Keesje From Netherlands, joined Apr 2001, 9320 posts, RR: 45 Posted (1 year 7 months 4 weeks 1 day 22 hours ago) and read 32767 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, 3254 posts, RR: 9 Reply 1, posted (1 year 7 months 4 weeks 1 day 21 hours ago) and read 32767 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, 9320 posts, RR: 45 Reply 2, posted (1 year 7 months 4 weeks 1 day 21 hours ago) and read 32767 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, 3254 posts, RR: 9 Reply 4, posted (1 year 7 months 4 weeks 1 day 21 hours ago) and read 32767 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, 1527 posts, RR: 0 Reply 5, posted (1 year 7 months 4 weeks 1 day 21 hours ago) and read 32767 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, 3889 posts, RR: 8 Reply 7, posted (1 year 7 months 4 weeks 1 day 21 hours ago) and read 32767 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.
For unto us a Child is born- unto us a Son is given!
Kaitak744 From United States, joined Jul 2005, 1956 posts, RR: 3 Reply 8, posted (1 year 7 months 4 weeks 1 day 20 hours ago) and read 32767 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, 284 posts, RR: 0 Reply 9, posted (1 year 7 months 4 weeks 1 day 20 hours ago) and read 32767 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, 3254 posts, RR: 9 Reply 10, posted (1 year 7 months 4 weeks 1 day 19 hours ago) and read 32767 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, 389 posts, RR: 0 Reply 11, posted (1 year 7 months 4 weeks 1 day 19 hours ago) and read 32767 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, 2313 posts, RR: 10 Reply 12, posted (1 year 7 months 4 weeks 1 day 19 hours ago) and read 32767 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, 14933 posts, RR: 63 Reply 13, posted (1 year 7 months 4 weeks 1 day 19 hours ago) and read 32767 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, 947 posts, RR: 1 Reply 14, posted (1 year 7 months 4 weeks 1 day 18 hours ago) and read 32767 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, 389 posts, RR: 0 Reply 15, posted (1 year 7 months 4 weeks 1 day 18 hours ago) and read 32767 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, 4960 posts, RR: 53 Reply 16, posted (1 year 7 months 4 weeks 1 day 18 hours ago) and read 32767 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, 14933 posts, RR: 63 Reply 17, posted (1 year 7 months 4 weeks 1 day 17 hours ago) and read 32767 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, 389 posts, RR: 0 Reply 18, posted (1 year 7 months 4 weeks 1 day 15 hours ago) and read 32767 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.
Dw747400 From United States, joined Aug 2001, 947 posts, RR: 1 Reply 19, posted (1 year 7 months 4 weeks 1 day 14 hours ago) and read 32767 times:
Quoting Scipio (Reply 18): I have noticed that Smile 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
And with the A350 poised to take over what little market share the A340 still has, Airbus will be pushing ETOPS just as hard.
XT6Wagon From United States, joined Feb 2007, 1673 posts, RR: 3 Reply 20, posted (1 year 7 months 4 weeks 1 day 14 hours ago) and read 32767 times:
Scipio, please realise that the odds of a ETOPS twin suffering twin engine failure that would leave a 4 engine plane with operating engines is so long, its approaching the same odds as you winning the lottery two times in a row.
Such failures are so rare that it would be LESS safe to specifically plan for twin engine failure on a ETOPS twin that wasn't from a single common source. IE no fuel, or FOD to name just a couple ways engines can fail from a single source. Quads would suffer quad engine failure in such an instance and thus provide no extra safety.
Disturbingly, despite the far higher safety of a ETOPS MX program. thus far quad engine planes have not been required to follow those practices. Thus giving quad engine planes MORE sources for single failures as a Single mechanic can botch a job on all 4 engines in a single night, leaving the plane to suffer engine failure on all 4.
Keesje From Netherlands, joined Apr 2001, 9320 posts, RR: 45 Reply 21, posted (1 year 7 months 4 weeks 1 day 11 hours ago) and read 32634 times:
Apart from safety concerns I think the simple fact there are no 150 klbs engines must not be ignored. GE say they are still working on recovering of GE90 investments. Building on such an engine would probably get them more enthousiatic then investing in an all new much bigger engine..
For the APTU i think a existing EA or CFM engine in the 30-35 klbs could be the basis. The tail design would have to be adjusted or this engine, it would be designed for the APTU from the start..
If the B747-8i doesn't become a succes, which is not entire imaginable anymore, the A350-1000 proves as good as Airbus and the Airlines think and the A380 becomes more then a niche aircraft, Boeing IMO must act to defend their currently dominant positioning in the >300 seats market.
Creating a 2 subtype HGW 787 family with 330 and 370 seats succeeding the 777 and a new super efficient twin VLA to replace the good old 747 could be the future strategy.
Airlines prove to be conservative. Blended wing bodies, higher speeds etc were skipped recently as show by the moderate compromise Boeing created with Sonic cruiser. The airlines were clear they wanted fuel efficiently, an even more efficient A330, which Boeing did with great succes. A foresee no dramatic configuration innovations, providing a 747 replacement that provides significant fuel saving while using proven technology could be the way out for all the airlines that have to replace 747 fleets and /or want to grow above twin ailse fleets. http://i191.photobucket.com/albums/z...ner6fleetforecast.jpg?t=1194949972
I think the configuration with Boeing 777 like 3-3-3 / 3-4-3 maindeck and narrowbody like 3-3 upperdeck could be a sort of optimal compromise between aircraft outer dimensions, frontal area and constructive simplicity. The upperdeck provides amble opportunities for premium cabins and could provide terminal competibility with the A380 gates / lounges created on all the world major hubs.
Stitch From United States, joined Jul 2005, 14933 posts, RR: 63 Reply 22, posted (1 year 7 months 4 weeks 1 day 8 hours ago) and read 30942 times:
Quoting XT6Wagon (Reply 20): Disturbingly, despite the far higher safety of a ETOPS MX program. thus far quad engine planes have not been required to follow those practices. Thus giving quad engine planes MORE sources for single failures as a Single mechanic can botch a job on all 4 engines in a single night, leaving the plane to suffer engine failure on all 4.
Which is why LROPS - Long Range OPerationS - is starting to come to the focus of world aviation safety and certification authorities.
Quoting Keesje (Reply 21): Apart from safety concerns I think the simple fact there are no 150 klbs engines must not be ignored. GE say they are still working on recovering of GE90 investments. Building on such an engine would probably get them more enthousiatic then investing in an all new much bigger engine..
With respect, what I think also should not be ignored is why must the Ecoliner be so heavy that it requires more then ~115,000lbs of thrust at any operating point?
With CFRP structures, a more efficient frame design then the A380 (as the first of her kind, the A380 was a bit over-built for safety's sake, if nothing else), and improved wings offering greater lift at slower speeds (thereby needing less thrust to achieve V2 and positive climb performance), I think Boeing can "get er done" within that thrust regimen.
Flipdewaf From United Kingdom, joined Jul 2006, 584 posts, RR: 1 Reply 23, posted (1 year 7 months 4 weeks 1 day 8 hours ago) and read 30775 times:
may be the possibility of making it w quad but with engines that are different? A small engine could be placed on the wing, the placement of this engine could help with max load at 2.5g and the larger moment arm would allow a smaller rudder in the case of an engine failure. obviously it would need to be stowed inflight and this is probably the main disadvantage.
Keesje From Netherlands, joined Apr 2001, 9320 posts, RR: 45 Reply 24, posted (1 year 7 months 4 weeks 1 day 8 hours ago) and read 30683 times:
Quoting Stitch (Reply 22): With respect, what I think also should not be ignored is why must the Ecoliner be so heavy that it requires more then ~115,000lbs of thrust at any operating point?
hi Stitch, an additional 25% passenger payload and everything that comes with it. Capasity is not for free. Carbon structures are lighter, but only account for ~50% of the structure. Everything else; food, drinks, galleys, lavs, IFE, luggage, fuel, crew, everything goes up, leading to a higher MTOW and higher thrust requirement. Not 25% but still a good percentage. As can been seen in the graph in the opening post, there are no exceptions.
I took the 777 airframe as a basis and added structure seats and passengers, estimated the weight & took of a percentage for more efficient composite materials. I could have taken the XWB of maybe 787 as well. The 777 offers IMO a more realistic 10 abreast high density option with reprofiled cabin walls. The upperdeck was widened after a first try to create more realistic hand luggage capasity to optionally seat 6 abreast economy class.
NwAflyer07 From , joined Dec 1969, posts, RR: Reply 25, posted (1 year 7 months 4 weeks 1 day 8 hours ago) and read 30680 times:
I like the idea of an Ecoliner, especially like the one shown above. However, would Boeing ever build such an aircraft? Since the 748i is doing so terribly right now, wouldnt Boeing much rather focus on the 737/A320 replacement?
Thorny From , joined Dec 1969, posts, RR: Reply 26, posted (1 year 7 months 4 weeks 1 day 7 hours ago) and read 30494 times:
Quoting NwAflyer07 (Reply 25): I like the idea of an Ecoliner, especially like the one shown above. However, would Boeing ever build such an aircraft? Since the 748i is doing so terribly right now, wouldnt Boeing much rather focus on the 737/A320 replacement
"Right now" is the operative phrase. A380 and 748i aren't selling like hot cakes now, but the time might be right in 2018-2022 or so for a new VLA.
Dambuster From Switzerland, joined Nov 2006, 121 posts, RR: 1 Reply 27, posted (1 year 7 months 4 weeks 1 day 7 hours ago) and read 30373 times:
I like your ideas of the ecoliner Keesje, however, as many said it already, I wouldn't see the need for an auxiliary engine, I'm no expert, but I think the engine problem is smaller than it appears, maybe the GE-90 technology doesn't allow any more than 120k, but the GEnx might be able to do that if required. Boeing published a study (I'll post the article if I find it) that 2 engines were more efficient than 4. You'll probably shoot me for saying that the 773ER vs A346 is a good example. For clear reasons [maintenance and consumption plus the bigger risk of engine failure (with 4 engines you are likelier to have a problem no matter how reliable they are, 50% more chance to be precise)] twins have a clear advantage over quads.
Other than that, very good study you've done there Keesje, quite realistic given the size restrictions Boeing is facing right now (no longer and wider than the 773 but not a real problem if you add a second deck). BTW, I've added you to my respected list.
Keesje From Netherlands, joined Apr 2001, 9320 posts, RR: 45 Reply 28, posted (1 year 7 months 4 weeks 1 day 7 hours ago) and read 30194 times:
Quoting Thorny (Reply 26): A380 and 748i aren't selling like hot cakes now
I think 20 passenger 747s were sold during the last 5 yrs to one carriers. The A380 hasn't been selling real fast before its EIS but steady over the yrs, including followup orders.
everybody is looking t the 200, but thats not really fair, maybe we can count each one double (would not be to far sought : double decks, engines, seats, cost price, MTOW etc.).
I have the feeling the 747-8i must score some serious business soon or Boeing beancounters will step in. Remember Airbus killed the A350 after customer remarks with a lot more orders/ commitments in the bag..
My prediction would be upgrading the 777-300ER with improved GE90/GENX technology engines, AlLi and other smart improvements. Perhaps even a small stretch keeping the range intact and start work on a state of the art, super efficient aircraft serving markets were the A380 is too large including many upcoming 747 replacement markets.
UA, BA, NW, KLM, JAL, NH and many other might be interested, Lufthansa would get a real good discount & additional support to keep the 747 in the air for some longer..
In about 5 years a lot of 747-400 will turn 25 yrs and will flood the 747-8F cargo market spoiling thing there. The move has aready started. Boeing shouldn't think to long IMO.
RayChuang From United States, joined Jun 2000, 7031 posts, RR: 9 Reply 29, posted (1 year 7 months 4 weeks 1 day 6 hours ago) and read 29962 times:
Keesje,
Why do I keep on thinking the Boeing Y3 development project is closer to your Ecoliner idea than you think?
I do think the Ecoliner makes sense for another reason: going to a double-decker fuselage allows for an overall shorter plane, which avoids the gate size issue that plagued the A380 project (Airbus more or less had to plead and beg with the ICAO to accept the 80 x 80 meter gate spacing to accommodate the A380-800).
As for the ATPU, I think GE would likely win the contract, especially given their experience using gas turbine engines for marine applications; they could use a modified CFM56 rated at around 28,000 lb. thrust to provide extra thrust on takeoff in "hot and high" conditions in addition to two slightly uprated GE90-115B main engines.
Also, since the Ecoliner is a "clean sheet" design, they could go for a lower-drag wing that could allow the plane to fly faster, with efficient cruise speeds as high as Mach 0.89.
JoeCanuck From Canada, joined Dec 2005, 1589 posts, RR: 0 Reply 30, posted (1 year 7 months 4 weeks 1 day 6 hours ago) and read 29671 times:
One problem the 380 has with the double decker design is that the upper deck passengers end up using very valuable cargo space for luggage. The same issue would occur with this double decker design.
I think that Boeing could easily go for a wider plane, somewhat of a bridge between the tube and BWB. If they made it wide enough for even 11 across, (12 would be better), they'd end up with the passenger capacity to replace the 748i and maintain a cargo capacity which you can only get with horizontal area.
With CFRP construction, a wider, squashed tube wouldn't be too much of a challenge...same height as a 777 and up to 2m wider. Almost a double decker on it's side without the weirdness of a BWB, (cool though that may be).
(On that note, I would not be surprised at all if the next heavy lifter for the military is a BWB).
I've thought, (since learning of it on the 777 project), that using the APU as a booster was a great idea. There are tons of engines on the market right now that could be slotted in. Since it would only be needed for very short periods of time, it wouldn't even have to be all that efficient.
Anyway, long and wide is the way I imagine them going.
Stitch From United States, joined Jul 2005, 14933 posts, RR: 63 Reply 31, posted (1 year 7 months 4 weeks 1 day 6 hours ago) and read 29449 times:
Quoting JoeCanuck (Reply 30): One problem the 380 has with the double decker design is that the upper deck passengers end up using very valuable cargo space for luggage. The same issue would occur with this double decker design.
And it might even be worse in a shorter plane like the Ecoliner. LH's 747-8Is, for example, has 33% more LD3 positions available for revenue cargo after passenger bags are accounted for then their A380-800s.
If you figure around, say, 32 LD3 positions (same as a 772 or A333), 400 passengers would have 675 bags. At 35 bags per position, you would need to allocate 19-20 of those to passengers, leaving 12-13 open for revenue cargo. Not bad, but when a 425-seat 747-8I will give you 20 free...
Quoting JoeCanuck (Reply 30): I've thought, (since learning of it on the 777 project), that using the APU as a booster was a great idea. There are tons of engines on the market right now that could be slotted in. Since it would only be needed for very short periods of time, it wouldn't even have to be all that efficient.
But then you have to haul that dead-weight around the rest of the time. And the easier you make it to maintain, likely the mechanisms to do it make it even more heavier.
I don't wish to dismiss the idea out of hand, as it does have merit, but I really think an airplane called the "Ecoliner" will try to be as economic and eco-friendly as possible. And a third engine or "thrusting APU" strikes me as benefiting neither goal...
Keesje From Netherlands, joined Apr 2001, 9320 posts, RR: 45 Reply 32, posted (1 year 7 months 4 weeks 1 day 6 hours ago) and read 29486 times:
Quoting JoeCanuck (Reply 30): Anyway, long and wide is the way I imagine them going.
I think Boeing considered it and decided not to go this way about 10 years ago. The wide body creates a lot of inefficiency. Cargo container dimensions seem to be a given, giving them extra width doesn't add capasity. Boeing at that time also considered sky-loft, like they did with the 747-8i. Airlines ignored it then and do now.
Premium passengers don't like to walk around between their bed, bar, seat, dining room and entertainment and working stations. They want and get it all at arms lenght these days. Still someone has to pay for the additional weight, crew maintenance etc. of the Skyloft areas.. Right know it seems only technical feasible, not economical..
Keesje From Netherlands, joined Apr 2001, 9320 posts, RR: 45 Reply 33, posted (1 year 7 months 4 weeks 1 day 5 hours ago) and read 29132 times:
Quoting Stitch (Reply 31): I don't wish to dismiss the idea out of hand, as it does have merit, but I really think an airplane called the "Ecoliner" will try to be as economic and eco-friendly as possible. And a third engine or "thrusting APU" strikes me as benefiting neither goal...
The alternatives are 130-150 klbs engines, who aren't even on the drawing board or 3 / 4 engined + APU aircraft weighing more. At this moment big twins are overpowered for cruise. Having a little more optimal balanced engines for cruise might influence the overall fuel consumption for the better. Remember conventional aircraft have APU's too. Furthermore more direct polar routes might become feasible saving fuel. Twins often don't take the routes quads do for some reason we will not discuss..
I did a quick check comparing it to a 4 engined aircraft. Fuel efficiency negates the additional weight of 1 NB engine+APU instead of APU only..
Stitch From United States, joined Jul 2005, 14933 posts, RR: 63 Reply 34, posted (1 year 7 months 4 weeks 1 day 5 hours ago) and read 29062 times:
Quoting JoeCanuck (Reply 30): Anyway, long and wide is the way I imagine them going.
Quoting Keesje (Reply 32): I think Boeing considered it and decided not to go this way about 10 years ago. The wide body creates a lot of inefficiency. Cargo container dimensions seem to be a given, giving them extra width doesn't add capasity.
I agree with you, Keesje that an oval fuselage that would handle 11 or 12-abreast at 17-18" would be very space inefficient above and below the main deck if configured like current airliners. But their might be some ways to work around it with some ingenuity.
For example, how much long-haul belly freight is palletized versus in LD3s? A wider and taller cargo bay would allow more cargo to be carried on pallets. So perhaps the aft bay could be set that way, with a wider cargo door. The forward bay would then hold the LD3s. Then perhaps you could store hydraulic fluid or potable water or other non-fuel liquids plus equipment bays and such along the left-hand side of the forward cargo bay, freeing up volume in the center-line and wings for additional fuel. Being able to store fuel along the left-hand side would be even more ideal, but safety and impact damage concerns would likely prevent such a thing.
The larger crown area would allow for full crew-rest facilities, including meals, recreation, and sleep. You might even be able to put the entire galley up there, or at a minimum most of the carts which would free-up more floor-space for seats. There would be a bit of a cost for a cart or people lift, but it might pencil out in the end...
JoeCanuck From Canada, joined Dec 2005, 1589 posts, RR: 0 Reply 35, posted (1 year 7 months 4 weeks 1 day 5 hours ago) and read 28987 times:
Quoting Stitch (Reply 31): I don't wish to dismiss the idea out of hand, as it does have merit, but I really think an airplane called the "Ecoliner" will try to be as economic and eco-friendly as possible. And a third engine or "thrusting APU" strikes me as benefiting neither goal...
True...everything is a tradeoff. But without a smaller engine providing supplemental thrust in the back, (and serving real duty as an apu), then the primary engines must be larger so you still deal with extra weight, regardless. And you still need an APU to deal with the huge electrical load required of, what I assume, would be another electric plane.
Quoting Stitch (Reply 31): And it might even be worse in a shorter plane like the Ecoliner. LH's 747-8Is, for example, has 33% more LD3 positions available for revenue cargo after passenger bags are accounted for then their A380-800s.
I figure with the extra floor are you get from going wide, you can still haul the cargo and you have the extra room for the bags built in.
Quoting Keesje (Reply 32):
I think Boeing considered it and decided not to go this way about 10 years ago. The wide body creates a lot of inefficiency. Cargo container dimensions seem to be a given, giving them extra width doesn't add capasity. Boeing at that time also considered sky-loft, like they did with the 747-8i. Airlines ignored it then and do now.
I can't see any benefit to a huge tube...I was thinking of something the same height as the 777 but wider. This gives more area in the hold for both bags and cargo. Screw the skyloft and stuff. More weight and frontal area for little benefit.
EK already crams 400 or so into a 777ER so 2 more rows would get close to 500, I imagine. Between 4 and 5 hundred pax is probably close to max for a twin.
I suspect they're just going to make the 787 match the 350, size for size and let the 748 be their VLA entry for the near future. Pretty cost effective in the long run, I reckon.
Heck, it's all just guessing, right? Who knows? The VLA market might just be maxed out already with the 380 and 748. Building an all new VLA is a huge, scary undertaking, especially considering how iffy the perceived market is. Odds are, the 380 will barely break even after a decade so what's the point, eh...?
You know...this kind of speculation, I like...thoughtful, reasoned and calm. Well done, all.
LAXDESI From United States, joined May 2005, 3254 posts, RR: 9 Reply 36, posted (1 year 7 months 4 weeks 1 day 5 hours ago) and read 28388 times:
Quoting Keesje (Reply 33): I did a quick check comparing it to a 4 engined aircraft. Fuel efficiency negates the additional weight of 1 NB engine+APU instead of APU only..
It is not clear to me why 4 Genx engines will burn so much more more fuel than two GE90 engines+APTU--you show a difference of 10%. I would think the higher fuel efficiency of Genx engines will bring about parity between Genx quads and GE90 twins.
What is the fuel burn difference between 777LR and A345 where the engine technologies are of similar generation?
RayChuang From United States, joined Jun 2000, 7031 posts, RR: 9 Reply 37, posted (1 year 7 months 4 weeks 1 day 4 hours ago) and read 27792 times:
I think the Ecoliner as configured could have a surprisingly strong market for one reason: the possibility that airports may impose landing slot restrictions as air pollution and noise pollution abatement measures. That will force the usage of larger planes, and what better plane to fill this role for landing-slot restricted long-range flights than the Ecoliner for the majority of the world's airlines? (The vast majority of the world's airlines don't need a plane the size of the A380-800.)
777236ER From United Kingdom, joined Aug 2001, 12706 posts, RR: 55 Reply 39, posted (1 year 7 months 4 weeks 1 day 2 hours ago) and read 27605 times:
What is the point of all this? Do you want a job?
The thrust-providing APU is a bad idea - it's dead weight for the majority of the flight and I'd love to see the compressor map for that inflow to a 30-35klb engine.
Balls. 10% fuel burn improvement just for moving the drag of the two extra engines and 'bigger generators'? I'd like to see how you estimated that number, or whether you just guessed it.
Suggesting the wing will be lighter without the two outer engines is also wrong - it'll be heavier. The engines provide bending and twisting relief.
You idea has no impact on ETOPS flights. The failure of the two main engines results in the loss of the aircraft at ETOPS ranges. Consider the extension of ETOPS onto 4-engined aircraft that EASA and FAA are in the process of doing.
But you're comparing the 777-300ER + 20% with your design, which is also a twin, probably less structurally efficient and just as draggy and come up with a fuel burn that is 10% lower.
Let's do a quick Breguet range equation with constant speed in cruise etc, although it's late and this is probably wrong:
Range = (V(L/D) * ln(W1/W2)) / g*SFC.
You've said the ranges are equal, and both the 777-300ER and your aircraft use GE90-115, so the SFC is equal. The velocity is presumably very similar so let's assume equal. The above then reduces to
Keesje From Netherlands, joined Apr 2001, 9320 posts, RR: 45 Reply 42, posted (1 year 7 months 4 weeks 23 hours ago) and read 27525 times:
Quoting 777236ER (Reply 41): You've said the ranges are equal, and both the 777-300ER and your aircraft use GE90-115, so the SFC is equal.
I'm not digging into this, its been 20 years seen I did this stuff & but remember to distrust numbers & assumptions.
Assuming the Ge-115 won't be improved is not mine, GEnx should have a 6.9% SFC advantage over the GE90-94B, which powers the 777-200ER. The -115 should be better but there certainly is room for improvement here. Boeing is pushing GE to act.
About the L/D I think a wing more 787 like could improve a lot. It's a 777-200 stretched wing. Leaner and longer could do a lot.
Starlionblue From Greenland, joined Feb 2004, 13368 posts, RR: 65 Reply 43, posted (1 year 7 months 4 weeks 22 hours ago) and read 27485 times:
Quoting Scipio (Reply 11): - 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.
That's all dead weight. A thusting APU is at least an APU for the rest of the flight.
Quoting Scipio (Reply 11): I am a bit of a sceptic towards the current "two engines but no backup system" philosophy.
Quoting Scipio (Reply 15): 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.
From a visceral point of view I understand all that. From a design point of view, I do not. Your odds calculation is flawed. If both engines go on a twin, this typically means something is wrong apart from the engines and the same problem would stop all engines on a triplet or a quad. Cases in point would be Air Transat or the Gimli Glider. Both ran out of fuel. More engines do not save you from that.
As mentioned, the chances of both engines failing INDEPENDENTLY are astronomically small and this scenario has NEVER occured in all the years of ETOPS. In fact I struggle to remember any incident where this has occurred since the dawn of the jet age. Past history doesn't mean it will never happen, but I will take my chances.
Quoting Keesje (Reply 21): Apart from safety concerns I think the simple fact there are no 150 klbs engines must not be ignored. GE say they are still working on recovering of GE90 investments. Building on such an engine would probably get them more enthousiatic then investing in an all new much bigger engine..
Indeed. Big investment + small market = bad idea.
Tact Is For People Who Aren't Witty Enough To Be Sarcastic
Dw747400 From United States, joined Aug 2001, 947 posts, RR: 1 Reply 44, posted (1 year 7 months 4 weeks 15 hours ago) and read 27441 times:
Quoting Starlionblue (Reply 43): Indeed. Big investment + small market = bad idea.
The problem is, an ATPU doesn't exactly help increase the aircraft's attractiveness in what little market is out there. Even assuming Keesje's assumptions are accurate (though well thought out an presented, they are still educated guesses), its going to be tough to design a three-engine jet with better CASM than a slightly smaller twin.
If you are going to go through the trouble of reinforcing the tail, setting up the associated systems, and taking care of what is, for all real purposes, a third engine (with the associated upkeep), why not just stick with a trijet? The ATPU is essentially another engine to pour money into that hardly ever pulls its weight.
And remember, the extra power that a twin needs is not a total loss. For normal operations, it allows a steeper climbout, something that helps with noise restrictions. The ability to climb more quickly and directly to altitude will increase flexibility and potentially reduce fuel burn.
Starlionblue From Greenland, joined Feb 2004, 13368 posts, RR: 65 Reply 45, posted (1 year 7 months 4 weeks 10 hours ago) and read 27403 times:
Quoting JoeCanuck (Reply 30): I think that Boeing could easily go for a wider plane, somewhat of a bridge between the tube and BWB. If they made it wide enough for even 11 across, (12 would be better), they'd end up with the passenger capacity to replace the 748i and maintain a cargo capacity which you can only get with horizontal area.
As Keesje mentioned, there are issues. Airbus looked at joining two 340 fuses next to each other. The weight penalties were pretty stiff compared to the design they ended up with.
Tact Is For People Who Aren't Witty Enough To Be Sarcastic
777236ER From United Kingdom, joined Aug 2001, 12706 posts, RR: 55 Reply 46, posted (1 year 7 months 4 weeks 4 hours ago) and read 27370 times:
Quoting Keesje (Reply 42):
I'm not digging into this, its been 20 years seen I did this stuff & but remember to distrust numbers & assumptions.
My assumptions are valid and you 'distrust numbers'?! The difference between engineering and pointless pretty pictures are numbers! The data sets you free.
Edit: If you say there's a 6.9% decrease in SFC from the GE90-115 and the engines powering your aircraft then the ratio of the L/D for your aircraft vs. the 777 becomes 1.3 * (1/1.069) or 1.21. Where are you going to find the 22% L/D increase to make your numbers work? Bear in mind that your aircraft is heavier than a 777-300ER so the lift-induced drag will be higher.
Keesje From Netherlands, joined Apr 2001, 9320 posts, RR: 45 Reply 47, posted (5 months 2 weeks 12 hours ago) and read 10701 times:
Because of another post on civil I googled the Boeing Ecoliner and a lot of links, forums, posts popped up everywhere, also a guy on the aviation forum "fightingirish" did an official livery I hadn't seen before
Looking a bit further, someone made an QF Ecoliner flight sim ..
Stitch From United States, joined Jul 2005, 14933 posts, RR: 63 Reply 50, posted (5 months 1 week 6 days 21 hours ago) and read 10352 times:
I think the plane still has merit, but not in it's original specification. It needs to be lighter, with an MTOW at or below 350t and preferably a wingspan of 65m.
Viscount724 From Switzerland, joined Oct 2006, 9405 posts, RR: 7 Reply 51, posted (5 months 1 week 6 days 15 hours ago) and read 10236 times:
Quoting Stitch (Reply 13): Why? Commercial jet twin-engine ops have been in existence for four decades (with the 737-100).
Make that over 5 decades. The first twin-engine commercial jet, the Tupolev 104, first flew in 1955 and went into service in 1956, 12 years before the 737. From 1956 to 1958 the Tu-104 was the only commercial jet in service worldwide.
Four other twin-engine jets were carrying passengers up to 8 years before the 737, including the Caravelle (1959), Tu-124 (1962), DC-9 and BAC 1-11 (both 1965), and Tu-134 (1967).
Tdscanuck From Canada, joined Jan 2006, 4960 posts, RR: 53 Reply 52, posted (5 months 1 week 6 days 14 hours ago) and read 10216 times:
Quoting SCAT15F (Reply 48): I still think Boeing would be better off going with a three engine BWB design.
Better off how? They're struggling with the 787. Take that, then add all new interiors, structure, aerodynamics, flight controls, nacelles (and probably engines), and an entirely new set of FAR's...this does not sound fun.
Parapente From United Kingdom, joined Mar 2006, 383 posts, RR: 0 Reply 53, posted (5 months 1 week 6 days 10 hours ago) and read 10137 times:
Sadly I think real world economics will lay the last card. Boeing has the 77W. There is nothing better out there and there is nothing even planned. The 351 just cannot do what the 77W does. If you really, really require more capacity then...Boeing have the 748.
So Boeing only have to (say) improve the 77W by what 5-7% and it offers a payload/range/economics that is unbeatable.
Its not as if airlines are beating a path to Airbus' door over the A351 is it? This would suggest that they would rather have something bigger (and many have said just this). If you want smaller then yes there is loads of choice from both manufacturers.
I think Boeing know all this and whilst many airlines will try and bully them into a 777-400 I think they will hang tough -offer the above 5-7% and stare them all down.
Flipdewaf From United Kingdom, joined Jul 2006, 584 posts, RR: 1 Reply 54, posted (5 months 1 week 6 days 7 hours ago) and read 10074 times:
Quoting Parapente (Reply 53): I think Boeing know all this and whilst many airlines will try and bully them into a 777-400 I think they will hang tough -offer the above 5-7% and stare them all down.
Well I personally don't believe a 5-7% improvement is feasible, 3-4% max in my opinion.
An 80 meter stretch would certainly not work. My estimates give it a range of about 4500nm and that would need to be between major hubs as it would have a hideously long takeoff roll. Maybe it would work as an Atlantic shuttle but I can't see many airlines wanting it as it would only carry about 10 tons in the belly.
The T7 is a fine machine but where you don't need the uplift the A350 will be finer, that's how it works, same argument of having the T7 over the A380. If the market needs it then use it, if it doesn't use something cheaper to operate (if you can).
Rheinwaldner From Switzerland, joined Jan 2008, 621 posts, RR: 2 Reply 55, posted (5 months 1 week 6 days 6 hours ago) and read 10041 times:
Quoting Parapente (Reply 53): The 351 just cannot do what the 77W does. If you really, really require more capacity then...Boeing have the 748.
The size/payload reduction is so marginal (going from 773ER to A351) that the better efficiency will kill the 773ER. That does not mean that 773ER will no longer be sold. I expect the 773ER to fulfill a lot of demand until A351's start to roll out of the factory. And even then the A350 productivity may not immediately cope with all demand. This leaves a lof of opportunities but it depends on availability. If I order a 350-seater to be delivered at day X and both products have free production slots the A351 has a huge advantage over the 773ER or any derivative.
Quoting Parapente (Reply 53): Its not as if airlines are beating a path to Airbus' door over the A351 is it? This would suggest that they would rather have something bigger (and many have said just this). If you want smaller then yes there is loads of choice from both manufacturers.
Has to do with a saturated market. The 773ER sat in the middle of one of the biggest demand hotspots in this decade. The aircraft industry does not provide at any time a winning product in any aircraft class. The advantages offered by the 773ER are so outstanding that you can say such an offering does not appear very often. The 350-seat demand culminated in this decade after a long time again driven by this great offering. That the markets sees such a clear leader and that one product can gain so much market attraction is something seldom not something usual. Usually after such an event the market is saturated.
Now the A351 follows the 773ER almost in an atypical short time. Because of that the A351 is almost premature. The A351 impact on the market will largely not start before 773ER are phased out. When will this happen? Not so soon! Probably the present 773ER will remain active longer than most other present aircrafts. At least they are the most modern aircrafts currently flying in large numbers. Thus the A351 gets what is left over or what can wait. Which is not so much until now. I expect that trend to continue for quite some time.
Parapente From United Kingdom, joined Mar 2006, 383 posts, RR: 0 Reply 56, posted (5 months 1 week 6 days 5 hours ago) and read 10017 times:
Accepting that both the above posts are true -which I think they probably are. Then OK say its just a 4% increase in efficiency. The plane is already bigger (than the 351) we also hear from potental 351 buyers that they would like more range than they are being offered. Well now they would have both from Boeing. Furthermore since the 77W has been so wildly popular then for all these existing owners any "top up" would go to Boeing.
As is stated above the bulk of the market has already gone (in the last 5 years) so nothing big for another 15 (Excepting BA) - but look at them they are already half way into the 77W honey trap (although they say they are not).
Why in this situation and economic climate would Boeing need to act (with big bucks) now?
Just enough improvement and they can sit back and watch. No need to panic.
As for the -200er series -well thats a different matter. I go along with nearly everybody here with the 787-10/11. RR has kindly made the engines as have the GE/PW combo. When they have the 8/9 sorted I feel sure they will move along on this. Hell who knows when the 787 -9 takes to the air they may even find they don't even need more than a wing mod (as opposed to a brand new one!
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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.
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