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Spanair accident at Madrid

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Spanair accident at Madrid

Old 27th Aug 2008, 14:17
  #1061 (permalink)  
 
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For me it's quite sure that the nose was up at that moment.
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.
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Old 27th Aug 2008, 14:36
  #1062 (permalink)  
 
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You are probably right, but ....

Blackboard:

I agree that is what the board stated. They are however being imprecise. I am familiar with that airframe and:

It is the actual composite tailcone that the board was referring to as first detached, because: ...
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.

Sorry it did not get to you in time, cos I know it was a time-consuming task!
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.
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Old 27th Aug 2008, 14:55
  #1063 (permalink)  
 
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PJ2
Time will tell all, and by that time no one will remember who said what on the thread.

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.
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Old 27th Aug 2008, 14:58
  #1064 (permalink)  
 
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"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.
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Old 27th Aug 2008, 15:03
  #1065 (permalink)  
 
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Attenton moderators, here's another post that you can delete

I value a lot of the info in these threads, including expressed opinions.

However I feel that expanding opinions in a specific accident thread to specific fault finding is counter productive albeit causal chain identification is fine.

I specifically believe that it is a waste of bandwidth to argue about accepted certfied standards of operation, design or airport layouts in a specific accident thread. The standards by which this industry operates are way too detailed and complex to nit pick in a wide ranging thread and as such any specific standard needs to be argued in its own dedicated thread free of fault finding
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Old 27th Aug 2008, 15:19
  #1066 (permalink)  
 
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I'm confident the inner tracks are from a car.
They are identical with other car tracks in the area

Either there were there already before the crash
OR, made afterwards by some rescue vehicle or something



XPM
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Old 27th Aug 2008, 15:20
  #1067 (permalink)  
 
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"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."

if the airplane is not tracking straight relative to the wheels (in a drift, sideways, whatever) the nosewheel can very well be a lot outside the main wheels, expecially considering the lenght of the MD82 fuselage. heavy use of rudder while on the ground will put the airplane in a drift, and produce asymmetrical skidmarks where the nosewheel mark is not in the center of the mainwheel marks, expecially on a non-gripping surface like gravel/dirt. easily reproducible with a car.

in the picture there are probably something like 500 meters between the beginning of the marks and the side road/embankment so the swerving is not so tight at it looks in the picture
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Old 27th Aug 2008, 15:21
  #1068 (permalink)  
 
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Am convinced Gianmarko and earlier poster making a simile with a "drifting" car whose front wheels are tracking normally while the rear wheels skid across are correct. The easiest way I can think of putting this across it is to place the tips of the first three fingers of your hand in a triangle shape on a flat surface, the tips being the gear. Make your forefinger the straight, nosewheel track, and your thumb and middle finger the MLG track, and move them forward following the plot of the skid marks from the photograph. It is easy to imagine a plane behaving this way.

Whether by momentum, or rudder, or differential engine power, they seemed to be swinging back to a bearing parallel to the runway but not making it before the gully appeared.

I just don't see how the gear doors could make any such tracks as they would break off and not make a consistent mark all the way down their track. Nor would their track be black.
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Old 27th Aug 2008, 15:28
  #1069 (permalink)  
 
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Grrr

This thread has been a pain in the proverbial for some time, with the usual wild uninformed speculation taking up pages and pages ( never mind that the mods have had several culls ) and now more pages trying to identify marks on the grass. Gentlemen, even if after two or 3 pages of this you do identify the marks , as mere laymen, do you really think you are going to tell the difference between a reverser unlocked/ a stall at low altitude possibly due incorrect config/ screw up following engine failure / loss of rudder control following uncontained engine failure with breakthrough of debris affecting flight controls ? ?
I don't think so either.

Surely the FDR, CVR will yield some clues, flap levers make nice easily identified clicks for investigators to hear, for example.
If there is truly nothing else new to say for chrissake give it a rest , so that those of us looking for any actual new facts/ news don't have to wade through 3 pages of tosh to get to it. Thanks
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Old 27th Aug 2008, 15:45
  #1070 (permalink)  
 
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In a probably futile attempt to put to bed this business about the nosewheel tracks having some definite relation to mainwheel tracks, I can assure you that this would not be the case.

We had a C404 land on the grass, at night in fog (don't ask..) alongside a runway. I walked the tracks left by the gear the next day and was very surprised how the nosewheel track weaved greatly, at times almost touching the mainwheel tracks.

It's a red herring to try to read anything into marks that may or not be the nosewheel track marks in this accident.
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Old 27th Aug 2008, 15:55
  #1071 (permalink)  
 
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I believe what we are looking at with regards the straight deep gouge is the nose gear, the marks running symmetrical to the main gear have to be the gear doors, with respect to your observation XPMorten, the marks change to wards the crash site at the point where the straight line gouge mark reduces, indicating either the nose is lifted or the ground drops. So these clearly cannot be tire marks left by a vehicle, they also appear to start at the point that the straight line commences. Considering how low the MGD run to the ground any digging in of the nose gear would surely present them to the ground as well, thus when the nose gear comes away the MGD marks recede.
However after having now read STRONGRESOLVES post directly below and considering that there appears to be what looks like the reverser end of a engine to the north of the tracks, i think it would do to wait for the report.

Last edited by bia botal; 27th Aug 2008 at 16:07.
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Old 27th Aug 2008, 15:56
  #1072 (permalink)  
 
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I want to remark one thing.

As is stated in the briefing of the investigators, the plane strike tail first. That mean that the plane was flying at a very high AOA when it hit the ground.

We have only few reasons for this.
- That the plane was flying slow for its current configuration.
- Excesive pitch up.
- CG out of limits.
- Something was draging the aircraft, unbalacing it.

I flew the DC-9 long time ago, but I remember one sim lesson in which a reverser got deployed just after Vr. I think that it was my first training related to a reverser failure, and I can remember that the first reaction of the plane was a very strong an violent yaw to the side of the reverser, at the same time the incredible rate of speed loss suprised me, I remember me trying to mantain the correct pitch to climb and hold the speed, but one the things that most amazed me was that the plane tryed to pitch up.

I dont want to make my judgement until the end of the investigation, but I am start to believing that this accident is reverser related.

Last edited by Strongresolve; 27th Aug 2008 at 23:27.
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Old 27th Aug 2008, 16:07
  #1073 (permalink)  
 
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Old 27th Aug 2008, 16:51
  #1074 (permalink)  
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Investigators Look At Flap Settings In Spanair Accident

Findings Dispute Initial Reports Of Engine Fire

In the aftermath of last week's devastating takeoff crash in Madrid,
investigators immediately focused on witness reports of a fire coming from
the left engine nacelle of the Spanair MD-82... but it now appears those
reports may have been inaccurate.

According to the Wall Street Journal, officials are taking a closer look at
the flap settings at the time of takeoff, after determining both turbofans
were making power as the jet sped down the runway at Madrid Barajas
International Airport on August 20.

People close to the investigation told the WSJ that based on components
recovered in the wreckage, along with airport video footage that shows the
plane taking off, there's little evidence to support earlier claims the
airliner's engine was aflame before the aircraft departed the runway at MAD.

153 people were killed in the accident, out of 172 people
onboard.

Authorities warn it's still too early to lay blame on any one factor. Data
from the airliner's cockpit voice and flight data recorders is still being
analyzed, and investigators' jobs are made more difficult by the severe fire
damage to the wreckage.

Given what's known of the accident situation, however -- a heavily-laden jet
that failed to climb out of ground effect, on what should have been a
routine takeoff from a 10,000-foot runway -- investigators say if there
wasn't a power problem, one of the few remaining possibilities is an issue
with the configuration of the plane's flaps and wing slats.

They add it's possible the plane's flight crew was distracted during their
preflight, and neglected to set takeoff flaps... or, they may have received
a faulty indication in the cockpit.

Another possibility -- and one supported by reports the plane swerved off
the runway -- is that the flaps deployed asymmetrically, resulting in each
wing producing different levels of lift. Improper flap settings would have
also been especially problematic if, in fact, the airliner did suffer an
engine problem on takeoff.

Again, investigators stress it's too soon to say for certain if there was a
flap problem on Spanair Flight 5022. In fact, at this stage they are fairly
certain of only one thing.

An earlier defect with one of the plane's outside temperature sensors, that
led the flight crew to abort their first takeoff attempt and return to the
gate for repairs, doesn't appear to have been a direct factor in the
subsequent crash.

FMI: www.spanair.com, www.ntsb.gov, www.boeing.com
aero-news.net
***************
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Old 27th Aug 2008, 16:57
  #1075 (permalink)  
 
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Just a quick experiment.
Right engine thrust reverse deployed during MD80 rotate
in X-Plane simulator. Weather & place like real.
Acf at MTOW, flap 15, N1 92%

7Mb Quicktime movie

I'm no pilot, and this is by no means a very scientific test, but I can
atleast draw 2 conclusions.
1. The right wing will drop
2. Heading moves to the right

XPM
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Old 27th Aug 2008, 16:58
  #1076 (permalink)  
 
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bia botal.
I believe what we are looking at with regards the straight deep gouge is the nose gear,
Despite all I said before - I agree with you 100% - and I've learnt something. From PJ2's earlier sketch of (unusual) MD-80 gear geometry it takes only 7 degrees drift/yaw to put the nose gear outside of the mains. Live and learn Red line is 7 degrees offset.

[IMG][/IMG]
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Old 27th Aug 2008, 16:59
  #1077 (permalink)  
 
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Frangible, Gianmarko. In skid or not, the triangle made for the contact point of the nose gear and the each center of left and right parts of the main is a very well definted triangle; isn't it?. So you could perfectly place the nose gear (supposing no elevation) if you had the right scale, at every situation of the main gear. What can be done for the moment is a quite inexact estimation, but in my opinion quite enough to make clear a very different path.

The composition I made is very far from being accurate, but I think it gets quite clear

[url=http://imageshack.us]

CaptainPlyStation. I'm not trying to conclude a complete identification of the marks from here. But if you are suggesting that concluding the centre marks cannot be the nose gear could need several months from an Official Investigation then you are not giving much hope worth waiting for the real explanation of the accident
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Old 27th Aug 2008, 17:05
  #1078 (permalink)  
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forget;
From PJ2's earlier sketch of (unusual) MD-80 gear geometry it takes only 7 degrees drift/yaw to put the nose gear outside of the mains. Live and learn Red line is 7 degrees offset.
Exactly my point.
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Old 27th Aug 2008, 18:17
  #1079 (permalink)  
 
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Grass tracks

I agree that there's plenty of information to be gained from the tracks;
however, remember that the low-resolution photo taken from a single,
shallow angle that is fueling the current discussion (e.g as shown in 1034)
gives only a tiny fraction of the available information.

The investigators will have a great deal more information from walking the
ground, by measuring the width/depth of the gouges, finding debris and
scrape marks along and alongside the tracks, and seeing which features
are lower and which higher.

XPMorten reasonably convinces me that the light curved marks following
the main gear tracks are from a car, and may be much tougher to make
out in a non-foreshortened photo. Driving over the evidence might not
have been the best plan in hindsight, but remember that the ground is
probably very hard, having been baked for most of the Madrid summer,
and so the effects are probably slight. The hard ground also means that
any inferences that grow out of experience of tracks made on a nice, green
field could be severely awry. I suspect that any visible gouge in this
ground reflects a very violent impact/ploughing action.

(My background is just as frequent SLF, but as an astrophysicist I have
experience of dynamics and (over-?)interpreting faint hints in inadequate
images.

Back to an earlier subthread, I would very much regret losing the chance to
follow discussions on these forums for not being a pro - I have used examples
informed by your collective discussions many times in undergrad classes.)
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Old 27th Aug 2008, 18:43
  #1080 (permalink)  
 
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Driving over the evidence might not have been the best plan in hindsight,
In fairness to those involved on-scene, any vehicle tracks could well have been made before the accident. Unlikely; but possible.
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