Thrust From United States of America, joined Sep 2003, 2673 posts, RR: 11 Posted (8 years 4 months 3 weeks 1 day 6 hours ago) and read 8751 times:
Hi. I wanted to ask several questions regarding the differences in performance of the DC-10 tail mounted engine on a strut vs. the L-1011's S-duct design for its no. 2 tail engine. What are the advantages and disadvantages of each design? What, in your opinion, is the better design, the DC-10's no. 2 engine design, or the L-1011's?
AUAE From United States of America, joined Apr 2004, 296 posts, RR: 4 Reply 1, posted (8 years 4 months 3 weeks 1 day 6 hours ago) and read 8722 times:
I am not sure of the total length of the ducts, but by intuition, the s-duct is a bit longer and probably has a slightly bigger negative effect on engine efficiency. The plus side to the s-duct however, is that it puts the engine closer to the ground making it slightly easier to service and it also puts the thrust line closer to the c.g. of the aircraft. Since the thrust line is closer to the c.g. in an s-duct configuration, I would also think the overall structure would be lighter. But that might not necessarily be true. Personally, I think the Lockheed design is better, just because it looks better.
Shawn
Air transport is just a glorified bus operation. -Michael O'Leary, Ryanair's chief executive
Starlionblue From Hong Kong, joined Feb 2004, 15872 posts, RR: 66 Reply 2, posted (8 years 4 months 3 weeks 1 day 5 hours ago) and read 8699 times:
Apart from the servicing improvements with the engine closer to the ground, the S-duct allows for a smaller fin/rudder. This decreases drag and also decreases the tendency for Dutch roll. However the aerodynamic design of an S-duct is more complex. The 727 had surge problems on the center engine early in it's design due to turbulence in the duct, and still suffers from occasional surges on rotation today.
"There are no stupid questions, but there are a lot of inquisitive idiots." - from Citadel by John Ringo
A350 From Germany, joined Nov 2004, 1098 posts, RR: 23 Reply 4, posted (8 years 4 months 3 weeks 22 hours ago) and read 8601 times:
A bit OT:
What was the reason why the L-1011 had such little success compared to the DC-10, although many people claim it to be the more innovative a/c? Was it simply the range of the DC 10-30?
Thanks in advance for answers
A350
Photography - the art of observing, not the art of arranging
Broke From United States of America, joined Apr 2002, 1322 posts, RR: 4 Reply 5, posted (8 years 4 months 3 weeks 21 hours ago) and read 8593 times:
Early in the development of the L-1011, Rolls-Royce has significant problems with the RB211-22C engine resulting in several design changes that delayed the introduction of the L-1011.
This led to the bankruptcy of Rolls-Royce and the near bankruptcy of Lockheed.
Delta hedged their bets by ordering 5 DC-10-10 airplanes and stayed with the L-1011. Eastern tried to start wide body service by leasing 3 747-100's from Pan Am, but their reliability (or lack of) did not help Eastern at all.
Then further major reliability problems with the RB211-22C, including a fan disc burst in December, 1972 and Eastern losing the first wide body ever in the Everglades west of Miami at the end of December did nothing to help L-1011 sales.
The changes to the RB211-22C became so significant that the engine was redesignated the RB211-22B. I don't know why the "B" succeeded the "C", but it did.
Until the RB211-524 engine came out, the RB211 was not considered a very good engine.
P&WA had the same problem with the JT9D-3, but for other technical reasons, and the JT9D-7 series were much better engines.
Gigneil From United States of America, joined Nov 2002, 16215 posts, RR: 88 Reply 7, posted (8 years 4 months 3 weeks 20 hours ago) and read 8567 times:
This led to the bankruptcy of Rolls-Royce and the near bankruptcy of Lockheed.
It actually caused the bankruptcy of both. The State of California paid to keep Lockheed alive.
The major problem with sales was the continuous slippage of the delivery date. The RR and Lockheed problems kept causing the plane to miss deadlines, and potential purchasers fled.
Moose135 From United States of America, joined Oct 2004, 2009 posts, RR: 12 Reply 8, posted (8 years 4 months 3 weeks 19 hours ago) and read 8548 times:
the S-duct allows for a smaller fin/rudder
Actually, it allows for a larger rudder. By having more rudder surface, it allowed for greater control in an asymmetrical (wing-engine out) situation. That allowed the 1011 wing engines to be mounted further outboard on the wing, improving wing loading, making it more efficient that the DC-10.
Thrust From United States of America, joined Sep 2003, 2673 posts, RR: 11 Reply 10, posted (8 years 4 months 3 weeks 18 hours ago) and read 8527 times:
Excuse me, I meant all L1011-500s in general, not just DL's
Doug_Or From United States of America, joined Mar 2000, 3163 posts, RR: 4 Reply 12, posted (8 years 4 months 3 weeks 17 hours ago) and read 8519 times:
FWIW, I've heard the DC-10 almost wasn't made becuase of the lack of customers, until United decided to purchase it instead of the L-1011 (they wanted to make sure both were built to keep prices lower). Don't know if this is true, or just a tristar fans view of the facts.
SATL382G From , joined Dec 1969, posts, RR: Reply 16, posted (8 years 4 months 3 weeks 3 hours ago) and read 8330 times:
IMHO..
That little fairing also did a lot for the asthetic qualities of an already good looking airplane. Gives the leading edge of the vert stab a nice long "sweep".
Starlionblue From Hong Kong, joined Feb 2004, 15872 posts, RR: 66 Reply 17, posted (8 years 4 months 3 weeks ago) and read 8296 times:
the S-duct allows for a smaller fin/rudder
Actually, it allows for a larger rudder. By having more rudder surface, it allowed for greater control in an asymmetrical (wing-engine out) situation. That allowed the 1011 wing engines to be mounted further outboard on the wing, improving wing loading, making it more efficient that the DC-10.
Sorry I was unclear. The S-duct allowed for a smaller fin/rudder in total including the engine. That is, the part that sticks upward over the fuse is smaller in total.
"There are no stupid questions, but there are a lot of inquisitive idiots." - from Citadel by John Ringo
2H4 From United States of America, joined Oct 2004, 8950 posts, RR: 62 Reply 18, posted (8 years 4 months 2 weeks 6 days 20 hours ago) and read 8251 times:
AIRLINERS.NET CREW HEAD DATABASE EDITOR
Every other three-engined jet I can think of uses the S-duct layout, as opposed to the DC-10/MD-11 design. For example, the Falcon 50 and 900, the Yak-42, the Trident, the Tu-154, etc, etc.
I may be forgetting an exception, but the popularity of the S-duct design certainly lends some credibility to it.
Mlsrar From United States of America, joined Mar 2000, 1417 posts, RR: 9 Reply 19, posted (8 years 4 months 2 weeks 6 days 17 hours ago) and read 8204 times:
I may be forgetting an exception, but the popularity of the S-duct design certainly lends some credibility to it.
The DC-10 was originally designed to be a twinjet that, if produced, would have borne a significant similarity to a shorter 777. The lack of a suitable powerplant was the genesis of the mounting scenario of engine 2.
I mean, for the right price I’ll fight a lion. - Mike Tyson
Buzz From United States of America, joined Nov 1999, 697 posts, RR: 24 Reply 20, posted (8 years 4 months 2 weeks 6 days 14 hours ago) and read 8174 times:
Hi Thrust, Buzz here. I've worked DC-10's a lot, and L-1011-500's a little. My opinion is that the Lockheed was more expensive over the long run, it wasn't really a tail engine issue. Lockheed does tend to make innovative airplanes (Model 18 Electra, P-38, Constallation, C-130, U-2, C-141, A-12) where as Douglas uses proven technology.
I'm no fan of the "patio party" under a #2 engine of a DC-10, in that regard i think the L-1011 has an advantage... not as cold / windy / oily.
And i think the extra metal required to reinforce the vertical fin to carry the load of the #2 engine is a drawback. I don't know how much weight penalty that carries... not a factor anymore.
g'nite
Buzz Fuselsausage: Line Mechanic by night, DC-3 Crew Chief by choice, taildragger pilot for fun
AeroWeanie From United States of America, joined Dec 2004, 1601 posts, RR: 52 Reply 22, posted (8 years 4 months 2 weeks 5 days 13 hours ago) and read 8089 times:
A couple of points:
1) RR went bankrupt and was rescued by the UK government. Lockheed did not go bankrupt. They only got loan guarentees from the US government that were never exercised. The loans being guarenteed were paid off ahead of schedule.
2) An S duct suffers higher total pressure losses than a straight duct, plus it creates flow distortion, both being bad things. The 727-100 prototype suffered a surge of the #2 engine on its maiden takeoff due to flow distortion. This was solved by a series of rather large vortex generators in the #2 inlet. I am not aware of the L-1011 having such a problem.
3) The "frisbee" fairing should be "Frisbee" fairing, as it is named after Lloyd Frisbee, an aerodynamicist at Lockheed.
2H4 From United States of America, joined Oct 2004, 8950 posts, RR: 62 Reply 23, posted (8 years 4 months 2 weeks 5 days 13 hours ago) and read 8084 times:
AIRLINERS.NET CREW HEAD DATABASE EDITOR
AeroWeanie,
Did the large vortex generators in the #2 inlet have (or need) any kind if ice protection?
AeroWeanie From United States of America, joined Dec 2004, 1601 posts, RR: 52 Reply 24, posted (8 years 4 months 2 weeks 5 days 12 hours ago) and read 8081 times:
I seem to recall they do have anti-ice protection. The AIAA design case study on the 727 says for certain, but I don't have it available to me right now. I'll check...
25 AeroWeanie: I just checked the AIAA case study - they are anti-iced. The case study also indicates that the 727-100 (with JT8Ds) has one row of 11 VGs and the 727
26 Max Q: Having the engines further out on the wing also allowed for a quieter cabin, quite noticable compared to the DC10.
27 A350: My opinion is that the Lockheed was more expensive over the long run, it wasn't really a tail engine issue This is something you can read quite often.
28 Thrust: Question: did the 727 also receive the frisbee fairings at some point? Remember that the 727 also had the S-duct.
29 AeroWeanie: The 727 never received Frisbee fairings. I proposed them to Valsan at one point...
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