• Hi Guest! Forum rules have been updated. All users please read here.

Lockheed Martin Skunk Works Hybrid Wing Body (HWB)

fightingirish

ACCESS: Top Secret
Senior Member
Joined
Jun 3, 2006
Messages
2,395
Reaction score
733
Something new to watch out for... ;) :)
FUEL-SAVING HYBRID
By Guy Norris
Lockheed Martin plans to conduct detailed studies of an advanced hybrid wing-body transport concept under a second phase of the U.S. Air Force Research Laboratory’s (AFRL) Revolutionary Configurations for Energy Efficiency (RCEE) program. The study is part of AFRL-led efforts to identify ways to radically reduce the amount of fuel used by the Air Force’s air mobility fleet for "a severely energy-supply—constrained future scenario," says AFRL. Reducing fuel burn has become a top priority for the U.S. Defense Department, which consumes almost 4 billion gallon per year according to its latest figures. RCEE covered the conceptual design of five different aircraft types that would likely make up a future airlift fleet. The version displayed at the American Institute of Aeronautics and Astronautics Joint Propulsion Conference in Atlanta is the second largest concept studied by Lockheed Martin’s Skunk Works and provides a payload capacity of 220,000 lb., putting it between the Boeing C-17 and Lockheed Martin C-5. General Electric and Rolls-Royce are participating in Lockheed’s study, providing data on the advanced open rotor and UltraFan turbofan, respectively. The advanced airlifter design combines the span-loader aerodynamic qualities of a lifting body with the improved military utility of a conventional fuselage-configured aircraft. A loading ramp is located beneath a high-mounted C-5-like T-tail. The next phase is set to cover further propulsion-airframe integration work, including both open rotors and UltraFan concepts, and will culminate in wind-tunnel tests around 2014.


Source: AW&ST, 6 August 2012, page 27
 

Attachments

  • LM_SW_RCEE_AMF.jpg
    LM_SW_RCEE_AMF.jpg
    24.7 KB · Views: 783

Mat Parry

ACCESS: Secret
Joined
Jan 25, 2011
Messages
417
Reaction score
8
fightingirish said:
]Lockheed Martin plans to conduct detailed studies of an advanced hybrid wing-body transport concept under a second phase of the U.S. Air Force Research Laboratory’s (AFRL) Revolutionary Configurations for Energy Efficiency (RCEE) program. The study is part of AFRL-led efforts to identify ways to radically reduce the amount of fuel used by the Air Force’s air mobility fleet for "a severely energy-supply—constrained future scenario,"

A welcome outbreak of common sense, I imagine I will see the progeny of this program flying
 

Triton

Donald McKelvy
Senior Member
Joined
Aug 14, 2009
Messages
9,719
Reaction score
561
Website
deeptowild.blogspot.com
A little clearer scan of the Lockheed Martin advanced hybrid wing-body transport concept.

Source:
http://www.aereimilitari.org/forum/topic/2790-a400m-la-scelta-italiana/page__st__240
 

Attachments

  • 2hol4eu.jpg
    2hol4eu.jpg
    12.6 KB · Views: 756
1

1st503rdSGT

Guest
This appeared in AV Week nearly 2 years ago.

http://www.aviationweek.com/Blogs.aspx?plckBlogId=Blog:27ec4a53-dcc8-42d0-bd3a-01329aef79a7&plckController=Blog&plckBlogPage=BlogViewPost&newspaperUserId=27ec4a53-dcc8-42d0-bd3a-01329aef79a7&plckPostId=Blog:27ec4a53-dcc8-42d0-bd3a-01329aef79a7Post:4ed2785f-832c-4f7f-8a7b-1d820cb2b07a

I read some speculation that such a transport platform could be adapted for AWACS and and tanking roles as well (solving a number near-peer situations), but it seems to have disappeared from view. Does anyone know if work continues?
 
1

1st503rdSGT

Guest
How about that. Didn't realize it had so many other names. Of course, a moderator somewhere here said that this sight's search tool wasn't very good, and it still seems to have been awhile since there was any news on the project (nice graphics though).
 

quellish

I am not actually here.
Senior Member
Joined
Aug 6, 2007
Messages
2,174
Reaction score
203
1st503rdSGT said:
How about that. Didn't realize it had so many other names. Of course, a moderator somewhere here said that this sight's search tool wasn't very good, and it still seems to have been awhile since there was any news on the project (nice graphics though).

When in doubt:

https://www.google.com/search?hl=en&safe=off&site=&source=hp&q=site%3Asecretprojects.co.uk+speed+agile&oq=site%3Asecretprojects.co.uk+speed+agile&gs_l=hp.3...1035.11583.0.11868.47.42.5.0.0.0.76.1780.42.42.0.les%3B..0.0...1c.1.V93wKdV-7MA
 

flateric

ACCESS: Above Top Secret
Staff member
Top Contributor
Senior Member
Joined
Apr 2, 2006
Messages
9,085
Reaction score
982
other view of LM RCEE hybrid wing-body concept
 

Attachments

  • 0009-.jpg
    0009-.jpg
    61.7 KB · Views: 1,712
  • 0009.jpg
    0009.jpg
    32.7 KB · Views: 1,110

fightingirish

ACCESS: Top Secret
Senior Member
Joined
Jun 3, 2006
Messages
2,395
Reaction score
733

Attachments

  • AW_02_17_2014_00_cover.jpg
    AW_02_17_2014_00_cover.jpg
    19.1 KB · Views: 717
  • Skunkworks_HybridWingBody_LockheedMartinConcept.jpg
    Skunkworks_HybridWingBody_LockheedMartinConcept.jpg
    31 KB · Views: 1,297

NUSNA_Moebius

I really should change my personal text
Joined
May 26, 2012
Messages
173
Reaction score
34
'Lots of volume in a design like that, though I wonder what it's internal capacity would be versus a C-5. And only two engines? I suspect GE-90s, hopefully 115s ;)
 

TomS

ACCESS: Top Secret
Senior Member
Joined
Apr 16, 2008
Messages
4,417
Reaction score
1,389
All discussed in the article. It has a central fuselage/payload bay similar to the C-5 (big enough to carry all of the C-5's outsized cargoes), plus unpressurized side bays (loaded through the main bay) for palletized cargo. Sounds like a nice compromise, avoiding the hassles of how to load a full-fledged blended wing-body design.


Several engines are mentioned. Simplest is a GEnx version (maybe enlarged, since they mention a diameter considerably larger than the GEnx on the 787), then a Rolls-Royce Ultra Fan for more fuel efficiency, and then an enormous (21-foot) open rotor design for the highest efficiency.
 

flateric

ACCESS: Above Top Secret
Staff member
Top Contributor
Senior Member
Joined
Apr 2, 2006
Messages
9,085
Reaction score
982
via Graham Warwick twitter feed
 

Attachments

  • BeIS0_yCIAAi-8z.jpg
    BeIS0_yCIAAi-8z.jpg
    50.1 KB · Views: 646
  • BesZP1eCYAA2xIn.jpg
    BesZP1eCYAA2xIn.jpg
    17.3 KB · Views: 628
  • BesXnOeCcAAeTGD.jpg
    BesXnOeCcAAeTGD.jpg
    14.5 KB · Views: 576

NUSNA_Moebius

I really should change my personal text
Joined
May 26, 2012
Messages
173
Reaction score
34
TomS said:
All discussed in the article. It has a central fuselage/payload bay similar to the C-5 (big enough to carry all of the C-5's outsized cargoes), plus unpressurized side bays (loaded through the main bay) for palletized cargo. Sounds like a nice compromise, avoiding the hassles of how to load a full-fledged blended wing-body design.


Several engines are mentioned. Simplest is a GEnx version (maybe enlarged, since they mention a diameter considerably larger than the GEnx on the 787), then a Rolls-Royce Ultra Fan for more fuel efficiency, and then an enormous (21-foot) open rotor design for the highest efficiency.

Thanks. We really need a new airlifter, and if the government gave the USAF the go ahead to build this plane today, I would not have any qualms.
 

fightingirish

ACCESS: Top Secret
Senior Member
Joined
Jun 3, 2006
Messages
2,395
Reaction score
733
fightingirish said:
A new view of LM RCEE hybrid wing-body concept, this time with turbofans. B) :)
Maybe more new pictures in the next issue of AW&ST, February 17th 2014. ;)
IMHO an interesting successor for the C-5 Galaxy.
Source:
Aviation Week & Space Technology - Lockheed Martin Refines Hybrid Wing-Body Airlifter Concept By Graham Warwick
flateric said:
via Graham Warwick twitter feed


A cutaway published in AW&ST, February 17th 2014, page 40.
I edited it to point out the inside fuselage cargo doors, through where the pallets are rolled into the unpressurized outer bays. :)
 

Attachments

  • Skunkworks_HybridWingBody_LockheedMartinCutaway_edit_AWST_02_17_2014.jpg
    Skunkworks_HybridWingBody_LockheedMartinCutaway_edit_AWST_02_17_2014.jpg
    101.4 KB · Views: 1,838

LowObservable

ACCESS: Top Secret
Senior Member
Joined
Oct 18, 2006
Messages
2,209
Reaction score
143
Machdiamond and Flateric - The Airbus Military Moles are apparently British.
 

Attachments

  • victor.jpg
    victor.jpg
    274 KB · Views: 141
  • tb2.jpg
    tb2.jpg
    48.8 KB · Views: 105

Triton

Donald McKelvy
Senior Member
Joined
Aug 14, 2009
Messages
9,719
Reaction score
561
Website
deeptowild.blogspot.com
Source:
http://www.lockheedmartin.com/us/news/features/2014/air-mobility-move-it.html

Leaner defense budgets are driving the need for “greener” tankers, and strategic and tactical airlifters. In 2010 alone, the U.S. Air Force spent $10 billion in fuel, with mobility aircraft being the biggest gas guzzler.

“Saving even one percent is a huge amount of fuel and a big reduction in cost,” said Rick Hooker, Skunk Works® manager of the Air Force Research Laboratory’s Revolutionary Configuration for Energy Efficiency (RCEE) program.

Current efforts such as the RCEE program are seeking to identify the highest fuel saving technologies and develop their maturation plans for the 2035 timeframe.

“We can improve mobility capabilities with 70 percent less fuel than a C-17,” says Hooker. “The cornerstones of our Hybrid Wing Body (HWB) concept are efficiency, affordability, and compatibility. Designed with an eye to the future, the HWB program would save 400 million gallons of fuel per year and would be capable of dual use as both an efficient transport and tanker.”

While it’s important to look ahead, there are opportunities that are already being implemented today. For instance, the C-130’s fuel efficiency can be boosted thanks to lightweight devices called microvanes, which reduce the aircraft’s drag. These miniature strake-like devices are located on each side of the aircraft’s aft fuselage near the cargo ramp door and horizontal tail.

“Both legacy and C-130J operators can benefit because the shape of the back end of the aircraft hasn’t changed,” said Edward DiGirolamo, Skunk Works research engineering manager. “Microvanes can be installed on the production line or as an easy retrofit with no structural impact. They are relatively inexpensive and offer a good payback.”

The greening of engines also appears to be paying back in dividends.

“We constantly work with major engine companies to ensure that our designs include the latest engine technologies and concepts for greater efficiency and reduced fuel burn,” noted DiGirolamo. He explained that those technologies include engines with higher pressure ratios for engine thermal efficiency as well as higher bypass ratios for propulsive efficiency. The next generation engines even promise to reduce fuel burn by as much as 35 percent for the same amount of thrust.

And larger artist's concept! B)
 

Attachments

  • XX-Blended-Wing.jpg
    XX-Blended-Wing.jpg
    206.4 KB · Views: 211

flateric

ACCESS: Above Top Secret
Staff member
Top Contributor
Senior Member
Joined
Apr 2, 2006
Messages
9,085
Reaction score
982
long roots back in 2002?
 

Attachments

  • 300dpi_joinwing.jpg
    300dpi_joinwing.jpg
    256.4 KB · Views: 129
  • Skunkworks_HybridWingBody_LockheedMartinCutaway_edit_AWST_02_17_2014.jpg
    Skunkworks_HybridWingBody_LockheedMartinCutaway_edit_AWST_02_17_2014.jpg
    101.4 KB · Views: 179

Sentinel36k

Nothing to fear but a high radar cross section
Joined
Oct 31, 2013
Messages
43
Reaction score
0
Could it be possible that this is the realization of these programs? The timeline fits. http://www.secretprojects.co.uk/forum/index.php/topic,21745.0.html

Sentinel
 

Attachments

  • AFRL mobility roadmap.jpg
    AFRL mobility roadmap.jpg
    782.1 KB · Views: 217

Triton

Donald McKelvy
Senior Member
Joined
Aug 14, 2009
Messages
9,719
Reaction score
561
Website
deeptowild.blogspot.com
Not a Disney alien inspired by a manta ray - commercial version of @LockheedMartin Hybrid Wing Body airlifter concept.

Source:
https://twitter.com/TheWoracle/status/426460552487919616
 

Attachments

  • BesXnOeCcAAeTGD.jpg
    BesXnOeCcAAeTGD.jpg
    14.5 KB · Views: 76

Triton

Donald McKelvy
Senior Member
Joined
Aug 14, 2009
Messages
9,719
Reaction score
561
Website
deeptowild.blogspot.com
"Lockheed Martin Refines Hybrid Wing-Body Airlifter Concept"
Fuel costs and logistics burden spur efforts to design dramatically more efficient military transport aircraft
by Graham Warwick

Feb 17, 2014

Source:
http://aviationweek.com/awin/lockheed-martin-refines-hybrid-wing-body-airlifter-concept

Traditionally, performance drives military-aircraft design decisions and the energy implications of those choices are secondary. But as fuel costs eat into reduced budgets, the balance is shifting. Energy is fast becoming a critical constraint on operations, and the results could reshape aircraft design.

For now, the U.S. Air Force's efforts to cut fuel bills are focused on its transport and tanker fleet, which consumes two-thirds of the aviation fuel the service burns each year. While near-term retrofits—such as formation flying, winglets and other drag-reduction devices—can reduce the fuel consumption of existing aircraft, they will not provide the scale of savings sought in the long term.

The name of the Air Force Research Laboratory's (AFRL) Revolutionary Configurations for Energy Efficiency (RCEE) program says it all: Dramatic changes in aircraft design may be required to achieve significant reductions in fuel consumption.

The goal of RCEE Phase 1, which ran from 2009-11, was to define a next-generation mobility fleet that would use 90% less fuel than today's transports and tankers. Under Phase 2, which began in 2011 and will run until 2015, companies are taking a closer look at specific configurations.

In Phase 1, Boeing defined a mixed fleet that met the 90% savings target: an all-electric truss-braced-wing design with 20-metric-ton payload; a 40-ton-payload distributed-thrust hybrid-electric design; and a 100-ton payload hybrid-electric blended wing-body (BWB). In Phase 2, the company is taking a closer look at the distributed-thrust, hybrid-propulsion design.

Lockheed Martin, meanwhile, studied a wide range of configurations and technologies in Phase 1 in search of the 90% goal, concluding a hybrid wing-body (HWB) offers the most potential. In Phase 2, the company is further refining the concept, which combines a blended wing and forebody for aerodynamic and structural efficiency with a conventional aft fuselage and tail for compatibility with current airlift missions, including airdrop.

The twin-engine HWB is designed to take off in less than 6,500 ft. and fly 3,200 nm carrying 220,000 lb. of payload, including all the outsize cargo now airlifted by the Lockheed C-5. Lockheed calculates the aircraft will burn 70% less fuel than the Boeing C-17 through a combination of better aerodynamics, newer engines and lighter structures. “We use mature technologies to be affordable and could build it today,” says Rick Hooker, an aeronautical engineer at Lockheed Martin Aeronautics

The HWB study is marked by a high degree of aerodynamic optimization using computational fluid dynamics (CFD) tools not available when today's airlift fleet of C-17s and Lockheed C-130s and C-5s was designed. Starting with a cruise Mach number of 0.7 as originally lofted, extensive shape optimization using CFD increased cruise speed to Mach 0.81 and reduced transonic drag by 45%, says Lockheed aeronautical engineer Andrew Wick.

Lockheed estimates the aircraft is 65% more aerodynamically efficient than the C-17, which is penalized by its 1980s design and the requirement for short-takeoff-and-landing (STOL) capability. The HWB is 30% more efficient than a C-5, and Lockheed says it is even able to achieve an aerodynamic efficiency 5% better than the Boeing 787, albeit at a lower Mach number.

That efficiency comes from several sources. To start, the blended forward fuselage carries 25% of the lift and moves the wing roots outboard, extending span and reducing drag without increasing wing weight. The spanwise lift distribution is improved and wing aspect ratio increased to 12 for the weight of a conventional aspect-ratio 9 wing,

The aft fuselage, meanwhile, ensures the aircraft is compatible with current loading and airdrop operations—a challenge for pure flying-wing designs like the BWB, says Hooker. The conventional T tail incurs a 5% drag penalty relative to a pure BWB, but provides robust control and avoids the cost and risk of developing new control effectors and algorithms for a flying wing to enable STOL and manage the abrupt center-of-gravity (CG) shift when airdropping heavy loads.

The aft fuselage is designed to provide a smooth flow field around the aft paratroop doors and cargo ramp, similar to a C-5, says Hooker. The tail is sized to handle a CG range of 20% mean aerodynamic chord, the same as a C-5. And the aircraft is designed so the tail is not needed for trim in the cruise, avoiding a drag penalty.

An unusual aspect of the HWB design is that the blended forebody encloses a circular pressurized fuselage. Some cargo is carried in unpressurized outer bays—pallets are loaded via the rear ramp, moved forward on floor rollers, then sideways through fuselage doors and into the outer bays on ball mats. The result is a pressurized fuselage that is smaller and lighter than the C-5's despite the similar cargo capacity. Lockheed calculates the HWB's structure is 18% lighter than a conventional design.

Another unconventional element of the configuration is the engine location above the wing trailing edge. Over-wing nacelles have long been avoided in aircraft design because of adverse transonic interference with the wing, but careful optimization by Honda of the engine location on the HondaJet has given the configuration new credibility.

Lockheed studied cruise interference drag with engines mounted in several locations—under and over the wing leading edge, over the trailing edge and on the aft fuselage—and generated more than 15,000 Navier-Stokes CFD solutions. The results showed that mounting the nacelles over the inboard trailing edge improved lift-to-drag ratio, regardless of engine type, for an aerodynamic benefit of up to 5% over a conventional under-wing location.

Three potential powerplants have been identified. General Electric's GEnx is available today, providing a 25% reduction in specific fuel consumption (sfc) over the C-17 and C-5M engines. Rolls-Royce's conceptual Ultra Fan has a 30% lower sfc and could be available by 2030. Third is a GE open rotor that could be available after 2025 with a 35% lower sfc. Combined with the improved aerodynamic efficiency and lighter weight, lower sfc results in the HWB burning 70% less fuel than a C-17 with GEnx engines, 75% with Ultra Fans and 80% with open rotors, Lockheed calculates.

Interestingly, despite diameters ranging from the GEnx's 11.8 ft. to an open rotor's 21 ft., “the wing optimized out to the same shape for all three engines,” says Wick. “The same wing for all three allows the engine installation to be modular. We could build it today and it would be designed to be able to be reengined.”

Analysis showed the over-wing installation offers other benefits, he says. The long wing chord ahead of the nacelle acts as a flow straightener to reduce inlet distortion and also shields fan noise from the ground. The overhang from the trailing edge means the engine is still accessible for maintenance and removal. And a smaller tail is possible with over-wing engines, says Hooker.

There is a powered-lift benefit from placing the engine nacelles over the trailing edge of the wing. “The inlet flow provides a large amount of suction lift on the wing,” says Hooker. This has a similar effect to the high-pressure area generated by under-wing engines blowing over deflected flaps, as happens in the C-17, and allows the over-wing engines to achieve a similar 15% increase in maximum lift coefficient.

To provide STOL capability, excess fuel volume could be traded for flap blowing to create a circulation-control wing, as in the STOL airlifter concept developed by Lockheed for AFRL's Speed Agile program. Another possibility is deflecting thrust downward, using flaps aft of the engine, core flow vectoring with an F-35B-style swiveling nozzle, or rotating the engines when the flaps deploy, “so they go along for the ride,” Hooker says.

Although RCEE is just a study effort, the Air Force will have to begin work on its next strategic airlifter in the near future if the C-17 is to be retired as planned starting in 2033. Noting it took 21 years to field the C-17, Hooker says ,“We need to start today to avoid a future gap.”
 

Jemiba

ACCESS: Above Top Secret
Staff member
Top Contributor
Senior Member
Joined
Mar 11, 2006
Messages
8,255
Reaction score
1,014
The C-17 to a large extent is a replacement for the C-5 and it does quite well without, I think.
 

yasotay

ACCESS: Top Secret
Senior Member
Joined
Oct 19, 2006
Messages
2,430
Reaction score
611
Weight of the gear associated with the raised nose may not make its way onto an already astronomically expensive aircraft.
 

sferrin

ACCESS: USAP
Senior Member
Joined
Jun 3, 2011
Messages
13,574
Reaction score
1,597
yasotay said:
Weight of the gear associated with the raised nose may not make its way onto an already astronomically expensive aircraft.
Why astronomically expensive? It's not a stealth aircraft.
 

yasotay

ACCESS: Top Secret
Senior Member
Joined
Oct 19, 2006
Messages
2,430
Reaction score
611
sferrin said:
yasotay said:
Weight of the gear associated with the raised nose may not make its way onto an already astronomically expensive aircraft.
Why astronomically expensive? It's not a stealth aircraft.
That is what the USAF Inc. told their primary customer last time they asked.
 

sferrin

ACCESS: USAP
Senior Member
Joined
Jun 3, 2011
Messages
13,574
Reaction score
1,597
yasotay said:
sferrin said:
yasotay said:
Weight of the gear associated with the raised nose may not make its way onto an already astronomically expensive aircraft.
Why astronomically expensive? It's not a stealth aircraft.
That is what the USAF Inc. told their primary customer last time they asked.

What? The USAF has customers? They told them it wasn't a stealth aircraft? They told them it would be expensive? Who is the customer and who is "USAF Inc."?
 

Sundog

ACCESS: Top Secret
Senior Member
Joined
Aug 2, 2006
Messages
2,843
Reaction score
288
sferrin said:
yasotay said:
sferrin said:
yasotay said:
Weight of the gear associated with the raised nose may not make its way onto an already astronomically expensive aircraft.
Why astronomically expensive? It's not a stealth aircraft.
That is what the USAF Inc. told their primary customer last time they asked.

Name a manned military aircraft, besides the A-10, developed in the past four decades, that wasn't expensive.

What? The USAF has customers? They told them it wasn't a stealth aircraft? They told them it would be expensive? Who is the customer and who is "USAF Inc."?
 

sferrin

ACCESS: USAP
Senior Member
Joined
Jun 3, 2011
Messages
13,574
Reaction score
1,597
Sundog said:
Name a manned military aircraft, besides the A-10, developed in the past four decades, that wasn't expensive.

"astronomically expensive aircraft"

Suggest B-2-like expensive. Why? It's not a stealth aircraft. (Of course that much composite won't be cheap either but still. . .)
 

donnage99

"Robert Gates, is that you??" sublight
Joined
Jun 17, 2008
Messages
984
Reaction score
36
How revolutionary was the c-17 compared to previous and consider how much that program went over budget and how expensive that aircraft is. Now, think this beast ::)
 

sferrin

ACCESS: USAP
Senior Member
Joined
Jun 3, 2011
Messages
13,574
Reaction score
1,597
donnage99 said:
How revolutionary was the c-17 compared to previous and consider how much that program went over budget and how expensive that aircraft is. Now, think this beast ::)

Don't know. Not familiar at all with C-17 costs.
 

DrRansom

I really should change my personal text
Joined
Dec 15, 2012
Messages
537
Reaction score
9
I was at a presentation for the Lockheed transport and they were careful to emphasize how inefficient the C-17 is and how efficient the Lockheed design would be.

Lockheed suggested that their plane could all but pay for itself through higher fuel efficiency.

Some STOVL was discussed, but that required a degree of thrust vectoring from the engines.

Other interesting part they mentioned, the Lockheed design with engines above the wing is set for an open rotor engine replacement down the road.
 

AeroFranz

ACCESS: Top Secret
Senior Member
Joined
May 4, 2008
Messages
2,283
Reaction score
172
Just like with airliners, three-quarters of cost reduction (however you want to measure it) will come from better engines. There just isn't nearly as much to harvest from improved aerodynamics. Fuel burn is proportional in equal measure to L/D and SFC. Improving L/D by 5% is a near miracle. Compare to each generation of engine lowering SFC by 15% (more if switching to entirely new architecture, like an open rotor). It ['d be] educational to know how much worse than a clean sheet design a hypothetical legacy transport like the C-17 with open rotors would fare.
 

Triton

Donald McKelvy
Senior Member
Joined
Aug 14, 2009
Messages
9,719
Reaction score
561
Website
deeptowild.blogspot.com
DrRansom said:
I was at a presentation for the Lockheed transport and they were careful to emphasize how inefficient the C-17 is and how efficient the Lockheed design would be.

Lockheed suggested that their plane could all but pay for itself through higher fuel efficiency.

Some STOVL was discussed, but that required a degree of thrust vectoring from the engines.

Other interesting part they mentioned, the Lockheed design with engines above the wing is set for an open rotor engine replacement down the road.

Thank you for your post, DrRansom.
 

marauder2048

"I should really just relax"
Joined
Nov 19, 2013
Messages
3,148
Reaction score
445
AeroFranz said:
Just like with airliners, three-quarters of cost reduction (however you want to measure it) will come from better engines. There just isn't nearly as much to harvest from improved aerodynamics. Fuel burn is proportional in equal measure to L/D and SFC. Improving L/D by 5% is a near miracle. Compare to each generation of engine lowering SFC by 15% (more if switching to entirely new architecture, like an open rotor). I'd educational to know how much worse than a clean sheet design a hypothetical legacy transport like the C-17 with open rotors would fare.

This was mostly my reaction as well. I'm wondering how much of the gain is coming from replacing four narrower diameter decidedly last generation turbofans with two of the large diameter, high bypass new generation types.

As a further thought exercise, once Boeing has some experience mating a CFRP wing to a conventional wingbox (777X style) I'm wondering if that expertise could be applied to re-winging the C-17 with two of the next-gen engine types.
 

DrRansom

I really should change my personal text
Joined
Dec 15, 2012
Messages
537
Reaction score
9
About airframe improvements: Lockheed's design is aerodynamically superior. Boeing can improve incrementally, but it cannot make the jump forward to march Lockheed's efficiency.

The major risk is not the wheel, it is the fact that nobody has built a blended wing body aircraft before.

Other points from the presentation:
1) Lockheed retains the C-17 tail design for the military variant, allowing for easy paradrop qualification. This has a negative aerodynamic impact. Lockheed said that a tentative civilian variant would use a more efficient tail design.

2) The pressure section of the aircraft is still a cylinder. There is additional unpressurized cargo storage on either side of the cylinder inside the wing. Cargo containers are passed on a carriage system from the tail access through hatches on the sides of the pressurized hull. Lockheed said they made this decision to avoid the design difficulty of a non-cylindrical pressurized hulls. That gives the aircraft options for a high cargo carry mode or a low cargo paradrop / STOL mode.
 
Top