Keesje From Netherlands, joined Apr 2001, 8291 posts, RR: 26 Posted (1 year 2 weeks 6 days 2 hours ago) and read 21627 times:
About a month ago I posted a thread on a possible new 370-500 seat aircraft fitting in between the B777-300ER and A380-800. It could become a full composite twin, incorporating a double deck to limit weight and seize and have additional power available from an APTU. Everyone including me has been busy since then but a.net member "Kaktusdigital" / Henry Lam was able to produce some new graphics. http://www.airliners.net/discussions...general_aviation/read.main/3656278
Focusing on todays requirements for such a passenger aircraft, Boeing at some point might look into this segment when the 777 design is caught up by the lighter A350-1000 and bigger 787s and the Boeing 747 passenger design reaches the end of its improvement opportunities.
Questions were asked about the need for the ATPU configuration, the third combined APU / thrusting engine in the tail... IMO GE or RR would probably not be willing to build an engine much bigger then say 110-120 klbs. A very large number of those big twins will have to be sold to recap the investments. Implementing GENX technology into the GE90 might be more feasible.
Still the -200 and -300 version of the Ecoliner would need 130-150 klbs of thrust during the most critical flight stage : just after V1 at MTOW with an engine failure. A sustained take-off and climb out is required because the runway is to short to bring the aircraft to a halt.
Looking at current aircraft minus 1 engine for comparison it becomes clear the 130-150 klbs required thrust estimate for the Ecoliner with one engine out is a realistic assumption. e.g. one GE90-115 couldn´t do the job.
Therefore an additional 30-35 klbs could be installed in the tail providing the additional power required for take-off under extreme conditions. Boeing considered this for the 777LR and 777-300ER, but then GE came up with a suitable engine.
Providing a bigger engine then the GE90-115 for the Ecoliner could, apart from ROI issues, cause ground clearance problems. The engines have to be located as close to the cg as as possible to limit unsymmetrical thrust and resulting controls induced drag/lift. A 3 or 4 engined + APU aircraft would be significant heavier / consume more fuel.
An ATPU located in the tail (like e.g. an a Tristar) could be a conventional NB type of turbofan also functioning as an APU. A number of retractable inlets is situated in the tail & melts into it when the ATPU is not used.
To further limit the use of the APTU during ground operations and start up the APTU when no GPU is available an additional 1000lbs battery pack was included in the design.
LAXDESI From United States, joined May 2005, 3034 posts, RR: 6 Reply 1, posted (1 year 2 weeks 6 days 1 hour ago) and read 21545 times:
Quoting Keesje (Thread starter): About a month ago I posted a thread on a possible new 370-500 seat aircraft fitting in between the B777-300ER and A380-800. It could become a full composite twin, incorporating a double deck to limit weight and seize and have additional power available from an APTU.
I thought the Ecoliner-200's MTOW was close enough to 777, and therefore it would be possible to use current engines without an APTU.
Why not work with 4 787 engines, or improve upon them given there will be room to do so under the wings. Four enhanced 787 engines may turn out to be not that more expensive in total long term costs when compared to two large engines plus an APTU.
Keesje From Netherlands, joined Apr 2001, 8291 posts, RR: 26 Reply 2, posted (1 year 2 weeks 6 days 1 hour ago) and read 21500 times:
Quoting LAXDESI (Reply 1): Why not work with 4 787 engines, or improve upon them given there will be room to do so under the wings. Four enhanced 787 engines may turn out to be not that more expensive in total long term costs when compared to two large engines plus an APTU.
LAXDESI From United States, joined May 2005, 3034 posts, RR: 6 Reply 4, posted (1 year 2 weeks 6 days 1 hour ago) and read 21403 times:
Quoting Keesje (Reply 2): LAXDESI, it seems the total system (4 engines + APU) is less efficient. E.g. the 747-8 has for "787 engines. Last month a did a rough comparison looking at alternative GENX engines. It doesn´t look like a good idea.
How about my point that the existing 787 engines could be enhanced to give better fuel economy for a very low R&D cost.
Could the availability of room under wings allow the 787 engines to have larger fans and achieve higher efficiency? The enhanced/improved engines could potentially negate the delta of 40,000 lbs that you show in your analysis.
I am not well versed in engine technology, but would like to see some feedback on my point above.
DL767captain From United States, joined Mar 2007, 1318 posts, RR: 0 Reply 5, posted (1 year 2 weeks 6 days 1 hour ago) and read 21335 times:
Well would the cockpit layout be similar to the 787?
What i'm thinking, boeing adopts this idea, and makes the cockpit so similar to the 787 that pilots could go back and forth between the two with extremely little training, probably taxi practice for something that big. This would give airlines the perfect combo, two planes, both fill a perfect market need, and 1 pilot is capable of flying both due to the same cockpit.
As for the engines, i'm sure it wouldnt be that hard to improve the GenX to give it enough thrust to power this thing, boeing might look to this as a possible Y3, but the 748 could be around for a while.
AA737-823 From United States, joined Mar 2000, 3578 posts, RR: 5 Reply 7, posted (1 year 2 weeks 6 days ago) and read 21295 times:
Quoting LAXDESI (Reply 4): How about my point that the existing 787 engines could be enhanced to give better fuel economy for a very low R&D cost
The 787 engine is (both RR and GE) already at the cutting edge of efficiency, with an astronomical bypass ratio and incredible blades and a new combustion chamber, etc.
I think that to 'enhance' it would prove difficult, and your "very low R&D cost" hypothesis would prove untrue.
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Kaitak744 From United States, joined Jul 2005, 1915 posts, RR: 2 Reply 8, posted (1 year 2 weeks 6 days ago) and read 21235 times:
Good research Keesje, but in my opinion, it is still a tube with wings. (a more efficient tube with wings though).
In the past 50 years, commercial aviation has had advancements in passenger comfort, fuel efficiency, reliability, noise, range, and operation cost. However, there has been no advancement in speed*. Aircraft are still..... slow. Speed is the one area the Ecoliner fails to address.
Meta From United States, joined Aug 2005, 264 posts, RR: 0 Reply 9, posted (1 year 2 weeks 6 days ago) and read 21100 times:
Quoting Kaitak744 (Reply 8): Aircraft are still..... slow. Speed is the one area the Ecoliner fails to address.
I totally agree. Over the past years both Boeing and Airbus have enhanced their planes so much, but it would be nice for one of them to make something that goes faster. While at the same time safe and environmentally friendly.
LAXDESI From United States, joined May 2005, 3034 posts, RR: 6 Reply 10, posted (1 year 2 weeks 5 days 23 hours ago) and read 21041 times:
Quoting AA737-823 (Reply 7): The 787 engine is (both RR and GE) already at the cutting edge of efficiency, with an astronomical bypass ratio and incredible blades and a new combustion chamber, etc.
Isn't there R&D going on to come up with new engines for A320/B737 replacements? Whatever comes out of it could be scaled up and applied to A380/B748 and the proposed Ecoliner.
Scipio From Belgium, joined Oct 2007, 305 posts, RR: 0 Reply 11, posted (1 year 2 weeks 5 days 23 hours ago) and read 20899 times:
Keesje,
I like the thrust-providing APU idea and, just like you, I am a bit of a sceptic towards the current "two engines but no backup system" philosophy. However, I wonder whether the thrust-providing APU is the most efficient solution. It might require strengthening of the aft section of an airplane, which could add weight well beyond the weight of the larger APU itself.
So, please consider a few alternative solutions, based on the needs such an auxiliary power system would need to address (emergency thrust in case of an engine failure during a cricital flight stage and maintaining cruising altitude in case of a dual engine failure for as long as possible):
- some sort of afterburners in the main engines, which could function as independent rocket engines in case the main engine itself failed;
- very simple and lightweight rocket engines mounted in the pylons on top of the main engines.
Both solutions would have the advantage of capitalizing on the relative structural strength of any 2-engine design. And, in emergency situations, nobody really cares about fuel economy.
During a take-off emergency, it would actually be beneficial to burn lots of fuel very rapidly, thus reducing weight.
Ken777 From United States, joined Mar 2004, 1957 posts, RR: 0 Reply 12, posted (1 year 2 weeks 5 days 22 hours ago) and read 20844 times:
Quoting Meta (Reply 9): I totally agree. Over the past years both Boeing and Airbus have enhanced their planes so much, but it would be nice for one of them to make something that goes faster. While at the same time safe and environmentally friendly.
Boeing was working on that - it's called the Sonic Cruiser and it was a beauty.
Unfortunately we went through 9/11 and the airlines took a beating that put the SC on hold. In its place Boeing went with the 7E7/787 program and that hasn't done too bad in the market.
The SC might still be built in the future, but hopes for it go down a bit more as the price of fuel goes up a bit more. The key will be increased efficiencies in the engine to bring trip costs down to only about 5% more than the 787, which is no easy task.
Stitch From United States, joined Jul 2005, 12688 posts, RR: 53 Reply 13, posted (1 year 2 weeks 5 days 22 hours ago) and read 20843 times:
Quoting Scipio (Reply 11): I like the thrust-providing APU idea and, just like you, I am a bit of a sceptic towards the current "two engines but no backup system" philosophy.
Why? Commercial jet twin-engine ops have been in existence for four decades (with the 737-100). Trans-ocean jet twin-engine ops have been in existence for three (with the A300B4).
You are statistically more likely to suffer an engine failure on a tri-jet or a quad then on a twin. And any systems failure that would take down two engines on a twin is likely to take down three on a tri-jet or four on a quad.
Dw747400 From United States, joined Aug 2001, 862 posts, RR: 1 Reply 14, posted (1 year 2 weeks 5 days 22 hours ago) and read 20820 times:
As mentioned by many people in the previous thread, the ATPU was studied at length by Boeing, and even before the GE90-115s came into the picture, it really didn't have a chance. The structural complexity, additional tankage and fueling lines, large retractable inlet, and more, had the economics looking terrible. Boeing realized it needed the bigger engine, and had it not been available, the 77W probably would have been a much more modest increase in performance.
Ultimately, the question is not just can you justify a new large engine, but can you justify a new large plane. Going with the ATPU might make the engine folks happy, but if the airlines view it like they have in the past, the business case for the plane itself is in trouble.
That said, it is possible the economies could change with an even bigger airplane, but I doubt it.
Scipio From Belgium, joined Oct 2007, 305 posts, RR: 0 Reply 15, posted (1 year 2 weeks 5 days 22 hours ago) and read 20795 times:
Quoting Stitch (Reply 13): Why? Commercial jet twin-engine ops have been in existence for four decades (with the 737-100). Trans-ocean jet twin-engine ops have been in existence for three (with the A300B4
Statistics. The whole argument to allow extended ETOPS is that it is "sufficiently" improbable that two engines will fail during the same flight.
The crux of this debate boils down to this "sufficiently". Boeing and some airlines seem to have convinced the FAA to accept their definition of "sufficiently". But there is no denying that, everything else equal, the probability of a tri-jet or quad suffering a catastrophic multiple engine failure is a lot lower than that of a twin. Even the FAA recognizes this in its publications.
Moreover, and this is in part where I understand Keesje is coming from, a twin with no back-up systems needs engines that can get an airplane airborne at MTOW on just one engine. This requires a level of potential thrust from each engine that is totally irrelevant for day-to-day operations on two running engines.
So, the trade-off is between having some kind of back-up power system and having engines that are way too large and powerful for what you need during routine operations.
Tdscanuck From Canada, joined Jan 2006, 3820 posts, RR: 28 Reply 16, posted (1 year 2 weeks 5 days 22 hours ago) and read 20689 times:
Quoting Meta (Reply 9): Over the past years both Boeing and Airbus have enhanced their planes so much, but it would be nice for one of them to make something that goes faster. While at the same time safe and environmentally friendly.
Except nobody wants to buy that. Boeing and Airbus are fully capable of building a safe, environmentally friendly, faster commercial jet. Boeing went so far as offering one for sale. No airline wanted to buy it. With fuel costs higher than they were when the Sonic Cruiser was offered, everybody will want to buy one even less now. Boeing and Airbus are very very good at what they do, but they still have to deal with the laws of physics.
Quoting LAXDESI (Reply 10): Isn't there R&D going on to come up with new engines for A320/B737 replacements? Whatever comes out of it could be scaled up and applied to A380/B748 and the proposed Ecoliner.
The R&D is going on right now. First commercial application will be on the Mitsubishi Regional Jet, then the Bombardier C-Series (assuming it gets built). However, it's not yet clear how well those technologies will scale. I'm sure it will be done eventually, but they're not likely to jump from the RJ market straight to the 115K-class market.
Stitch From United States, joined Jul 2005, 12688 posts, RR: 53 Reply 17, posted (1 year 2 weeks 5 days 21 hours ago) and read 20664 times:
Quoting Scipio (Reply 15): Statistics. The whole argument to allow extended ETOPS is that it is "sufficiently" improbable that two engines will fail during the same flight. The crux of this debate boils down to this "sufficiently". Boeing and some airlines seem to have convinced the FAA to accept their definition of "sufficiently". But there is no denying that, everything else equal, the probability of a tri-jet or quad suffering a catastrophic multiple engine failure is a lot lower than that of a twin. Even the FAA recognizes this in its publications.
Uh, point of order Councilor. Boeing isn't the only manufacturer of long-range twin-engined planes. Airbus has these things called A300s, A310s, and A330s. And they're developing one called the A350. And the FAA is not the only sanctioning body in the world. EASA and the JAA have their oars in the sanctioning water, as well.
Quoting Scipio (Reply 15): Moreover, and this is in part where I understand Keesje is coming from, a twin with no back-up systems needs engines that can get an airplane airborne at MTOW on just one engine. This requires a level of potential thrust from each engine that is totally irrelevant for day-to-day operations on two running engines.
Uh, yes. That is why the A300, A310, A320, A330, A350, 737, 757, 767, 777 and 787 all have engines with sufficient thrust to get the bird into the air if they drop one on the tarmac right after rotation. A Nationwide Boeing 737 demonstrated it last week, as a matter of fact.
Quoting Scipio (Reply 15): So, the trade-off is between having some kind of back-up power system and having engines that are way too large and powerful for what you need during routine operations.
It is plainly clear that having two more powerful engines is preferred to having three sufficiently powerful engines.
Scipio From Belgium, joined Oct 2007, 305 posts, RR: 0 Reply 18, posted (1 year 2 weeks 5 days 19 hours ago) and read 20463 times:
Quoting Stitch (Reply 17): Boeing isn't the only manufacturer of long-range twin-engined planes.
I have noticed that But Boeing is the one who has been pushing the scope of ETOPS over the last few years, trying to get any practical limitations removed for its 777.
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But Boeing is the one who has been pushing the scope of ETOPS over the last few years, trying to get any practical limitations removed for its 777.