md80fanatic: NG track vs MG DOORS
 

It looks like the track you are pointing out is actually dual (faint) parallel tracks that likewise parallel the MG tracks (in fact they go back almost as far as MLG first impact). In that case, such tracks cannot be the NLG, but surely point out to the open (why open?) MLG doors.

As a sidenote, the MLG retract sequence in the MD-80 is MLG door unlock, then open, then MG unlock & retract, then MLG door close&lock. Is that pointing out to something? ...or maybe just the impact unlocked the MG doors?

Now that I think of it, most likely a crew LG 'up' selection, or (-manual unlock and-) loss of hydraulic pressure (due to ruptured engine pylon lines???) or mechanical door mechanism failure would also be required for MG doors to open...someone with an MD-80 manual can confirm?

For what it’s worth – an attempt to identify witness marks etc. Tell me where I’m wrong.

The nose wheel hit at point A and was forced up into its well.
The two parallel lines B, inside of the main gear marks, are caused by the sides of the (probably distorted) fuselage digging through the soil.
At point B the aircraft is pointing directly towards camera.
No 2 engine detached at C and its inertia took it into the ravine.
C is the relatively light intake of No 2 engine.( Sorry, it's the C on the right :bored:)
D is the detached Tail Cone.

[IMG]http://i21.photobucket.com/albums/b2...pas/mad3-1.jpg[/IMG]

Witness markcs
 

That would imply a major structural MLG failure and hence many more marks. The fact that they are parallel to the MLG tracks with the aircraft turning implies they are located at a similar FS (fuselage station) as the MLG. Such defined marks are surely the lower parts and/or skids of the (open) MLG doors.

Perhaps, but I doubt it. I'd say fuselage.

[IMG]http://i21.photobucket.com/albums/b270/cumpas/mad4.jpg[/IMG]

Can you ellaborate why?

Wrong.

Yes. As both main gears were intact the landing gear doors would leave no marks.

[IMG]http://i21.photobucket.com/albums/b270/cumpas/mad5.jpg[/IMG]

Explanation picture from a spanish forum:

Se sale de pista un Spanair en Barajas - Página 46 - Foroaviones

http://www.g-sims.com/spaw/images/te...febarajas3.jpg

blackboard, I see now what you are getting at. If the Main Gear doors unlocked due to impact they may, indeed, leave the marks we see.

[IMG]http://i21.photobucket.com/albums/b270/cumpas/mad6.jpg[/IMG]

MLG Doors
 

We are talking INBOARD MLG doors (non-existant on 737 and A320, which may be confusing you), not the OBD ones visible in your (second to last) pic.

They are closed and thus not visible in your (second to last) picture above. Find a pic with them open and you will see what I mean.

Edit to say: just saw you did find a picture, thanks!

Notice that the two fainter parallel lines (perhaps MLG doors?) commence at exactly the same point that the broad straight mark (perhaps starboard engine detatching itself?)

Thus engine separates at the moment nose the wheel collapses.

Still unsure how the straight line exists - it suggests engine "follows" path of aircraft slightly behind it??

Some of the proceedings of the judiciary investigation from the accident, have leaked to the press (as it was expected). It's 700 pages of documentation so far that the judge has put together.

-It shows that all 10 air traffic controller personnel declared not to have received further communication from the Spanair flight after all normal communications relevant to take-off maneuver (permission to take-off, weather, etc).

It's not stated, but it's implied in the article that they couldn't shed much light on the accident (i.e. everything seemed normal to them from the ground until they realised it had crashed). One traffic controller did take a look at the flight "briefly" and had the gut-feeling that it had some "difficulty to lift off".

-So far, the judge has interviewed 39 witnesses, including 6 of the survivors.

-So far, the crew's work schedules etc during the prior weeks seems normal and according to regulations. Same with the ground personnel.

-The accounts of witnesses all match that they felt "some weird movement" (i.e. roll), "some (small) vibration", and "little more" (i.e. everything else seemed normal). Some were interviewed for over 2 hours, mostly about what happened after they crashed and found themselves near (on) the creek.

-Most detailed account comes from the only crew survivor, the flight attendant that declared: "I felt like a vibration, like if the airplane didn't have enough power to go up". Her words match those of other witnesses.

-The security camera footage is brief (7 seconds). No indication of fire/smoke/explosions while the airplane was on the air. Wild estimation on the plane elevation obtained by the judge just from witnessing the tape: no more than 6 or 7 meters, although the angle of the recording is very wide (wide angle) and the airplane only shows in a corner from very far away (therefore, this is just preliminary "wild" speculation, but it tells the judge that it didn't go up too much). There is no audio in this airport recording. The "tape" is in the judge's hand.

-Judge has not had access yet to the air traffic control communications with the airplane, as they have not yet been "deciphered". He has requested a deciphered copy. He has requested the neccesary DVD/MP3 equipment to play them back from the company Seisa. The recording will include the crew's conversation with at least 3 controllers: ground, taxiing and take-off. From that point on, they'll be no more communications received. According to procedure, some 20 (or more) seconds later, ground control would've contacted the pilots to request the tune into Torrejon air control center, usually when the plane reached 300/400 feet (which the airplane, in any case, never reached). The pilot would've normally only contacted ground below that altitude if he had aborted T/O or was planning to go back (turn around) and land. It seems the pilot didn't have time. The plane went up and came back down in at most 7 seconds (other sources speak of no more than 6 seconds maximun since the wheels leave the ground until the plane touches the ground again). I guess we can assume, until more information is known, some 3-4 seconds going up and 3-4 seconds falling again.

-The judged also received the official statement from the technician that did the prior repairs.

-Police was ordered to guard the airplane remainings at the site for the duration of the investigation, allowing the technicial investigators to pick up or look at the pieces.

-Only both "black boxes" and both engines (fairly intact) have been transported from the crash site to other facilities. One clearly shows the reverser deployed.

this is what i see...

using the picture in this post (http://www.pprune.org/rumours-news/3...ml#post4353744) as a reference, it looks like blackboard is correct about those tracks (marked A) being for the MLG doors. the lines are not as straight forward as the tracks known to be from the MLG and i would suggest these lines were caused by something which could move side to side (the doors?). the fact that they do not appear or disappear at the same point as the MLG itself could be due to differing terrain height and shock absorption from the suspension, not necessarily a nose gear collapse.

the high aspect photo provided by forget proves something i was suspecting a while back, none of the marks could come from the nose gear due to the width. a nose gear track will be approximately half the width of a main gear track.

just to try and put into perspective the picture, i have played a little with google earth. judging by the angle of the picture of the airplane skid marks and by how runway indicators are aligned. there should be over 500metres between the edge of the rwy and the side road/embankment

so the angle of the skidmarks is very compressed by the lenses used

http://gianmarco.dyndns.org/varie/skidmarks.jpg

The straight track surely cannot be the NOSE GEAR. Given the obvious MAIN GEAR track, it is purely geometry to know where the nose was at every moment, and it's path would also a curve; it can be easily deduced it cannot be the straight track of the image. (And never mind the possible drifting, of course).

If I knew how to attach an image I would post a somewhat approximate drawing

For me it's quite sure that the nose was up at that moment

"The straight track surely cannot be the NOSE GEAR"

it cannot be anything else. i can guarantee you from personal experience that it is perfectly possible for a tricycle airplane to skid laterally and leave that type of assymmetrical marks

YouTube - Very bumpy landing

do you really think this errmm.. "landing" left parallel, symmetrical skidmarks? :-)

They may as well been open as the pilot commanded gear up, and the sequence starts with opening the doors, but never came far enough to unlock and retract the gear itself.
However, I would assume that the LDG doors would have been torn off if they plow the ground and leave such marks.

Highly unlikely. A JT8D, without accessories, reverser and cowlings, weighs over 4,000 pounds. Remove that from the far back end (when the engine separated) and the nose will come down fast - whatever the tail plane may be trying to do.

You are probably right, but ....
 

Blackboard:

I reckon you are probably right. Nevertheless, (and this is a more general observation), I do believe that we should at all times make a clear distinction (ie, for our fellow, non-spanish speaking forum-readers) between what was actually said in Spanish and our own interpretations based on our expertise, how skilled the latter may be.

When CAIAIC in their press conference states that "it is the entire part after the pressure bulkhead which came off" then I believe that a translated transcript of that conference should state so, how ambiguous and/or unclear such statement may be. Our own interpretations of what they probably meant can be included, but not without making a clear distinction between the two (translated transcript / interpretation).

This might be 'splitting hairs' but I honestly believe that it is important, for the sake of this discussion, to accurately reflect even the tiniest details.

My remark was not meant as criticism, more as an example of my own stupidity. I have yet to fully understand how this board works and locate posts rapidly. I never saw your post # 1012 as a result of this.

PJ2

I sure hope so

Somebody mentioned the camera distortion of the track marks. This is critical to our discussions so mayby somebody can graphically undistort them on a Google image

As to the swerve, I am interested in the forces involved so here are my challenges to any theories

Can you do this with rudder alone at these speeds and over this distance?

can you do this with nose wheel steering in dirt?

Can you do this with a single engine reverser activation?

Can you do this with a wing tip walk in the dirt from side to side?

My gut feeling is that side forces necessary to swerve this much are not obtainable along the fuselage centerline (nose gear, engines, rudder) but I await further discussion on this.

"The straight track surely cannot be the NOSE GEAR"

"it cannot be anything else. i can guarantee you from personal experience that it is perfectly possible for a tricycle airplane to skid laterally and leave that type of assymmetrical marks" By gianmarko


Well, assymmetrical marks can be most of the times if you want, but if you have the position of the main gear at every moment, you will ALWAYS know where the nose gear is, unless it is spread off. Actually, if the aircraft would be a lot shorter those relative marks could be possible.

But really, you could deduce at every point which is the possible position of the nose gear (regardless its elevation). I have made a drawing but don't know how to post it.

A possibility would be the last part of the aircraft body, after the main gear. It seems much easier to have created those marks.