On page 5 it says that at rotation the DFDR captured the change of signal from ground to air mode originating from the sensor the nose gear (N/G strut ground sense).
Yeap. I included that piece of information in the summary posted.
It is somewhat puzzling, since the report sort-of-implies the failure may have to do with the R2-5 relay not energizing (in last term) the TOWS, noticing how this relay feeds off the N/G strut ground sensor group, but then the DFDR does record a change of state from those sensors from ground to air.
So one of the two:
-The circuit is such that a signal from the front gear sensors go to the DFR prior to reaching R2-5, and it was R2-5 (i.e.) the relay actually failing to energize on the proper conditions (i.e. faulty relay, not faulty sensors).
-R2-5 didn't fail and the TOWS failure is further down the circuit (i.e. L/H GND CTRL RLY circuit breaker, not the relay itself)
Not having the schematics of related circuits, I have NO IDEA WHAT I'M TALKING ABOUT, but the CIAIAC report doesn't help at all to make it clear(er).
So, at least this part did not previously think the plane was in the air when it was still on the ground. This is in my view important for the origin of the TOWS-failure, since apart from the RAT, based on the data available, other parts of the aircraft were sensing that the plane was in ground mode when it was in take of run and the TOWS should normally have sounded in this case.
But remember the sensing signal captured by the DFR may have come from an EARLIER part of the circuit, before it affected TOWS energizing. An MD-82 engineer could pbbly shed more light here as to how it works exactly, that is, how can the DFR record a front wheel "up" signal and the TOWS/RAT heater be still inop/affected.
Also, remember that some systems depend on the front gear ground sensor while others depend on the ones from the main wheels.
However, the said draft report also seems to state to me very significantly that the relay (R 2-5) of the RAT (which was switched off) is the same as the one feeding the CAWS of which the TOWS is a part. So "inop RAT" according to MEL is something completely different than switching the RAT off by pulling the C/B, which apparently also directly compromised the TOWS, which is clearly not MEL-covered.
The report, once again, doesn't mention exactly which c/b was pulled by the technician in order to disconnect the RAT probe HEATER (not the RAT probe itself). It seems the procedure was outlined in the manual, so there seems to be a fuse somewhere that you can pull out and leave only RAT heater inoperative.
I guess.
What I also do not understand compeltely is the length of the take-off run stated in the draft report (1950 m) in relation to the airport CCTV-video, where the plane seems to only get airborne just before the end of the actual end (not the paved surface) of the very long runway. Didn't they commence take-off run at the very beginning ?
Yeah, that's a little bit puzzling to me also. Let's see. The runaway is about 4400m, and I believe the last (grey) area before the end is at about 600m (guessing, please someone correct me if this is wrong).
The airplane seems to have reached V1 38 seconds after acceleration commenced. Reached calculated Vr 4 seconds later. For all we know, 15 seconds later it had to be on the air (stick shaker on CVR) and before that the change of state (F/G sensor "up") took place.
It's guessed to have stayed on the air around 7 seconds (go up, roll left, roll right, roll left, roll right, aureal warning says "stall" twice 4 seconds after stick shaker, go down).
Reached 40' and max pitch 18º.
Then the first marks of the plane appear on the ground at about the 3207 meter mark on the runaway (and about 60m too much to the right and at a 16º angle).
So perhaps the report is saying that the length is that used until rotation is called (sensor signals "front wheels on the air"), rather than when it became fully airborne, and it was rotation that actually was found unusually long by the witnesses.
So, it is my guess, that the videos we have seen correspond to the time the airplane is actually FALLING DOWN, rather than "going up". Of course, it's an "erratic" fall down, as it was indeed nose up and trying to elevate, but with each consecutive wing stall (and violent roll) it probably descended a bit and then ascended again (I'm no aerodynamics engineer, just plain old physics, so this may be way off).
Also, the video has some obvious missing frames ...
And I have difficulties to precisely understand the (elaborate part) of the report text that deals with where the thrust reversers were found and in which state.
You are not the only one. Basically it says that both reversers were found detached from their engines. One found with many signs being deployed and the other one not. The picture that showed one of the recovered engines seemed to have it still attached, so it doesn't quite make sense to me what they are saying there either.
Literal translation:
"The reverser system of right engine nº2 was found aprox. 235m from the first marks left by the a/c on the ground and at about 846m from where the main body of the engine was found. The buckets were retracted. The left engine reverser system was found, also detached from the main (engine's) body, at 913m from the first marks of the plane on the ground and 144 meters away from the engine's main body. Its inversion buckets were deployed. Examinations didn't reveal previous mechanical defects." (<-- which incidentaly is also "funny", as one of them was out of service for maintenance, so there must have been something wrong somewhere with it, or, at least, it should've been mentioned in the report).
Once more, not a stellar job on CIAIAC's part, it seems ... Hopefully it'll be more clear on the final preliminary report which, BTW, has been delayed by a week or so, they now say.
Some of the members of the CIAIAC's had resigned, but their resignations have not been accepted by the minister. They have to continue working there against their will.
Judge is not happy with the investigation. He has ordered Spanair to release all maintenance and operational procedures data. He has requested Boeing to supply all current operational procedures and any history of repairs on the a/c. He has requested European Civil air authorities to determine current operational requirements for the a/c.
He is just not trusting CIAIAC, and I don't blame him.
