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CNN Reports FEDEX crash in Tokyo

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CNN Reports FEDEX crash in Tokyo

Old 15th Apr 2009, 05:13
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Dont have a clue

The terms stability, stable, and unstable have specific meanings with respect to the flying qualities of an airplane. Those meanings are confined to "static stability" and "maneuvering stability" and refer to control force gradients vs. speed, and vs. normal acceleration ('g') respectively. Unfortunately, in common practice the terms are used indiscriminately by "aviation experts".


The software changes (implementation of the -908 FCS load, and some subsequent set mandated by the FAA to allow certification of the MD-10 on the same type cert) improved the predictability of the MD-11 in the landing phase; they did nothing to correct the omission of a simple lead-lag pitch SCAS (ą la F-4) which was designed into the Rate Command CWS of the LSAS (which is there, but set to zero gain, making it non-functional), which would have compensated for the extremely low short period natural frequency of the airplane in the landing configuration (making the airplane prone to APC). The change in geometry from DC-10 to MD-11 made this item a required addition from a handling qualities standpoint, yet the FAA still certified the airplane. They also did nothing to correct the gross elevator load feel (force vs. displacement) gradients in the landing configuration, which make it virtually impossible for a normal pilot (and in particular a soft-handed airline pilot) to access the necessary deflections for control of the airplane. Nor did they compensate for the inadequate bandwidth of the elevator hydraulic actuators, which incur significant lags when rapid elevator control inputs are required (as in turbulence).


The DC-10, and MD-10, does not suffer from the above problems for several reasons: it has a lower max landing weight, and thus much reduced pitch inertia (Iyy), the elevator throws required for adequate control are significantly reduced as a result of greater elevator control power (area) along with correspondingly lower required control forces. Additionally, the DC-10 (as employed at most airlines) does not employ RCWS, a ludicrous, parallel roll control "enhancement" on most MD-11s; FedEx, incidentally, ordered its airplanes to have RCWS turned off; a wise decision.
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Old 15th Apr 2009, 14:39
  #422 (permalink)  
 
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I“m very sorry for the crew.

Turbogy, what you describe all sounds familiar from my experience.
I“ve flown analog 737s, FBW ABs and the MD11.

Gusty x-wind landings on the MD11 were always more than a "challenge":
- Rudder displacement didn“t "match" necessary aileron inputs.
- RCWS was a pain during just about every approach.
- The overall "sluggishness" at high gross weights coupled with an extreme G-load sensitivity at the same time.
- nose-up aircraft reaction after spoiler deployment forcing you to actually push the nose down (great "feature" after a bounce!)
etc., etc.

The point is that you have to have all paramaters (pitch, pwr, speed) for a stabilized approach absolutely stabilized so much earlier than with other aircraft, that consequently in some weather conditions it might become effectively impossible to fly a "stabilzed" approach with this plane more so than with others...
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Old 15th Apr 2009, 15:34
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The point is that you have to have all paramaters (pitch, pwr, speed) for a stabilized approach absolutely stabilized so much earlier than with other aircraft, that consequently in some weather conditions it might become effectively impossible to fly a "stabilzed" approach with this plane more so than with others...



Exactamundo! Buy that man a beer!

Cheers
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Old 16th Apr 2009, 20:08
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This is an interesting thread with interesting 'Creep', however it seems we should wait till the investigation is complete , so we don't insult our good colleagues...but it would be nice to discuss the stability/controllability/ aspects of the type,...and engage in creep in Techlog,...with out referencing this accident too much,...look at what the buffula accident showed us,...but,....don't speculate here


Yes, I've read everything!!!

PA
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Old 10th May 2009, 13:21
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Investigation Update

Hallo everyone. This is my first post at PPRuNe.
Before I begin, I like to inform the forum member that English is not my mother tongue, so if there is anything strange about the way I write, my apologies in advance.

I am now in Japan and would like to inform that NHK broadcast has televised a news yesterday(May9,Tokyo) that Japanese investigation authority is tracing the cause of FX80 accident to the faulty design of MD11. Namely, no machanical fuse between main landing gear and spar.

If my memory serves right, I remember reading a post (somewhere) explaining that when MLG of the MD11 recieves inputs beyond certain load, strut of the MLG bottoms and the impact force will directly convey to the spar of the wing and breaks them. Which could lead to rollover/flipover of the fuselage due to loss of LG and wing and immediate fire from a erupture of the fuel tank caused by MLG penetration to the wing structure.


Funny thing is, NHK does not show any news concerning this accident anymore on their website so I cannot provide you the URL ,so I guess I am risking creditablity from the start but I thought it was too important piece of information not to post here.


I was also unable to find any media relaying NHK news (in English) so I should recommend this information is kept as reference and not an official kind.

Thank you for your attention, and Good Day.
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Old 10th May 2009, 14:06
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Japanese investigation authority is tracing the cause of FX80 accident to the faulty design of MD11. Namely, no machanical fuse between main landing gear and spar.
No surprise there as it has been known for many years. Of course it's only one causal factor and unlikely to be changed so I guess we'll have to look elsewhere for a solution. I wonder what their final recommendations will look like?
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Old 10th May 2009, 14:33
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Copy the Past Report?

Dear lomapaseo-san

Pure speculation but since NTSB is assisting the Japanese Investigation Authorities, no suprise if they tipped about the findings in the past as part of their "assistance". Based on the fact that Japanese Investigation Authority's inexperience in investigating crash of a particular aircraft type, it wouldn't surpise me if this "tip and assistance" would have seemed somewhat tempting to them and effected the course of investigation somehow.

I hope the report doesn't turn out be copy&paste of the Newark crash report

Fingers crossed.
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Old 10th May 2009, 22:55
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Thank you for your post Mr. Goh.

That was interesting information.

Welcome to PPrune.
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Old 11th May 2009, 14:11
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Dear Huck san

Thank you for your kind welcome.

Hope the Japanese investigators and NTSB team members in assistance will be able to provide information to the aviation community (and to the families of the crew members) what FX80 experienced before it became unstable and flipover at Narita Airport.

(Just a thought but) I guess what happened between final approach and the second touchdown is unique to FX80 accident and this is where past investigation report on MD11 accidents involving MLG and spar design/structure failure does not cover.

Good Day
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Old 12th May 2009, 16:27
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MD11 and DC10 main gear is fused at the trunnion pins that attach the main gear to the structural trunnion fitting on the rear spar however as far as I know this is designed to protect the wing against rupture caused by high drag loads such as an off runway incident not high vertical loads. The forward attachment pin is designed to fail allowing the gear to fold rearwards away from the fuel tanks. The L1011 uses exactly the same main gear attachment and fusing arrangement as the DC10/MD11. Possibly the design requirement only requires protecting the wing from such off runway incidents.
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Old 14th May 2009, 08:30
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The design requirements cover both cases, vertical and horizontal overlod.

The landing gear system must be designed
so that when it fails due to overloads during takeoff
and landing
, the failure mode is not likely to
cause spillage of enough fuel to constitute a fire
hazard. The overloads must be assumed to act in the
upward and aft directions in combination with side
loads acting inboard and outboard. In the absence
of a more rational analysis, the side loads must be
assumed to be up to 20% of the vertical load or
20% of the drag load, whichever is greater.
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Old 14th May 2009, 08:50
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I think i did see a similar landing for some years ago were the Pilot after the first "bounce" put full trust and got in the air again.

Could that be possible here?
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Old 17th May 2009, 09:25
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Will be interesting hearing/reading the full CVR on this one.
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Old 17th May 2009, 16:16
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Does anyone know the current status of this investigation? Have not seen any NTSB postings nor for that matter anything from the JCAB.
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Old 26th May 2009, 10:30
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Is it possible that a contributory factor in this tragedy, could have been "elevator blanketing" at the point of touch down? This can be prevalent on some aircraft at high AA, where the elevator and stabilizer is in "stalled air" from the main planes and is ineffective or control even unpredictable, until the nose is lowered and the elevator is back in clean air.

Just my 2 cents worth.

Apologies if it has been mentioned before but haven't the time to read every page of this thread.
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Old 27th May 2009, 07:25
  #436 (permalink)  
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Volume

The design requirements cover both cases, vertical and horizontal overlod.

Gear load specs are worthless after failure when the engine/wing contact ground at the variable of airspeed/ dynamic force. The gear "shear safety" info being discussed becomes a non factor after the fact.

To state that even if gear load factors had not been exceeded but a sufficient strike had occured on the wing or engine the outcome would have been the same. DFDR released data will clarify all of this.

Why all this speculation. Obviously the aircraft experienced a contact with the ground out of operational limits resulting in a bad landing, obsolute the only type of bad landing....

Respect the operating limitations of the equiptment you are operating, understand this through and through and the odds of safe operation are on your side.
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Old 27th May 2009, 07:30
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slamer.

I am sure we can assume the CVR release will not surprise anyone in this case. Not much time to say anyting than the obvious.
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Old 27th May 2009, 09:58
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Why all this speculation. Obviously the aircraft experienced a contact with the ground out of operational limits resulting in a bad landing, obsolute the only type of bad landing....

Respect the operating limitations of the equiptment you are operating, understand this through and through and the odds of safe operation are on your side.
The point being made is that the MD-11 is the only big jet that during a heavy landing enough to shear the gear, rolls on it's back because the wing breaks off. Just because you do a really bad landing that should not be the result.
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Old 27th May 2009, 21:49
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muduckace

Maybe...and I dont know yet. But I suspect it (CVR) will be more revealing than that.
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Old 27th May 2009, 22:22
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Not so sure the MLG sheared, that's the problem. Attached to the Main Spar, all load transfers to the wing, which broke off. The NLG surely didn't fail, if only it had. Any bounce is -G, not the wings strongest resistance format.

Had the MLG remained intact on the 777 at LHR, what might have resulted? Ruptured Hull? Instead, the a/c belly skid to a standstill, no deaths. The MD11 needn't be stressed to land on the Carrier, eg another McD, F-4.

Had the NLG failed, the a/c may not have bounced to pitch up and reload the wings, causing the roll onto its back.

Given the choice, I would prefer my wing remain attached rather than the gear.
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