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Spanair accident at Madrid

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Spanair accident at Madrid

Old 21st Sep 2008, 12:18
  #1921 (permalink)  
 
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strobe lights

Thanks, Justme69 and others for the enlightning info on the RAT-heater and TOWS relay issues.

Concerning the strobe lights, I thought the MD-80's strobes would only come on on change to "air mode" of the signal in the N/G strut, as discussed in earlier posts. I have been able to verify that this is indeed the case as a passenger during 4 SAS MD80/90 operated flights earlier this week: N/W lift-off: strobes on; weight on N/W on landing: strobes off.

So, the earlier question on which relay the strobes are is indeed an interesting one, if (as a mechanic on the ground seems to have declared after the accident) he saw the strobes of HFP working when it taxied away from the ramp for the fatal take-off.
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Old 21st Sep 2008, 13:27
  #1922 (permalink)  
 
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Dutch Bru,
I thought the MD-80's strobes would only come on on change to "air mode" of the signal in the N/G strut
no, look post #1280.

Also there is no circuits which marked a/c lights on posted diagram.
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Old 21st Sep 2008, 13:38
  #1923 (permalink)  
 
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This is UNOFFICIAL information, otherwise known as rumor: Sources leaking investigation details confirm that investigation is centered on failure of R2-5 relay and pretty much specifically discard (don't know the reasons) c/b GND CONT being pulled.

Here is a photo of part of Spanair's official declaration to the judge on the airplane's content:

http://img502.imageshack.us/img502/2...rcargo1ew0.gif

It basically just gives the known number of passengers, crew, PAX+cargo+luggage weight, empty plane's weight, weight w/o fuel, fuel's weight, take off weight, fuel expected to have been used in the flight (17.000 lb), expected weight upon landing (124.863 lb) (1 lb=453gr). Besides the 400kg of fresh fish cargo, there was also 1.095kg of textile products (mostly Timberland).

Landing gears on the plane were frequently serviced on the craft. On Aug 9th parts of the lighting system were also serviced, including "lights at the sides of the landing gear". "Inspection lights of both, left and right side, of the main gears found light bulbs out". "Portable flashlight in cabin, also with a blown bulb". "Light at the end of left wing: also blown bulb.".

Other maintenance actions during August: cockpit security door not able to open with key. First aid kid change requested. The list goes on and on ... Nothing seems relevant, though.

Last edited by justme69; 21st Sep 2008 at 14:01.
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Old 21st Sep 2008, 14:23
  #1924 (permalink)  
 
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Good analysis justme69. I agree with you that if the FDR signal was received at rotation the L gnd control relay CB was in. R2-5 is in air mode when not energized so a failure of the relay would put it in air mode. One of the contacts goes to the position lights, obviously strobes in both position. If the strobes were on on the ground, not anticollision light, R2-5 wasn't energized. Also I had a nose oleo strut overinflated one night and along with strobe lights on the ground I could not reduce power on taxi below flight idle. I am sure they would have noticed that on taxi out. Another relay controls flight idle off the same circuit breaker.
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Old 21st Sep 2008, 14:30
  #1925 (permalink)  
 
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DFDR.......

justme69,

Many thanks for your many enlightening posts!

I agree with you 100% in your reasoning regarding the (possible) failure of relay R2-5 being a factor in this regrettable accident.
I also is convinced that relay R2-212 was working.

I flew the DC-9/MD80 series aircraft for many years - although it is 16 years since I flew the types, my memory is still more or less intact - I think!

So, therefore this comment/clarification:

You wrote in post #1937:

"It's the one ultimately feeding data flight recorder 31-31, which I'm guessing is the one recording the change of air/ground logic state (therefore, R2-212 was getting the 115VAC, sensed the oleo switch and changed the state of 31-31, so it was also working."

It appears to me that you think(?) that the DFDR starts operating when an airborne condition is sensed by the L oleo switch (and relay R2-212).
This is not so.
The only thing that happens to the DFDR is the reception of a signal indicating an airborne condition.
The DFDR starts operating when the parking brake is released and continues to operate until parking brake is set again - in order to have data whenever the aircraft is moving on the ground and in the air.
At least it was so on the DC-9.
On the MD80 I am a bit uncertain - I think that it started to operate when fuel was selected to on in the start sequence of the first engine - somebody correct me!


The CVR (23-71) is operative as long as there is electrical power on the aircraft.
The CVR gets a signal when airborne via R oleo switch and relay R2-08.

BRGDS
grebllaw123d

Last edited by grebllaw123d; 21st Sep 2008 at 15:08.
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Old 21st Sep 2008, 14:42
  #1926 (permalink)  
 
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We forgot to set T/O flap once,a long time ago full pax, and from an intersection.Rotated,obviously weren't going anywhere.If it hadn't been for the FO's clear and anxious communication I often wonder how it would have turned out.Not much time to play with!
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Old 21st Sep 2008, 14:45
  #1927 (permalink)  
 
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BRGDS,

I was just going to clarify that. I believe the FDR starts functioning on first engine start and the FDR contact on R2-5 is a signal saying the oleo strut is extended. Otherwise aborted take offs wouldn't be recorded.
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Old 21st Sep 2008, 14:54
  #1928 (permalink)  
 
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Strobe lights....

bubbers44,

If you look at the diagram in post #1936 you will see that the position lights/strobe lights are controlled via relay R2-308 and NOT via relay R2-5, which is suspected to be a factor in this accident.

I also think that it was clarified(?) many posts ago, that it was the anti-collision lights (and not the strobe lights) that was observed to be in ON position, while the RAT fault was dealt with.

Brgds
grebllaw123d
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Old 21st Sep 2008, 15:05
  #1929 (permalink)  
 
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bubbers, there is no R2-5 contacts as far as i can see, which goes to FDR. Did you mean R2-212?

BTW it's interesting which circuit is feeded from R2-5 24-22 contacts.

Last edited by Kulverstukas; 21st Sep 2008 at 15:20.
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Old 21st Sep 2008, 15:16
  #1930 (permalink)  
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Raredata

So how did you save the day ?
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Old 21st Sep 2008, 15:19
  #1931 (permalink)  
 
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Pilots were never going to work this all out..it needed engineering input.A GO team comprises specialists in many differing fields.I think Pichu17 was obviously an engineer judging by his posts early on but the help from Wodrick and the schematic from SPA83 have been invaluable.

Last edited by Rananim; 21st Sep 2008 at 23:32.
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Old 21st Sep 2008, 15:20
  #1932 (permalink)  
 
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You are correct. I was thinking of what the CB controlled and typing without having the electrical schematic to reference. A lot of people were calling the strobe lights anticollision lights in this thread. Obviously only the strobes are controlled by the oleo switch so would be the only ones relevant on the ground as to gnd/air sensing. If anticollision lights were on during the return it was because they forgot the switch on.
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Old 21st Sep 2008, 15:32
  #1933 (permalink)  
 
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grebllaw123d, thanks, i see...
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Old 21st Sep 2008, 15:49
  #1934 (permalink)  
 
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Strobe lights - AC cross-tie

I went back into the 1200's series of posts and found that there is indeed no agreement about which exterior lights were on as observed by the ground-technican when the A/C was still on the ground prior to t/o: either the anti-collision lights or the strobes on the wingtips. The first are just put on or off from the cockpit, but the strobes will only start working on N/G lift-off (provided that the cockpit switch is on BOTH (pos+strobes).

If the R 2-5 relay installed were to be of a certain type, it has already been subject to Boeing Alert SBs and FAA AD's in the early 2000's because of unreliability issues with potentially serious consequences (E/B fire or in case of engine failire not connecting certain circuits linked to the generator of the failed enginewith the generator of the still working engine, i.e. the essential function of the AC cross-tie). The latter makes me still wonder about the earlier reported witness statements indicating engine failure and what is stated in the draft report, namely:
1.the apparent excessive length of the runway covered by HFP before rotation,
2.the apparent fact that both engines were producing thrust during take-off run and for the remainder of the flight and
3.the statement that the first visual inspection of the engines didnít show pre-crash anomalies.

One of the issues of a non-functioning AC cross-tie relay in case of engine failure seems to be that the electrical circuits fed from the generator of that engine may cease to work, freezing e.g. the EPR reading of that engine in the cockpit and not giving any master caution warnings in the cockpit either, making it very difficult for the pilots to notice any malfunction with the affected engine (as it apparently did in a DC-9-32 accident in 1994 in Canada, as reported on in TSB A94C0034).
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Old 21st Sep 2008, 15:57
  #1935 (permalink)  
 
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AC cross-tie on the ground

grebllaw123d

The report on the DC-9-32 1994 accident Canada (TSB A94C0034) does not seem to preclude AC cross-tie activation on the ground. On the contrary, AC cross-tie activation would have been essential for correct EPR readings in the cockpit during the take-off roll, giving earlier clues to the f/c that in fact they had an engine failure, the continuation of the functioning of FDR and CVR, as well as the functioning off anti-skid during the subsequent rto

Last edited by Dutch Bru; 21st Sep 2008 at 15:59. Reason: linguistic
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Old 21st Sep 2008, 16:13
  #1936 (permalink)  
 
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Looking back a few pages.........
The fault which caused the return to stand seems to be air/ground sensing failure and not probe heat failure because the probe heat was working. Shouldn't have been working on the ground though.
In that case you could say that the MEL should not have been applied for probe heat failure and that the defect should have been investigated further.
I agree with an earlier post that the FIM (fault isolation manual) should caution about possible other effects associated with the failure observed but having seen how often the FIM isn't used I fear it wouldn't have helped.
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Old 21st Sep 2008, 16:59
  #1937 (permalink)  
 
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ground/flight shift

Many ppruners still seem to go out from a ground/flight shift fault. However, in the leaked draft CAIAC report it said that the FDR recorded the shift from ground to flight when the NLG lifted off on rotation...

And a question to the guys in the know: how is a RAT probe heat fault to be 'isolated'? is there a switch on the IP? or can it only be done by pulling the relevant CB, with the known consequences...
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Old 21st Sep 2008, 17:05
  #1938 (permalink)  
 
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borghha, post #1944
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Old 21st Sep 2008, 17:13
  #1939 (permalink)  
 
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It appears to me that you think(?) that the DFDR starts operating when an airborne condition is sensed by the L oleo switch (and relay R2-212).
Nah, I always had it clear the DFR was working way before the airplane was in "air mode". I had guessed upon release of parking brakes. Incidentally, the DFR seems to have data from many, many flights before this one, so maybe other diagnosis are possible (i.e. did the switch to "fly mode" recorded by it ever failed, etc).

It's just that we don't know for sure what the CIAIAC means by "a sensor in the front wheels changed state to air mode". We can only guess they mean what we think they mean, as discussed before (i.e. R2-212-D).

But good reasoning.

I also agree that a "possitive, reverse logic" TOWS is in call in new airplane designs.

You push the handles and a voice comes up: "TAKE OFF CONFIG OK".

If you don't hear anything: TOWS are not operative, so you are NOGO.

If you hear: "BEEP - SLATS - BEEP - FLAPS" ... you know what you should do.

I also agree that, technically, MEL was probably not well applied in this case.

Although most engineers would've done the same thing, MEL probably only stated that the airplane can fly with inop RAT probe heater in good weather. It didn't say that a WORKING HEATER could just be disconnected. Also, at somepoint, somewhere, I read that the technician (from memory, but I noticed the caveat) "isolated the problem to the RAT probe heater .... more specifically to the circuit that controlled when it was on ..." So, perhaps, the technician DID know that the R2-5 or related circuitry was the one producing the problem ... and I don't know why he could've fail to see that it would also affect other non-MEL items.

Of course, if the problem is isolated to ONLY the heater being permanently on for "no reason", then it can be disconected and be done with it.

But that requires better diagnosis.

It's not a RAT probe's heater failure. The RAT probe heater was working just fine (pbbly). It's something else's failure (i.e. R2-5 relay), that is making the heater do something "ahead of time" (i.e. on the ground instead of in the air-only).

Last edited by justme69; 21st Sep 2008 at 17:45.
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Old 21st Sep 2008, 17:18
  #1940 (permalink)  
 
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AC X-tie on ground

Dutch Bru, kulverstukas,

I just cancelled my post concerning X-tie.

Reason: I am not sure if the information given is correct.

grebllaw123d
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