Unfortunately, there is also a possibility that a faulty WOW switching device MIGHT have resolved itself during the TO roll?

As they say, the devil is in the details and we simply may never know. There is a need for more information but given the condition of the wreckage, there might just not be more data available.

Not likely, as the status change to flight mode was signaled to the DFR soon after rotation was called (still some 20 seconds before the "end" of the accident) and the TOCW alarm didn't sound at all at any time during/after TO.

As it's been explained here by those who know, the sensors (switches) on the gear strut were probably fine and feeding the logic to a large set of relays in parallel, most of which were also probably working fine.

It is a subset of this path that may have been interrupted by either:
-one of the relays not working (i.e. R2-5 coil blew open or switch stuck close)
-or its current interrupted further down (or even before) in the line by a circuit breaker or other cause (i.e. faulty cable, connection, etc).

All these, of course, speculative.

Thank you very much for your posting.

All clear now.

Can you also post more details on the LEFT GND CTRL RELAYS B1-23 c/b?

Is it only one c/b or a whole set of them and this schematic is just simplified?

If it is only one, I guess it was in. 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).

But to be certain, CIAIAC needs to clearly state the nature of the "front wheels flight mode state change" recorded by the FDR. Was it coming from R2-212 D contact?

- If so, the LEFT GND CTRL RELAYS c/b was probaly pushed in.

It would make sense then that only R2-5 was malfunctioning, as it only controls 4 devices, two of which are redundant on R2-6 (radio rack vent) and r2-8 (ac cross-tie). So only the RAT sensor heater and, amazingly and w/o redundancy, the Takeoff config warning, would be affected.

Therefore, little warning signs, hard to diagnoses w/o a good test, and would de-activate TOWS all by itself w/o any other problems (once RAT heater probe is disabled).

-If not, it's anybody's guess, as the +20 systems energized exclusively (i.e. not redundant from the right tire logic) by the 11 relays that this c/b services, are mostly "subtle" or "unusual" (heating, venting, etc) and most are only needed on flight and give probably little warning/signs on the ground. After all, the austrian Mapjet crew of OE-LMM in Lanzarote did take off clean with all those systems switched off ... if the MD-83 is any similar in that respect to the MD-82.

The schematic doesn't show Heating sensor 30-30 details. Could you please post one showing where the fuse that the technician removed would be in the path? Thanks.

WOW logic
 

Thank you, SPA83, for this extraordinary piece of information. It shows that:

1. the air ground mode relies entirely on the left and right nose wheel switches. The two switches are not combined into a redundant logic (Left OR right), they control different sets of logic.
2. The line from the left switch and the switch itself must have been operational to to get the FDR record "air mode" (R2-212).
3. The R2-5 may have got stuck to fail to actuate the take off warning and to set the air data heating off. It may also have become disconnected.
4. There is no cb in this said line, so R2-5 may not have been disengaged by a quick intervention when the RAT heating had to be switched off. Whatever the mechanics did to get the RAT heater of, theres nothing in this circuit that would switch off R2-5.

http://www.elpais.com/articulo/espana/avion/empezo/balancearse/pasajeros/gritar/elpepiesp/20080921elpepinac_2/Tes

google translation


MECHANICAL SPANAIR "There is no cause of the accident"
Philip G. R. was the mechanic who came to repair the damage of the MD-82. "Uploaded by stairs to the cockpit. The captain explained to me that the resistance of the heating of the probe was functioning on the ground, must operate only when in flight. I tried to troubleshoot the failure. I got a fuse and found that the resistance stopped heated on the ground. I consulted the manual Minimum Equipment (MEL) and found that the plane could be despatched and defer the settlement of the problem to a maximum of 10 days. The commander also found that the temperature was corrected. "

July N. is maintaining technician Spanair. It was next to Felipe to repair the plane. "We saw that the heater is the RAT Heating ashore. The commander was with us in the cabin. I told my partner that he had to pull the fuse and see if the temperature fell. We put the sticker inoperable at the scene of fuse when the temperature began to drop. The MEL permitted. All this with the journey of flight and the temperature was not going to be of extreme cold. In that case, it would have crippled the ship. But that damage is not caused directly or Indirect accident. "

Jose Antonio V., head of maintenance of Spanair on the turn that crashed the plane, who was sent to the technicians to repair the damage in the parking lot 11. "An operator of Newco [company responsible for coordinating the flights clue] I warned by radio that the plane had a problem with the test of RAT. Upon reaching the ship, confirmed to me that the technical fault. It was deactivated heating the test and, according to the MEL, the aircraft was dispatched. It can be made if there are no conditions for freezing. In addition, the pilot agreed to the procedure. "

Can't see no circuit to control collision lights on/off in this diagramm. So if they was On it's just coincendence?

2 SPA83 - so it seems no manual stated that technician MUST think WHY something doesn't work right? :mad:

Here is a post discussing it: http://www.pprune.org/rumours-news/3...ml#post4360097

"I told my partner that he had to pull the fuse and see if the temperature fell."



Is that conform with the Aircraft Maintenance Manual (AMM) please ?

So, putting all facts together, this tragicall accident could have been avoited if just one smart brain would have asked why the RAT probe-heating was working on ground.

SPA83 has an advantage over me in that he can scan the schematic. The LAMM schematics are still some of the best in the world and generally nothing is missing and the cross references are all clear and work. 30-30 shows a cb B1-62 "ram air temp & probe heater" via contact of R2-100 the right probe and port heat control relay via contacts of R2-5 via a current sensing transformer direct to the heater element. There is shown one further tap from the cb which is to the Thrust Rating panel power supply.

To answer the question about routine pulling of the Left Ground Control Relay to put some systems "into the air" yes routine, the only simple way. I can't remember if it was a daily item.

Justme69, can you please provide post #, my browser can't open link :(

Sure.

It's post #1280, on page 64. A couple of posts in the pages before that also refer to the issue with the a/c lights.

Well ..., in these THEORETICAL scenarios we are working with, it COULD've been avoided in many different ways.

1) -If the crew would've made very sure the flaps/slats were down.
2) -If the crew would've tested the TOWS system prior to take off.
3) -If the TOWS system wouldn't have failed.
4) -If the crew or the engineers would've figured out that a seemingly unrelated issue with the probe's heater potentially also made TOWS inop.
5) -If the weight/air/wind conditions would've been different.
6) -If a more skillfull handling of the situation on the air would've ocurred.

Etc, etc.

All those, of course, are very big "ifs" and none of them actually "guarantees" that the accident could've been avoided. Except, perhaps, number 1.

After all, the LAPA flight took off clean and the TOWS did sound ...

And a couple of flights took off clean, w/o TOWS, and they still made it alive ...

So there is no single unavoidable cause for the accident. Just a main and very important factor: the flaps/slats weren't out. This big problem means that everything else has to play in your favor if the accident is to be avoided. And that day, the stars weren't aligned, I'm afraid. :rolleyes:

Justme69, i read it (i read all this thread from the very begining, but thanks anyway). And more and more evidencies about human factor (not only pilots, but also technicians and ground workers...) :ugh:

UPS! Same time posting, just couple seconds later! :cool:

Can I dramatise this IF'S a bit?

1) If the crew would read checklist properly?
2) If Spanair would not missed boeing recommendation?
3) -
4) If the engineers would ask WHY before HOW?
4a) If ground worker wouldn't hesistate to ask WHY collision lights are ON?
5) -
6) -
etc etc
:ugh:

Sure, but it's a game that can be played both ways. I.e.

1) If the crew would've carried out procedures as trained.
2) If Boeing would've made sure all operators of its airplanes knew about recommendations after manufacturing.
2a) If air safety regulation bodies would've made mandatory those recommendations.
3) -
4) If engineering manuals gave more clear information to assist diagnosis ...
4a) If Boeing would've developed a knowledge database that could be downloaded on a laptop, type in: "RAT probe heater activates on the ground" and it would respond: check LEFT GRD CTRL RELAY C/B pushed in, check R2-5 relay operative, run additional TOWS check.
5) -
6) -

etc etc

BTW, just to make clear, I think the anticollision lights on the ground is only a sign of a distracted crew not completing parking checklist. It doesn't seem to me related to faults in the circuits, etc.

Also, ultimately, it's all in the hands of the crew. Whether TOWS checks are mandatory or not, if the crew fails to carry out the checklist (i.e. Northwest), then they could as well just skip the TOWS test.

Also, even if not mandatory, and knowing their own lifes are at stake, nothing prevents the crew from making a test more than once a day or once every change of pilots or long stop overs.

Lastly, even if the check is carried out and the TOWS works fine, the crew could still "ignore it" (i.e. LAPA accident). Or the TOWS could fail at any given moment in time, like anything electric. I.e. you test it with the flaps in ... you taxi for 20 minutes to line up ... TOWS fails around that moment ... you forget to deploy flaps ... you take/off.

Of course testing TOWS before each takeoff is the best "solution" as it decreases chances of clean TO a lot ... but still, the only true way to avoid this accident, is making sure the pilots just do not ever attempt to take off without the flaps deployed for sure (as sure as humanly possible).

If they fail to check this, they can just as well fail to test the TOWS, and then all recommendations (or requirements) by Boeing, Spanair or the FAA won't matter at all.

My PERSONAL take on this as an ignorant layman not related to the industry:
-Remind pilots/industry of the "killer items".
-Improve operational procedures so that they are harder to miss.
-Make Boeing build in some more redundancy on this system/more diagnosis (even a little "TOWS inop" light could help).
-Make a requirement that crews perform a TOWS test before each flight.
-Warn/train crews on take offs with wrong wing configurations.

It would also be nice if Boeing improved the engineering support of these older planes (if they are not doing it now) and trained technicians to better recognize TOWS failures.

So we may all be a little safer ... hopefully.

Justme,

exactly, and ground worker (they might decide to start over without refueling) is just another small flagpost God or Fate placed on the (grim) way... :sad:

PS and I belive that this

must be telegrafed to each DC-80 owner RIGHT NOW

PPS me too, but more than 20 yrs ago I used to work on Sukhoi ;)

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.

Dutch Bru,
no, look post #1280.

Also there is no circuits which marked a/c lights on posted diagram.