When the aircraft made those tracks, it must have been traveling in excess of 130 knots or more. The nose wheel is not particularly effective at this speed while on pavement, and should be even less effective off of it. For the nose wheel to remain in a visible straight line while all else rotates around it, would take incredible energy (proportional to the distance between the nose wheel and the actual center of rotation of the aircraft). I imagine the spoilers being out...adding to the weight felt over the mains and contributing to the lightened nose. The nose wheel was probably physically on the ground, without enough down force to leave any track (or to affect the lateral handling of the aircraft).

That means that although it swerved you shouldn't expect wild giration on that piece of grass. Beleive me that is a short distance for an MD80 travellen in excess of 100 knots. Probably a quick swerve and correction before going down the edge. I guestimate he wasn't on there for more than 5 or 6 seconds.

Xander

How does one command an aircraft to swerve like that?

Whatever fell from the plane (the third track) gives us a clue as to the direction of the velocity vector of the aircraft, at the moment the object separated from it. It looks like they were using rudder (the only control that would account for the curved tracks), however it appears that all that was happening was the aircraft rotating around it center of mass while the velocity vector of the aircraft remained aimed helplessly at the ravine.

It looks like there may be a slight bit of evidence of nose wheel contact. Look just left (and above) the two yellow jacketed fellows in the foreground, just inside the left main track. That is where I would expect the nose wheel to be, if it were making a track.

http://i21.photobucket.com/albums/b270/cumpas/mad1.jpg

Based on the observation on the distance between the begin of central and side marks on vegetation, one may think that in fact, a/c nose touched first.

This is a possible explanation for this distance to be shorter than the "wheelbase" of he a/c itself, as mentioned above.

The central mark appears to be wider at the beginning. That could indicate nose gear has collapsed immediately so the forward fuselage hit and began sliding. Weight to this area was then relived by main gear getting on ground, hence the mark becomes narrower and less distinct.

I've to say I'm a bit puzzled by the relatively tight yawing, occurred when the plane had three points on the ground already, and wings level as I hypnotized before. Not able to imagine if strong rudder action could have caused that but do not seen any other explication.

lomapeso,

beleive me, at that point these guys were using max rudder deflection of the ground top aim the nose back to the left. Maybe the poor crew stood up on the left brakes, maybe even tried tilting the steering tiller. Point is, there are SO many forced working on that plane at that time, and so much mass that it is nothing more than just going along for the ride.....

I am trying to grasp in what conditions the plane would end in a nose right slip. You should see me with my imaginary controls in my hand and looking over to the left as I imitate a nose right slip condition. Of course in a normal situation left rudder and right aileron would give you that result. But it's quite a feat to imagine what could have gone wrong to get it in this slip.

Does everybody somewhat agree with me that if the MD took off without flaps/slats as we mentioned as a possibility, the plane would have acted more violently if placed in a slip like that? E.g. one wing stalling?? I'm still not very convinced about the slatless TO theory. Both for this and for the total distance travelled. I'm going to far out on that limb now.....let me get back to the bark.

Xander

Go Back a step
 

The TR theories are only possible as a cause if it was the #2 engine. Problem is, from the picture angle of the engine which had TR deployed it is not possible to determine WHICH enegine that was. Please correct me if I am wrong here or if there are reliable reports as to which engine that was.
Regarding terrain, it seems a no-brainer to me that this area should have smoothed and the stream diverted or submerged. This is not a huge project and really shoud have been done IMHO. THe comparisons with LHR are not entirely relevant because, as a legacy field, there are many things which cannot now be chnged. Also, one poster suggested that they normally build hotels in such places. I am not aware of any airport anywhere with hotels built between parallel runways. Again, please correct me if I am wrong.
I believe the inevitable litigation will make much of this, although Europe is not the US. The risk of litigation alone would ensure that no such terrain would exist at a US airport between parallel runways.

There are many, many airports all over the world that have all kinds of obstacles, buildings, and even water hazards very near the runway.

I think it would be difficult, if not impossible, to mandate that all unused lands near a runway must be perfectly flat. If you could, how far out would you consider safe?

PVG, TPE, SIN and MCO come to mind immediately, they all have hotels in the terminal between parallel runways, I'm sure there are many more.

One thought that has been expressed in some earlier posts is to have smoothed out the so-called ravine. It most likely can’t be made flat, as some have suggested, because the topography of the whole area slopes downwards to the right (east). The right hand runway, 36R, is about 25m lower in elevation than the left hand runway used by the aircraft, 36L, at a point abeam the aircraft’s final resting place.

I’ve looked at getting a cost for smoothing out the so-called ravine a few times, and it is hard to estimate accurately as I am using only Google Earth for topographical data. Plus costs on airports in capital cities have a habit of being anything up to three times higher than in rural airports due to the multiplicity of services, authorities, work constraints, etc. However what I’ve got so far is the following.

To make things smooth, we need to fill in the ravine. This ravine carries a river which is obviously part of the airport and area drainage system, so it needs a main stormwater drain to be installed to carry the river water, and then the ground to be filled in above the drain. We need 2.5 km of main piped stormwater drain for the river between the two runways and extending around the end of 18R, and another 1 km of pipe drain for the smaller river that flows between the runways about halfway along the runway. My cost estimate for those two stormwater pipe drains is US $20 million. We also need a large amount of fill to cover the drainage pipes and to smooth out the terrain. A really approximate guess, using Google Earth data, is that 2 million cubic metres would be needed. That could cost anywhere between $20-70 million depending on haulage distance and cost of quarry/fill material in Madrid. Then add in design, contract administration, and contingencies, and the sort of cost to smooth the terrain is about US $100 million. That could of course be more because of the urban factor.

That is a lot of money. My concern, and this has been expressed by other posts, is where do you stop making the area around an airport smooth? Here, and assuming we do make the ground smooth between the two runways, albeit at an overall slope of 2% downwards, let us look to the left of the runway. The ground rises at a gradient of 9% for some 500m. There is also a small ravine on the left about halfway along the runway. If the aircraft had gone off to the left, and assuming it missed the ravine, I would have thought the aircraft with a tricycle undercarriage configuration travelling at say 160 knots diagonally up a 9% slope over grass would still be rather likely to break something or wobble and clip the ground with a wing. The chance of a crash and fire is significant, and the success of a diversion to the left is not assured. So do we remove that hill? And what about the end of the runway, and running over the end. Maybe we need to extend the RESA of this already very long runway. And don’t forget the distant high ground to the north of the runway; maybe we need to level some of those distant mountains. Where does the work stop?

The answer IMHO is the balance between risk and cost. Despite this tragic accident, if I look at the collective risk for airline passengers in Spain and relate it to individual risk, it is still below the accepted individual risk level. The Dutch government assessed the individual risk level of 1 x 10E-6 as that which would trigger effort to reduce risk (from the Schipol accident, 1992). Even after this accident, Spain is below this, and as such effort is probably not justified to further reduce the risk.

Bringing the argument back to ICAO rules, I suggest that despite this accident, the cost to reduce the risk by smoothing the terrain beyond ICAO requirements is not justified by the reduction in risk.

There remains the test of negligence. For risk analysis, this is prefaced by dictum of the former Chief Justice of the High Court of Australia, Hon. Justice Gibbs, who in determining negligence on the handling of risk stated:
“Where it is possible to guard against a foreseeable risk which, though not perhaps great, nevertheless cannot be called remote or fanciful, by adopting a means which involves little difficulty or expense, the failure to adopt such means will in general be negligent.”
IMHO by meeting ICAO standards, as it seem evident that Madrid does, it means the risk of this tragedy is remote. Furthermore my cost estimate shows that to guard against it involve great expense and some difficulty. So no negligence could be attached in the handling of risk.

IMHO, the buck stops if an airport meets the ICAO rules. I reckon ICAO rules are a very good balance between risk and cost, and they have stood the test of decades of time.

Take a look at where you would expect the right wingtip to strike, back at the start of the tracks. Is that it?

Wouldn't that put the nose gear right about where the third track starts? Where it obviously broke off on contact and held it's expected natural direction afterwards. If it would have still been attached it would have left a very un-straight track.

philipat,

Maybe a bit off-topic but the clear winner in the "obstacles between the runways contest" is DMK (formerly BKK):

Google Maps

Yep, that's a golf course between the runways... ...fancy a golf ball or two between the fan blades?

I arrived at the same guesstimate.

OverRun Input
 

Thanks for the comprehensive professional input and I stand corrected. The scope of such work is not immediately obvious to a non-professional. Your Risk/Reward logic and legal persective is also vey clear and understandable.
I apologise for the ignorance and it would seem that this issue has now been comprehensively closed. Thanks again for taking the trouble to elucidate.

I would like to ask the golden question to pilots of MD-82 or similar planes.

In your opinion, *assuming perfectly working engines and no reverser deployment*, *assuming no windshear*, and assuming said airplane took around 500m more of air strip than estimated as normal for its
(pretended) configuration to lift-off (i.e. it took longer to accelerate to speed than predicted or it rotated for longer than "it should've" or a combination of both, etc), what is the most likely cause of a fully loaded airplane like that being able to become airborne for 3-5 seconds but yet just "fall" after rolling left & right and w/o an experienced crew being able to do much about it on time?

Again, let's assume both engines were working properly and reversers were never deployed, just for the scope of this question.

Thank you in advance.

My last post for this topic:

Try fitting the same triangle, like plotting, to those marks and then check what you get.

What could have brought here down excluding engine problems? Controllablity issues rising from operations near stall conditions (flaps/slats retracted) or maybe a tail shear of 20 to 30 knots. But this couldn't be the case as there was no storm and mountainwave turbulence tends to be a bit less hit and miss. Other than that I can't think of anything more.


Xander

LuckyStrike;
Here's a schematic of main gear to nosewheel, width-to-base measurements on the MD83 -16' wide by 72' long, approximately, illustrating the ratio of length to width - I believe there was a question earlier in the thread about this.

Because the image of the tracks is viewed from an angle it's not possible to accurately template a triangle (such as the one below) onto the jpg image of the main gear tracks. I remain open to the "engine alternative" of course - any other stance or certainty at this time is foolish. For me it fits for the reasons I give, for others it looks like an engine track - the large item to the port of the track (to the right in the photo) looks to me like an engine cowl but again the photos are quite poor in resolution.

Time will tell all, and by that time no one will remember who said what on the thread.

http://img222.imageshack.us/img222/9...arratiosv8.jpg

Well, I just cannot comment on the 3rd mark (the one that follows a straight path) because it can be a number of things, as you and others have mentioned. What I am arguing here is that I find it hard to believe it was the nosewheel which left out that particular pattern on the ground.

PS: This was the real last post :} Thanks for the LVL discussion :ok:

LS;
LOL!...hearya. Take care.