C5LOAD From United States of America, joined Sep 2008, 917 posts, RR: 0 Posted (4 years 4 months 1 week 3 days 5 hours ago) and read 13400 times:
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"
Richiemo From United States of America, joined Jul 2008, 206 posts, RR: 0
Reply 2, posted (4 years 4 months 1 week 3 days 5 hours ago) and read 13397 times:
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.
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 From United States of America, joined Jul 2000, 2769 posts, RR: 6
Reply 6, posted (4 years 4 months 1 week 3 days 4 hours ago) and read 13151 times:
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.
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 From United States of America, joined Feb 2004, 9375 posts, RR: 52
Reply 7, posted (4 years 4 months 1 week 3 days 4 hours ago) and read 13142 times:
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.
If you have never designed an airplane part before, let the real designers do the work!
FX1816 From United States of America, joined Mar 2004, 1400 posts, RR: 4
Reply 8, posted (4 years 4 months 1 week 3 days 2 hours ago) and read 12861 times:
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.
VirginFlyer From New Zealand, joined Sep 2000, 4537 posts, RR: 42
Reply 9, posted (4 years 4 months 1 week 2 days 23 hours ago) and read 12664 times:
A larger horizontal stab,
(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.
"So powerful is the light of unity that it can illuminate the whole earth." - Bahá'u'lláh
EHAM From Netherlands, joined Sep 2003, 448 posts, RR: 0
Reply 11, posted (4 years 4 months 1 week 2 days 20 hours ago) and read 12407 times:
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.
777fan From United States of America, joined Jan 2006, 2480 posts, RR: 3
Reply 13, posted (4 years 4 months 1 week 2 days 18 hours ago) and read 12171 times:
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!
EBJ1248650 From United States of America, joined Jun 2005, 1932 posts, RR: 1
Reply 15, posted (4 years 4 months 1 week 2 days 17 hours ago) and read 12018 times:
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.
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.
Dreadnought From United States of America, joined Feb 2008, 8711 posts, RR: 24
Reply 17, posted (4 years 4 months 1 week 2 days 17 hours ago) and read 11958 times:
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.
WA707atMSP From United States of America, joined Oct 2006, 2179 posts, RR: 12
Reply 18, posted (4 years 4 months 1 week 2 days 16 hours ago) and read 11854 times:
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.
SolarFlyer22 From US Minor Outlying Islands, joined Nov 2009, 814 posts, RR: 2
Reply 19, posted (4 years 4 months 1 week 2 days 15 hours ago) and read 11365 times:
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.
Brucek From United States of America, joined Nov 2004, 256 posts, RR: 0
Reply 21, posted (4 years 4 months 1 week 2 days 15 hours ago) and read 11105 times:
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 From , joined Dec 1969, posts, RR:
Reply 22, posted (4 years 4 months 1 week 2 days 15 hours ago) and read 11062 times:
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.
Richierich From United States of America, joined Nov 2000, 4199 posts, RR: 6
Reply 23, posted (4 years 4 months 1 week 2 days 14 hours ago) and read 11020 times:
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.
Md80fanatic From United States of America, joined Apr 2004, 2659 posts, RR: 10
Reply 24, posted (4 years 4 months 1 week 2 days 14 hours ago) and read 10895 times:
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]
: 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.
: 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 some
: 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 thin
: They should have been. Again, I'll repost what I've previously written.
: 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.
: 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 riva
: 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
: Was that a Freudian slip? Disturbing imagery.[Edited 2009-12-10 11:09:39]
: The MD11 was a good aircraft but it should have had more range. You can't compare the 1011 with the MD11. The 1011 is same generation as the DC 10 and
: Your absolutely correct the L-1011 was far more advanced.
: 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 se
: The overturn wasn't exactly an instability problem. The flying charachteristics resulted in landing hard on one main landing gear. It was a structura
: Then why does it do so good as a freighter?
: 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 smal
: Because it carries 90t of payload well within the typical stage lengths of freighter operation. Freight's not complaining for some stopping...
: Boeing and Airbus had the same engines to work with. The problem with the MD-11 was too much drag.
: 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
: How would that be? Have certification standards changed in any way? These should take into account manual landings with windshear and crosswinds, sho
: 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
: 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
: 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) publi
: The thread question is : What would you have done to make the MD11 better? My answer is : All to avoid this (the lucky one, that only had it's RH mai
: 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,
: 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
: What makes you doubt it? I'm sure the relevant regulations are available, and unless I've really missed something, nobody in the accident investigati
: They came on the horizon because Boeing asked for them. Same as when they built the 747, they went to GE and Pratt and said this is what we need; bui
: However aircraft with tail mounted engines often can get away with slightly smaller wings as they do not need quite as much lift. The reason for this
: Having an engine at the tail does not reduce the downward lift needed by the tailplane. The CG is further aft, so the wings have to be relatively fur
: This is not the issue. The DC-9, DC-10, 727, and other rear engined planes have similar CG ranges to aircraft with the engines just on the wings. Thi
: Well, the 777-200 was actually a fair chunk lighter than the MD-11, so a two engined (base model, non-heavy) MD-11 would likely have needed 85,000lb
: And that, in a nutshell, is what is wrong with the MD-11. Another application of the old adage, you get what you pay for.
: Although that is what happened with the 777, it's not what happened with the 747. The original 747 engine (the Pratt JT9D) was developed for the USAF
: A keg and hot female strippers! Oh, you mean technical stuff to improve performance. Pretty much what everyone else has said. New wing and bigger hor
: Finnair will retire the type early next year after a service of about 19 and 1/4 years, operated without any accidents or incidents. Sheer luck or pur
: Skill. Whereas I doubt they never had an incident, like a high g landing or else. Then again, pax planes tend to have much lower landing weights than
: Having defined "incident" as an irregularity for which an official investigation of some sort is initiated, there are none recorded, surprising as it
: Capt. Eric Genotte, FO Steeve Michielsen and FE Mario Rofail would probably be just a bit offended by that statement, as would Airbus and indeed DHL.
: I don't really accept this sort of statistics. No accidents is and must always be the norm in aviation. It isn't so that MD-11s are falling out of th
: I understood it that the C-5 engines were not suitable for the 747 because the speed of the C-5 was so much lower than what they wanted for the 747.
: In this particular case, I don't have any primary sources. I'm working from secondary and onwards...if anyone out there has good primary source data
: Off-topic but that's one thing I never quite understood: with such a massive airframe, why did Boeing go for such high design speeds with the 747? II
: You are of couse right, but you can easily count it as dialectics. If some are repeatedly accusing the MD11 of challenging landing characteristics, w
: Training, re-training, extra landing training did the job properly. Finnair has his own Full Flight MD11 Simulator., so for a few extra sessions, whe
: We all know that the MD-11 is a duly certified airliner. The inference from the above would be that certain aircraft should be certified to be flown
: Well, the original point was the praised stability of the DC-10 alone, we all know Airbus are designed rock stable and solid. "Nice" pictures all the
: Because Juan Trippe wanted it; in fact, he wanted even higher speed but Boeing refused, as it would have made low speed handling too dicey. You are i
: Thanx for the interesting feedback; I had the somewhat hazy impression that the regulators were (to a large degree) all-knowing all-powerful. I guess
: That is a frequent misconception, not only in this field but in many others. I have a very interesting book, "The Road to the 707" written by one of
: This is rather unfair on the regulators. It certainly is not true that the regulators are all bureaucrats. The technical people at the FAA, CAA, etc
: I'm not sure how to respond to this ignorance other than to say you know nothing about modern aircraft certification. To imply that the original CAR
: We've been here before have we not. You say the MD-11 is allowed to fly because there's a bureauratic conspiracy by officials unknown, I say there's
: No, it isn't so. But things evolve over time. One example: Once the DC--3 was considered a "safe" aircraft. About fifteen years ago "my" DC-3 (well,
: I did not mean to imply that the regulators do not know what they are doing; some of them definitely do. As in any large organization, there is a wid
: I'm confused with this statement. How can the FAA have little influence on airliner design when they control the entire process? Yes, new technology
: Almost all FAR's are written in terms of performance...if the OEM can show that their design meets the performance required by the FAR, regardless of
: Pretty much. He wanted a 40 degree wing sweep for a higher speed but Boeing felt that 35 was better for low speed handling and field performance. The
: I agree; simply, the regulators may then be deemed legally responsible for any damages in MD-11 incidents/accidents where relaxed longitudinal stabil
: They do NOT control the process, that is the point. They only have to put their stamp of approval on the final result. In a sense that is true, at le
: Correct and this happens more often than not. Well its a little more involved than that. How are you so sure since you've never been involved in it?
: My point is that the FAR's have been developed from the design advances that the manufacturers have developed, not the other way around. The FAR's do
: They do control the certification process, (it's their process after all) and its not bureaucrats who do it either. We're off topic here, but it make
: L-1011 is a dinosaur compared to MD-11.
: So, basically, most of the above suggestions boil down to (excepting the snarkier comments): 1) Most importantly, a brand-new, larger wing (at least 2
88 Max Q
: Well, the L1011 never had a design caused accident. Certainly can't say that for the MD11 !
: And most important they can be bought for very little $$$.