c5load
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What Would Have Made The MD-11 Better?

Thu Dec 10, 2009 1:56 am

Everyone talks about how dangerous the MD-11 is to fly, and how flawed it is, and how it never rose to par with airlines' expectations. So, I throw out to everybody, what would you have done to make the MD-11 better. More efficent engines? (if available), Different wing design, bigger elevator? What could have been done if we could go back to the drawing board with this airplane so it wouldn't have fallen through as fast as it did?
"But this airplane has 4 engines, it's an entirely different kind of flying! Altogether"
 
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Mortyman
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RE: What Would Have Made The MD-11 Better?

Thu Dec 10, 2009 2:00 am

Did'nt know the MD11 was dangerouns to fly ?? First time I've heard that. I have flown it many times and never had a problem.
 
richiemo
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RE: What Would Have Made The MD-11 Better?

Thu Dec 10, 2009 2:01 am

great question. And I wish we had the ability to go back to the drawing board cause this wonderful aircraft had too short a time in the respective fleets. I thought it would continue the great legacies of the L1011 and DC10s for a few decades but unfortunately no. AT the end of the day though I suspect more carriers opted out early on this due to its lack of range. It never had the legs McDD said it would. AA and Delta were diappointed (I think) in its performance. Too bad. One of the last great "novelty" aircraft.
 
deltal1011man
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RE: What Would Have Made The MD-11 Better?

Thu Dec 10, 2009 2:08 am



Quoting Mortyman (Reply 1):
Did'nt know the MD11 was dangerouns to fly ?? First time I've heard that. I have flown it many times and never had a problem.

2nd that. I did a pretty good bit of M11 flights and thought they were great rides(but lets be clear, the L1011 was the best plane ever)

Quoting Richiemo (Reply 2):
AA and Delta were diappointed (I think) in its performance. Too bad. One of the last great "novelty" aircraft.

The plane wasn't want MD said it would be. The 777 is what killed it really. Boeing did what MD didn't and made a plane that had the range the M11 didn't and only two engines.

DL had to add fuel tanks to 2 M11s(I can't remember the tail numbers anymore) so they could do LAX-HKG.(this is one of the reason the route failed because they could carry any cargo.)
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c5load
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RE: What Would Have Made The MD-11 Better?

Thu Dec 10, 2009 2:25 am



Quoting Mortyman (Reply 1):
Did'nt know the MD11 was dangerouns to fly

I think because it's known to be hard to fly and if you don't master it just right, it can turn on you.
"But this airplane has 4 engines, it's an entirely different kind of flying! Altogether"
 
thegeek
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RE: What Would Have Made The MD-11 Better?

Thu Dec 10, 2009 2:25 am

Regarding the safety of the MD-11, this is an interesting link:
http://www.airlinesafety.com/faq/faq9.htm

I would expect that you are more likely to be killed driving to the airport than actually on the MD-11 though.

In answer to the OP,
I think a bigger stabilizer and much larger wings are pretty obvious changes you would make to it if you could go back in time. Also, the artifical stability system which cuts out below a certain altitude probably shouldn't. Focusing on the minor issue of negative lift from the stabiliser rather than the major issue of generating the lift from the wings more efficiently was a big mistake, in hindsight.

Also, failing to acknowledge that twins are the future wasn't good either.
 
modesto2
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RE: What Would Have Made The MD-11 Better?

Thu Dec 10, 2009 2:52 am



Quoting Mortyman (Reply 1):
Did'nt know the MD11 was dangerouns to fly ?? First time I've heard that. I have flown it many times and never had a problem.

A brief glance at the number of crashes and incidents involving the MD11, compared to the relatively small number of airframes, reveals that the plane has had more than its fair share of problems. I would feel completely safe flying in an MD11, but I do agree that something is suspect with its flying characteristics.

Quoting Thegeek (Reply 5):
Regarding the safety of the MD-11, this is an interesting link:
http://www.airlinesafety.com/faq/faq9.htm

That link offers an interesting perspective on the design characteristics of the airplane. Once again, I'm not saying that the plane is "dangerous," but it does suffer from some questionable design characteristics.
 
roseflyer
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RE: What Would Have Made The MD-11 Better?

Thu Dec 10, 2009 2:54 am

I believe the fundamental problem was that McDonnell Douglas tried too hard to keep costs low. It essentially was a re-engine when in reality a fully modernized plane was needed. It kept the wing of the DC10 in order to save money rather than updating it to be more customized for the higher takeoff weights and improved fuel efficiency needed.

Boeing usually tries to keep as many common components (known as minimum change) when making derivatives. The 737NG kept many components of the classic, but it updated the areas that needed it such as wing, fuselage, structure, landing gear and engines. MCD did less than half of that with the DC10 to MD11 transition. A good part of that was because the company was perpetually short of money when designing new planes and could not fund it.

Regarding safety. The airplane does not appear to have the same level of safety margins as other airplanes based on the number of similar events of crashing during landing. While perfectly safe, the airplane has limits that make it more susceptible to pilot error. If the wing to body join was stronger and the gear were stronger, some structural failures which caused the plane to invert during hard landings may not have happened. While not flaws, it is a more challenging airplane than others.
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FX1816
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RE: What Would Have Made The MD-11 Better?

Thu Dec 10, 2009 5:34 am



Quoting RoseFlyer (Reply 7):
I believe the fundamental problem was that McDonnell Douglas tried too hard to keep costs low. It essentially was a re-engine when in reality a fully modernized plane was needed. It kept the wing of the DC10 in order to save money rather than updating it to be more customized for the higher takeoff weights and improved fuel efficiency needed.

Are you sure that they kept the same wing because I remember hearing that they were fairly different. Yes they did look alike but I believe they were pretty different. According to Boeing:

DC-10 Technical Specifications
Series 10 Series 15 Series 30 Series 40
Wing Span 155 ft 4 in (47.3 m) 155 ft 4 in (47.3 m) 165 ft 4 in (50.4 m) 165 ft 4 in (50.4 m)

MD-11 Technical Specifications

Wing Span 169 ft 6 in (51.70 m)

My uncle is a Captain for DL on the T7 but back when they leased the two GE powered MD-11's from Mitsubishi back in the very early 1990's he was an FO on them. After the FX crash at NRT I spoke with him about the MD-11 and he didn't have anything bad to say about it but that it was just a much less forgiving aircraft than anything else he has flown. Now since I'm not an engineer I don't know if it is an unsafe aircraft or not but it is had to ignore that they have a had very shaky history, especially of late. Don't get me wrong though I think they are really great looking aircraft.

FX1816
 
VirginFlyer
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RE: What Would Have Made The MD-11 Better?

Thu Dec 10, 2009 8:32 am

A larger horizontal stab,

Signed,

SEPilot

(Sorry mate, couldn't resist!)

But in all honesty, I reckon if they'd been able to make use of the same engine technology the 777 did, and built it is a twin rather than a tri-jet, it may have made it easier to meet their promises. I also recall reading that the original wing failed under static testing well below ultimate load (I want to say in the vicinity of 110% limit load), and resulted in a lot of extra weight having to be built into the aircraft to strengthen the wing (I can't find a reference to this at the moment - I'm certain I'm not dreaming though...).

Probably the biggest problem though was that the decision making process at MD Commerical Airplanes was pretty much hobbled ever since the McDonnell - Douglas merger.

V/F
"So powerful is the light of unity that it can illuminate the whole earth." - Bahá'u'lláh
 
keesje
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RE: What Would Have Made The MD-11 Better?

Thu Dec 10, 2009 10:32 am

A 420 seat stretch, efficient 72klbs GENX engines, better wiring protection, leaner longer wings..

The result could have been a Pacific champion, without ETOPS, with greater cargo capasity then a 777-300ER and far more efficient then a 747.
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eham
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RE: What Would Have Made The MD-11 Better?

Thu Dec 10, 2009 11:12 am

The major issue here is the experience of the flight crews, the MD-11 is a little bit tricky to fly and needs some extensive training (= experience). KLM hasn't many issues on their MD-11. Only when they just introduced the type in their fleet they suffered a tail-strike on PH-KCA just weeks after delivery.
 
c5load
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RE: What Would Have Made The MD-11 Better?

Thu Dec 10, 2009 1:22 pm

Was the MD-11 the last hoo-rah for MCD? Was it their chance to try and stay in business, or was Boeing already going to buy them regardless?
"But this airplane has 4 engines, it's an entirely different kind of flying! Altogether"
 
777fan
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RE: What Would Have Made The MD-11 Better?

Thu Dec 10, 2009 1:40 pm



Quoting Richiemo (Reply 2):
It never had the legs McDD said it would. AA and Delta were diappointed (I think) in its performance. Too bad. One of the last great "novelty" aircraft.

I had the pleasure to fly on one earlier this year and thought it was a great ride - definitely more "character" than the usual 767 or A330 TATL or transcon flight. I must admit, though, that I was a bit unnerved during our approach as we had to battle some gusty crosswinds on final (this was about two weeks after the FX incident).

I also will never forget the UA232 incident; I can't help but cringe when I see an engine mounted atop the fuselage. On the aforementioned flight, I couldn't help but notice that I was practically standing beneath the engine while using one of the rear lavs!

777fan
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seabosdca
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RE: What Would Have Made The MD-11 Better?

Thu Dec 10, 2009 1:48 pm



Quoting C5LOAD (Thread starter):
So, I throw out to everybody, what would you have done to make the MD-11 better.

Boeing figured it out by 1994: a new wing and one fewer engine.
 
ebj1248650
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RE: What Would Have Made The MD-11 Better?

Thu Dec 10, 2009 2:13 pm

I understand MD corrected the performance deficiencies with some external mods; nothing earth shaking but they got the job done. However, by the time those mods were introduced the 777 was in the wings and it promised a lot that airlines wanted. The MD-11 is still one of my favorites though.
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777STL
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RE: What Would Have Made The MD-11 Better?

Thu Dec 10, 2009 2:24 pm



Quoting C5LOAD (Thread starter):
Everyone talks about how dangerous the MD-11 is to fly, and how flawed it is, and how it never rose to par with airlines' expectations.

"Dangerous" might be a bit overdramatic, "not as forgiving to mistakes as other aircraft" might be more accurate.

Quoting DeltaL1011man (Reply 3):
The 777 is what killed it really.

MD killed the MD11 when it didn't initially deliver the stated performance. The 777 only hastened the MD11's demise.

Quoting C5LOAD (Reply 12):
Was the MD-11 the last hoo-rah for MCD? Was it their chance to try and stay in business, or was Boeing already going to buy them regardless?

It wouldn't have a difference, IMO. McAir's real value lied in its defense division, not so much in the commercial aircraft division. Afterall, Boeing killed McD's commercial aircraft programs relatively quickly after the merger - with the MD95/717 being the only airframe that remained somewhat viable.
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Dreadnought
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RE: What Would Have Made The MD-11 Better?

Thu Dec 10, 2009 2:31 pm

The DC-10 was a famously stable aircraft - remember the Sioux city incident and others, where the DC-10's propensity for natural stability saved a lot of lives. In designing the MD-11, MD took what was until then a stable design and then destabilized it by changing fuselage length, wings, and basically keeping the same tail. A cousin of mine used to fly DC-10 and then MD-11 for Swissair, and he told me that while the DC-10 would land itself (not with autopilot, just the fact that it was so stable), the MD-11 was a handful, and pilots had to really pay attention to avoid a major upset. More than one MD-11 overturned and landed on their backs (FedEx and Mandarin come to mind, and I think there were others) - and that is purely a result of instability. I can't recall any other widebody aircraft (including the DC-10) ever flipping over on landing like that.
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WA707atMSP
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RE: What Would Have Made The MD-11 Better?

Thu Dec 10, 2009 3:10 pm

I think what doomed the MD-11, more than anything else, was that it came out ten years too late.

In the late 1970s, McDonnell Douglas proposed the DC-10 61/62/63. The -61 would have been a stretched DC-10-10 with US Transcontinental or California-Hawaii range. This aircraft was designed as a 747-100 replacement for American and United - both airlines could have gone to an all DC-10 widebody fleet.

The -63 would have had the range and capacity of the early models of the 747-200, but with three engines. It was aimed at airlines like Air New Zealand and Thai that did not have 747s, but needed an aircraft larger than their DC-10-30s.

The -62 would have had the wing and engines of the -63, but the shorter DC-10-30 fuselage. Its range would have been close to the range of the 747SP / 747-400. Swissair would have been the launch customer for this variant.

McDonnell Douglas was very close to launching these aircraft in the spring of 1979. However, concerns about the DC-10's safety following the AA ORD DC-10 crash made airlines reluctant to buy more DC-10s, By the time the safety concerns had dissipated, the 1979-82 recession made airlines reluctant to buy more aircraft.

If the -61, -62, and -63 had been launched, many airlines, especially in Asia, would have stayed with all DC-10 fleets, or replaced their 747-100s / 200s with -61s and -63s in the interests of fleet commonality, instead of operating mixed DC-10 / 747 fleets.

By the time the MD-11 was launched a decade later, many potential customers already operated mixed DC-10 / 747 fleets, and Boeing and Airbus were offering more modern products than the MD-11. This limited the sales of the MD-11, and made the sales McDonnell Douglas did make much less profitable than they could have been if the MD-11 had fewer competitors.
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solarflyer22
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RE: What Would Have Made The MD-11 Better?

Thu Dec 10, 2009 4:19 pm



Quoting WA707atMSP (Reply 18):
I think what doomed the MD-11, more than anything else, was that it came out ten years too late.

Agreed. If they had beat the 777 out the door they could have sold an extra 50 which would have made for a good market share. The real problem though is that the 777 was more efficient and innovative. The only way they could have really competed with the 777 would be to have been larger 320+ capacity but less than 747-400. That's a small niche though. Range was a problem too. It would have helped if it had more wing area and was more stable.
 
md80fanatic
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RE: What Would Have Made The MD-11 Better?

Thu Dec 10, 2009 4:31 pm

One thing would have changed the whole game in today's aviation world (and the MD-11 in particular),

MD having the $$$ to remain an independent manufacturer. I doubt we'd have seen many Airbii stateside if MD was still around.
 
brucek
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RE: What Would Have Made The MD-11 Better?

Thu Dec 10, 2009 4:37 pm

I have also read about the issues with the wing that resulted from cost cutting at MD. There is enormous risk and associated cost when designing a new wing as it has the ability to make or break an aircraft design. While the MD11 wing is larger than the DC-10, it is basically an extrapolation of the DC10 wing- just a larger version of the same wing design.

One of the issues with retaining the DC-10 wing design was that the aircraft could not achieve the fuel efficiencies that were promised, so additional modifications were done with the horizontal stabilizer (I’m not sure of the exact details) which had the effect of moving the center of gravity. That’s a lot of the reasoning as to why there is so much in automatic flight control on this aircraft, as I understand it.

This is all anecdotal information that I have read, I have no links or references to substantiate this. Do these factors make the aircraft unstable?- I’m not sure.
 
AverageUser
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RE: What Would Have Made The MD-11 Better?

Thu Dec 10, 2009 4:40 pm

Quoting Dreadnought (Reply 17):
The DC-10 was a famously stable aircraft - remember the Sioux city incident and others, where the DC-10's propensity for natural stability saved a lot of lives. In designing the MD-11, MD took what was until then a stable design and then destabilized it by changing fuselage length, wings, and basically keeping the same tail

Never mind the fact that both are naturally stable aircraft by design, with that "natural propensity". The MD-11 has been flown by the NASA all the way to a fine landing by engine thrust control alone during their PCA research. I don't know what "other" cases than the Sioux City you had in mind regarding real-life engine-only control, but at least there the control failed just before landing with the regrettable consequence, the a/c crashing. The MD-11 tests have indicated a computer is in practice required for a controlled last phase of flight with thrust alone.

Quoting Brucek (Reply 21):

This is all anecdotal information that I have read, I have no links or references to substantiate this.

Never mind, you're not alone. Like money, good anecdotes need and will be passed on.

[Edited 2009-12-10 09:10:20]
 
richierich
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RE: What Would Have Made The MD-11 Better?

Thu Dec 10, 2009 4:43 pm



Quoting SeaBosDca (Reply 14):
Boeing figured it out by 1994: a new wing and one fewer engine.

Funny, I was going to say something like that!
One fewer engine was crucial because of the obvious economies of one less engine to maintain, etc., as well as a far less complex tail area. The 777 proved that ultra-long-distance twin flying is acceptable, safe, and the future of long-haul aviation.
None shall pass!!!!
 
md80fanatic
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RE: What Would Have Made The MD-11 Better?

Thu Dec 10, 2009 4:51 pm

Quoting SeaBosDca (Reply 14):
Boeing figured it out by 1994: a new wing and one fewer engine.

This is a common misconception, advanced on this website and a few others.

Difference in wing loading (at MTOW) between MD-11F and 777F is a scant 13 oz / sq ft, with the 777 being the lower of the two.

3 MD-11 engines burn roughly the same as 2 777 engines achieving the same thrust factor. Not a big deal really, except for the T7 that lost thrust on both engines at the most inopportune time. I believe a high point tail engine, with highly pressurized fuel pump system to feed it, would have saved that airframe in the same situation.

EDIT: Although the resulting nose down moment from the loss of both "gravity feed" wing engines at such a low level would likely result in a big bounce ..... leading to something potentially worse unless flown properly.

[Edited 2009-12-10 08:57:51 by MD80fanatic]
 
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aerdingus
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RE: What Would Have Made The MD-11 Better?

Thu Dec 10, 2009 5:20 pm

I heard it was going to incorporate the A330 wing design, but it never went through. Such a sad airplane story really, so beautiful & quirky.
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BMI727
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RE: What Would Have Made The MD-11 Better?

Thu Dec 10, 2009 6:15 pm

The bottom line is that the MD-11 should have arrived earlier and when it did it should have met its performance expectations.

Allow me to repost something I wrote about it a few weeks back to expand:

Quoting BMI727 (Reply 24):
I think that the MD-11 failed in the passenger marketplace for two major reasons:

1. It came out too late. Ideas for a more advanced DC-10 started in the mid 1970s and had McDonnell Douglas gone further with either the DC-10 Super Sixty in the late 70s or the MD-100 in the early 80s and had a plane (with 757/767 generation technology) flying by the mid 1980s they would have probably seen much more success.

2. It just did not meet the performance expectations that were set for it which was, understandably, a major issue for airlines. By the time the MD-11 was finally up to spec it was just too late. The 777 had appeared and was showing just how good of a performer it was and the Boeing merger was the final nail in the coffin. It is kind of a sad story, and it is hard to not think about what could have been.



Quoting SeaBosDca (Reply 14):
Boeing figured it out by 1994: a new wing and one fewer engine.

I believe that they briefly considered building a twin engine MD-11 after the merger but scrapped it. One has to wonder if that would have slowed the success of the A330, but I have to think that Boeing made the right decision.
Why do Aerospace Engineering students have to turn things in on time?
 
DIJKKIJK
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RE: What Would Have Made The MD-11 Better?

Thu Dec 10, 2009 6:22 pm

The one thing that would have made the MD-11 better? More powerful underwing engines and the removal of the tail engine.

It is a pity MCD weren't thinking ETOPS at that time..
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BMI727
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RE: What Would Have Made The MD-11 Better?

Thu Dec 10, 2009 6:25 pm



Quoting DIJKKIJK (Reply 27):

It is a pity MCD weren't thinking ETOPS at that time..

They should have been. Again, I'll repost what I've previously written.

Quoting BMI727 (Reply 24):
ETOPS 180 was already approved by 1988 and operated by 1989, so it wasn't as if McDonnell Douglas got totally blindsided by the emergence of twins on longer routes. And really, ETOPS had become so commonplace by the mid 90s when the 777 appeared that it was given 180 certification right off the bat without the 1 year evaluation.

Why do Aerospace Engineering students have to turn things in on time?
 
JBirdAV8r
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RE: What Would Have Made The MD-11 Better?

Thu Dec 10, 2009 6:32 pm



Quoting DIJKKIJK (Reply 27):
It is a pity MCD weren't thinking ETOPS at that time..

Well in McD's defense when they were designing the MD-11, more powerful engines weren't really on the horizon...they came along a few years too late.

The real problem with the MD-11 from a safety standpoint IMHO is its twitchy characteristics on landing.
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1stfl94
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RE: What Would Have Made The MD-11 Better?

Thu Dec 10, 2009 6:55 pm

Had McD gone for a cleansheet design they might have had better chance. The MD-11 was very obviously a modernised older aircraft whereas its main rivals (the 777 and the A340) were brand new.

The other problem was that McD couldn't really offer a fleet package to an airline in the same way that Airbus and Boeing could. Once you had the MD-80 and the MD-11 you had to look elsewhere to fill any gays (e.g Boeing 757/767, Airbus A330) at which point Boeing would probably offer a nice deal on a bunch of 737 and 777 whilst Airbus can do the same with the A32X and A340.
 
AverageUser
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RE: What Would Have Made The MD-11 Better?

Thu Dec 10, 2009 7:05 pm



Quoting JBirdAV8r (Reply 29):
The real problem with the MD-11 from a safety standpoint IMHO is its twitchy characteristics on landing.

I have the recipe here: flare correctly, keep your vertical speed within limits, and you can't be going terribly wrong, same is in all aircraft. You will at all costs want to avoid getting into a pilot-induced (pitch) oscillation so rather go-around than attempt to salvage a bad landing or attempt landing outside operational margins. 100% of all known MD-11 landing accidents for which reports have been prepared cured.
 
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Dreadnought
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RE: What Would Have Made The MD-11 Better?

Thu Dec 10, 2009 7:09 pm

Quoting 1stfl94 (Reply 30):
Once you had the MD-80 and the MD-11 you had to look elsewhere to fill any gays

Was that a Freudian slip? 

Disturbing imagery.

[Edited 2009-12-10 11:09:39]
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ZRH
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RE: What Would Have Made The MD-11 Better?

Thu Dec 10, 2009 7:11 pm

The MD11 was a good aircraft but it should have had more range.

Quoting DeltaL1011man (Reply 3):
2nd that. I did a pretty good bit of M11 flights and thought they were great rides(but lets be clear, the L1011 was the best plane ever)

You can't compare the 1011 with the MD11. The 1011 is same generation as the DC 10 and not the MD11 which was a newer plane and better.
 
474218
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RE: What Would Have Made The MD-11 Better?

Thu Dec 10, 2009 8:27 pm



Quoting ZRH (Reply 33):
You can't compare the 1011 with the MD11.

Your absolutely correct the L-1011 was far more advanced.
 
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Faro
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RE: What Would Have Made The MD-11 Better?

Thu Dec 10, 2009 9:28 pm

Any airliner that misses its performance targets by a significant margin will have trouble. Be it range or payload, you will suffer. The MD-11 also seems to be somewhat of a challenge to handle. However let's not forget that it meets the regulatory safety minima since it was successfully certificated.

In terms of innovation too, let's not forget that it introduced the "wedge" on the wing trailing edge which was indeed a success though not enough to rectify performance shortfalls.

Faro
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tdscanuck
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RE: What Would Have Made The MD-11 Better?

Fri Dec 11, 2009 6:07 am



Quoting Dreadnought (Reply 17):
More than one MD-11 overturned and landed on their backs (FedEx and Mandarin come to mind, and I think there were others) - and that is purely a result of instability.

The overturn wasn't exactly an instability problem. The flying charachteristics resulted in landing hard on one main landing gear. It was a structural problem from there that the gear would collapse and, in the collapse, harm the wing to the extent that the wing on that side would fail. That causes an enourmous rolling moment from the still-good wing on the other side, resulting in the rollover. *All* aircraft will flip on their back if you lose one wing right as you're landing.

Tom.
 
c5load
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RE: What Would Have Made The MD-11 Better?

Fri Dec 11, 2009 5:14 pm



Quoting Faro (Reply 35):
Any airliner that misses its performance targets by a significant margin will have trouble. Be it range or payload, you will suffer.

Then why does it do so good as a freighter?
"But this airplane has 4 engines, it's an entirely different kind of flying! Altogether"
 
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Zkpilot
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RE: What Would Have Made The MD-11 Better?

Fri Dec 11, 2009 7:26 pm



Quoting FX1816 (Reply 8):

DC-10 Technical Specifications
Series 10 Series 15 Series 30 Series 40
Wing Span 155 ft 4 in (47.3 m) 155 ft 4 in (47.3 m) 165 ft 4 in (50.4 m) 165 ft 4 in (50.4 m)

MD-11 Technical Specifications

Wing Span 169 ft 6 in (51.70 m)

I don't know if it had a new wing or not, but those differences in wingspan would probably be entirely taken care of by the winglets...they look small but are actually quite significant...
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Nicoeddf
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RE: What Would Have Made The MD-11 Better?

Fri Dec 11, 2009 7:55 pm



Quoting C5LOAD (Reply 37):
Then why does it do so good as a freighter?

Because it carries 90t of payload well within the typical stage lengths of freighter operation. Freight's not complaining for some stopping...
 
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Jetlagged
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RE: What Would Have Made The MD-11 Better?

Sat Dec 12, 2009 12:08 am



Quoting C5LOAD (Thread starter):
More efficent engines? (if available),

Boeing and Airbus had the same engines to work with. The problem with the MD-11 was too much drag.
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prebennorholm
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RE: What Would Have Made The MD-11 Better?

Mon Dec 14, 2009 12:32 am

The MD-11 wing isn't an exact DC-10 copy.

First of all, from a safety viewpoint at least, the slats are locked in the extended position, so they won't retract in case of a hydraulic problem.

The wing tips are extended slightly and equipped with winglets. But most of the very slight span increase comes from the outward pointing winglets.

Its span is some 30 feet shorter than the head on competitors - A330/340 and B777. At the same weight the MD-11 comes out with a much higher wing loading, therefore higher landing speeds. And during cruise the short span MD-11 wing will of course be a lot more draggy.

The main issue, however, is connected to some "spin". In order to try to compete on economy and range MDD did just about anything to reduce drag. Most significantly they reduced the area of the horizontal stabilizer by 40%. That narrowed the center of gravity margins, and they also designed it for flight with an aft center of gravity to further reduce drag of the horizontal stabilizer.

That all gave "poor pitch stability". But MDD invented a new word in the English language to describe "poor stability". That new word was "relaxed stability". This is where the spin came in, even before the word "spin doctor" was invented.

MDD also invented some electronics to deal with it - the LSAS system. It has become better over time with some software updates. But they "forgot" that sometimes the plane has to be flown by humans, especially at landings, sometimes in nasty weather as well - side wind, wind shear. At such conditions a more forgiving plane is simply an advantage.

I doubt that the MD-11 way of "relaxted pitch stability" could be certified today, but I'm not sure. But I am sure that for the foreseeable future none of the remaining airliner manufacturers will dare to try to copy the MD-11 in this respect. All the new airliners - A380, B787, A350 - have generously dimentioned horizontal stabilizers. And with tail fuel tank automatic trim of best stability both for cruise flight and landing.

Quoting C5LOAD (Reply 37):
Then why does it do so good as a freighter?

Well, it is certified with a pretty high MLW which means that you can stuff a lot of cargo inside it. Also a lot of not very old pax planes were offered for sale and cargo conversion, which without doubt pressed second hand prices. Cargo bean counters love cheap planes which are not worn out.

But following the last MD-11 freighter incidents and accidents their love may be reduced when they read their next insurance invoice. Insurance companies also read newspapers, and they will of course meet a 330F of 777F customer with a wider smile than an MD-11F customer.
Always keep your number of landings equal to your number of take-offs
 
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RE: What Would Have Made The MD-11 Better?

Mon Dec 14, 2009 10:47 am



Quoting Prebennorholm (Reply 41):
That all gave "poor pitch stability". But MDD invented a new word in the English language to describe "poor stability". That new word was "relaxed stability". This is where the spin came in, even before the word "spin doctor" was invented.



Quoting Prebennorholm (Reply 41):
I doubt that the MD-11 way of "relaxted pitch stability" could be certified today, but I'm not sure.

How would that be? Have certification standards changed in any way? These should take into account manual landings with windshear and crosswinds, should they not? Otherwise, its a certification shortfall...

Faro
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seabosdca
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RE: What Would Have Made The MD-11 Better?

Mon Dec 14, 2009 12:28 pm



Quoting Md80fanatic (Reply 24):
3 MD-11 engines burn roughly the same as 2 777 engines achieving the same thrust factor. Not a big deal really, except for the T7 that lost thrust on both engines at the most inopportune time. I believe a high point tail engine, with highly pressurized fuel pump system to feed it, would have saved that airframe in the same situation.

Why would the third engine have kept running when the other two did not? The problem was a design flaw in the engine's fuel system. The third engine would have been exposed to the same combination of cold temperatures and low loads that the two engines on BA38 saw.
 
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RE: What Would Have Made The MD-11 Better?

Mon Dec 14, 2009 6:20 pm

To answer your question : MD should have started with a clean paper to design a DC-10 successor, this derivative has inherited most of the weak points of the DC-10 design and added a few very nasty extra minus points.

Regarding the high accident rate of the MD11, the following is important :
An accident has almost never only one cause but it's a combination of several factors.......
the dead end street.
On the MD 11 you have already several negative factors that could lead to an incident or accident. So on a bad day (strong gusty winds and heavy rain/snow) you have already a head start during landing with a MD11 due :

- Small wing area ,high wing load, high landing speed.
- Small stabilizer, pitch stability is not optimal.
- Very high payload on MD11 freighter aircraft, MLW increased by a considerable amount, even higher landing speeds.
- Largest MD11 airline is operating MD11-MD10 aircraft on a common type certificate. Both aircraft have a very different landing behavior.

These factors could partly be counteracted by very high training standards and extra landing training on the MD11 with leading airlines.(LH,KL,UPS, Finnair, etc)
However in the coming years the MD11 will be operated by a growing number of (freight)airlines, that are not so safety/training minded and don't have "in house" training facilities.

It will be a recipe for disaster, the MD11(F) is an unforgiving aircraft on a bad day.

For the record (again) the following figures (until/incl. 2008) from Boeing, the current manufacturer/rights owner of the MD11 and MD/DC-10, after the take over of MD :
http://www.boeing.com/news/techissues/pdf/statsum.pdf
see page 21.

Of all comparable aircraft, with approx. the same certification date as the MD11, the MD11 has the worst accident rate (Hull loss).
B767................0,41
B757................0,26
B747-400......... 0,53
B737-3/4/5....... 0,54
A320 series..... 0,36
MD11.............. 2,57

Also the DC-10/MD10 is high on this list of accident rates. Compared to aircraft, designed and certificated during the same time frame it's again number one :
MD/DC-10.........3.03
Operating a twin over the ocean, you're always one engine failure from a total emergency.
 
474218
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RE: What Would Have Made The MD-11 Better?

Mon Dec 14, 2009 7:21 pm



Quoting 747classic (Reply 44):
To answer your question : MD should have started with a clean paper to design a DC-10 successor, this derivative has inherited most of the weak points of the DC-10 design and added a few very nasty extra minus points

Why would MD even think of starting with a clean paper design for the MD-11, they didn't with the DC-10.

Many years ago I had a MD (or Douglas) publication called something like DC-10 Technical Review. Each chapter started with the same basic statement: the DC-10 wing is based on the proven DC-9 wing, the DC-10 environmental control system is based on the proven DC-9 environmental control system, the DC-10 hydraulic system is based on the proven DC-9 and so on.

MD had to cut corners because Lockheed was over a year ahead in the design of the L-1011 and James McDonnell demanded that the DC-10 fly first.
 
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747classic
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RE: What Would Have Made The MD-11 Better?

Mon Dec 14, 2009 9:26 pm



Quoting 474218 (Reply 45):
Why would MD even think of starting with a clean paper design for the MD-11, they didn't with the DC-10.

The thread question is : What would you have done to make the MD11 better?
My answer is :

Quoting 747classic (Reply 44):
To answer your question : MD should have started with a clean paper to design a DC-10 successor, this derivative has inherited most of the weak points of the DC-10 design and added a few very nasty extra minus points.

All to avoid this (the lucky one, that only had it's RH main gear destroyed, without flipping over)


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Operating a twin over the ocean, you're always one engine failure from a total emergency.
 
prebennorholm
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RE: What Would Have Made The MD-11 Better?

Mon Dec 14, 2009 11:54 pm



Quoting 474218 (Reply 45):
Why would MD even think of starting with a clean paper design for the MD-11, they didn't with the DC-10.

Because the MD-11 was a rather different thing.

The DC-10 has a normal size horizontal stab, normal center of gravity limits, normal pitch stability, normal wing loading.

The DC-10 is "normal" in all those issues where MDD with MD-11 departed from what was normal and accepted industry standard in order to reduce the drag on the "old" wing as much as possible, because they knew very well that no way could that old wing compete on level terms with the new, head on competing products from Airbus and Boeing.

The MD-11 should have had a new 200 ft wing. And a normal horizontal stab. Then it would have been a more fuel efficient plane, and some of the landing accidents wouldn't have happened.
Always keep your number of landings equal to your number of take-offs
 
LMP737
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RE: What Would Have Made The MD-11 Better?

Wed Dec 16, 2009 1:12 am

From a servicing standpoint it would have been nice to have had a single point for hydraulics. With the 11 you had to climb up into the l/h wheel well and service each individual system. Actually on all Douglas planes require each system to be serviced individually. On Boeing aircraft there's a single point with a selector valve for each system.
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AverageUser
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RE: What Would Have Made The MD-11 Better?

Wed Dec 16, 2009 12:50 pm



Quoting Prebennorholm (Reply 41):
I doubt that the MD-11 way of "relaxted pitch stability" could be certified today, but I'm not sure.

What makes you doubt it? I'm sure the relevant regulations are available, and unless I've really missed something, nobody in the accident investigation reports has ever suggested they would or should have been changed.

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