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Old 01-23-2010, 02:47 AM   #1  
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Default DC-10 vs L-1011

Just curious if there are any pilots out there who have flown both aircraft. Which one do you think was better more reliable and a joy to fly? Anyone who is an knowledgeable on both aircraft, please chime in. Thank you.
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Old 01-23-2010, 09:07 AM   #2  
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I'll jump into this, having flown all three widebody tri-jets (and I'll throw in the MD-11 at no extra charge).

I'll say this for the DC-10: it does fly nicely. I was actually pleasantly surprised at how well it handled. And the GE engines are very good powerplants.

The MD-11 is not quite as agreeable (I don't think it's bad, just different) - the smaller stabilizer makes it a bit touchier, particularly in pitch. The initial ground spoiler deployment on the -11 is virtually worthless (they only partially deploy until the nosegear is on the ground to prevent a tailstrike) - I don't recall the DC-10 being so light on the gear after touchdown. The aircraft feels like it's ready to hop back into the air at the slightest provocation. I like that the -11 has tremendous amount of power, I'm flexing at altitudes/temperatures I never would have dreamed of.

Then there is the L-1011. It's really hard to find fault with it. It handled well, had tons of redundancy, and was WAY ahead of it's time. The pitch trim system is the best of any aircraft I've ever flown, you had control over virtually everything (you could actually control the pitch in the event of a jammed stabilizer by deselecting spoiler panels and deploying the remaining ones), the spoilers were infinitely selectable (unlike the 3 notches on the Douglas), the ground spoilers worked very well initially and fully deployed. It has the biggest cockpit of any airliner I know of (much roomier than the Douglas products).

Systems-wise, the L-1011 design is still far superior to the DC/MD. First, the DC-10/MD-11 are virtually identical systems wise. Douglas did very little re-engineering of the systems when they created the MD-11, they simply automated the cockpit controls and added EFIS and an FMC.

Hydraulics are one of the DC/MD's weaknesses - three systems with eight power sources vs. four with eleven power sources (IIRC) on the 1011. The L-1011's system architecture also provides more redundancy than that of the DC/MD. Even after Douglas refitted the aircraft with the "Sioux City valve" the system is still a weak link. Lose one system and you will lose some capability on the aircraft. On the L-1011, with one system loss you still have everything operating.

Electrically, both types are pretty good. I like the architecture of the L-1011 better in that the APU can (and is) paralleled with the engine generators on the tie bus, but so far I haven't had any problems with the DC/MD system where the APU NEVER is on the tie bus. I do like the no-break power transfer system on the MD.

The L-1011 APU is also weak in the air delivery department (noticed mainly on engine starts with low pressure). I don't recall the DC having that problem, and the MD definitely doesn't (excepting high altitude airports, but that's to be expected).

Air systems on all three work well enough, the IIRC the L-1011's was a bit more versatile, but not a huge difference. The DC/MD's don't have the "steam train" chugging the the L-1011's packs occasionally did, and the MD's temperature control system does a better job than the L-1011/DC-10.

Fuel systems are a toss up. The L-1011 wins in the simplicity department (at least from the engineer's panel), but the DC/MD gives you more control and versatility (and more ability to mess things up). If it were just that, there would be no clear winner on this one. Unfortunately, the DC/MD has one other minor vice - if you lose all AC electrical, the #2 engine WILL fail due to fuel starvation. Just in case you don't have enough to do with the widebody equivalent of a "9 light trip," we'll throw in an engine failure to make it sporting. Really, they couldn't come up with a better system?!?

Aside from that minor consideration, I think the fuselage mounted #2 engine is better than the tail mounted one for the DC/MD - it doesn't create the pitch issues when doing one and two engine inoperative approaches that the high mount of the DC/MD does. Also the loss of #2 on the DC/MD near V1 causes an auto-rotating tendency with can lead to an early liftoff or tailstrike.

While the RB-211 is a good powerplant, the original -22B's weren't too powerful, and it does not like cold weather (Note - the later RB211's such as on the 757 are a different animal). It wasn't uncommon to have 3+ minute starts, and more than once I've come close to the 5 minute starter duty cycle. Also, the pneumatic reversers were somewhat prone to sticking. Again, it wasn't unheard of to have one MEL'd and pinned out (deactivated). I haven't observed any such problems on the DC/MD.

Flight control-wise, the DC/MD's are very dependent of slats (having only slotted flaps, not Fowlers) - hung up slats result in very high approach speeds (more so than the L-1011 with Fowler flaps). This combined with the fact that the original slat actuators on the DC-10 did not lock when extended (but were held extended only by hydraulic pressure) directly contributed to the crash of AA191 at KORD. To me, that is a serious design flaw. The L-1011 also had DLC (Direct Lift Control) - on approach with landing flaps, the spoilers biased up 7 degrees and then modulated between 0 and 14 degrees in response to pitch inputs from the control wheel, greatly reducing the amount of pitch change while tracking the glideslope. Worked great, particularly on a coupled approach! Also the L-1011 had a speed "doughnut" on the ADI, which sensed AOA, configuration, acceleration, phase of the moon, and sever other inputs. It took some getting used to, but once you understood what it was telling you if you couldn't hold your approach speed within one or two knots, you just weren't trying. The -500's also had MDLC (maneuvering direct lift control) and ACS (active control system) as part of the wing extension. Essentially ACS would deflect the ailerons to unload the outboard section of the wing in turbulence, MDLC would deploy the spoilers in maneuvering flight (though I'd be lying if I tried to tell you the purpose at this moment).

Also in the design flaw department, there is the whole cargo door/floor venting debacle on the DC-10. How Douglas got away with that travesty I will never know. History indicates the issue has been successfully resolved, but it never should have occurred in the first place (or should have been resolved after the first incident).

As far as reliability, it seems to me that all of them do reasonably well IF you keep up on maintenance (don't let little things slide) and have mechanics who really know the airframe and are provided with the resources to maintain them. Attempt to cut corners, and you will pay the price in reliability. Also, keep them flying - airplanes hate to sit (when we flew the heck out of the L-1011's during the CRAF activation reliability was quite good).

My ultimate analysis is pretty much this:

I picture a bunch of engineers sitting around tables at both Lockheed and Douglas. The Lockheed engineers are focused on producing the best aircraft possible. The Douglas engineers are focused on producing an airplane before Lockheed. On the whole, the design of the DC-10 seems like it was cobbled together without a great deal of thought, and it shows. Even items as small as the space for a chart case (too small on the DC/MD, and the cute fold out table is mounted too low to be useful with a chart case there), to cockpit lighting (poor on the DC/MD), or the passenger door system (stone simple of the L-1011, unnecessarily complicated on the DC (and with at least three different variations on the ones I flew).

Two old sayings come to mind:

1) Lockheed has always built the most technologically advanced aircraft available. Unfortunately, they've never figured out how to make money doing so.

and

2) Lockheed should design them, Boeing should build them, and Douglas should market them.

Sorry to go on so long - but you did ask!
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Old 01-23-2010, 09:27 AM   #3  
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Wow...bcrosier, you have flown the 3 jets I can honestly say I've wanted to fly the most. Thanks for letting me live vicariously through your descriptions
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Old 01-23-2010, 09:55 AM   #4  
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I better not let my old man see this post. He's been an engineer on both (and many other Lockheed products) and all he talks about is the L10.
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Old 01-23-2010, 12:59 PM   #5  
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Excellent little essay Mr. bcrosier. I like the short descriptions and the (probable) ramifications...if only each chapter of a AFM had a short /preview/review or summary like that. If you assigned a weighted point system I'd think the L1011 would come out leagues ahead over the DC-10. But then, as I recall the L1011 cost about $1.5 million more than the DC-10 when new - so less takers. (Also their were delays in engine development/certification, not Lockheed's problem, but it cost them).

The L1011 is/was the nicest cockpit I've been in, seemed to be laid out exceptionally well. I've never flown it, but it was my favorite jump-seat living room.
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Old 01-24-2010, 10:26 AM   #6  
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whoaa! this was clearly over the top. many thanks bcrosier for the excellent essay you took the time to write. it is much appreciated and extremely informative.
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Old 01-24-2010, 03:35 PM   #7  
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Quote:
Originally Posted by chazbird View Post
Excellent little essay Mr. bcrosier. I like the short descriptions and the (probable) ramifications...if only each chapter of a AFM had a short /preview/review or summary like that. If you assigned a weighted point system I'd think the L1011 would come out leagues ahead over the DC-10. But then, as I recall the L1011 cost about $1.5 million more than the DC-10 when new - so less takers. (Also their were delays in engine development/certification, not Lockheed's problem, but it cost them).

The L1011 is/was the nicest cockpit I've been in, seemed to be laid out exceptionally well. I've never flown it, but it was my favorite jump-seat living room.
I flew the 767 for about 3 years then the L-1011 for the last 3 years of my time at TWA.

The L-1011 flight deck, as you say, was awesome. But, the first 10 TWA 767s (all they had when I was there) had a nice flight deck, too, because they were put together with a F/E station. Then, ALPA lost the F/E arbitration, so these 10 TWA 767s went from Seattle to Boeing ICT for removal of the F/E station and reconfiguration of the pilots' systems panels. Fortunately for the crews it wasn't feasible to move the cabin bulkhead forward.
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Old 01-24-2010, 03:49 PM   #8  
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I jump-seated on some of those TWA 76's too. There was plenty of room to lay out and nap back there, or, install a self leveling pool table.

The DC10 had good views and was wide (the 747 never comes close to cockpit comfort/views) but riding transcon on a nice day in the L1011 was just splendid.

Thinking of it, I can't remember a systems/airframe issue on the L1011 that led to or was attributable to an accident. There's the DFW micro-burst & the Saudi cabin fire due to a on-board cook stove and landing pressurized, but really, I can't come up with anything else. Wait, there's the JFK RTO with false shaker activation, maybe that counts? Certainly no catastrophic systems/airframe/control failures?
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Old 01-24-2010, 04:46 PM   #9  
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Quote:
Originally Posted by chazbird View Post
Thinking of it, I can't remember a systems/airframe issue on the L1011 that led to or was attributable to an accident.?
Only a 3 cent lightbulb one night over the Everglades
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Old 01-24-2010, 04:58 PM   #10  
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Oh yeah, I totally forgot about that one (the aftermath being perhaps the start of CRM/human factors, of course the DC-8 in PDX 6 years later, is what which cemented the path to CRM...)

I suppose you could call a light bulb part of a system, and in that case consider it something that led to an accident (perhaps, more correctly, a factor), but I'd say in that circumstance it is certainly not not attributable, like a faulty cargo door handle leading to a door failure, leading to the floor failure, the total hydraulic failure, etc. (Paris, 1973).
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