An Airworthiness Review - China Air MD-11 Hong Kong

Some info on the other Fedex Md11 accident on that link , plus link to the Mandarin Md11 accident in HK

Seems the Md11 is not suited to landing in strong winds, and a diversion is a better preference when such conditions exist?

Some good posts here above on cert requirements as well as the one quoted.

I think the issue here might be that the designers assumed that when/if the loads were exceeded it would be a crash landing and no amount of analysis could predict the results.

Unfortunately it looks like a crash landing with a still flying wing on one side is what is unique in these accidents (lesson learned?)

MD-11 X Cross wind
 

It is not correct to say that the MD-11 is not suited to land in strong or gusty cross winds.
Respecting the limitations, it is a perfectly fine aircraft to operate in all weather conditions as any other wide body.
MD-11 pilots must understand the LSAS and this is the key to fully appreciate this beautiful airplane.
I believe that pilot qualifications to fly the MD-11 are more of the concern, not the aircraft.
The secret to land the MD-11 in gusty cross winds is to align with the runway using the rudder not later than 500 feet and don’t allow the auto-throttle to retard at 50 feet RA. In other words, hold the thrust levers to maintain the Vref + wind additives and manually retard the throttles to idle at touchdown.
This is not an easy task and requires a lot of experience to achieve this technique, that’s why pilot qualification has an important role here.
two cents from who operated the great MD-11 for long time
:ok:

So, in your view, where should this "experience" be gained in order for this task, which is "not easy", to become part of a line pilot's repertoire? With pax in the back (thankfully now a relatively rare occurence) or with thousands of dollars of other people's goods on the main deck or in the simulator?

You may have mastered the beast but clearly other pilots haven't and even the most experienced can be caught out by a set of circumstances.

If the aircraft is that tricky to deal with in an everyday situation such as a cross wind the question has to beasked about its suitability for continued service for the sake of those who still ride down the back, including many American troops, the freight shippers and you and the other crew who fly the aircraft.

I've seen many an MD-11 landing in cross winds over many years. The aircraft has always looked to handle the situation far less tidily than other wide bodies before or following

The 346 in Quito landed with 1100fpm - without structural damage. Only the MLG bogies where damaged which in turn damaged the Air/Ground logic leading to the overrun.
Noteworthy is furthermore that at 249t they where close to Max. landing wheight which is 259t.

Marcus

MD
 

With its institutional memory, builds a/c to land on the Carrier. The LG division is a little over exuberant. After the wing fails, (pick a side) the remaining wing is accelerated (pivoting around a dug in MLG) gaining great lift. The remaining (Starboard in this case) wing failed also, at its most pronounced AOA and at the pylon. The video shows this, it is unusual it remained in position post crash, but not startling; skin, and rib/stringer assemblies carried it along. IMO. It is amazing to see the NLG defiantly stuck in the Air after those horrendous bounces and pre-roll skid.

AF

I doubt you have every worked in an a/c design office, because nobody positions a wing on anything other than 'where it should be' and there's only one place which is 'where it should be' :rolleyes:

And for BA038, the B777 at Heathrow, "The aircraft’s initial impact was at a descent rate of about 1,400 fpm and a peak normal load of about 2.9g." (source: AAIB). Landing gears came off but the fuselage stayed together.

Some of the certification requirements posted so far do not give the full picture. For example the safety factor of 1.5 does apply to static loads, however landing gears are typically safe life structure designed for a fatigue life that matches the aircraft service life. Therefore most landing gear components are stronger than they need to be for static reason. On the other hand you cannot use the safety factor to scale impact speed, at certain rate the shock absorber will bottom and the loads will rise significantly, so you can not assume that a landing gear can always take 1.5 the design descend speed.

It is also a requrement that in a minor (otherwise survivable) crash landing the landing gear must safely break off the airframe without rupturing any fuel tank, taking into account all reasonable combinations of horizontal and vertical forces. It does therefore not matter whether Douglas or McDonnell was designing the landing gear, the requirements are the same. Typically specific shear pins are designed to break off first, they are often tailored to exact rupture loads by taking material samples and machining the inner diameter to the exact required dimension.

Regarding the break off of the left wing, as a huge ammount of fuel is obviously released (and ignited), the wing must have ruptured in the area of a fuel tank that still contains a lot of fuel during landing. I am not aware of the exact fuel system layout. The left landing gear is still attached to the wing, so it looks like the wing fractured somewhere between the fuselage and the landing gear.

What puzzles me at the moment is the fully deployed right wing (Nr. 1) thrust reverser. At which point during the event was the T/R activated ? It obviously had time enough to fully deploy, which for a translating cowl design driven by spindles should take a little time, and not happen accidentially. Auto T/R at the firm first tochdown ?

Regarding the positive statements about FedEx, I work with some of their maintenance engineers and I am always impressed by their competence and their focus on safety. My thoughts are with the colleagues they lost.

Flying the MD11
 

Now, I actually fly the MD11. Left seat.
Too much speculation going on here.
Fact: An MD11 is just a plane. Certified and all, just like all the other birds out there.
Fact: LSAS provides PPL after touch down and I must say the new software makes it much easier to master for rookies. The fact that LSAS moves the elevator without the pilot handling the aircraft knowing it is to some disturbing. Not to digital jocks out there: they've given that up long time ago.
Fact: MD11 is actually certified with LSAS. It's got to operate and all redundant system working before departure.
Fact: main gears are fitted onto wing spar and THAT is not allowed in a new model anymore before certification. Gears are nowadays designed to shear i.s.o. taking the wing off.
Fact: I almost always fly with autothrottle and rarely override it. It's that good. Also in gusty wind conditions. It's even certified to auto fly itself out of windshear.
I wouldn't dare to say something about the skill of the pilots involved. May they rest in peace. But everybody who's been to Narita knows of the conditions with high wind.
Has anyone thought of an LSAS failure? The wind was strong enough to preclude an autoland so the LSAS should've kicked in as soon as the autoflight was disconnected. What if it didn't work as expected.
How about the following. How aware is any pilot of the longitudinal attitude of an airplane in the flare? A gust after a bounce could've sent the wings flying again without the pilots being aware of the aircrafts' negative pitch attitude developing, the flight deck still at an altitude above the runway that would've been expected.
Just a thought.
SM

"What puzzles me at the moment is the fully deployed right wing (Nr. 1) thrust reverser. At which point during the event was the T/R activated ? It obviously had time enough to fully deploy, which for a translating cowl design driven by spindles should take a little time,"

On wheel spin up, #2 does not deploy until ground prox is made with NLG compression. 526 had prats on her, this means hydraulically actuated reversers. Not really important, even if deployment is a bit quicker even with wormgear actuation it is still only a few seconds.

No, I haven't but the stretch of over 18 feet compared to the DC10-30, almost all ahead of the wing, changed centre of lift and the handling characteristics. Coupled with the smaller tailplane the MD11 is a "handfull" in certain conditions, a reputation the DC10 never had.

"Has anyone thought of an LSAS failure?"

Doubtfull, the only LSAS failures I have ever encountered have been FCC boot failures. If it did fail all it would have done is provide full pilot elevator authority.

Fact: poor landing conditions.
Fact: poor landing.
Fact: aircraft crash from time to time.

I am with you on the over speculation. I believe it to be probable poor judgement mixed with horrible conditions. After the first bounce the nose down attitude reason will be determined from DFDR paramaters.

Did the landing pilot try to lower the angle of attack after he realized he flared too late too much?

Did he make the input after the hard landing in a desperate attempt to just get her on the ground?

Probably the first scenario mixed with the jar and force adding to the A.N.D. command. After the nose struck the first time they lost all control.

None the less, I believe the procedure to be to GA. in this scenario (bounce in windshear/crosswind) .#3 eng T.R. was deployed.

So nothing to do with 'military thinking' then, as aerodynamics is a rather unforgiving witness...
I am also still having a lot of trouble getting my head around sizing a tailpane based on de-icing criteria. I hope to learn something here other than repeated hearsay.

This is not the pertinant to the issue at all. Different performance charicteristics require different procedures. As long as the driver respects the machine and understands her limitations the MD-11 is an excelent aircraft.

Also the smaller tail was all about drag reduction. Anti-Ice is a trivial issue in reference to the tails design.

There are some rumours that according the investigation the main suspected reason is the stabilizer runaway.
Any one has heard anything?

That is probably the most likely explanation. (Also the wrong thing to do as you probably know...)

What is curious is after the initial bounce, the apparent rotation to a G/A attitude, the appearance of an initial go-around (the proper choice), the airplane seems to be climbing away from the runway, and then the sudden pitch over.

Did the crew simply lose control of the airplane?

It appears they had it made had they selected TOGA gone around.

Looking at the video, is it not possible for the
cargo to have been buffeted whilst on approach,loosened when
it landed hard, and moved mid bounce - therefore shifting C/G to
an unrecoverable position.

MM

Correct. The penalty for drag reduction was the cost of anti-icing equipment. It is a matter of record that MDD decided the DC10 tailplane would not be de-iced as the drag penalty of the larger tailplane in the days of cheap fuel was a minimal handicap to sales and more metal was cheaper than a whole extra system.

If the machine is so good, why did the major carriers who bought it spend zillions getting rid as fast as possible. The cost to AA and DL, to name but two, to replace the 11 with more 767s and to retrain crew, engineers and other staff was not an insignificant decision and the excuse of poor fuel economy compared to promised performance seems not to trouble FedEx.

Of course the crew need to respect the machine and understand the limitations - as with any machine or device, but a machine with inbuilt, and almost covert, vices needs more than repect.