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Spanair accident at Madrid

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Spanair accident at Madrid

Old 27th Aug 2008, 22:13
  #1101 (permalink)  
 
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Telecinco seems to have some errors. First the speeds. Second it says that the airplane never get airborned. Why then the discontinnued wheels track at the beginning of the out of runway excursion?
I see this accident very similar
http://www.ntsb.gov/publictn/2004/AAB0401.pdf
PS
I have seen the wheel marks live and are exact to the ones in the photographies
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Old 27th Aug 2008, 22:19
  #1102 (permalink)  
 
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Why on earth would anyone be calculating take off speeds in KPH?
A journalist might to make it easier for readers/viewers to understand. I'm sure the poster wasn't suggesting a conversion error from Kts to Kph was the cause of the crash.
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Old 27th Aug 2008, 22:24
  #1103 (permalink)  
 
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we are very close to getting some real info, if we are now hearing that the thrust reverser (never to be called the reverse thruster) was locked out, the real info should be coming soon.
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Old 27th Aug 2008, 22:30
  #1104 (permalink)  
 
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Figure also the rather long distance this airplane traveled on the ground, nearly 1 kilometer from first contact to the ravine. Although the one able TR was deployed...was there any thrust being used against it? Shouldn't it have been able to slow significantly after nearly a kilometer without power alone, set aside a possible single reverser?

Many things don't add up (yet).

Edit: changed to kilometers
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Old 27th Aug 2008, 22:38
  #1105 (permalink)  
 
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Accidental thrust reverser deployment now ruled out.
Quote: Telecinco reports .... The recovered deployed reverser was activated by the pilot, but the right side reverser could not be deployed as it had been deactivated since August 17.
Far too pedantic I know, but someone has to ask. How, from the above, is right side reverser deployment categorically ruled out? How are MD-80 reversers normally deactivated? Mechanically? Disconnected hydraulics? Electrically? The right side reversers were already carrying a defect so; highly unlikely but ..............
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Old 27th Aug 2008, 22:43
  #1106 (permalink)  
 
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Shouldn't it have been able to slow significantly after nearly a kilometer without power alone, set aside a possible single reverser?
In a word, No!

Especially if it was ripped off after less than few hunderd yards (metres? What is dem 'tings, some sort of Napoleonic re-engineering of the world?)
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Old 27th Aug 2008, 22:45
  #1107 (permalink)  
 
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there is a way of cutting off the hydraulics and locking them out to the thrust reverser, indeed, there is something visible indicating such during the walkaround (remembering the 9)

also, the thrust reverser lever on the throttle is wired closed so that you cannot attempt to use said reverser.

now, this could mean alot of stuff was broken on this plane. we shall see

I now think that the crew realized that the flaps/slats were not properly set and they attempted to abort the takeoff

I also think there was probably a huge amount of discussion between pilots during this phase.

wondering if the anti skid worked, or if it went to manual modulation.
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Old 27th Aug 2008, 22:53
  #1108 (permalink)  
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The tyre tracks don't matter. They were made after the crew lost control of the a/c.

Looks a lot like a plain stall. While an unlocked TR could have caused it, they'd be very unlucky to get that at Vr- which it would have had to have been to have caused this accident.

Hitting the tail hints at the kind of pitch up that the a/c s pusher is there to prevent- but it does not work that close to the ground- so that points to a stall also.

In other words if the TR had unlocked earlier than V1- they'd have stopped and if it happened after Vr they'd be airborne and have climbed some way. So while it maybe could be an unlocked TR.........

In my own experience, taxi back in for some reason-shutdown- start up and taxi out again is the IDEAL situation for missing something.

You've done the 'Runway checks', then you abort.

Right: do the 'after landing checks' (but it's not quite right as you've not 'just landed'). Maybe not put some things away as you expect to go again very soon?

Then you shut down- deal with pax, deal with whatever the problem was etc.

Then you taxi again, more checks etc, maybe you left some items as you knew you'd be going again. Speeds, for example "as before".

It's totally easy to miss something in the rush and I've always had to take it slow and try not to miss anything.

Say they retracted the flaps or slats on the way back in and forgot to redeploy them on the way out? Easy to do. Especially as they were now late and so on.

All you need is a failure in the config system to line up that last hole in the cheese......
 
Old 27th Aug 2008, 23:35
  #1109 (permalink)  
 
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TOCW check.
Question to Mad Dog or any other pilots..do you always
a)perform functional check ie.preflight check with parameters out of limits so warning sounds OR
b)perform nuisance check..during taxi after configuring,quickly advance TL to ensure you wont have to abort OR
c)both

Also,do you see the check in (a) as mandatory before every takeoff and whether or not it can be performed by either pilot.Thank you for your answers.
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Old 27th Aug 2008, 23:42
  #1110 (permalink)  
 
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Its clear that the aircraft was close to the stall. There is almost no other way it should impacted tail first.

If the problem with the reverser is rulled out, probably the main cause should be an anormal take off config or CG position.

If you are bellow the real rotation speed for your config is easy to raise the nose, if you continue to picth up and you have ground effect probably the a/c is going to lift off.

I never have seen this in the sim, but I believe that if you manage to go to the air bellow your rotation and V2 speed and put a normal take off actitude, you will begin to lose speed very fast and that will make your AOA increase.

That is consecuent with the loss of control of the aircraft and the impact actitude of the plane.

Last edited by Strongresolve; 28th Aug 2008 at 00:00.
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Old 27th Aug 2008, 23:51
  #1111 (permalink)  
 
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Air temperature.

I am curious about the time of the accident mid afternoon. Do you think that ground or air temperature was a factor in the accident? To me if the aircraft was around mauw a failure of power at the critical moment might have required a higher airspeed to rotate in less dense air on that day. The loss of power consequently affected the air speed and the aircraft simply would not fly.
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Old 27th Aug 2008, 23:55
  #1112 (permalink)  
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Escubic;

Very fine, skillful mathematical & graphic work indeed...tx.

We may see that the 'S' turns aren't nearly as violent as might be assumed from the fore-shortened view as taken by a strong telephoto lens. Also we may see that it doesn't take a large difference between heading and track to place the nosewheel outside the physical paths of the main gears. Such wide lateral "gyrations", (now far less so), while the nosewheel's track was straight, are realistic when considered as shown in this corrected photo.

I was searching all over for a program that would "know" that the perspective was in the original photo of the ground tracks and of course no program does - they only know pixels - it is us who interpret according to the rules of perspective...thanks for your excellent post.
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Old 28th Aug 2008, 00:17
  #1113 (permalink)  
 
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I want to ask an open question.

What happen if with correct flap config, trim, cg and engines, you select wrong V1/VR/V2 speeds, with values bellow the real ones?

You may get airborne, but you will stall and depart from a controlled flight as soon as you leave the ground effect.

May were not a mechanical failure at all, they simply used incorrect speeds with values bellow the real ones. I dont want to say this, but I am starting believing that this was what really happened.

I hope that the investigators find something mechanical, I dont want to be right.

Last edited by Strongresolve; 28th Aug 2008 at 00:42.
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Old 28th Aug 2008, 00:50
  #1114 (permalink)  
 
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I want to ask an open question.

What happen if with correct flap config, trim, cg and engines, you select wrong V1/VR/V2 speeds, with values bellow the real ones?

You may get airborne, but you will stall and depart from a controlled flight as soon as you leave the ground effect.

May were not a mechanical failure at all.
This may partially answer your question, although it was a rather significant miscalculation of gross weight:

MK Airlines Crash

I may be wrong but I suspect that the error in V1/Vr/V2 calculation, if any, wasn't so large in the Spanair accident. In the MK case, the take-off weight from a previous sector had been used to calculate the take-off data at Halifax, resulting in a very large error in take-off data.
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Old 28th Aug 2008, 01:23
  #1115 (permalink)  
 
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My believe is that perhaps a bit "short" calculations (thrust for VR) had something to do with the accident being "unavoidable" after other factors (i.e. failure to select proper flaps angle or deploy slats) made it already hair-thin hard to avoid it. The airplane could've easily been a bit heavier than estimated, air density a bit lower, tail wind a bit heavier, taking a bit longer to reach V1-VR and using more airstrip. Once on VR, the plane took longer to leave the ground due to the wing configuration.

Perhaps by the time they realized it and try to correct the situation, it was too late and engines didn't have time to go from slightly "underthrust" to "full thrust" (if at all commanded after stall alarms) at such (lowish) air speed/temperature/conditions.

How "responsive" are those engines? How many seconds would you say they can take on those conditions to, say, increase thrust from 65% to 75% if firewalled at near stall speeds?

If the airplane takes off w/o slats and/or (way off) flaps on ground effect but on correct thrust calculations, is it unavoidable (for a heavy-ish plane) to hit the ground if you react quickly to the stall alarm? (nose down, flaps 15, full thrust at 30).

Last edited by justme69; 28th Aug 2008 at 02:00.
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Old 28th Aug 2008, 01:29
  #1116 (permalink)  
 
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Strongresolve,

what's your explanation for the activated reverser?

And if the speed calculation was wrong - you don't think the accelerating plane would take off, even if it happens later than expected?
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Old 28th Aug 2008, 01:38
  #1117 (permalink)  
 
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I doubt the sums were far wrong for the 'believed' configuration... they would have known the figures looked too low!
Much more likely the configuration was wrong or something unexpected happened during the latter part of the roll...

Let's leave it at that eh? there's been umpteen people asking these same 'what ifs' now for several days and the pros here have given up and gone home I think....

Best let those sort of questions rest for a while, or ask elsewhere!
Night, night....
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Old 28th Aug 2008, 01:58
  #1118 (permalink)  
 
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I think that they activated the operating reverse as soon that they realized that they were on the ground, the plane was not flyable anymore and needed urgent braking by all means.

And I talking about a very big miscalculation of speeds. There is going to be hard to raise the nose and make the plane fly, but once it is in the air it becomes uncontrolable.

Another suspect is incorrect config Flaps/Slats, trim, spoilers, but in this case the config alarm should not be working, and this is very strange, because if you realize problems during the take off lift off and both engines are running normally, someone is going to look at the flaps, Spoilers, etc, and you will sense some kind of buffeting.

I bet that something very simple is behind this. 20-25 knot of speed error is enough to make this crash happen.
You wont notice it during the lift off because you will looking at abnormal config items or engine parameters. If your speeds are wrong and you dont notice it, everythings is going to appear normal, and you dont know what is really wrong with the plane.
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Old 28th Aug 2008, 02:12
  #1119 (permalink)  
 
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Insufficient thrust due to faulty sensing?

The long takeoff roll still seems highly signifigant,
being the first clear indication of a problem.

1) Could an issue with the ram air temperature transducer
whose output signal is necessary for the accurate calculation
of EPR, have led to a falsely high reading of actual takeoff EPR and hence giving a lower than indicated actual takeoff thrust?

2) Could an issue with the air/ground sensing equipment
have had an affect on the airplanes allowable EPR
and hence thrust on takeoff?
(eg. arent there different epr limits for each flight mode ?)

There have been cases in the past for example air florida flight 90 disaster
where falsely high EPR indications caused by faulty / contaminated sensors (in this case ice) led to the pilots experiencing insufficient thrust and stalling on takeoff despite apparently normal epr and thrust readings:


As it turned out, the failure to operate the plane's anti-icing system caused exactly what could be expected to happen: the engine pressure ratio (EPR) thrust indicators provided false high readings when the pilots thought they had throttled up to the correct take-off EPR of 2.04, the actual EPR was only 1.70. The aircraft traveled almost mile (800 m) further down the runway than is customary before liftoff was accomplished.
full version:
Air Florida Flight 90 - Wikipedia, the free encyclopedia

Although this was a 737 and the EPR values
were distorted by an ice contaminated sensor,
it shows how critical it is for sensors
such as the RAT probe to be functioning correctly.

Inadequate thrust of the airplane would explain the long takeoff roll
(extra 500m)
A symptomatic RAT probe and an airplane that doesnt know if its on the ground or in the air could easily lead to false EPR values and hence lower than indicated takeoff thrust.
Despite reaching vr it is possible the airplane had not sufficient thrust
to takeoff without stalling.

possible ? il leave it to the experts
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Old 28th Aug 2008, 02:39
  #1120 (permalink)  
 
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Given the circumstances (regularly flown sector, full airplane, etc), a 20-25 knot error in V1/Vr/V2 is preposterous. That would require a heck of a weight error.
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