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CNN Reports FEDEX crash in Tokyo

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CNN Reports FEDEX crash in Tokyo

Old 26th Mar 2009, 01:49
  #261 (permalink)  
 
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Er... can anyone explain why would the nose rise when the spoiler is deployed
Read back a bit...

Initial spoiler deployment creates a nose up pitch. This would be due to the particular way that the spoilers affect the wing aerodynamics, not to do with wing positioning (lots of rather loose talk here about 'wrong' positioning )
Spoiler deployment only continues further upon nosewheel contact.
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Old 26th Mar 2009, 03:50
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On the spoiler/pitch question:

MD-10/11 spoilers (as in many other jets) are located to the rear on the wing, at the leading edge of the flaps, and to the rear of the 1/4-chord point that is roughly where the lift is centered for any segment of the wing.

A partially-raised spoiler at a low angle will tend to act like the elevator on a tail plane (or an elevon on a flying wing), converting the force of rearward airflow into a downward force behind the lift center.

A pretty small force compared to the other aerodynamic surfaces, and one that would become smaller as the spoiler is further deployed, becoming a wall blocking the airflow rather than a ramp deflecting its force.

However - IF - as some familiar with the MD-11 seem to believe, the MD-11 wing itself is a "bit too far back" relative to CG or gear location, then the "elevon" effect of partially-deployed spoilers might be more pronounced in that craft as well.

If the general experience of MD-11 drivers is that initial spoiler deployment tends to induce nose-up pitch, then that's their experience. I'm just noting a mechanism that seems consistent.
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Old 26th Mar 2009, 12:54
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All,

From someone who flies the MD-11 and MD-10 regularly, it is my experience that the pitching moment upon touchdown is significantly greater in the MD-10 than the MD-11.

Also, the crosswind limitations are 35 kts for the MD11 and 31kts for the MD10.
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Old 26th Mar 2009, 13:20
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The wing itself supplies some moment about the CG. If the wing's lift is suddenly canceled , the lever about the CG coming from the downforce on the stabilizer will be greater and the tail will drop more quickly than the nose, with a resulting pitch up. But, I thought the spoilers on the MD-11 did not deploy until the nose wheel touched down - unlike the previous DC-8 and DC-10, which allowed manual deployment on the flare.

See this, where pitch up was pilot induced, and not from premature spoiler deployment:

http://www.ntsb.gov/Recs/letters/1993/A93_57_60.pdf

-drl
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Old 26th Mar 2009, 14:32
  #265 (permalink)  
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Emergency Egress

capt_zman

What do you guys think of the EFB and hindrance of emergency egress. Not understanding the horror that may have occurred in the cockpit, if the guys were alive, if the fire outside just made egress impossible. None the less, the EFB makes opening the secondary exit quite a bit harder. I was surprised the FAA granted the STC for this reason.

Your thoughts?

Last edited by muduckace; 26th Mar 2009 at 14:57.
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Old 26th Mar 2009, 14:39
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Hehe! Glad some of you 'aerodynamicists' are not designing the next generation of aircraft

I think the main effect is simply this: Camber and therefore flaps produce a distinct increase in -ve PM on the 2D wing section. Separate the flap-flow and the -PM will reduce, hey ho a +ve (nose-up) change in PM.
(3D effects will alter this, especially on a swept wing )

Positioning of the wing Vs the CG is a static margin issue. The CG of a DC-10, MD 10/11 3 engine style aircraft is further aft than it may seem, hence the wing position 'looks' further aft than a twin. It is not though, necessarily further aft in stability terms. The static margin increases with aft movement of the wing, not forward. However, associated with this, is an increased trim-drag.
If the MD-11 has relaxed stability, this implies the wing Vs CG is further forward aerodynamically, than otherwise it would be for a given tail volume (moment-arm * area)

Last edited by HarryMann; 27th Mar 2009 at 11:31.
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Old 26th Mar 2009, 15:43
  #267 (permalink)  
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But, I thought the spoilers on the MD-11 did not deploy until the nose wheel touched down - unlike the previous DC-8 and DC-10, which allowed manual deployment on the flare.
You get 66% deployment with MLG compression.

You get the rest when nosegear compresses.

As for the EFB - it rolls back with the window. It does make it harder to reach the locking lever but not enough to delay anything.
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Old 26th Mar 2009, 15:52
  #268 (permalink)  
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Question

Doesn't increased "trim drag" result in a slightly lower AOA of the wing, which lessens overall Drag enough to make the type slightly more fuel efficient (at cruise)? Although it may add "Handling" issues that need to be accomodated?

AF

Aft loading always produces Pitch sensitivity, to the extent that Controls can actually reverse. IMO
 
Old 26th Mar 2009, 16:07
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No, trim-drag is what is says, drag due to having to trim out unbalanced PMs, which is the tail's job. If it has to work hard one way or the other in the cruise, you get high induced drag from it, and maybe some additional profile drag. The tail of course is working in the downwash field from the mainplane, which itself changes with AOA, but in a stabilising sense.
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Old 26th Mar 2009, 18:53
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AOA of the wing at a given airspeed is determined by the lift required to equal weight plus tail download. Moving the CG back means less tail download is required so less AOA meaning less drag.
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Old 26th Mar 2009, 19:06
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.. and a reduced static-margin.
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Old 26th Mar 2009, 20:38
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This looks like a case of very bad handling.

Day 1 PPL flight training "after a bounced landing NEVER NEVER NEVER push the nose down always go around"

Case closed me thinks.
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Old 26th Mar 2009, 20:54
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Originally Posted by 3 Reds
This looks like a case of very bad handling.

Day 1 PPL flight training "after a bounced landing NEVER NEVER NEVER push the nose down always go around"

Case closed me thinks.
Because two heavy jet driver's suddenly forgot their Day 1 PPL Training and shoved the nose of an MD11 towards the ground...Don't you think handling a bugsmasher and something like an MD11 after a "bounce" just may have slightly different techniques?

But how silly of all of us. Of course that's what it was.

Now, if you'll just let the NTSB and JAA know and you can singlehandedly save them millions of dollars investigating the real cause of the accident.
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Old 26th Mar 2009, 21:07
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Don't you think handling a bugsmasher and something like an MD11 after a "bounce" just may have slightly different techniques?
Er no same technique....apply power and go around

You drive trains I fly aeroplanes who do you think knows best eh!
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Old 26th Mar 2009, 21:43
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"Because two heavy jet driver's suddenly forgot their Day 1 PPL Training and shoved the nose of an MD11 towards the ground...Don't you think handling a bugsmasher and something like an MD11 after a "bounce" just may have slightly different techniques?

But how silly of all of us. Of course that's what it was.!"


Maybe these pilots renembered their specific MD11 training (Pushing to counter the pitch up tendency due to the spoilers and fly the nosewheel activ into the ground) and overcontrolled a little bit under extreme difficult circumstances.

Greetings Thomas
flying little Bugsmackers
but also renembering that a specific aircraft has specific handling characteristics.

EDIT: German study regarding elevator control in B737, A320 and MD11

Last edited by krohmie; 26th Mar 2009 at 23:59.
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Old 26th Mar 2009, 22:41
  #276 (permalink)  
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Foregone Conclusions?

The Pacific troops at FedEx are highly experienced extreme weather drivers, anyone who has operated in and out of Anchorage during the winter months can attest to this. With the possible exception of Hong Kong during typhoon season, there are few large airports on the planet that present so many difficult weather challenges.

I have my own opinions, but I expect the investigation results will show changes in wind velocity and direction on short final beyond the performance capabilities of the aircraft on that day.

Sometimes, it's a rotten business we all work in. Saddest of all, two less freight dogs to share beers and stories with at the F-Street after a long and dark Pacific crossing.

Godspeed.
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Old 26th Mar 2009, 23:03
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Originally Posted by 3Reds
Er no same technique....apply power and go around

You drive trains I fly aeroplanes who do you think knows best eh!
Who do I think knows best? Someone who doesn't come out and say "Looks like bad handling to me...Case closed" based on little more than CCTV footage from a traffic camera a mile away.

Maybe it's just me, but I'd prefer to see a little more hard evidence, CVR/DFDR printouts, preliminary reports and the like, before I'd come out and say something that badmouths a crew that's not around to defend themselves.

But then again, that's just me.
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Old 27th Mar 2009, 03:01
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As a former MD11 driver ( 744 now) I was curious what FX landing flap guidance is, flaps 35 or 50 or your choice. As for you poor handling theorists, I have personally been caught in PIO's caused from a hard landing coupled with the "enhancements" to the LSAS system and it is amazing how little it takes for the bounce recovery and the LSAS to get out of sync. I have witnessed this situation happen to new guys and very experienced MD11 pilots and the look on their faces and words are always the same from them......"how the hell did that get so jacked up, so quickly?" the MD11 is a handful, it is manageable, but she will bite you and you will not know why or how until you "debrief" it in your head. So I wouldnt be too quick to "figure it out" just from the video as a lack of pilot 101.

The flaps thing I asked about stems from my experience with both settings, I like 35 for all landings, personal preference. I dont like 50, flatter approach but more pull required in the flare and can lead to a bounce more easily......my opinion only. So if you forget those differences, you could end up buying everybody beers and chiropractic.

Tailwinds to the crew who lost their fight, and my condolences to the families and you Dawgs at FX. God speed.

TRey
WOA
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Old 27th Mar 2009, 07:44
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Here's the thing: the MD-11 will soon be grounded.

No question in my mind. Failure to do so will see massive lawsuits against a company flying that bird that suffers an even remotely similar accident.

Doubt it?

Imagine another CLK accident only the flightless, hapless airframe is now a raging fireball turned upside down with 300 passengers hanging outa their seat belts, burning alive.

Nightmare, true, but a very real possibility. The above is not a figment of a wild imagination. And on that score, lawyers around the world would be drawing up response scenarios right now.

But with every cloud, there's a ray of sunshine.

With the grounding of the MD-11, well positioned cargo operators will reap hay while that sun shines. Yeah, I'm down about the crew. Who isn't? But as tough and as dark as things may be, life moves on.
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Old 27th Mar 2009, 08:24
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Thanks Pigboat. Nice of you to say.

They just brought the bodies through MEM last night. Everyone and their families turned out.

As for this forum - it's getting pretty deep, ain't it?

Flaps were at 35. 50 is for ILS's to mins, and short short runways.

If you bounce an MD11, you stick the pitch at 10 degrees up and firewall the power.

Just my speculation, but after watching the video too many times, I'd say there's a fair chance the crew was incapacitated by the nosegear strike after the first touchdown. One hell of an impact. I heard rumors it blew the tires clean off the axle.....
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