<p>The C-17 was developed as the USAF's next-generation cargo airlifter for Military Airlift Command (now Air Mobility Command). The C-17 will carry out the long-range strategic airlift mission, joining the C-141B and C-5A/B in this role, but also be capable of delivering troops and equipment near the front lines in a combat zone, using thrust reversers to land on unimproved runways as short as 3,000 ft (914 m). The C-17 was also developed with the LAPES (Low-Altitude Parachute Extraction System) delivery capability found on the C-130 and C-141B. Design of the C-17 included coordination with the US Army and Marine Corps over the size and bulk of items of military hardware to be transported, including armor items, some of which cannot be effectively airlifted by C-130, C-141B or C-5A/B.
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<p>The C-17, intended to replace those C-141B StarLifters with highest-hour airframes, was to be the first four-engined airlifter to have a two-member flight cabin crew—the pilots' duties facilitated by an EFCS (electronic flight control system) and integrated mission computer. The EFCS was to employ all-digital FBW (fly-by-wire) flight controls. Its short-field landing capability is based on powered lift using an externally-blown flap principle, directed-flow thrust reversers, and avionics for the air crew, including the first HUD (head-up display) in a transport. Remaining members of the four-person crew are a flight engineer and a loadmaster.
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<p>The C-17 is a high-wing, T-tailed aircraft with a rear loading ramp. Wing and tail surfaces are swept 25 and winglets protrude from the wing tips to enhance fuel efficiency. The C-17's ground-level, roll-on/off ramp is located at the rear of the fuselage. A 68 ft 1 in (20.76 m) long cargo compartment with powered rollers accommodates up to 18 standard 463L pallets. Typical cargo loads can include two armored personnel carriers, a five-ton truck and a Jeep; or four UH-60 Black Hawk helicopters; or two AH-64 Apache and three OH-58 Kiowa helicopters. Fifty-four people can be accommodated in permanently-installed sidewall seats.
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<p>Power is provided by four 41,700-lb (185.49-kW) thrust Pratt & Whitney F117-PW-100 (civil PW2040) engines, also used on commercial airliners such as some Boeing 757s.
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<p>The C-17 dates from February 1980 when the USAF issued a draft RFP (request for proposals) for a C-X transport able to perform strategic airlift and to land close to the battlefield. Design features of aircraft proposals from three manufacturers drew on experience in the 1970s with the experimental Boeing YC-14 and McDonnell YC-15 transports. C-X proposals by Boeing and Lockheed lost out when Douglas was selected in August 1981 to build the C-X; the C-17 designation was assigned the following month.
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<p>The C-17 program was sidetracked in February 1982 when the USAF decided to purchase 50 C-5B Galaxy and 44 KC-10A Extender aircraft (the latter subsequently increased to 60) and purposely delayed development of the C-17, which until then had been scheduled to enter service in 1987. The USAF's AMP (Airlift Master Plan) of 29 September 1983 re-established the development schedule and scale of the C-17 effort.
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<p>A full-scale fuselage mock-up, including cargo compartment and flight deck, met with favorable USAF reception. During 11-20 September 1984 a cargo-loading test, using active-duty Air Force loadmasters and users from the Army and Marine Corps, handled 11 load combinations successfully.
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<p>The AMP schedule originally called for a first flight in August 1990, but subsequently incurred additional delays. Once the C-17 program was restored, fabrication of the first airframe (87-0025) began in November 1987. The aircraft is manufactured by Douglas, with LTV in Dallas, Texas, supplying C-17 engine nacelles, UARRSI (universal aerial refueling receptacle slipway installation), and tail sections.
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<p>The USAF's planned purchase of 210 C-17 Globemaster IIIs was cut to 120 in the wake of Defense Secretary Richard Cheney's MAR (Major Aircraft Review) program in March 1990. Given the cost of the C-17 project and the magnitude of force reductions scheduled for the mid-1990s, it appeared possible that the final purchase would be reduced still further, perhaps to as few as 40 examples. That is the limit that has currently been imposed by Congress, although it is subject to review and may yet been rescinded.
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<p>The manufacturer's case for a full commitment hasn't been helped by structural problems and an inability to satisfy certain performance criteria and the AMC's newest airlifter is still perceived as being very much on 'probation', with the final decision on the eventual buy not expected to be made until November 1995 at the latest.
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<p>Assembly of the first aircraft was completed in December 1990 with this making a successful maiden flight from Long Beach, California to Edwards Air Force Base on 15 September 1991. The latter site has been the primary center for development flight testing, with the program using a total of six aircraft at its peak, five of which will eventually be brought to operational status and assigned to AMC.
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<p>Entry into service in fact predated the completion of the various test objectives by a significant degree, with the appropriately designated 17th Airlift Squadron, 437th Airlift Wing at Charleston AFB, South Carolina formally accepting its first Globemaster III on 14 June 1993. The unit's tenth C-17 was handed over about a month ahead of schedule at the end of September 1994 and the squadron anticipated achieving an IOC (Initial Operating Capability) by the end of the year, when it should have its full complement of 12 aircraft. Attention will then turn to equipping a second squadron within the 437th AW. In the longer term, if the program is carried through to its full extent, the 120th and last C-17A should join AMC in the middle of 2001.
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<p>However, in view of the high unit cost and changing mission concepts, it now seems unlikely that the Globemaster III will ever routinely be used to furnish direct support to the battlefield, as was the original intent. As for other applications, McDonnell Douglas has put forward a number of alternative uses to the USAF, including one proposal for an EC-17 airborne command post version to replace existing EC-135 Stratotankers. For now, though, the main concern must surely be to ensure that the basic transport is able to fulfil the tasks for which it was ordered in the first place.
