MD80 slat system...
 

doodahdave, very good description of the system!

I flew the DC9/MD80 series aircraft for 16 years, and I have the same positive impression of the system - safe, simple and reliable. No failures except the odd Auto Slat failure, as doodahdave mentions may happen.

To the best of my knowledge the failure reported in post #1671 is of this category - and it is NO factor in the accident.

doodahdave, agree?

Autoslat failure?
 

grebllaw123d

Thanks for the feedback. All I can say is that I learned from some of the best pilots in the industry! I use what they taught me every day.

And yes, I agree. It appears that the Autoslat failure previously noted in the logbook is not related to the accident.

borghha

Althought I don't ever remember seeing any "Dial-a-Flap" settings of less than 4 degrees for takeoff on the MD80, I'd bet that with both engines operating, a successful takeoff could be made with the slats in partial extension or mid-seal. I remember a rough estimate of 40 knot reduction in stall speed with slat extension on the MD80.

Slat-only takeoffs were routine on the DC9-50 series when operating from hot and high airports like Denver or Colorado Springs.

Dave

Isnt this the wrong way round?The RAT probe failure was caused by the aircraft being in air mode in the first place.

doodahdave,
Can you give us your analysis of posts 1489 and 1500?
Is this c/b thats mentioned routinely pulled by maint to check strobes for first flight of the day check?Is this your experience?This aircraft was on its second flight,having arrived from BCN.If the daily checks been done in BCN(Spanair base?),why pull this breaker in MAD?Is it possible they flew with it pulled from BCN or will the RAT probe overheat whatever the ambient conditions?BCN am departure=temp 15/59 vs. pm departure MAD=temp 30/86??
Autoslats only work with flaps/slats set ie slats already mid-seal..they re-position slats from mid-seal to full extend.Pls confirm.Is a slats only takeoff possible on this bird or just the DC9?How much stall speed margin does full extend from mid-seal buy you?Im just thinking of something to try to explain the awkward CVR leak that has the pilot saying Flaps/slats SET.A flapless takeoff combined with autoslat failure and incorrect TO thrust might be a way to explain the call and the accident.If flapless takeoff is not possible,then the call must have been rote or the leak is incorrect...
With RAT probe disabled,pls confirm that AT cannot be engaged(contrary to MEL)?TCI requires a temp input,even an invalid one,to function.Can it be pilot-entered?

Thanks.

Ranamin, you are right, I wrote it the wrong way round. Apologizes.

"The RAT probe failure was caused by the aircraft being in air mode in the first place."
Then the CWAS could not function properly, which is a NOGO.
The RAT probe failure analysis made by maint was not good.

Only my opinion.

Lets look at the no flap/slat scenario.

The given TOW is 64.263 kg. Lets assume they were
planning a F15 takeoff.

- The clean acf will stall at 166 kts
- A slat only will stall at 131 kts
- A slat/F15 acf will stall at 123 kts.

So obviously, the slats are the main contributers of lift on the MD80
in takeoff config. No slat will set you back 35 kts, no flap
will set you back only 8 kts.

Assuming they had slat but no flap, they would be 11 kts ABOVE
stall speed at Vr, so I think we can rule out this scenario since
the acf would most likely be flyable.

Assuming they were clean and went for F15 takeoff speeds,
at rotate Vr, they would have been 24 kts below stall speed, at V2
they would be 17 kts BELOW stall speed.

So the million $ questions are
1. Were the SLATS exended?
2. Would a clean MD80 be able to accelerate from Vr 142
to Vclean/stall 166 at a high AoA possibly scraping the tail
in a distance of about 500m?

XPM

http://www.xplanefreeware.net/morten/DOCS/mdstall2.jpg

XPMorten,
Thank you for that.The figures point convincingly at the clean scenario but then we have to reconcile this with the CVR leak....if he really did say SET to the FLAPS/SLATS challenge,then it was a rote response which puts the accident in a different category to Michigan where the checklist was omitted altogether.
Rote response in a checklist?It can happen of course.But to the most important challenge of the most important checklist?Thats hard to believe which makes me wonder about the authenticity of the CVR leak.

As a summary on this aspect:

The observed flight (takeoff) path and behaviour seem now to be looking very much like a slat-less take-off, which is somewhat more important than flap-less, albeit they often go together unless 2nd-segement climb performance becomes critical...

Slats provide ability to attain higher incidence whilst maintaining unstalled flow; flaps provide greater lift without necessity for higher incidence (reduce zero-lift incidence)...

Reported high aircraft incidence at rotation, subsequent loss of lift, including wing-dropping and loss of directional control are all very much pointing at slat-less and (now reported from one source) flap-less take-off.

Tragically, this very same situation seems to have taken place 2 years ago on the same type in the Canary Islands, but with just sufficient margins to allow 'hedge-hopping' flight until acceleration above safe flight speed for that configuration was achieved.

Take-off configuration warning systems designed and in-place to prevent this possibility may not have been working or compromised, in both cases.

Didn't a LAPA 3142 flight (a 737 in that case) also crashed when it attempted to take off w/o flaps/slats? In that case, I think, the configuration alarms sounded, but the pilots neither aborted the take off nor figured out to deploy them on time (or couldn't, for whatever reason).

LAPA 3142. Video with (what may be) the actual CVR.

YouTube - LAPA 3142 "Dead Dusk"

Far fetched speculations
 

..Just for the record. VERY unlikely theoretical reason
why the flaps might have been found in the "up" position.

1. They got retracted at touchdown e.g. got accidentally hit by the F/O
on hard impact.

2. Flap/slat only got deployed one ONE WING.. .
This might explain the wing drop and significant right turn.
Also this might explain a no config warning situation... .

XPM

Lumping both Dallas (B727) and Michigan (MD80) together in one sentence implies that both omitted the checklist which is not the case.

The FO in Dallas replied 15 15 green green to the checklist.

LAPA 3142 CVR. 31:37 - Cop.: "Rotate." 31:39 - Cop.: "V 2." 31:41 - 31:45 - Continuous mechanical sound of the stick shaker.

So where does the 737 get 'airborne' (WOW) signal from?

Much better: YouTube - Audio de la caja negra del accidente de LAPA (completo)

>> So where does the 737 get 'airborne' (WOW) signal from?

Main gear strut. When compressed, it presses the WoW switch.

ECAM Actions.

I see that I am deleted when I post....this is image of the track left by the LAPA flight. It never left the ground.

http://www.lanacion.com.ar/archivo/a.../38/692638.jpg

Wouldn't that have generated a flap/slat asymmetry warning?


Green-dot

Don't need an asymmetric flap/slat config to get a wing drop, just an asymmetric stall, which can be due to any number of reasons, including pure randomness.

Unfortunately I don't speak spanish, and I don't pilot, but isn't there too much conversation going on to take any notice of what the airplane is telling them?
Having tested config warnings on the 737 hundreds of times I don't know how you could miss it. Wrong config and it sounds as soon as you advance the throttles just as in the video/audio.

Only possibility I can think of is noise cancelling headsets, and too much verbal masking the horn.

The pilots are talking nonsense with a CC woman, and you can hear that one of them says that everything is all right when the alarm sounds. The whole thing was about lack of maintenance of the planes and poor trainement of the pilots.

Yeah. In that particular case, the pilots of LAPA heard the warning early enough (they reacted to it), one of them asked what the hell that was, the other replied he didn't know but everything looked fine, and basically it looks like they decided to ignore it and continue with the TO, although it can be guessed from the audio that they kept looking around to see if they found the cause (obviously, didn't look hard enough or couldn't figure the right cause, for whatever reason, which seems to have been the lack of flap deployment).

Seems the pilot had 6,500 hours of experience, but only 1,710 on 737. The copilot 4,085, but only 560 in the 737. During the CVR conversation the pilot comes across as a bit overcondident, perhaps, but this, of course, is subjective and can not be extrapolated in general but to the minutes before the accident.