DL767captain From United States of America, joined Mar 2007, 2539 posts, RR: 0 Posted (5 years 6 months 4 weeks 1 day 3 hours ago) and read 9608 times:
I look at the 747 using 4 engines and people complaining that 4 engines are less efficient than 2, but it seems obvious that an aircraft the size of the 747 needs 4 engines, 2 engines might not work. So Boeing could make it into a trijet. I know they MD-11 and DC-10 were retired because twin jets were more efficient but that's because the 777 was able to replace that capacity. With the advances in engine technology and the use of composites to make the plane and engines lighter that could do away with the weight problem of 3 engines. Using 777 (or 787 style i guess) and a somewhat smaller engine for the middle back should give the plane enough power as the current 747 (or a few little changes might be needed) But would this be possible, boeing tried it a while ago with the 747 but materials and designs have changed since then, so would this be possible.
Dtwclipper From , joined Dec 1969, posts, RR: Reply 1, posted (5 years 6 months 4 weeks 1 day 3 hours ago) and read 9582 times:
Quoting DL767captain (Thread starter): But would this be possible, boeing tried it a while ago with the 747 but materials and designs have changed since then, so would this be possible.
Alessandro From , joined Dec 1969, posts, RR: Reply 2, posted (5 years 6 months 4 weeks 1 day 3 hours ago) and read 9533 times:
No one expect the large trijets to return, Lockheed, McDonnell-Douglas failed to make money from theirs, Airbus and Boeing never tried to make a larger one than the B727.
Russians settled with the similar sized Tu-154, same size as the B727.
No it was a 70ies thing, now long gone, choice today, 2 or 4 underneath the wings, sad I know....;(
Richierich From United States of America, joined Nov 2000, 4022 posts, RR: 6 Reply 3, posted (5 years 6 months 4 weeks 1 day 3 hours ago) and read 9517 times:
Quoting Dtwclipper (Reply 1): Just so people know what you are talking about.
Thanks for sharing the picture but that looks utterly ridiculous.
Can't say that I think it will ever happen... except for the largest behemoths (747, A380), the world is going twin-jets. The 777 has proved that long-range twin jet operations is not only possible, it is the future.
PanAm747 From United States of America, joined Feb 2004, 4242 posts, RR: 10 Reply 6, posted (5 years 6 months 4 weeks 1 day 3 hours ago) and read 9406 times:
With the increased thrust capability of modern engines, the days of tri-jets is long gone. The added thrust of the third engine is not only not needed, but is overruled by the added weight, complexity, and servicing logistics (such as reaching up to it!!). As an example, look at the 777 and A330 - in many cases, they are flying routes that were the domain of 3 and 4-engine planes, and they are doing so with more thrust AND better fuel efficiency.
Not all is lost for the multi-engine planes - ETOPS certification can only extend so far, and some planes, such as the A380, really need four engines for maximum thrust. Lan Chile really would have a tough time flying SYD-AKL-Chile with a two-engine plane, simply because the ETOPS routing would add hundreds of miles to the flight.
Pan Am:The World's Most Experienced Airline - P(oor) S(ailor's) A(irline): San Diego's Hometown Airline-Catch Our Smile!
Zkpilot From New Zealand, joined Mar 2006, 4739 posts, RR: 10 Reply 7, posted (5 years 6 months 4 weeks 1 day 2 hours ago) and read 9259 times:
If you look at some of the latest Ads for Boeing plus persistant rumours etc.. Y3 is looking like its going to be a 400-600 seat (in normal 3 class config) BWB aircraft... such an aircraft will very likely have 3 engines mounted on top as 4 engines won't be needed for symmetry and 2 engines will not be powerful enough (unless something bigger than the GE115 comes along which is unlikely as it starts to lose efficiency gains from there).
KYAir From United States of America, joined Jan 2004, 362 posts, RR: 3 Reply 8, posted (5 years 6 months 4 weeks 1 day 2 hours ago) and read 9183 times:
Quoting Dtwclipper (Reply 1): Quoting DL767captain (Thread starter):
But would this be possible, boeing tried it a while ago with the 747 but materials and designs have changed since then, so would this be possible.
Just so people know what you are talking about.
If I'm not mistaken, I believe Boeing found the "hump" disrupted airflow to the third/tail engine when testing this model???
Don't cry because it's over, smile because it happened - Dr. Seuss
Rbgso From United States of America, joined Jun 2006, 575 posts, RR: 0 Reply 9, posted (5 years 6 months 4 weeks 1 day 2 hours ago) and read 9163 times:
Quoting Richierich (Reply 3): Thanks for sharing the picture but that looks utterly ridiculous.
I think that bird has a certain "something" about her.....looks kinda nice.....
Lightsaber From United States of America, joined Jan 2005, 10671 posts, RR: 100 Reply 10, posted (5 years 6 months 4 weeks 1 day 2 hours ago) and read 9091 times:
Quoting Itsnotfinals (Reply 4): the day of the trijets is sadly over except for the Falcon 900EX.
Except for a BWB, very true.
The biggest issue is with moving the thrust from the engine to the greatest source of the drag, the wing. Not putting hte engines on the wing adds quite a bit of structure and complexity. With weight being the enemy of all aircraft, I really doubt we'll see body mounted engines on a large airframe again.
This thread comes up on a.net about every 4 months. Reality is that the aircraft market is brutal. With Honda paving the way for overwing mounted engines, I'm doubting even business jets will have tail mounted engines, on a new design, after 2015.
For Y3, the weight reductions will allow it to be powered by two 125k thrust engines. Since that is within today's technology, there is no reason to go with the maintenance costs of a three engine airframe.
Quoting PanAm747 (Reply 6): ETOPS certification can only extend so far
Why? Engines are no longer the big risk on long haul flights. Its fire or a medical emergency. Yes, triple redundancy should be kept on the support systems; but its no longer required for propulsion.
The 787/A350/772LR/Y3/A380 will drive long haul travel for the next decades. Notice something? Only the A380 isn't a twin.
Nitrogen inerting of the fuel tanks will do far more for aircraft safety than an additional engine.
Expect even quads to become rare. Except for VLJ's, twins will be the money makers. Now, above a certain size, quads are very efficient. But the cross over point to go to a quad keeps going up in size as technology progresses.
Corey07850 From United States of America, joined Feb 2004, 2519 posts, RR: 5 Reply 12, posted (5 years 6 months 4 weeks 1 day 1 hour ago) and read 8977 times:
Quoting Itsnotfinals (Reply 4): the day of the trijets is sadly over except for the Falcon 900EX.
Saab2000 From Switzerland, joined Jun 2001, 1605 posts, RR: 12 Reply 14, posted (5 years 6 months 4 weeks 15 hours ago) and read 8426 times:
Quoting Lightsaber (Reply 10): Why? Engines are no longer the big risk on long haul flights. Its fire or a medical emergency. Yes, triple redundancy should be kept on the support systems; but its no longer required for propulsion.
........
Nitrogen inerting of the fuel tanks will do far more for aircraft safety than an additional engine.
DEVILFISH From Philippines, joined Jan 2006, 4427 posts, RR: 1 Reply 15, posted (5 years 6 months 4 weeks 11 hours ago) and read 8226 times:
Quoting Lightsaber (Reply 10): For Y3, the weight reductions will allow it to be powered by two 125k thrust engines. Since that is within today's technology, there is no reason to go with the maintenance costs of a three engine airframe.
Posts to the linked thread in Reply 13 were skeptical about achieving 25% weight reduction for next-gen airliners over current conventional (non-CFRP) airframe construction. What's a realistic figure?
Quoting Lightsaber (Reply 10): Notice something? Only the A380 isn't a twin. ..... Expect even quads to become rare. Except for VLJ's, twins will be the money makers.
Does that mean Y3 will be <=744 size - is 748 the limit or would it still grow? Somehow, I have this crazy hunch the two 748 orders so far would be converted to Y3.
AlexPorter From , joined Dec 1969, posts, RR: Reply 16, posted (5 years 6 months 4 weeks 7 hours ago) and read 7182 times:
Honestly, I'm thinking that this scenario is more likely:
- Engine manufacturers continue to improve engine designs and make something bigger than 777 engines and more powerful.
- Ultra-large airliners get higher above the ground with longer, stronger landing gears
- The massive engines, now powerful enough to replace two 747 or A380 engines, replace them, and fit on the plane with enough ground clearance due to the higher height above the ground.
0NEWAIR0 From United States of America, joined May 2007, 836 posts, RR: 0 Reply 17, posted (5 years 6 months 4 weeks 3 hours ago) and read 4687 times:
Quoting Zkpilot (Reply 7): Y3 is looking like its going to be a 400-600 seat (in normal 3 class config) BWB aircraft...
I may have heard incorrectly...however...I heard that there would be a freighter BWB aircraft and that it isn't the right time to introduce this kind of body to passenger travel. I'd look for Y3 being similar to the aircraft that are currently flying.
"The future belongs to those who believe in the beauty of their dreams."
Charliejag1 From United States of America, joined Aug 2006, 238 posts, RR: 0 Reply 18, posted (5 years 6 months 4 weeks 3 hours ago) and read 4659 times:
Quoting DL767captain (Thread starter): MD-11 and DC-10 were retired because twin jets were more efficient
True, but the safety concerns probably sped the retirement also.
Quoting DL767captain (Thread starter): Using 777 (or 787 style i guess) and a somewhat smaller engine for the middle back should give the plane enough power as the current 747 (or a few little changes might be needed)
The maintenance impact of using two different engine types/models on a single aircraft is too much. Depending on how similar the engines are, you add thousands and thousands of part numbers to the inventory and double the task cards, procedures, and training requirements for engine maintenance and overhaul. We will never see a trijet with the third engine appreciably different than the other two (except of course ducting, which isnt part of the actual engine).
Hmmmm... From Canada, joined May 1999, 2088 posts, RR: 5 Reply 19, posted (5 years 6 months 4 weeks 3 hours ago) and read 4624 times:
There's no reason you can't have a trijet with the engines on the wings. United and Singapore have been doing testing of their own in this respect for cases where ETOPS certification may not be forthcoming for certain routes.
An optimist robs himself of the joy of being pleasantly surprised
Itsnotfinals From , joined Dec 1969, posts, RR: Reply 20, posted (5 years 6 months 4 weeks ago) and read 4459 times:
Quoting Corey07850 (Reply 12): I'd like to introduce you to the Falcon 7x
Neyjets has a few on order I think, so we will be seeing those in the US too
Quoting Hmmmm... (Reply 19): There's no reason you can't have a trijet with the engines on the wings. United and Singapore have been doing testing of their own in this respect for cases where ETOPS certification may not be forthcoming for certain routes.
Zkpilot From New Zealand, joined Mar 2006, 4739 posts, RR: 10 Reply 21, posted (5 years 6 months 4 weeks ago) and read 4427 times:
Quoting Hmmmm... (Reply 19): There's no reason you can't have a trijet with the engines on the wings. United and Singapore have been doing testing of their own in this respect for cases where ETOPS certification may not be forthcoming for certain routes.
Fake and Fake...
Quoting 0NEWAIR0 (Reply 17): Quoting Zkpilot (Reply 7):
Y3 is looking like its going to be a 400-600 seat (in normal 3 class config) BWB aircraft...
I may have heard incorrectly...however...I heard that there would be a freighter BWB aircraft and that it isn't the right time to introduce this kind of body to passenger travel. I'd look for Y3 being similar to the aircraft that are currently flying.
Y3 may still be a decade+ off as B is more likely to concentrate on Y1 (737 replacement). With fuel prices remaining high and not likely to drop much in the future, the advantages of a BWB aircraft become much more pronounced...especially once B has more experience with composites etc
Rbgso From United States of America, joined Jun 2006, 575 posts, RR: 0 Reply 22, posted (5 years 6 months 3 weeks 6 days 23 hours ago) and read 4328 times:
Quoting Hmmmm... (Reply 19): There's no reason you can't have a trijet with the engines on the wings. United and Singapore have been doing testing of their own in this respect for cases where ETOPS certification may not be forthcoming for certain routes.
I thought both carriers were participating in GE's buy 2, get one free promotion.......
Stratosphere From United States of America, joined Sep 2007, 1614 posts, RR: 3 Reply 23, posted (5 years 6 months 3 weeks 6 days 22 hours ago) and read 4236 times:
Quoting Hmmmm... (Reply 19): There's no reason you can't have a trijet with the engines on the wings. United and Singapore have been doing testing of their own in this respect for cases where ETOPS certification may not be forthcoming for certain routes
I am no engineer but it would be interesting if you did have a configuation like that what would happen in the event of an engine failure on the one engine side I would think the yaw rate would be hard to manage.
Viscount724 From Switzerland, joined Oct 2006, 21465 posts, RR: 24 Reply 24, posted (5 years 6 months 3 weeks 6 days 21 hours ago) and read 4159 times:
Quoting Charliejag1 (Reply 18): Quoting DL767captain (Thread starter):
MD-11 and DC-10 were retired because twin jets were more efficient
True, but the safety concerns probably sped the retirement also.
What safety concerns are you referring to? NW only recently retired their last DC-10s after operating the type for over 35 years, and AA and UA (among others) operated their DC-10s for almost 30 years. I wouldn't call retiring an aircraft type after 30+ years of service as "speeding" their retirement.
And how many MD-11s have actually been retired/scrapped? Very few as far as I know. While newer twin-engine types are more efficient for passenger use at current fuel prices, the MD-11 has become an excellent freighter.
25 Tugger: I have been castigated several times for suggesting a third engine option that I call a "thrusting APU" but per Keesje recent thread (the Ecoliner?) i
26 Tdscanuck: This it the design condition for all twins and it's worked fine up to the 777 size. What that means, in practical terms, is that a "thrusting APU" is
27 Hmmmm...: I look at it this way. If you were to put three GEnx engines rated at 75,000 lbs on a 747, the #2 in the tail, that is about the same thrust as 4 RB-2
28 Tdscanuck: But you couldn't certify it. In an engine-out condition, which is the critical one for required thrust, two GEnx's put out 150,000 lbs while three RB
29 Hmmmm...: Good point. So change the engine from a GEnx to a de-rated GE90.
30 Futurecaptain: But what about engine out on takeoff scenarios? If you want the same performance out of the plane you need to end up with the same thrust available a
Sponsor Message: 
From United States of America, joined Mar 2007, 2539 posts, 
From , joined Dec 1969, posts, 
From New Zealand, joined Mar 2006, 4739 posts, 
From Thailand, joined May 2000, 38503 posts, 
From United Kingdom, joined Feb 2006, 680 posts, 
From Switzerland, joined Jun 2001, 1605 posts, 
From Philippines, joined Jan 2006, 4427 posts, 
From Canada, joined May 1999, 2088 posts, 
Printer friendly format 
