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American Airlines jet goes off runway in Jackson Hole, Wyoming

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American Airlines jet goes off runway in Jackson Hole, Wyoming

Old 7th Jan 2011, 17:30
  #201 (permalink)  
 
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However, failure of spoiler deployment might explain nil (or reduced) braking action: No spoilers = more residual wing lift = less weight/force holding the wheels tight to the ground for friction.
Yes, and even on a dry runway, significantly so.

From the limited scope provided by the video recording, it appears that the spoilers did not deploy on the outboard port wing. The spoilers are symetrically paired. Without the lift dump from normally operating spoilers, the extra required runway length would be significant.

Where it being planned to use manual speedbrake deployment after touchdown, it would be at least 850 feet. Even though reverse thrust may not be included in the performance planning figures, a combination of no spoiler deployment, late or no reverse application, and a limiting runway with any contamination at all, is never going to be a good combination.

If the perspective of the video confirms there was no or limited spoiler deployment at touchdown, (automatically or manually) whatever the reason established for that, undoubtably from a runway performance standpoint, that is where the problem started.
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Old 7th Jan 2011, 17:46
  #202 (permalink)  
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Leaving spoiler deployment out of it for the moment, I still cannot fathom the odd movement of the reverser sleeve. Does selection of reverse on the 757 crack open the case while waiting for the interlock to open?
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Old 7th Jan 2011, 17:55
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I have never witnessed it from the cabin perspective, but as it utilizes a hydro mechanical system that would auto-stow the reverser, if the activation conditions were not satisfied, then I think it is quite likely this is what you would witness.

Perhaps a qualified engineer, or somebody who has witnessed it from this perspective, could give a better response?
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Old 7th Jan 2011, 18:09
  #204 (permalink)  
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Hating to sign on as a detractor, to join the nemesis himself of AA, but the pilot possibilities should be looked at. The Human factor bears a peek too. I think there is a 'chance at least' that this landing going wrong may have started before the "loss" of Spoilers. It may have started rolling from the point of the PA announcement to the back re: a "hard" touch. The conditions were dicey on the natch, did the PF challenge himself further to show his pilotage to good effect? Was the Captain joined in? I personally doubt it, but since the pilots will eat their lunch on this anyway, it bears a look, if only to gauge 'a priori' the upshot.
 
Old 7th Jan 2011, 18:46
  #205 (permalink)  
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beazlebub:

Physically the thrust levers must be in idle for the reverser levers to be moved through the interlock position. This is in addition to the aircraft being on the ground with the main trucks untilted.
If the thrust levers aren't at idle, won't moving the reverser levers force the thrust levers to idle, followed very shortly by the ability to move through the interlock position?
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Old 7th Jan 2011, 20:30
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pattern is full - I find the bashing and defense of American to both be premature at this point - except for the fustercluck surrounding the handling of the FDR data.


Exactly. The video shows some know events - touchdown point, reverser operation, spoilers. The whole 'what and why' is completely unknown.
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Old 8th Jan 2011, 00:19
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This is from the SWA1248 accident public-docket on the NTSB site.

From the final report:
"FDR data indicated that the thrust reversers were eventually fully deployed about 18 seconds after touchdown, and the pilots held maximum reverse thrust until the airplane came to a stop off the end of the runway." (edit: added)

I'm extremely surprised that the pilot's notes were made public ! In no way can we judge pilots' actions without looking at the final and full report !!

From SWA1248 copilot's PNF notes. Bruce is captain PF.

"I looked at TR's. Bruce's hands were on them in the down position. I pulled his hands off and went to max reverse" (the remaining text is about after stopping)

Last edited by alph2z; 8th Jan 2011 at 05:29.
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Old 8th Jan 2011, 00:47
  #208 (permalink)  
 
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...except for the fustercluck surrounding the handling of the FDR data.
And, regarding this very strange action on the part of AA, we may never truly know what difficulties the specific flight experienced.

American Airlines, apparently trying to sweep any(every)thing under the rug.
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Old 8th Jan 2011, 05:11
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@Beazlebub,
Correct me if im wrong but with the first three conditions that Cwatter mentioned above having been met, when the reverse thrust is deployed the speedbrake should move to the up position even if the lever was not initially armed
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Old 8th Jan 2011, 07:04
  #210 (permalink)  
 
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Yes, that is correct. As I mentioned in post # 177:
The reversers on the 757 can occaisionally be awkward to get through the lever interlock position, and the reverse levers may well be re-cycled in order to achieve the desired result. If one or both reversers are selected through to reverse idle, the speedbrakes (all 12 spoiler panels) will drive up irrespective of the lever position being armed or down.
That is the normally the only condition where auto speedbrake occurs on landing, without the speedbrake lever being armed.

If the thrust levers aren't at idle, won't moving the reverser levers force the thrust levers to idle, followed very shortly by the ability to move through the interlock position?
Well, not in itself as such, however the act of pulling up the levers should result in the thrust levers being moved aft. The problem then is that you are applying force that will likely prevent succesfull movement through the interlock position. The best way I can describe it, being like trying to unlock a door that you are pulling against.
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Old 8th Jan 2011, 12:09
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Google Image Result for http://cdn-www.airliners.net/aviation-photos/photos/9/9/7/0967799.jpg

Does anyone else agree that from the video posted earlier it is impossible to see if spoilers were deployed or not since they are on the rear portion of the wing? The video only shows the front of the wing.
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Old 8th Jan 2011, 12:54
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Bubbers can you please walk back to the cabin and verify. From the not-so-good 3D I have I would believe the camera goes down enough to show the portion of the wing where the spoilers should show at 55 seconds down the video. I stand to be corrected.

Reg
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Old 8th Jan 2011, 13:27
  #213 (permalink)  
 
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Much of the left the wing is visible several times during the landing rollout and at least the outermost panel of the 4 outboard spoilers would be easily visible from the vantage point in the video. The outermost panel ends about 2/3 of the distance to the wingtip and, when fully extended, is easily visible from cabin window seats anywhere along the left side of the aircraft, probably even from a viewpoint near the lower edge of a window frame.
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Old 8th Jan 2011, 22:36
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Unless you can see inboard of the left aileron on the trailing edge of the left wing in the video spoilers are not in the video. They could be up or down. If it was a WOW squat switch problem How did the reversers come out and if the reversers come out the spoilers automatically deploy even if spoilers are not armed. Brakes are always available. Spoilers can be deployed in the air. The 757 lets you do most anything you want manually. This time it is not pilot error. Reports of prior WOW switch failures might be a clue on this aircraft. Maybe it was an intermittent WOW problem and eventually it sensed being on the ground and allowed TR actuation. How can a TR come out less than an inch ? Is that what it would do if you were in the air and selected TR? These questions will be answered eventually. I don't want to be patient. Tell me now.
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Old 8th Jan 2011, 22:53
  #215 (permalink)  
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Pilot Error. Poor Planning. Brain Lock. I think the 757 is not weight on wheels, but "Untilt". Oh, and what happens when the trucks bounce, oscillating twixt tilt/untilt?? Especially when the a/c is not put firmly on the ground??
 
Old 8th Jan 2011, 23:28
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bubbers44: FWIIW, I'd say that in the video at 30 seconds you see the left aileron move and can localize where its inboard end is. Later, after the landing, you can see clearly further the inboard part of the wing but no spoilers. You can compare this with the video in #24 YouTube - northwest airlines 757 landing in seattle where the view is from front but you can estimate how far outboard the last spoiler seen from the cabin in fact is.
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Old 8th Jan 2011, 23:30
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Untilt or WOW this was a text book landing before the thousand foot point. The crew did a great job. We will see what happened to make it go off the end. It wasn't because of the pilots. They did everything right.
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Old 8th Jan 2011, 23:48
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we do have to at least acknowledge the idea that one can do everything right and still end up off the end of the runway.

braking action and its reporting and measuring has been a topic for years.

I did read once that in some types, british airways has the non flying pilot operate the reversers.
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Old 9th Jan 2011, 01:45
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The pilots did everything right.

The pilots made mistakes.



The reality is you can't PROVE either of those statements. Geez, how about waiting for the facts to be known?
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Old 9th Jan 2011, 02:00
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it's easy really.....until it's you operating.

OK chaps,

Imagine the following,

Big aeroplane, short snowy / icy runway, runway reports that are hit and miss in terms of reliability and quality, little or no traffic to give actual braking reports or track changing conditions.

This would be an approach that I can assure you both pilots would be rolled "fully forward".

I haven't met an airline pilot yet who doesnt pay very close attension in mountainous approaches. Those who havent learned to pay attension don't fly in mountains, are very lucky, or are dead.

Yes you might get away with large aircraft, short runway ops most of the time but there are flaws in every system. American found one. A bunch of stuff lined up and they got bit. Thats what happens when you try to run a winter sched. operation into a po-dunk (small, understafed, underequiped) mountain airport.

some basics after 28 winter seasons of flying.

Go elsewhere if it does not feel right and have the gas to do it. (you sould always have that option if your planing was up to snuff, check the notams and runway condition reports) Check friction tables and cross wind limits. Plan your landing accordingly but expect worse.

If it's clear blue or good wx . No special action required.

Anything else pay close attension.

If the wx is ****e or changing quickly, you must be a step ahead and anticipate..... We are all weather pilots after all.


Go easy on American, any one of us could be in their shoes tomorow.

Let's wait for the final report.

The Dog.

Last edited by skidoodog; 9th Jan 2011 at 14:00. Reason: edited for clarity.
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