Lockheed Martin c-24 Perseus
has since been deployed into theater by the USAF, where its vastly improved performance in “hot and high” environments has come in very handy. Unlike the pending Airbus A400M, however, the C-130J doesn’t solve the sub-survivable 20-ton armored vehicle limit that has stymied multiple US armored vehicle programs from the Stryker IAV to Future Combat Systems. As such, it represents an improvement that fails to address US tactical airlift’s key bottleneck limitation.”
Something called the Advanced Composite Cargo Aircraft (ACCA) may – or may not – represent a first step toward addressing that issue. It may also represent a US aerospace effort to avoid a looming future in which the Airbus A400M would be the only available tactical transport for survivable armored personnel carriers. With the light transport JCA made up of entirely foreign designs, the 20-ton transport market beginning to crowd, and the heavy-lift C-17 production line headed toward shutdown, the US aerospace industry risks a slip from a 1980-1990s position of market dominance in the military transport space to a position of fighting for its competitive life by 2020.
So where does ACAA fit in? How is it connected to the Composite Affordability Initiative, and the notional Advanced Joint Air Combat System (AJACS) program?
From CAI to ACAA
The AMC-X/ AJACS Program: Intent and Issues
Contracts and Key Events
Additional Readings & Sources
From CAI to ACAA
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The Advanced Composite Cargo Aircraft (ACAA) effort was made possible by an 11-year, $152 million Air Force Research Laboratory-led research and development investment called the Composite Affordability Initiative, which began in the mid 1990s. Despite the potential weight and hence performance advantages offered by composites, industry was reluctant to use them in new aircraft due to their perceived risks and costs. Under the CAI, government labs including NASA, worked collaboratively with industry, in order to develop advanced materials and manufacturing technologies. Composites World summed up the results:
“CAI research accelerated the maturation of materials and processes, increased our understanding of structural behavior in bonded joints, encouraged development of new quality assurance methods to ensure bonded joints remain bonded throughout an aircraft’s service life, and – critically important – ultimately gained large integrated and bonded structures the essential buy-off of DoD aircraft certification authorities…. As the use of CAI technology increases, we envision a day when composites become the default material in DoD airframes, exceeding 50 percent by weight of the structure.”
The Advanced Composite Cargo Aircraft (ACCA) illustrates why those changes are important.
In its RFP, the US Air Force Research Laboratory set out goals for a STOL aircraft that could fly 400kt (740km/h), pressurized and carrying 3 cargo pallets, 20 troops or 1 light-wheeled vehicle. This is obviously a scaled-down version of the eventual plane the Air force might want, but it does force the contractors to use appropriate designs as they work to address the cost and weight issues associated with “advanced structural design and manufacturing techniques integrated with advanced aerodynamic design.”
According to Flight International, Alenia North America, Lockheed Martin, Piasecki Aircraft and Dick Rutan’s Voyager Aerospace all expressed interest in the RFP. This is hardly surprising, given the manufacturing and design advantages that may accrue to the winning firm. Lockheed Martin won the ACCA contract, which it turned over to its famous “Skunk Works” advanced design & technology group.
The results have validated that belief. The X-55A ACAA was built using large, bonded unitized composite structures featuring low-temperature, out-of-autoclave curing. That’s ahead of even Boeing’s 787 Dreamliner, which uses out-of-autoclave curing in some areas but not for large fuselage parts.
The AJACS Program: Intent and Issues
YC-15 and F-4
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The USA has been here before, however, with the 1980s Advanced Medium STOL Transport competition that produced the Boeing YC-14 and McDonnell Douglas YC-15. Both planes were produced, both made extensive use of new technologies, both met all tests. The program ended up canceled.
ACAA lays the foundation for a second go-round, if the USAF wishes. Airbus’ new A400M medium-heavy transport will make extensive use of composite structures, and so will Embraer’s KC-390 medium tactical transport. If any future American military airlifter expects to offer competitive performance and costs, the ability to use similar technologies effectively will make a big difference to project risk, project timelines, and aircraft performance.
Ultimately, however, the Advanced Joint Air Combat System (AJACS, formerly AMC-X) requirements are likely to be considerably more ambitious than ACAA’s. A 2004 Air Force Magazine piece had this to say:
“Afghanistan and Iraq have underscored the need for a new tactical transport that would fulfill a variety of airlift and special operations roles, Air Force officials reported. The new aircraft – dubbed Advanced Mobility Concept, or AMC-X – would have about the same cargo capacity as a C-130 but be able to fly higher and faster, while operating from 2,000-foot runways. Moreover, the AMC-X would be stealthy.
“We’re talking about … airliner speed,” close to Mach 1, said Col. Marshall K. Sabol, Air Mobility Command’s deputy director of plans and programs. The C-130’s average speed is 345 mph.
AMC also wants an airplane that can fly at the altitudes used by airliners, with greater range and greater survivability, he said. Paramount for the new transport will be its ability to operate at austere locations and carry outsize cargo, said Sabol.
Moreover, the next tactical airlifter will have to be able to operate in blackout conditions at low level, perform paratrooper and equipment airdrop, operate in all weather, and be capable of accomplishing “autoland” – automatic, virtually hands-off landing, guided only by the runway and onboard navigation systems.
Such requirements are “not the future,” said Sabol, adding, “it’s where we operate” today.
AMC is also working with Air Force Research Labs and the Army to make sure that the tactical transport is compatible with the Army’s new Stryker vehicle. The Stryker was designed to be transportable on C-130s, but the vehicle’s weight has continued to grow.”
X-48B in wind tunnel
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According to Jane’s, potential competitors for the AJACS program could include Lockheed Martin’s MACK concept sketched out in response to Special Forces requirements, a modified Boeing C-17 Globemaster III, or a Boeing concept based on the company’s experimental X-48B blended wing body (BWB) design that offers higher lift, higher capacity in a given footprint, and even noise reduction.
Whatever the eventual platform looks like, in order to accommodate a Stryker vehicle in combat condition, as well as currently contemplated US and foreign armored personnel carrier designs with enough armor to be survivable on modern battlefields, a cargo capacity increase of at least 50% over the current C-130J (21.7 tons – 30-35 tons) would almost certainly be required.
One would think this imperative might be a higher priority than cost-turbocharging requirements like stealth and airliner-class cruise speed, but the 2004 Air Force Magazine article seems to suggest that it wasn’t. Those stealth and speed requirements certainly make sense for Special Operations aircraft beyond 2015, as Robert Martinage’s CSBA presentation [pdf] explains. They can add significant purchase and maintenance costs, however, which risks pricing aircraft intended for conventional military operations out of the market. All in exchange for capabilities that are rarely required by regular forces.
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In order for AJACS to emulate the C-130’s success and result in a competitive aircraft on the international market, as opposed to an aircraft that shares the fate of its AMST predecessors, it will indeed need next-generation manufacturing technologies and materials. It will also have to be designed according to Army priorities, rather than Air Force wish lists. The A400M’s focus on those needs, and smart international production arrangements, have booked it almost 200 orders before AJACS even has a notional design. If it can deal with its technological risks, it will be widely successful. If AJACS cannot compete on cost and capacity, countries that intend to transport survivable armored vehicles in their airlifters will have absolutely no option except the A400M. Especially if the larger and more expensive C-17 production line shuts down.
Even if the C-17 remains in production, however, the combination of proliferating choices in the 20-ton airlift market (C-130J, HAL-Irkut MRTA, Embraer 390), plus a practical 30-ton military requirement that must be met at or below the A400M’s $100-120 million cost, will leave large market slices without American coverage if AJACS is not thought through correctly at its earliest stages.
All of this assumes, of course, that AJACS is funded at all, amidst a wave of exploding public entitlements, demographic squeezes, and lower economic performance.
Contracts and Key Events
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At this stage, the Air Force Research Laboratory Air Vehicles Directorate at Wright-Patterson Air Force Base, OH is acquiring the design, development, and manufacture of a technology demonstration Advanced Composite Cargo Aircraft (ACCA) that features advanced structural design and manufacturing techniques integrated with advanced aerodynamic design. The purpose of this aircraft is to demonstrate the application of structural design and manufacturing technologies that can significantly reduce the structural weight and cost of future military transport type aircraft.
Oct 19/09: USAF officials announce “X-55A” as the ACAA’s new designation.
The X-55A is a technology demonstrator for the design and manufacture of future aircraft using advanced composite materials. The X-55A is a modified Dornier 328J aircraft with the fuselage aft of the crew station and the vertical tail removed and replaced with completely new structural designs made from composites using new out-of-autoclave curing techniques. The vertical tail was designed using tailored stiffness technology. These were joined with an existing Dornier 328J cockpit, wing, engines and horizontal tail. The test platform contains some 600 accelerometers and stress gauges.
The fuselage was built in 2 large half-sections (upper-lower), featuring sandwich construction with MTM-45 skins and Nomex core. These were bonded together with adhesive and ply overlays along the longitudinal seam, rather than the numerous frames, stiffeners and metal fasteners used commonly in traditional aircraft. Compared to the original metallic components, the X-55A’s composite structure uses approximately 300 structural parts, vs. 3,000 metallic parts for the original components; and approximately 4,000 mechanical fasteners compared to 40,000.
Sept 17/09: Phase III of the ACAA program is awarded to Lockheed Martin. This phase will expand the flight envelope, fully characterize the structure, examine the reliability and longevity of the design, and baseline the X-55A as a test-bed for other technologies. a href=”[link]
June 2/09: First flight of the ACAA at Air Force Plant 42 in Palmdale, CA. Working with Lockheed Martin’s Skunk Works, it was designed in 5 months, then built and flown 20 months after the go-ahead. Barth Shenk, the ACAA program manager with AFRL’s Air Vehicle Directorate, says that it was built at half the estimated cost of a conventional design of the same size.
Test flights on July 13 and August 8 expanded the aircraft’s maneuver envelope, and recorded external aerodynamic flow data. Source.
Oct 17/07: A Lockheed Martin release says that the USAF Research Laboratory (AFRL) has authorized them to proceed to Phase II of the Advanced Composite Cargo Aircraft (ACCA) Flight Demonstration contract. Lockheed Martin will build and flight-demonstrate an X-Plane type aircraft with emphasis on innovative structural configurations and concepts; its solution involves replacement of the mid/aft fuselage and empennage of a Dornier 328J aircraft with advanced composites within the required 12-month schedule. The Lockheed Martin release adds that AFRL is currently investigating opportunities for Aurora Flight Sciences to collaborate with Lockheed Martin and AFRL in the demonstration of additional technologies and capabilities for future transport structures.
The integration of advanced composites on the ACCA flight demonstrator is intended to reduce the aircraft’s parts count by 80-90%, and dramatically reduce corrosion and fatigue issues, sharply lowering conventional maintenance costs. ACCA will also offer production traceability, allowing its key technologies to be used in a broad spectrum of next generation aircraft. On the flip side, battle damage to composite airframes can be more difficult to repair, depending on the exact composites and design. Frank Mauro, vice president at Lockheed martin’s famous Skunk Works, says:
“With ACCA we are attempting to reinvent the manufacturing paradigm through the strategic use of composite manufacturing technologies…”
April 20/07: Aurora Flight Sciences Corp. in Manassas, VA received a $46.9 million cost-plus-fixed-fee contract to provide for an ACAA flight demonstrator. At this time, $2 million have been obligated (FA8650-07-C-3700).
Aurora currently builds about 1/3 of the airframe for the large, composites-heavy RQ-4 Global Hawk UAV.
not from Lockheed
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April 20/07: Lockheed Martin Corp. in Fort Worth, TX received a $49.1 million cooperative agreement contract to provide for an ACAA flight demonstrator. At this time, $2 million have been obligated. Solicitations began January 2007, and negotiations were complete April 2007 (FA8650-07-2-3745).
A 2005 Military Aerospace Technology article makes note of the Lockheed Martin Skunk Works’ MACK concept aircraft, proposed for Special Forces insertion, tanker, and gunship uses. It may exert a significant influence on Lockheed Martin’s ACAA/AJACS designs:
“Lockheed Martin Skunk Works has developed the concept of a modular large-body aircraft to undertake the range of roles listed. This aircraft, designated MACK, will be capable in M-X (special forces insertion), A-X (gunship), C-X (transport) and K-X (tanker) roles. Interchangeable modules can be fitted depending on the requirement.
MACK would have a tailless compound delta wing, with roughly the outer third bent upwards. Multi-spectral stealth characteristics would make it capable against both early warning and fire control radars. Its two engines would be installed inside the airframe. They would be high-bypass types, making them quieter and cooler.
The airframe itself would be made primarily of composite material, although existing composites would be employed in order to reduce costs. Like today’s dedicated strike/interdictor aircraft [DID: and all SOCOM fixed-wing aircraft], MACK would be capable of terrain-following and terrain avoidance flight. It would also be fitted with both offensive and defensive self-protection systems. Aircrew would include pilot, co-pilot and navigator. Gross take-off weight would be 230,000 pounds to 240,000 pounds The engines would each provide 63,000 pounds of thrust, and field length with a 22,000 pound payload would be 1,500 feet.”
Officers: 5 (pilot, copilot, navigator, fire control officer, electronic warfare officer)
Enlisted: 8 (flight engineer, TV operator, infrared detection set operator, loadmaster, four aerial gunners)
Length: 137 ft
Wingspan: 125 ft
Height: 38 ft 6 in
Wing area: 185.5 ft² (162.2 m²)
Loaded weight: 202.00 lb (55,520 kg)
Max takeoff weight: 155,000 lb (69,750 kg)
Powerplant: 4 ×Pratt & Whitney F119-PW-100 Pitch Thrust vectoring turbofans
Cruise speed: Mach 0.76 (450 knots, 515 mph, 830 km/h)
Range: 2,420 nmi (2,785 mi, 4,482 km)
Service ceiling: 45,000 ft (13,716 m)
Max wing loading: 150 lb/ft² (750 kg/m²)
Minimum thrust/weight: 0.277
Takeoff run at MTOW: 7,600 ft (2,316 m)
Landing distance: 3,500 ft (1,060 m)
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