from T2 to the 36s (especially R) is a long taxi. I'm not familiar with the procedures, but it appears that setting the flaps is executed after delayed start checklist.
So, with your (professional) speculation about mabye losing the config warning and my (slf) FACT that there is in my 3 yrs flying the carrier to/from madrid now the possibility of single engine taxi out procedure, calling for late configuration on an already delayed flight, it is a scenario that can line up some of the holes in the cheese.
Last edited by CecilRooseveltHooks; 23rd Aug 2008 at 17:34.
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The preliminary results and the full report will be found here when available:
Relación de accidentes e incidentes. Año 2008 - CIAIAC - Ministerio de Fomento
Relación de accidentes e incidentes. Año 2008 - CIAIAC - Ministerio de Fomento
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The pilot was well aware on conversation with the technician what the problems with the probe could be and one would like to believe that he was attempting a fully manual T/O or, at least, was wary of the readings coming from the RAT probe.
If the wrong fuse was disconnected or the failure that led to the (reportly) "overheat warning" of the heating device was more severe than thought therefore rendering Outside Air Temperature readings unreliable and assited automated take off mechanisms were being used, do MD-82 pilots believe it could have affected the thrust calculations to the point of severe danger w/o the pilots noticing?
If the wrong fuse was disconnected or the failure that led to the (reportly) "overheat warning" of the heating device was more severe than thought therefore rendering Outside Air Temperature readings unreliable and assited automated take off mechanisms were being used, do MD-82 pilots believe it could have affected the thrust calculations to the point of severe danger w/o the pilots noticing?
Last edited by justme69; 23rd Aug 2008 at 14:41.
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XPM, from what we know, it was the anti-ice/heating system of the RAT probe to have problems, so it has been switched off. In such a case, the RAT is supposed to be working normally unless ice form to prevent that.
Otherwise, please explain why it could case "a lot of problems", as just an abridged and highlighted manual section doesn't help in that.
Obviously, nobody at this point can exclude that any pre-existing fault, and/or the engineer actions, are indeed related to the crash.
It is simply that there is no direct indication of that being the case, anything else is pure speculation at this point.
Otherwise, please explain why it could case "a lot of problems", as just an abridged and highlighted manual section doesn't help in that.
Obviously, nobody at this point can exclude that any pre-existing fault, and/or the engineer actions, are indeed related to the crash.
It is simply that there is no direct indication of that being the case, anything else is pure speculation at this point.
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Report Timing
Since some have asked.
We can expect a preliminary report after 30 days, as stipulated by ICAO Annex 13.
This first report will usually have nothing to say about causes, only statistical information about aircraft involved, persons involved, number of fatalities and injuries, timeline (as far as known), a narrative about what happened, and what has so far been investigated, and what is being investigated in the future.
Interim reports are published when something substantial and interesting to the public has been found, the final report takes however long it takes to tie up all loose ends.
Urgent other information, not necessarily interesting for the public, will be made available to manufacturers, operators, and relevant rulemaking bodies.
Reports must be made available in one of the ICAO working languages (English, Arabic, Chinese, French, Russian and Spanish). For high-profile accidents in non-English-speaking countries, English translations are often made available. In this case, the NTSB may provide a translation, but the original version will be authoritative.
Bernd
We can expect a preliminary report after 30 days, as stipulated by ICAO Annex 13.
This first report will usually have nothing to say about causes, only statistical information about aircraft involved, persons involved, number of fatalities and injuries, timeline (as far as known), a narrative about what happened, and what has so far been investigated, and what is being investigated in the future.
Interim reports are published when something substantial and interesting to the public has been found, the final report takes however long it takes to tie up all loose ends.
Urgent other information, not necessarily interesting for the public, will be made available to manufacturers, operators, and relevant rulemaking bodies.
Reports must be made available in one of the ICAO working languages (English, Arabic, Chinese, French, Russian and Spanish). For high-profile accidents in non-English-speaking countries, English translations are often made available. In this case, the NTSB may provide a translation, but the original version will be authoritative.
Bernd
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sevenstrokestroll, based on you experience, in case of ground/air sensor failure, what other indications (if any) beside "RAT probe overheat" are given to deck or somewhere else ?
Also what is the flow (must be indicated in the maintenance manuals I guess) that a trained engineer shall follow in presence of the alarm above. It seem obvious that the working of the air/ground logic must be confirmed before assuming the heating system is faulty, and a certfied engineer would follow this logic even without consulting the manual.
Also what is the flow (must be indicated in the maintenance manuals I guess) that a trained engineer shall follow in presence of the alarm above. It seem obvious that the working of the air/ground logic must be confirmed before assuming the heating system is faulty, and a certfied engineer would follow this logic even without consulting the manual.
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RAT Probe....
Hi guys,
I'm 6 hours behind on your guys, so I'm always behind on answers.
To the poster whom asked about exactly what probe they were referring to.
If the captian indeed mentioned that a light came on, it would indeed be the RAT probe as no other temp probe malfunction is indicated by caution lights. The PITOT/STALL HEATER OFF caution light may be a possible light.
But, this caution light would not come on if the plane thought it was in airborne mode and started heating the plane on the ground. The light does not illuminate either if after the plane is airborne the RAT heating fails to illuminate. coincidentally a year or 2 ago, we focused on this system as it's circuitry is very complex, causing this light to illuminate in situations where the systems manuals would lead you to beleive it wouldn't. But the whole point of checking the current to the probe in the after TO checklist is that the system will not trigger the caution light if it fails to heat.
So with the current info I can't even suspect that the plane was in air mode. If it was, there would have been clues to that from earlier on. BUT !....if it was, if memeory serves me correctly they could also have problems in retracting the gear. This explains their decision to abort the N-1 takeoff. Max weight, engine failure and a gear that fails to retract???
In that case, we are talking about the wrong probe. Because the caution light DOES illuminate if the rudder limiter, pitot/static heats and AOA vanves fail to work. But on the other hand, it has nothing to do with being on the ground or airborne.
So you understand that I find this situation VERY vague. As someone also mentioned I find it unreasonably vague. In 2 days' time someone must know what light it was and what system it was. These explanations just don't make sense to me. In other words "I smell a rat". If it's there or net remains to be seen.
So being in airborne can make the crew decide to come back down, but I don't see any evidence that they could have been in airborne mode.
Xander
I'm 6 hours behind on your guys, so I'm always behind on answers.
To the poster whom asked about exactly what probe they were referring to.
If the captian indeed mentioned that a light came on, it would indeed be the RAT probe as no other temp probe malfunction is indicated by caution lights. The PITOT/STALL HEATER OFF caution light may be a possible light.
But, this caution light would not come on if the plane thought it was in airborne mode and started heating the plane on the ground. The light does not illuminate either if after the plane is airborne the RAT heating fails to illuminate. coincidentally a year or 2 ago, we focused on this system as it's circuitry is very complex, causing this light to illuminate in situations where the systems manuals would lead you to beleive it wouldn't. But the whole point of checking the current to the probe in the after TO checklist is that the system will not trigger the caution light if it fails to heat.
So with the current info I can't even suspect that the plane was in air mode. If it was, there would have been clues to that from earlier on. BUT !....if it was, if memeory serves me correctly they could also have problems in retracting the gear. This explains their decision to abort the N-1 takeoff. Max weight, engine failure and a gear that fails to retract???
In that case, we are talking about the wrong probe. Because the caution light DOES illuminate if the rudder limiter, pitot/static heats and AOA vanves fail to work. But on the other hand, it has nothing to do with being on the ground or airborne.
So you understand that I find this situation VERY vague. As someone also mentioned I find it unreasonably vague. In 2 days' time someone must know what light it was and what system it was. These explanations just don't make sense to me. In other words "I smell a rat". If it's there or net remains to be seen.
So being in airborne can make the crew decide to come back down, but I don't see any evidence that they could have been in airborne mode.
Xander
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Something that struck me after the SIA disaster (dep on wrong runway), the Paris Concorde crash and again after the Comair, Lexington crash is why in this day and age it is not a requirement for all major airports to have F/T video recording of all runways / taxiways.
It does seem quite incredible that such an obvious AND CHEAP technology is not already mandated. When there's a crime on the High St or even a theft of a can of beans from your supermarket, the first thing the police / investigators do is pull any available CCTV footage. The Paris accident investigators were left begging for images from any passengers in the terminals who might have snapped a picture or a passing truck driver who happened to be handy with a video.
Granted this would not be a 'catch-all' solution, but video images for the investigators would be a simple yet giant step forward from where we are now.
It does seem quite incredible that such an obvious AND CHEAP technology is not already mandated. When there's a crime on the High St or even a theft of a can of beans from your supermarket, the first thing the police / investigators do is pull any available CCTV footage. The Paris accident investigators were left begging for images from any passengers in the terminals who might have snapped a picture or a passing truck driver who happened to be handy with a video.
Granted this would not be a 'catch-all' solution, but video images for the investigators would be a simple yet giant step forward from where we are now.
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cecil...you make a great point...funny, if I had a full plane and it was hot in spain, I would start both engines just to keep the plane cool (air conditioning)
el#
if all human beings did everything correctly, we would have very few airplane crashes. I can't tell you what the mechanic did...he may have done everything perfectly...but with the only thing involved in mx items prior to take off being the rat probe, I had to come up with a failure path.
it has taken a few days to finally decide that the item in question was the RAT probe...before, some were calling it "an air intake valve"...which I have not heard of
as to the "other" things that might show up...I will stop for now and wait for the report
I've given one possible scenario involving the RAT probe which could possibly lead to a takeoff without flaps/slats extended.
it is just a scenario and may prove wrong
I DO ASK all my fellow pilots to always check the "killer" items just prior to takeoff...and that includes flaps/slats and trim
among other things
el#
if all human beings did everything correctly, we would have very few airplane crashes. I can't tell you what the mechanic did...he may have done everything perfectly...but with the only thing involved in mx items prior to take off being the rat probe, I had to come up with a failure path.
it has taken a few days to finally decide that the item in question was the RAT probe...before, some were calling it "an air intake valve"...which I have not heard of
as to the "other" things that might show up...I will stop for now and wait for the report
I've given one possible scenario involving the RAT probe which could possibly lead to a takeoff without flaps/slats extended.
it is just a scenario and may prove wrong
I DO ASK all my fellow pilots to always check the "killer" items just prior to takeoff...and that includes flaps/slats and trim
among other things
With the recent discussion on the RAT probe, I restate my questions in #576 (page 29) relating to the TAT probe = RAT probe.
…. is TAT (RAT) used in the calculation of thrust in the MD?
Is the standard MEL practice for isolating the RAT probe via a breaker, if so what breakers are adjacent to RAT?
…. is TAT (RAT) used in the calculation of thrust in the MD?
Is the standard MEL practice for isolating the RAT probe via a breaker, if so what breakers are adjacent to RAT?
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@el
Like I said, I'm no systems expert and don't know how the
CADC and Thrust Rating Computers utilizes the information
it gets from the RAT probe. However, I assume that feeding
these computers with the wrong/none information on temperature
could influence thrust output and airspeed readings/settings etc
which could end up in a stall as it appears has happened here.
Maybe some of the experts can comment on that.
Maybe the RAT inlet got blocked somehow.
Some ground crew left their lunch box in there, tools, gloves, bird - who knows.
Could this trigger the warning light if the airflow got blocked?
XPM
Like I said, I'm no systems expert and don't know how the
CADC and Thrust Rating Computers utilizes the information
it gets from the RAT probe. However, I assume that feeding
these computers with the wrong/none information on temperature
could influence thrust output and airspeed readings/settings etc
which could end up in a stall as it appears has happened here.
Maybe some of the experts can comment on that.
Maybe the RAT inlet got blocked somehow.
Some ground crew left their lunch box in there, tools, gloves, bird - who knows.
Could this trigger the warning light if the airflow got blocked?
XPM
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A more technical explanation of the (reportly minor) maintenance issue performed prior to take off will be offered by the company to the families of the victims today at 6:00pm (5:00pm GMT).
One of the passengers have been "downgraded" (got worse) to the very serious condition cathegory, meaning 4 people are still potentially in danger (up to 9 are, but it would be unlikely that any of the other 5 would get worse).
Although 1 is better, 1 is worse, 1 is the same and 1 is the critical condition patient. Doctors are still hopefull they will not lose any of them and victims will remain at 153 count. Of course, with 9 seriously injured, this is still unpredictable.
Expedited DNA identification of about 100 of those victims are thought to start producing results as early as tomorrow. Spanair started to pay the €3.8m it has agreed as a advanced payments for indemnizations, which insurance company is suppossed to take over after preliminary investigations and are believed to amount to about €50m.
One of the passengers have been "downgraded" (got worse) to the very serious condition cathegory, meaning 4 people are still potentially in danger (up to 9 are, but it would be unlikely that any of the other 5 would get worse).
Although 1 is better, 1 is worse, 1 is the same and 1 is the critical condition patient. Doctors are still hopefull they will not lose any of them and victims will remain at 153 count. Of course, with 9 seriously injured, this is still unpredictable.
Expedited DNA identification of about 100 of those victims are thought to start producing results as early as tomorrow. Spanair started to pay the €3.8m it has agreed as a advanced payments for indemnizations, which insurance company is suppossed to take over after preliminary investigations and are believed to amount to about €50m.
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It appears that there is a degree of confusion as to whether it was the RAT probe heater or the RAT probe itself that was the cause of the initial return to the gate.
However, whichever it was, there's provision in the (FAA) MMEL for either to be inoperative. For the heater, the provision is:
For the probe itself:
(Taken from rev 37 of the MMEL, available here)
Either way, there's a procedure for either case, which if followed should mean there's no impact on flight safety. Given the speed of the turn around I'd guess it was the heater, not the probe itself, which means the scope for subsequent issues is minimal.
However, whichever it was, there's provision in the (FAA) MMEL for either to be inoperative. For the heater, the provision is:
May be inoperative provided:
a) Flight is not made in known or forecast icing conditions, and
b) ER operations are not conducted.
or
May be inoperative provided an independent RAT system is operative
a) Flight is not made in known or forecast icing conditions, and
b) ER operations are not conducted.
or
May be inoperative provided an independent RAT system is operative
RAT/Thrust Rating System
The RAT portion may be inoperative provided:
a) A SAT or Standby RAT indicating System or PMS SAT readout is available,
b) Other Systems affected by the RAT Probe (DFGS, CADC, Thrust Rating, FMS, OMEG, PMS) are considered,
c) Thrust Rating System portion is considered inoperative for the Series 30, 40, and 50 and
d) Procedures are established to verify engine power setting.
The RAT portion may be inoperative provided:
a) A SAT or Standby RAT indicating System or PMS SAT readout is available,
b) Other Systems affected by the RAT Probe (DFGS, CADC, Thrust Rating, FMS, OMEG, PMS) are considered,
c) Thrust Rating System portion is considered inoperative for the Series 30, 40, and 50 and
d) Procedures are established to verify engine power setting.
Either way, there's a procedure for either case, which if followed should mean there's no impact on flight safety. Given the speed of the turn around I'd guess it was the heater, not the probe itself, which means the scope for subsequent issues is minimal.
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To accurately measure the aircraft weight would require additional sensors on the aircraft (there are some aircraft, mainly cargo types, with this feature) and that adds cost and the chance of that system breaking or being in error. So there's no real benefit to such systems.
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Mad (Flt) Scientist
Thanks for you reply. If you do not mind I have a couple of more questions/comments.
Understood, however I do wonder if what you say is correct, why such topic is being discussed so widely in this thread. I have seen so many different figures of estimated weight.
You are confirming what I was thinking however I am still puzzled because the cost of load cell weighing system will be a few tens of thousand of Euro. The measured weight could be compared with the estimated weight adding an additional layer of safety. If the system is broken or in error the estimated weight could be used.
Thanks once more
Thanks for you reply. If you do not mind I have a couple of more questions/comments.
Mainly because experience has shown that estimated weights, averaged across passengers (with the adjustments people have mentioned for time of year and so on), are accurate enough. Bear in mind that there's always an element of conservatism in the way the aircraft performance is calculated, and the standard 'weight and balance' process accuracy is consistent with the methods used.
To accurately measure the aircraft weight would require additional sensors on the aircraft (there are some aircraft, mainly cargo types, with this feature) and that adds cost and the chance of that system breaking or being in error. So there's no real benefit to such systems.
Thanks once more