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DC10 And MD11 Crosswind.  
User currently offlineb767 From Norway, joined Feb 2008, 127 posts, RR: 0
Posted (3 years 7 months 1 week 1 day 15 hours ago) and read 5829 times:

Because of the MD11 landing accidents in recent years,it is been well known that the DC10 and MD11 landing gear don,t tolerate crab landings the way some other airliners like 767,777,747 do.This have been discussed at earlier topics here.But how was this earlier,before the first accidents happened?I have seen some DC10 and MD11 landings earlier were they touchdown in a significant amount of crab.In the now famous Alitalia Kai Tak video,the pilot actually kick rudder into wind combinated with lovering the left wing when he realise he is drifting off in the flare.I guess he is touching down at around 500 ft/min in crab and wing low.How close was this to a crash?This happend I belive around 97 or 98. Was crosswind prosedures the same before the first Fed Ex crash in Newark? If I am not mistaken,the prosedure today is to start the sideslip at around 300 feet ground level,but not sure how it was earlier.And what did McDonnel Douglas say about it when the DC10 and MD11 was introduced?

43 replies: All unread, showing first 25:
 
User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 79
Reply 1, posted (3 years 7 months 1 week 1 day 15 hours ago) and read 5815 times:

Quoting b767 (Thread starter):
Because of the MD11 landing accidents in recent years,it is been well known that the DC10 and MD11 landing gear don,t tolerate crab landings the way some other airliners like 767,777,747 do.

It's not a crab problem. The DC10/MD11 were certified to the same FAR's regarding crosswinds and structural strength as everyone else.

What tends to happen on the DC10/MD11 is *if* you land too hard on the main gear (usually a too high sink rate coupled with a too high roll rate) the overload failure results in loss of integrity of the rear spar. This kills the lift on one side while the other wing is still working just fine, flipping the aircraft over. On most other designs, the same overload will cause the landing gear to separate without failing the wing, so the plane stays level.

It should be noted that touching down that way (vertically overloading the landing gear) is operation outside the design envelope and not allowed by the AFM. The DC10/MD11 gets maligned a lot in this regard because some of it's *other* flight characteristics that have nothing to do with the landing gear may make a high-sink rate landing more likely.

Tom.


User currently offlineKlaus From Germany, joined Jul 2001, 21469 posts, RR: 53
Reply 2, posted (3 years 7 months 1 week 1 day 14 hours ago) and read 5781 times:

Quoting tdscanuck (Reply 1):
What tends to happen on the DC10/MD11 is *if* you land too hard on the main gear (usually a too high sink rate coupled with a too high roll rate) the overload failure results in loss of integrity of the rear spar. This kills the lift on one side while the other wing is still working just fine, flipping the aircraft over.

Does the entire wing fail immediately at that point or just the inner flap?


User currently offlineCosmicCruiser From United States of America, joined Feb 2005, 2255 posts, RR: 15
Reply 3, posted (3 years 7 months 1 week 1 day 14 hours ago) and read 5764 times:

Neither of the jets are landed in a crab as say a 777 can. Of the 3 accidents I know about closely at least 2 were hit (hard) in a crab thus introducing a side load as well. The 3rd hit hard and then had a side load too I believe.

User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 79
Reply 4, posted (3 years 7 months 1 week 22 hours ago) and read 5433 times:

Quoting Klaus (Reply 2):
Does the entire wing fail immediately at that point or just the inner flap?

One end of the landing gear support is attached to the rear spar (this is not unique to the DC10/MD11), so it folds up the whole wing if it fails. The inner flap doesn't carry any landing gear load.

Tom.


User currently offlineKlaus From Germany, joined Jul 2001, 21469 posts, RR: 53
Reply 5, posted (3 years 7 months 1 week 21 hours ago) and read 5399 times:

Quoting tdscanuck (Reply 4):
The inner flap doesn't carry any landing gear load.

Sure; But it's ultimately connected to the rear spar (indirectly) which made it appear plausible that possibly just the inner flap might fail with the spar and losing lift that way.

Quoting tdscanuck (Reply 4):
so it folds up the whole wing if it fails.

Okay. I didn't know whether the frontal spar might still be able to keep that from happening in the situation.


User currently offlinewilco737 From Greenland, joined Jun 2004, 9037 posts, RR: 75
Reply 6, posted (3 years 7 months 1 week 20 hours ago) and read 5345 times:
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Ah, the famous discussion about the MD11 again, I missed it   

When I flew the MD11 we had to do a wing low landing as it was recommended to touch down in a zero drift condition. With 35 knots crosswind this was pretty difficult as you need quite some bank and full ruder deflection. That's why the recommended crosswind component was 25 knots. This was pretty good to handle.
On the 744 it is different. You basically cannot do a wing low landing as the engines would touch the runway if you have too much bank. And that happens pretty early. So either touchdown in full crab. On a dry runway this is pretty uncomfortable as the 16 tires straighthen the plane very soon. So on a dry runway you decrab during flare. On wet or contaminated runway you touchdown in crab and the airplane straighten up with the runway itself.

wilco737
  



It it's not Boeing, I am not going.
User currently offlineSEPilot From United States of America, joined Dec 2006, 6910 posts, RR: 46
Reply 7, posted (3 years 7 months 1 week 16 hours ago) and read 5224 times:

Quoting tdscanuck (Reply 1):
It's not a crab problem. The DC10/MD11 were certified to the same FAR's regarding crosswinds and structural strength as everyone else.

The MD-11 has had several landing accidents as you describe, but not the DC-10 (unless UA-232 failed in this manner-it did roll over). Since the design of the landing gear attachment is the same, I take it that the reason is that the MD-11 has much trickier handling characteristics that make it much more likely to land with a high sink rate. What's your take on it?



The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
User currently offlineCosmicCruiser From United States of America, joined Feb 2005, 2255 posts, RR: 15
Reply 8, posted (3 years 7 months 1 week 16 hours ago) and read 5217 times:

Quoting SEPilot (Reply 7):
but not the DC-10

First I want to correct one thing I posted, only ONE of our MD-10 accidents was due to a hard side load ldg. One was not at all. But in reference to the quoted post one WAS a MD-10 (DC-10).


User currently offlineSEPilot From United States of America, joined Dec 2006, 6910 posts, RR: 46
Reply 9, posted (3 years 7 months 1 week 12 hours ago) and read 5137 times:

Quoting CosmicCruiser (Reply 8):

First I want to correct one thing I posted, only ONE of our MD-10 accidents was due to a hard side load ldg.

If I remember correctly, the landing gear collapsed but the plane did not roll over; the only DC/MD-10 that has rolled over was UA-232, and I have never seen an analysis of why it did (it certainly had enough other problems). I believe that all of the MD-11 landing accidents where the gear collapsed also involved the plane rolling over.



The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 79
Reply 10, posted (3 years 7 months 1 week 9 hours ago) and read 5056 times:

Quoting SEPilot (Reply 7):
Since the design of the landing gear attachment is the same, I take it that the reason is that the MD-11 has much trickier handling characteristics that make it much more likely to land with a high sink rate. What's your take on it?

As far as I can tell, the MD-11's higher approach speeds and different handling (specifically in pitch) make it slightly more likely to end up in a high sink rate landing...there's still an open question about how much of that is the plane's fault (the plane should be "easy" to fly) and how much is the crews' fault (you're never allowed to land outside AFM limits in normal service).

Tom.


User currently offlineSEPilot From United States of America, joined Dec 2006, 6910 posts, RR: 46
Reply 11, posted (3 years 7 months 6 days 12 hours ago) and read 4837 times:

Quoting tdscanuck (Reply 10):

As far as I can tell, the MD-11's higher approach speeds and different handling (specifically in pitch) make it slightly more likely to end up in a high sink rate landing..

That has been my impression; thanks for confirming it.



The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
User currently offlineWilco737 From Greenland, joined Jun 2004, 9037 posts, RR: 75
Reply 12, posted (3 years 7 months 5 days 11 hours ago) and read 4671 times:
AIRLINERS.NET CREW
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Quoting SEPilot (Reply 11):

That is simply correct. You have a higher approach speed, higher speed over ground, so you have to have a higher rate of descent to stay on the glideslope. BUT in UIO or MEX you have high elevation airports and even a 744 or 340 has a lot higher approach speeds there (IAS is the same, but groundspeed is higher), so you have a higher rate of descent as well. So you need to watch out during landing flare as well.

I did 2200 hours on the MD11 and I had only one landing which was a littler harder, but no hard landing. She wasn't the easiest airplane, no doubt. But it is not as bad as most people say.

wilco737
  



It it's not Boeing, I am not going.
User currently offlineSEPilot From United States of America, joined Dec 2006, 6910 posts, RR: 46
Reply 13, posted (3 years 7 months 4 days 1 hour ago) and read 4499 times:

Quoting Wilco737 (Reply 12):
I did 2200 hours on the MD11 and I had only one landing which was a littler harder, but no hard landing. She wasn't the easiest airplane, no doubt. But it is not as bad as most people say.

But it has accumulated a much worse accident rate than any other modern jetliner, and most of those accidents have been landing accidents. And yet the airlines (Finnair, KLM) that have flown it the most have had none. Do you attribute that to better training? That is my take on it.



The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
User currently offlineWilco737 From Greenland, joined Jun 2004, 9037 posts, RR: 75
Reply 14, posted (3 years 7 months 4 days ago) and read 4460 times:
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Quoting SEPilot (Reply 13):
But it has accumulated a much worse accident rate than any other modern jetliner, and most of those accidents have been landing accidents. And yet the airlines (Finnair, KLM) that have flown it the most have had none. Do you attribute that to better training? That is my take on it.

The problem about statistics is: they are never correct and a reliable source. From a statistic the Concorde is incredible unsafe. Not a lot airplanes built, one bad fatal accident and it is bad already.
Yes, the MD11 had several landings accidents. I don't deny that fact. The question is simply why? Only the higher approach speeds is not enough. Too small stabilizer? Well, if it is too small, then you need higher or more control input to achieve the same result. Flying faster, higher airflow, higher efficiency. So that should compensate that already. Pitch problems? Well, there is a system installed LSAS which is a computer which should avoid tailstrikes and hard landings as this makes some control inputs as well.
Better training? I am sure that is a thing as well. If you know how to handle the MD11 and if you know what you do, then you have a far less risk to come into such a situation.
The MD11 accidents started with an initial touchdown. The important thing is, to find out what had led to that hard initial touchdown which iniated a bounce and the following incidents/ accidents.
The last 3 accidents are not finally investigated, so we cannot really say for sure what the problem is.
I personally haven't had any issues with the MD11. Not in crosswind weather, not in normal weather. She handled fine. Sure, some touchdowns were harder than others, but never a hard landing... Why? I don't know. Maybe lucky, maybe I knew how to handle it... No clue what it was...

wilco737
  



It it's not Boeing, I am not going.
User currently offlineSEPilot From United States of America, joined Dec 2006, 6910 posts, RR: 46
Reply 15, posted (3 years 7 months 3 days 23 hours ago) and read 4454 times:

Quoting Wilco737 (Reply 14):

The problem about statistics is: they are never correct and a reliable source. From a statistic the Concorde is incredible unsafe. Not a lot airplanes built, one bad fatal accident and it is bad already.

This is certainly true. Airliners have become so safe that ANY accident is really an outlier. But with the MD-11 you really have a cluster of very similar accidents; this does grab one's attention. And yet the airlines with the most experience with it have a perfect safety record. I do appreciate your comments; I very much respect the opinion of one with actual, real world experience instead of armchair experience.



The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
User currently offlineKlaus From Germany, joined Jul 2001, 21469 posts, RR: 53
Reply 16, posted (3 years 7 months 3 days 23 hours ago) and read 4452 times:

Quoting Wilco737 (Reply 14):
The problem about statistics is: they are never correct and a reliable source.

Sloppily defined or misinterpreted ones aren't. Well-defined and properly interpreted statistics very much are reliable sources of information!

The sample size of all MD-11 landings should be sufficiently large to compare against other types, so as long as the comparison is done to decently comparable aircraft, missions and operators, I would expect the statistics to be useful for pointing towards common or distinguishing factors.

That does not automatically mean that the distinguishing factors will necessarily be easy to identify, however (or at all).

And there is of course still the possibility that even a statistically significant elevation in accident numbers could still just be random.

The aircraft are obviously not breaking down at every second landing, so any potential issues are not severe. But they could still exist.

The question is if something can be learned there for future designs (or training) before they'll all be retired...


User currently offlineWilco737 From Greenland, joined Jun 2004, 9037 posts, RR: 75
Reply 17, posted (3 years 7 months 3 days 23 hours ago) and read 4452 times:
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Quoting SEPilot (Reply 15):
This is certainly true. Airliners have become so safe that ANY accident is really an outlier.

Any accident is tragic, sad and always makes me think about my job. Am I doing enough, am I prepared for everything? Well, you cannot be prepared for everything. But I like to do my job as good as possible to make it as safe as possible for everyone flying with me.

Quoting SEPilot (Reply 15):
But with the MD-11 you really have a cluster of very similar accidents; this does grab one's attention.

Yes it does grab one's attention. But we haven't seen the final reports what exactly happened. They all resulted out of a hard landing. So the question is: WHY did they land that hard? And what made the airplane go airborne again and what in the end led to the crash. We simply don't know.
Many people investigating, with all airlines who fly MD11 involved. It is a very difficult investigation and of course there are poeple who say: Ground is asap! Others say: Let's find out first what exactly is wrong. Maybe it is just a different landing technique the airlines have, or a different software version of the LSAS or.... etc etc etc. Problem with airplane investigation is: it takes long and it has many many MANY factors in there.
Actually one day I like to work or being part of crash investigation as I think one can learn a lot from it. It is tragic for sure and I feel always sorry for the people who lost their lives and of course I feel sorry for their families and friends...

Quoting SEPilot (Reply 15):
I do appreciate your comments; I very much respect the opinion of one with actual, real world experience instead of armchair experience.

You're welcome. And I am willing to answer the questoins as good as I can.

wilco737
  



It it's not Boeing, I am not going.
User currently offlineWilco737 From Greenland, joined Jun 2004, 9037 posts, RR: 75
Reply 18, posted (3 years 7 months 3 days 23 hours ago) and read 4449 times:
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Quoting Klaus (Reply 16):
The aircraft are obviously not breaking down at every second landing, so any potential issues are not severe. But they could still exist.

If that would happen, then it would be grounded very soon. But thank god not that many accidents happen! And I hope that stays that way.

Quoting Klaus (Reply 16):
The question is if something can be learned there for future designs (or training) before they'll all be retired...

Problem is, that a lot has been learnt from other accidents and that after accidents new things were built into airplanes or training was changed. I fear that this will be the same thing in the future. Less often, but it will happen. If the MD11 has serious issues then I for sure hope that the investigators will find out soon as I know a lot of the crews flying MD11F for LH Cargo and I don't want to see anyone of them dead.
I am glad that both pilots of the RUH crash survived! I Actually know the captain and flew with him twice. He is such a good guy!

wilco737
  



It it's not Boeing, I am not going.
User currently offlineKlaus From Germany, joined Jul 2001, 21469 posts, RR: 53
Reply 19, posted (3 years 7 months 3 days 23 hours ago) and read 4442 times:

Quoting Wilco737 (Reply 18):
If that would happen, then it would be grounded very soon.

Only if it was found to be sufficiently severe and only if a grounding was really seen as the best remedy. But that's not necessarily the case.

Quoting Wilco737 (Reply 18):
But thank god not that many accidents happen! And I hope that stays that way.

Definitely!


User currently offlinetravelavnut From Netherlands, joined May 2010, 1614 posts, RR: 7
Reply 20, posted (3 years 7 months 3 days 23 hours ago) and read 4437 times:

Quoting Wilco737 (Reply 17):
Many people investigating, with all airlines who fly MD11 involved. It is a very difficult investigation and of course there are poeple who say: Ground is asap!

I'm not of the opinion that the MD11 should be grounded, she's still a lot more safer than earlier types. But I must say, when comparing to airliners of her generation she does stand out;

http://www.boeing.com/aboutus/govt_o..._accidents_statistical_summary.pdf (Page 21)



Live From Amsterdam!
User currently offlineWilco737 From Greenland, joined Jun 2004, 9037 posts, RR: 75
Reply 21, posted (3 years 7 months 3 days 23 hours ago) and read 4434 times:
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Quoting travelavnut (Reply 20):
I'm not of the opinion that the MD11 should be grounded,

I never said she should be grounded. I only said: IF there are enough reasons and IF they find out the airplane has an issue, then it should be grounded.

wilco737
  



It it's not Boeing, I am not going.
User currently offlineKlaus From Germany, joined Jul 2001, 21469 posts, RR: 53
Reply 22, posted (3 years 7 months 3 days 23 hours ago) and read 4429 times:

Quoting travelavnut (Reply 20):
I'm not of the opinion that the MD11 should be grounded, she's still a lot more safer than earlier types. But I must say, when comparing to airliners of her generation she does stand out;

Together with the DC/MD-10 on a very similar level.

But one would have to look at the circumstances as well. MD-11s are mostly used for cargo hauling by now, aren't they?

Mission profiles, operator mix, pilot training levels, seniority, age, experience and many other factors may also differ substantially from other types.

All that goes to my point above: Statistics need to be read with caution; Valid Interpretations may be more limited than it appears at first glance.


User currently offlineWilco737 From Greenland, joined Jun 2004, 9037 posts, RR: 75
Reply 23, posted (3 years 7 months 3 days 23 hours ago) and read 4427 times:
AIRLINERS.NET CREW
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Quoting Klaus (Reply 22):
MD-11s are mostly used for cargo hauling by now, aren't they?

Only KLM has a couple MD11s left. All other operators are Cargo operators now.

wilco737
  



It it's not Boeing, I am not going.
User currently offlinetravelavnut From Netherlands, joined May 2010, 1614 posts, RR: 7
Reply 24, posted (3 years 7 months 3 days 22 hours ago) and read 4417 times:

Quoting Wilco737 (Reply 21):

Quoting travelavnut (Reply 20):
I'm not of the opinion that the MD11 should be grounded,

I never said she should be grounded. I only said: IF there are enough reasons and IF they find out the airplane has an issue, then it should be grounded.

Wilco, I never said that you said they should be grounded.. I was just responding to the people you describe in your post that DO say that (let it be clear I am not one of them).



Live From Amsterdam!
25 Post contains images Wilco737 : Alright, sorry for the missunderstanding then. wilco737
26 Klaus : Ah, thanks.
27 b767 : Always wondered about the 20 percent higher landing weight than the DC10-30, if that could be a contributing factor. Was the MD11 wing spar and landin
28 Post contains images Wilco737 : Good question. I flew the MD11F and we often were close to the max landing weight. I don't know how far you could've reduced it to still be in the pr
29 TZTriStar500 : Many forget that World still flies 7 pax MD-11s as well.
30 Post contains images wilco737 : but can you actually book these flights? I thought they are only for military transport, that's why I haven't added it to the list. wilco737
31 TZTriStar500 : No, but still pax aircraft as I thought the conversation was pax versus cargo MD-11s.
32 SEPilot : In any case aren't they strictly charter? While they are still pax, they are not regularly scheduled, are they?
33 Post contains images wilco737 : Yes ,you are right. It is a PAX aircraft. Even though one cannot really book flights on them, it is still per definition a PAX airplane. wilco737
34 vikkyvik : Wilco, what would a typical approach speed be for a MLGW or close-to-MLGW landing in an MD-11? Say, at sea level for example's sake. Just curious. Th
35 Post contains images wilco737 : If on sea level or not, doesn't make a change in the approach speed. We fly IAS, which are always the same. The TAS and GS are different. With MLGW a
36 Speedbird741 : Good God that is fast! Especially when compared to a 744 or an A340, even the -600. Speedbird741
37 Post contains images wilco737 : Yes. And now have a slight tailwind of 5 knots and high elevation in MEX or JNB or NBO and you are reaching a ground speed of 200 KIAS... Frigging fa
38 Post contains images vikkyvik : D'oh! Wow. Significantly faster than I had anticipated! Thanks for the info.
39 Speedbird741 : Put in a hot, rainy afternoon and may the 13,000 foot runway be with you! By the way, how did the MD-11's brakes behave at such high speed/temperatur
40 TZTriStar500 : They are operated in charter ops only, but why does that make a difference here? Its still a pax MD-11 and operated no different than another pax MD-
41 Post contains images wilco737 : Nicely said. The longer the runway the better. The approach to UIO is always nice in the MD11. What a shame I have only been there once. The brakes w
42 tdscanuck : Keep in mind that the brakes are always sized by RTO at V1 at MTOW...by comparison, the landing case is relatively benign. Tom.
43 SEPilot : Granted. But charter operations are usually a lot less frequent, and not anyone can get on them. But your point is valid.
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