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Technologies For Boeing 737 Replacement  
User currently offlineTomB From United States of America, joined Nov 2006, 79 posts, RR: 0
Posted (4 years 6 months 1 week 1 day 12 hours ago) and read 6378 times:

Graham Warwick of Aviation Week wrote an excellent article in May 2010 entitled Airliners in 2030: Subsonic Challenges. The article summarized the reports of four industry teams on advanced concepts and technologies for subsonic airliners to enter service in 2030-35. The four industry teams were Boeing, Northrop Grumman, MIT and GE/Cessna. The article also provides links to each industry study so in total you can read 800+ pages on new technology for airliners.

http://www.aviationweek.com/aw/blogs...=blogScript&plckElementId=blogDest

Since I have read all 800+ pages, permit me to summarize some of the technologies that may be incorporated into a clean sheet Boeing 737 (and 757) replacement.

Both Boeing and Northrop did similar type studies and arrived at similar conclusions on technology that may be incorporated into new airliners. Both Boeing and Northrop looked at number of aircraft configurations but in the end decided that conventional twin engine configuration like the B-737 was the preferred configuration. Both Boeing and Northrop looked at the Blended Wing Body (BWB) but did not see any advantages over the conventional configuration for B-737 replacement aircraft. Both Boeing and Northrop preferred high by-pass turbine engines rather than open rotor engines.

Based upon the Boeing and Northrop studies, I list the technologies that could be incorporated in the Boeing 737 (and 757) replacement aircraft, more or less in the order of importance.

Install CFM Leap X and P&W GTF engines for a 16% reduction in fuel burn.

Advanced composite structures for lighter weight. Ultra high performance composite fibers can permit higher aspect wings. Very tough composites – resin systems with greatly reduced suspectibility to impact damage and reduced curing temperature to support lower costs..

Natural laminar flow wings to reduce drag. The designers will probably eliminate leading edge slats to achieve laminar flow but also have wings with lower wing loadings to maintain or improve the takeoff field length.

Riblets on the fuselage. Same aerodynamic effect as dimples on a golf ball.

Relaxed static stability to reduce the size of the horizontal stabilizer.

Active/passive aeroelastic for load control so that you do not have to build the wings as strong.

Boeing would probably keep the 118 foot wingspan on a B-737 replacement, but lower the wing sweep to approximately 20 degrees, reduce the cruise speed to M.70 or M.75 and reduce the wing loading to compensate for the leading edge slats being removed. The lower wing loading means that the B-737 replacement can cruise at least 3000 feet higher than the B-737NG thus saving on the fuel burn. The new wing would increase the Lift to Drag ratio by 10% and have a higher aspect ratio.

The overall design improvements should reduce the Operating Empty Weight (OEW) by 10% and reduce the Maximum TakeOff Weight (MTOW) by 15% as less fuel is required for the same mission.

The new design would improve the design integration of the nacelles for less drag

Carbon nanotube electrical cables and bundle together advanced subsystem technologies for less weight.

Improvements in the Air Traffic Management system to permit more direct flying between cities and improvements in the interior of the aircraft (such as twin aisles) to permit faster turnaround times are expected to offset the slower cruise speed on the new aircraft.

MIT D8 Study

MIT designed a replacement for the Boeing 737-800 model which they called the D8.1 model. The MIT D8 is a double bubble fuselage lifting body fuselage with twin aisles and eight abreast seating. The D8 has the following physical features:

Double bubble fuselage cross section

Lifting nose

Nearly unswept wing for M.72 cruise at 40,000 feet.

Rear mounted engines with boundary layer ingestion to direct the exhaust into the low pressure zone behind the aircraft.

Lightweight Pi tail – two vertical stabilizers with a horizontal stabilizer mounted on top of the vertical stabilizers.

The MIT D8 configuration is said to offer the following advantages compared to the B-737-800.

The D8.1 fuselage is slightly draggier than the B-737-800 but it enables:

A lighter wing

Smaller lighter tail

Enables Boundary Layer Ingestion

Smaller lighter engines

Shorter, lighter landing gear

Based on a change in airframe configuration but using the same engines and systems technology as a Boeing 737-800, MIT is claiming that the MIT D8.1 configuration results in a 49% fuel burn reduction compared to the Boeing 737-800. Pretty impressive if it is true.

My Idea

Since I am intrigued by the lifting body fuselage and Boundary Layer Ingestion as envisioned by MIT, I think one viable Boeing 737 replacement may be a wide oval fuselage design with 7 abreast seating and twin aisles like the Boeing 767. The wide oval fuselage would be 16’ 6’ wide (same as B767) and 14’ 6” high (as compared to 17’ 9” in the B767). The wide oval fuselage would have about 85% of the frontal area of a B767 fuselage. The wide oval fuselage cross section would have two LD3-45 cargo containers side by side in the lower lobe. The front to rear cross section of the fuselage could be shaped liked a supercritical airfoil so that the fuselage generates lift. Or the fuselage could incorporate a lifting body nose to generate lift. The aerodynamics of a lifting body fuselage are well above my competence so I will leave the design to the experts.

The wide oval aircraft will have a low wing with two primary high by-pass turbofan engines hung from the wings. The engines mounted on the wings will reduce wing and fuselage weight and promote better access for the mechanics to service the engines.

To gain the benefits of boundary layer ingestion, I would install two or three electric ducted fans on the rear fuselage between the twin vertical stabilizers. The electric ducted fans would be designed to ingest the boundary layer and eject the exhaust into the low pressure zone behind the fuselage thus reducing form drag. The electric ducted fans would be designed to produce several thousand pounds of thrust – just enough to ingest the boundary layer – and their source of electric power would be the generators on the primary engines and/or the APU.

The electric motor to power to ducted fan could be a large diameter motor similar to a wheel motor. The electric rotor could be installed on the outer perimeter of the fan blades and the stator could be imbedded into the structural ring that holds the ducted fan in place.

Since Rolls Royce Liberty Works (formerly Allison) and Remy International (a noted electric motor manufacturer) are both in Indiana, they could joint venture to design the electric ducted fan.

The wing on the Boeing 737 replacement would have the 118’ wingspan so that the replacement aircraft can readily fit into the existing B-737 gates. Wing sweep would depend upon the cruise speed required by the airlines. The Boeing 757 replacement would have a stretched fuselage and new very high aspect wing. The wingspan may be 160 feet and the aspect as high as 16 to permit the aircraft to cruise at 41,500 feet. In their study, Boeing indicated that such a high aspect wing could produce another 19% reduction in fuel burn compared to the 118’ wing.

It will be interesting to see what designs Boeing actually brings forth in the next year or two as they begin their cleansheet B-737 replacement program.

22 replies: All unread, jump to last
 
User currently offlineparapente From United Kingdom, joined Mar 2006, 1664 posts, RR: 10
Reply 1, posted (4 years 6 months 1 week 23 hours ago) and read 6312 times:

So Rolls Royce (and others) has and is spending all these millions$ developing the open rotor - just for fun? Of course they never speak to the Worlds premier aircraft builder - no of course they would not.Oil consumption has and will keep on rising,oil deposits have and will keep on falling.Only deep "new" oil left - and we all know about that.So what do we know as an absolute certainty.Fuel prices will rise.Now look at any graph prepared by a reptutable source and look at what costs are important in a world of high fuel prices.You will see only one.
Whilst Leap-X and Purepower hope expect a 15% improvement all engine manufacturers (yup all of them) accept that open rotor brings another 10% to the party.10% - I repeat. And I havn't even bothered to mention the lower CO2 figures.

So Boeing is just going to ignore all this and leave it to Airbus to clean up? OR will be the 2020 powerplant I would bet the farm on that.

Could the fuse have some hybrid lifting body elements ? Quite possibly.

Might it be a narrow twin isle 2-3-2?.Quite possibly (They took some kind of patent out on such a configuration on this as I recall)

Cargo (particularly containers)? Is not a make or break factor in this marketplace (people are) see 737 sales. But no doubt it would include the ability to fly them.

What shape would it be? Thats the fun question! Personally (Given my view on OR) I look up in the Boeing Museum of flight and I see in pride of place a Jetstar,I look at what they really wanted the 787 to be (Sonic Cruiser).I would expect to see something akin to that but with OR powering it.


User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 2, posted (4 years 6 months 1 week 20 hours ago) and read 6280 times:

Quoting parapente (Reply 1):
So Rolls Royce (and others) has and is spending all these millions$ developing the open rotor - just for fun?

Of course not. But the time horizon for open rotor is too long for RR (or anyone else) to know for sure what will happen with it.

Quoting parapente (Reply 1):
Of course they never speak to the Worlds premier aircraft builder - no of course they would not.

Why do you think they're not talking? Boeing (or anyone else) saying "We'll probably to higher-bypass fan" in no way says that they haven't talked to the open rotor folks. PW didn't work very tightly with any OEM's until they were very far down the GTF development process.

Quoting parapente (Reply 1):
Whilst Leap-X and Purepower hope expect a 15% improvement all engine manufacturers (yup all of them) accept that open rotor brings another 10% to the party.10% - I repeat.

The findings from the last time were that most of the additional fuel burn benefit in the engine is lost when you make all the compromises necessary to integrate it with the airframe. Although the biggest issue (noise) has apparently come a long way, the integration issues are still there.

Tom.


User currently offlineparapente From United Kingdom, joined Mar 2006, 1664 posts, RR: 10
Reply 3, posted (4 years 6 months 1 week 16 hours ago) and read 6263 times:

I agree.For OR it's all about integration with the airframe.That why (personally) I can't see RR or anyone else spending time and money on OR - unless they are aready working very closely with a manufacturer who feels he can overcome the issues.

Otherwise - similar to TomB, Boeing might as well hang GTF's on a more conventional craft.I do recall seeing a Boeing example of a "shrunk" 787 on the forum.

If Boeing "go first" as is nearly a certainty (didn't say when - just that they would go first) then they have to be absolutly 100% certain that OR cannot be done (clearly the engine can - I am refering to airframe integration here).As if it can and Airbus do- after they go down a conventional route, then they can wave goodbye to the whole market.

-Which is why I feel they will do otherwise.


User currently offlineXT6Wagon From United States of America, joined Feb 2007, 3432 posts, RR: 4
Reply 4, posted (4 years 6 months 1 week 14 hours ago) and read 6221 times:

Quoting TomB (Thread starter):
reduce the cruise speed to M.70 or M.75

Not going to happen for tha 737RS. Gvien that the customers want MORE speed not less, there is no way to sell a reduction in speed. WN for example has routes that rely on very tight trip times so they can do 5 legs a day. The one I know about starts in the NW, makes its way down to florida, then somewhere in the NE. You fly a slower plane and its not going to get that 5th leg in. Lower utilization = higher costs for the use you do get. The airlines wanting to use them transatlantic will also need the extra speed.


User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 5, posted (4 years 6 months 1 week 5 hours ago) and read 6147 times:

Quoting XT6Wagon (Reply 4):
WN for example has routes that rely on very tight trip times so they can do 5 legs a day. The one I know about starts in the NW, makes its way down to florida, then somewhere in the NE. You fly a slower plane and its not going to get that 5th leg in.

The theory is that they can recover the lost cruise time (for short/medium range flights) by speeding up the load/unload process. In WN's case that's probably not realistic because their gate turns are so quick already, but it could work for a lot of other airlines.

Tom.


User currently offlineparapente From United Kingdom, joined Mar 2006, 1664 posts, RR: 10
Reply 6, posted (4 years 6 months 6 days 22 hours ago) and read 6100 times:

Re above.Speed (drag) and Fuel (burnt) will always be the trade off - you cannot have both. What is the most important? I guess this depemds on the trips involved.If (using Keejse's famous RR graph) the vast (90%) are short then loosing 10% off the cruising speed is of very little consiquence.If one is flying for 3 plus hours the half an hour begins to matter - I would have thought.

It is for this reason that I have always believed that the A320 re engine (if it happens) has far more to do with A320 and A321's replacing 757's on longer runs - than some short term gain on the typical short LCC A319 routes.


User currently offlineTomB From United States of America, joined Nov 2006, 79 posts, RR: 0
Reply 7, posted (4 years 6 months 6 days 2 hours ago) and read 5999 times:

Article - Southwest COO Pushes for New Narrowbody Replacement

http://atwonline.com/aircraft-engine...pushes-narrowbody-replacement-0624


User currently offline1GR8AIRLINE From United States of America, joined Mar 2009, 21 posts, RR: 0
Reply 8, posted (4 years 6 months 5 days 16 hours ago) and read 5968 times:

Quoting XT6Wagon (Reply 4):
Not going to happen for tha 737RS. Gvien that the customers want MORE speed not less, there is no way to sell a reduction in speed.

I think improvements in air traffic management could also negate some of the effects of slower cruise speeds. If airliners of the future can fly a more direct route and not have to enter holding patterns upon arrival, this will reduce the overall trip time. Certainly the benefits would be more pronounced on longer flights, but it might still be enough to allow airlines like WN to still fit five trips in per day with a slower-cruising aircraft. Now, if only the politicians can separate the FAA re-authorization/NextGen from pork, unrelated bills, etc...


User currently offlinenomadd22 From United States of America, joined Feb 2008, 1902 posts, RR: 0
Reply 9, posted (4 years 6 months 5 days 15 hours ago) and read 5955 times:

Nothing is going to "make up " for slower cruise speeds. Any improvement you make in loading ar ATC could be made regardless of how fast the plane flies. It might help airlines keep current schedules, but the simple fact is a slower plane will be covering fewer miles in an hour, generating less revenue per hour and cost more to operate in everything but fuel per trip.


Andy Goetsch
User currently offlinevoltage From United States of America, joined May 2007, 109 posts, RR: 0
Reply 10, posted (4 years 6 months 5 days 14 hours ago) and read 5947 times:

So I'm guessing the manufacturer has to pick a cruise speed at which to optimize the aerodynamics, but the airline could fly it at a different speed?

Let's consider two options:

Option A:
Manufacturer optimized cruise speed 0.85

Option B:
Manufacturer optimized cruise speed 0.70
Plane can still reach 0.85

What would be the likely difference in efficiency if both planes were flying at 0.85? at 0.70?


Or would the engines prevent going significantly faster than the designed cruise speed?


User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 11, posted (4 years 6 months 5 days 14 hours ago) and read 5938 times:

Quoting nomadd22 (Reply 9):
Nothing is going to "make up " for slower cruise speeds. Any improvement you make in loading ar ATC could be made regardless of how fast the plane flies. It might help airlines keep current schedules, but the simple fact is a slower plane will be covering fewer miles in an hour, generating less revenue per hour and cost more to operate in everything but fuel per trip.

If a flight takes two hours, it takes two hours. It doesn't matter if it's 60 minutes load/60 minutes flight or 20 minutes load/100 minutes flight.

Quoting voltage (Reply 10):
So I'm guessing the manufacturer has to pick a cruise speed at which to optimize the aerodynamics, but the airline could fly it at a different speed?

Yes.

Quoting voltage (Reply 10):
What would be the likely difference in efficiency if both planes were flying at 0.85? at 0.70?

Depends on the design, but likely you're talking about an efficiency change of about 20%.

Quoting voltage (Reply 10):
Or would the engines prevent going significantly faster than the designed cruise speed?

That depends a lot on the engines and what you do with weight...lower weight will allow higher speed with the same engines.

Tom.


User currently offlineRoseFlyer From United States of America, joined Feb 2004, 9827 posts, RR: 52
Reply 12, posted (4 years 6 months 5 days 13 hours ago) and read 5934 times:

Quoting tdscanuck (Reply 11):

Quoting voltage (Reply 10):
What would be the likely difference in efficiency if both planes were flying at 0.85? at 0.70?

Depends on the design, but likely you're talking about an efficiency change of about 20%.

One new technology from the 787 that can help is variable camber wings. They help regulate lift over the entire lifting surface and can help. The spoilers on the 787 are truly an incredible design. They vary the camber of the wing, lower when flaps are extended, and of course serve their normal function of reducing lift/creating drag.



If you have never designed an airplane part before, let the real designers do the work!
User currently offlinenomadd22 From United States of America, joined Feb 2008, 1902 posts, RR: 0
Reply 13, posted (4 years 6 months 5 days 7 hours ago) and read 5873 times:

Can't figure out selecting text on an iphone.
I still don't see what load time has to do with cruise speed. If you can load a mach .7 plane in 20 minutes you can load a mach .87 plane in the same time.



Andy Goetsch
User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 14, posted (4 years 6 months 5 days 7 hours ago) and read 5871 times:

Quoting nomadd22 (Reply 13):
I still don't see what load time has to do with cruise speed. If you can load a mach .7 plane in 20 minutes you can load a mach .87 plane in the same time.

A major change in boarding time requires a major change in the aircraft...just 'cause you can board an aircraft designed for it in 20 minutes doesn't mean you can do that with another aircraft.

Now, if you mean that you could apply the same design techniques to a faster designed aircraft, that's true. You could choose to build a M 0.87 plane with fast boarding just as well as a M 0.7 plane with fast boarding, but that misses the point of the M 0.7 plane. Dropping from M 0.87 to 0.7 is worth about 18-25% in reduced fuel cost, which more than offsets the increased in time-based costs. The point of faster boarding is that you could drop fuel costs significantly while holding time-based costs the same, resulting in a major drop in overall operating cost.

If you flip the situation around (fast boarding at M 0.87) you don't get any fuel burn advantage and only get the delta in time-based costs, which isn't that large.

Tom.


User currently offlineSeJoWa From United States of America, joined May 2006, 373 posts, RR: 0
Reply 15, posted (4 years 6 months 4 days 21 hours ago) and read 5832 times:

TomB Thank you for your interesting synopsis of the 800 pages. Could you repost the full link?

Would it be sensible to design a CFRP wing that swept up from the root (akin to the A380) to increase engine nacelle ground clearance, and keep the present fuselage?


User currently offlineTomB From United States of America, joined Nov 2006, 79 posts, RR: 0
Reply 16, posted (4 years 6 months 4 days 17 hours ago) and read 5778 times:

SeJoWa:
The link to the article is about 5 lines long and the computers choke on it every time I try to post the link.

Here is a work around:
Go to Aviation Week homepage - www.aviationweek.com
Click on Blogs on the top ribbon
Under the Leading Edge category, click on See All Leading Edge Posts (lower middle of your screen)
Under Archives, click on May 2010
Go to the bottom of the screen for article Airliners in 2030: Subsonic Challenges posted 5/14/2010

If you have the time, I would encourage you to read the slide show posted by each of the industry teams (see the links in the article). Each industry slide presentation is about 200 slides long but you get a lot of insight into their design processes and which technologies the aircraft designers are focusing on.

Tom B


User currently offlineTomB From United States of America, joined Nov 2006, 79 posts, RR: 0
Reply 17, posted (4 years 6 months 4 days 17 hours ago) and read 5774 times:

It is difficult to find good articles explaining Boundary Layer Ingestion (BLI) on the Internet.

However, Boeing Phantom Works designers working on the Boeing Blended Wing Body aircraft did a study. By replacing the podded engines sitting on a strut above the rear fuselage and instead going to a semi submerged nacelle with Boundary Layer Inlet, they estimate that they can reduce the fuel burn on the BWB by 10%.

I gather that designing for Boundary Layer Ingestion is very specific to the situation and the end fuel burn reduction results vary widely from design to design.

Tom - tdscanuck, since you have obvious design expertise, why don't you explain to us why the Boundary Layer Ingestion on the MIT D8.1 design would give give such large reductions in the fuel burn. Remember, MIT is claiming that their D8.1 airframe configuration, with the same technology as a Boeing 737-800, would give a 49% reduction in fuel burn.

How much power does it require to suck off the boundary layer? Do the main propulsion engines have to located to the rear of the fuselage to suck off the boundary layer or would smaller electric duct fans with several thousand pounds of thrust be adequate? Enquiring minds want to hear from the experts.


User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 18, posted (4 years 6 months 4 days 16 hours ago) and read 5754 times:

Quoting TomB (Reply 17):
Tom - tdscanuck, since you have obvious design expertise, why don't you explain to us why the Boundary Layer Ingestion on the MIT D8.1 design would give give such large reductions in the fuel burn.

I can't...BLI, done right, should allow you to maintain laminar flow over a much larger area, with a very nice drag reduction. But I have no idea how you'd get 49%. Just on the drag side alone, BLI doesn't do anything for form drag or induced drag.

Quoting TomB (Reply 17):
How much power does it require to suck off the boundary layer?

Depends on how much you're pulling, over how much of an area, and how much of it you want to pull off. I'm sure there are papers out there on what % of flow you need to pull to hold laminar flow, but I don't know what those values are.

Quoting TomB (Reply 17):
Do the main propulsion engines have to located to the rear of the fuselage to suck off the boundary layer or would smaller electric duct fans with several thousand pounds of thrust be adequate?

You don't need to do it with the main engines...small fans can do it (this has been tried with perforated skins before). I doubt you'd need airflow in the range of several thousand pounds of thrust for reasonably sized aircraft, but this is outside my area of expertise.

Tom.


User currently offlinenomadd22 From United States of America, joined Feb 2008, 1902 posts, RR: 0
Reply 19, posted (4 years 6 months 4 days 10 hours ago) and read 5687 times:

Gotcha Tom. But, I also wonder about the legitimacy of comparing the fuel burn of mach .85 plane to a new mach .7 design. It would be more informative to compare the new plane with a current design tweaked for mach .7 cruise.
It's like comparing the mileage of a hybrid to a conventional car when many of the improvements have nothing to do with being a hybrid.



Andy Goetsch
User currently offlineTomB From United States of America, joined Nov 2006, 79 posts, RR: 0
Reply 20, posted (4 years 6 months 4 days 8 hours ago) and read 5667 times:

Andy:

In the MIT study, they did an evolution study from a Boeing 737-800 to their D8.1 configuration. In their evolution study, they changed one parameter at a time. In one step, they changed the cruise speed of the airplane from M.80 to M.76 and then in another step, they further reduced the cruise speed from M.76 to M.72. Surprisingly, the reduction in the cruise speed did not save that much fuel.

To look at the MIT chart, go to the original article (see Reply #16), then click on the MIT link in the article and look at Slide 103.

I believe Northrop also had a chart which showed a gradual increase in fuel burn as the airplane increased speed from M.60 to M.74. After M.74, the fuel burn increased at a faster rate. I surmised from that chart that if fuel burn was a very important issue, the aircraft manufacturers may have to design their new narrowbodies for a M.74 or M.75 cruise speed.

Boeing has a patent on the wide oval fuselage design meaning that the horizontal axis is greater than the vertical axis. The patent covers a less than 200 passenger aircraft with two aisles and 6 to 8 seats abreast. Most of the drawings in the patent show seven abreast seating with two aisles (like the Boeing 767).

Here is the link to the patent #6,834,833. Be sure to also click on Images to see the drawings.
http://patft.uspto.gov/netacgi/nph-P...4833&OS=PN/06834833&RS=PN/06834833

TomB


User currently offlinedynamicsguy From Australia, joined Jul 2008, 887 posts, RR: 9
Reply 21, posted (4 years 6 months 4 days 7 hours ago) and read 5649 times:

Quoting RoseFlyer (Reply 12):
The spoilers on the 787 are truly an incredible design. They vary the camber of the wing,

It's not the spoilers which vary the wing camber, but the flaps. The spoilers' position is altered to maintain the seal against the flaps' upper surfaces. You are right that they droop as the flaps are deployed to control the size of the gap between flaps and spoilers.


User currently offlineSeJoWa From United States of America, joined May 2006, 373 posts, RR: 0
Reply 22, posted (4 years 6 months 3 days 16 hours ago) and read 5570 times:

Quoting TomB (Reply 16):
SeJoWa:
The link to the article is about 5 lines long and the computers choke on it every time I try to post the link.

Here is a work around:
TomB thank you!


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