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Spanair accident at Madrid

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Spanair accident at Madrid

Old 28th Aug 2008, 14:10
  #1161 (permalink)  
 
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a restatement for those coming to the thread late

New arrivers to the thread may keep finding references to the "in air mode" hypothesis.
To prevent the same questions again and again it might be useful to explain that it goes roughly like this (using lay terms throughout)

1. When (and only when) in the air, the RAT probe is heated (anti-ice). Certain.

2. The first take-off was aborted due to RAT probe being heated when on the ground. Definite.

3. Mechanic "rectified" inappropriate RAT probe heating by disconnecting the heater. Fairly definite.

4. Hypothesis: Mechanic did nothing else, not finding why this heating was happening.

5. Hypothesis: The reason for the heating was a fault with the system which senses (from weight on landing gear) that the aircraft is on the ground. This would mean that the aircraft "thought" that it was in the air throughout, so turned the heater on.

6. This aircraft will warn if flaps/slats are not deployed for take-off, but not if it thinks it is in the air. Fairly definite.

7. Hypothesis: Flaps/slats were retracted for the taxi back after the abort, and reconfiguring them for take-off was forgotten.

8. Conclusion: The take-off could have been without flaps/slats, and due to the hypothesized fault, the normal warning signal would have been absent.

Last edited by fg32; 28th Aug 2008 at 14:22.
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Old 28th Aug 2008, 14:19
  #1162 (permalink)  
 
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Sevenstrokeseven,

J/S'ing on MD80 last week and the takeoff EPR was 93.x %.

In EPR a/c N1's are frequently overlooked.

Last edited by misd-agin; 28th Aug 2008 at 14:20. Reason: grammar
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Old 28th Aug 2008, 14:40
  #1163 (permalink)  
 
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Reverser INOP during three days up to accident

... says Spanish paper El Mundo, quoting investigation sources

MD-80 Forum: Crash - Spanair JK 5022
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Old 28th Aug 2008, 14:52
  #1164 (permalink)  
 
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It's being said that there was a problem in reaching V1-V2, and as someone has already posted, in that case setting the flaps/slats configuration wouldn't have a role on that.

So do any of you know in which way could affect the same problem to available thrust?

In other way, does anybody know where the iinformation about that "slow take off" comes from?. (Because it may lose reliability by saying the aircraft didn't reach the necessary 210 km/h = 113 knots, which seems quite slow anyway)
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Old 28th Aug 2008, 14:53
  #1165 (permalink)  
 
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Concerning the 'locked' TR.
On the CRJ 100 LH technicians once 'locked' a faulty TR.
During the take-off run this very TR suddenly deployed because the pin had been inserted in the wrong place!!!
Don't know if that's possible on the MD.
Just a thought that this also might be a possibility in this case.
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Old 28th Aug 2008, 15:15
  #1166 (permalink)  
 
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Simple - really. All aircraft braking performance numbers are certified/predicted without reversers. If you've got them fine - if you haven't - also fine.
Actually, some operators on some planes do use the reversers when figuring performance on an icy or cluttered runway. Not a factor with Spanair but it was commented on in the NTSB report of the Southwest crash at Midway:

The Safety Board said the pilots received mixed braking action reports for the landing runway. The flight crew used an on-board laptop performance computer (OPC) to calculate expected landing distance. They entered multiple scenarios, including wind speed and direction, airplane gross weight at touchdown and reported runway braking action.

Observing OPC indications that they would stop before the end of the runway with either fair or poor braking action, they decided that they could safely land at MDW. However, the pilots were not aware that stopping margins displayed by the OPC for poor runway conditions were, in some cases, based on a lower tailwind component than that which was presented.

Also, the pilots were not aware that the stopping margins computed by the SWA OPC incorporated the use of thrust reversers for their model aircraft, which resulted in more favorable stopping margins.

Therefore, the Safety Board concluded in the report that had the pilots known this information, the pilots might have elected to divert to another airport.
NTSB Decides on Midway Crash | Air Safety Week | Find Articles at BNET
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Old 28th Aug 2008, 15:16
  #1167 (permalink)  
 
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There are THREE ways to read takeoff power on jet engines.

We all know about EPR... on Pratts (like the MD-80s) and Rolls noise machines...
We have N1 as an alternative (if EPR is dead) or as a crosscheck.
And if these guys had a good ground school, they would know what FF it takes to get "about" 19,000 lbs (?) thrust.
xxx
I knew what it took (as FF) on ALL engines types I had on my 707s, 727, or DC-8s...
On the JT9D-7Q (747s), it takes 9,000 kg FF (19,850 lbs FF) to get full thrust.
That is the gage I would look at, to crosscheck EPR/N1 in case of doubt.
(Or if either EPR or N1 is MEL'd) -
xxx
Sorry - I do not know the TSFC of the JT8D-217/219s...
I would say - probably around 4,300 kg FF...?
xxx

Sad contrails
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Old 28th Aug 2008, 15:20
  #1168 (permalink)  
 
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Some sources do speak of some sort of "wire" (pin) involved in the (presumed) lock-due-to-malfunction of the TR by the technician.

Most sources now speak of right TR not operative for the past 3 days, maintenance delayed (by MEL), and LEFT TR found deployed (assumed to be commanded when trying to stop the plane).

The sources speaking of the slow speed/long time to take off are: ground witnesses, airport video recording, ground radar. Video recording shows the plane finally leaving the ground close to the end of the strip, close to the portion of the paviment that changes color (which somewhere it's said to be 600m long of aditional paviment). This is estimated to be some 500m longer than usual for this flight.
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Old 28th Aug 2008, 15:38
  #1169 (permalink)  
 
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Doubt the crew would make the entire roll not knowing the right bucket was open. Too many different indications for all of them to have been inop or ignored simultaneously by two people. Perhaps this is a fuel quality and/or fuel delivery issue? Booster pumps?
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Old 28th Aug 2008, 15:39
  #1170 (permalink)  
 
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What keeps bugging me in the flapless scenario: If you depart without flaps, you should notice something is wrong when you rotate in the first place. It has been stated earlier that a plane would indeed fly in ground effect but stall as soon as climbing out of it.
I have never been confronted with that situation, but I imagine, if you figure on rotation that you have insufficient lift, the immediate guts reaction would be to lower the nose and gain some more speed. They had more than 1000m of asphalt ahead of them, followed by another kilometre or two without obstacles.
Wouldn´t the natural reaction be to get the nose down and accelerate to a higher -more flyable- speed (and let it touch down again, if it doesn´t fly yet with less AoA)?
I just try to visualize this scenario, anyone experience on this?
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Old 28th Aug 2008, 16:08
  #1171 (permalink)  
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philipat;
Given that confiuration related accidents are far from infrequent, would it be desirable and/or feasible to formalise this final check?
We can't really say that configuration accidents are "far from infrequent" as it just isn't the case, not in my experience anyway. That configuration errors have caused accidents is true, but not "frequently". For discussion's sake however I understand what you're saying and my own view on formalizing a "final check" is what the Before Takeoff Check is all about already. Let me provide what is perhaps a poor example but may illustrate the thinking involved -if you're leaving your house for a vacation, you do a formal run-through to ensure locked doors/windows, that the stove is turned off and all unnecessary lights are off...that could be called, (for lack of a better term for what is pretty informal for us all!), the "formalized" list. But....as we pull out of the driveway, we may quietly reassure ourselves that the stove is indeed turned off...

There isn't anyway to re-formalize this process so that it is more effective. Checking, re-checking is what all airmen do; it is habit borne out of hundreds, or thousands of hours of experience and moments of, to be blunt, stark terror at "what just about occurred"...No airman is without such experiences, (you've read a few here already), almost all of them quietly endured and without fanfare or "result". That's why, when discussing what pilots "are worth" to airline managements and other standard doubters who think of us as "expensive resources", I use the phrase, "We're paid thousands and thousands of dollars per minute but you'll never know which one. The rest is for free".
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Old 28th Aug 2008, 16:12
  #1172 (permalink)  
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Ancient Mariner - okay, thanks. Re wild speculations - yeah, thought so. This really is the best place for as close to a professional discussion one can have "in public".
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Old 28th Aug 2008, 16:18
  #1173 (permalink)  
 
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TR

Sevenstrikeroll,

Lets assume the acf was in "air" mode before taking off which
is one of the theory's. (RAT probe heater etc)
As we know this is controlled by weight on the NLG.
When the NLG later lifts on rotate, will the acf then revert to
ground mode??

If so, the question is, if the RIGHT reverser bucket was
not deactivated &stowed properly, could this trigger them to deploy on
NLG liftoff somehow?

Attach Reverser system schematics;





MD82 TR engage at rotate sim clip

XPM
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Old 28th Aug 2008, 16:41
  #1174 (permalink)  
 
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Where Next?

PJ2:

We're paid thousands and thousands of dollars per minute but you'll never know which one. The rest is for free
".

Like in business. I know that half of advertising expense is wasted; I just don't know which half?

Thanks for your patient and always relevant responses. Should that not have been your drift, and I would contend that at least 6 configuration-related accidents over a 30 year period (OK, maybe not justified in my earlier statement as "Not infrequent") IS a significant statistic, then please further elucidate? What should be done, in your opinion, to better, or more relevantly, address the issue of the three killers?
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Old 28th Aug 2008, 16:53
  #1175 (permalink)  
 
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...........and I would contend that at least 6 configuration-related accidents over a 30 year period.
There's an ICAO listing. See Dutch Accident Report, my post 1174.
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Old 28th Aug 2008, 17:03
  #1176 (permalink)  
 
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Like in business. I know that half of advertising expense is wasted; I just don't know which half?

........I would contend that at least 6 configuration-related accidents over a 30 year period (OK, maybe not justified in my earlier statement as "Not infrequent") IS a significant statistic, then please further elucidate? What should be done, in your opinion, to better, or more relevantly, address the issue of the three killers?
we can start with your above statistic. Now consider how many aborts occurred because of misconfigurations annunciated by warnings (horns or lights, etc.) That provides both a crew error rate as well as a safety barrier success rate. (note I'm ignoring checklist caught misconfigurations)

And of interest to me, how many aural warnings or lights failed to warn?

if it's 1 out of 20 or worse than that is way too much and should be addressed as the highest priority.

If on the other hand the crew missed not only the configuration but also the warning light or horn then we have the wrong crews flying planes.

the above is still hypothetical relating to the accident in this thread
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Old 28th Aug 2008, 17:13
  #1177 (permalink)  
 
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If on the other hand the crew missed not only the configuration but also the warning light or horn then we have the wrong crews flying planes
Yes. of course that goes without saying. The potential issues with Spanair MEL and pre-MEL matters not withstanding?
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Old 28th Aug 2008, 17:58
  #1178 (permalink)  
 
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What keeps bugging me in the flapless scenario: If you depart without flaps, you should notice something is wrong when you rotate in the first place.
I'm with you Avionero. It seems that no one is flying the airplane off the runway. They're just rotating at V1 and expecting the aircraft to do the expected.

I'm also disturbed with the idea that pilots are inputting data into calculators and not considering whether the output is reasonable. Garbage in, garbage out. One instance noted indicated that the crew ignored what to me would have been a very obvious 33 knot error in V1. When taking off in a heavy 747, wouldn't you think that something like 33 knots would stand out like a sore thumb? Are these guys robots or pilots?

Being a military pilot who only has a couple thousand hours in transport aircraft, all props, I don't know much about large high-bypass engines, but I seem to remember from ground schools that N1 isn't a viable indication of thrust in a twin spool engine. I thought that N1 was just along for the ride, although a very low N1 should certainly catch someone's eye.
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Old 28th Aug 2008, 18:14
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Ed, surely if the N1 is producing over 80% of the thrust, it is certainly a viable indication of thrust. (On a high-bypass turbo-fan).

Agreed a sanity check on V speeds seems obvious to me too.
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Old 28th Aug 2008, 18:21
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Hi Smilin Ed,

In the case of the Halifax 747 (MK airlines) tragedy, I can only say that I knew at least 2 of the crew members personally and they were certainly not robots - more like overworked, tired, but nevertheless trained and highly capable crew with family and other good things to look forward to. We always think we could never make these (often simple) mistakes, but believe me, even the most talented pilots can be caught out. Rather than simply chide others, every good pilot should just use every tragic accident as a lesson to learn and be safer in their own flying - without being judgemental.
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