PROGRAMME: US Air Force selected McDonnell Douglas to develop C-X cargo aircraft 29 August 1981; full-scale development called off January 1982 and replaced on 26 July 1982 by slow-paced preliminary development order; development and three prototypes (one flying) ordered 31 December 1985; fabrication of first C-17A (T-1/87-0025) began 2 November 1987; first production C-17A ordered 20 January 1988; assembly started at Long Beach 24 August 1988; assembly of first aircraft completed 21 December 1990; first flight scheduled for June 1991; second production C-17 (P-2) to fly 1992; production lot 3 (four aircraft, bringing total ordered to 10) ordered 1991; none funded in FY 1991; six and 12 planned for FY 1992-93; development to continue until 1993. First delivery in 1992 to 17th MAS at Charleston, South Carolina; IOC in 1994. By 1991, total requirement reduced from 210 to 120 aircraft; peak production target reduced from 24 to 18 per year; assembly in new 102,200 m² (1,1 million sq ft) facility at Long Beach, California. Feasibility study for hose-drogue tanker transport combi under way Spring 1991.
COSTS: Originally expected unit cost $125 million. Programme unit cost now $294 million (1991), or $35.274 million for 120 aircraft.
DESIGN FEATURES: Externally blown flap system based on McDonnell Douglas YC-15 medium STOL transport prototypes, with extended flaps in exhaust flow from engines during take-off and landing; combines load-carrying capacity of C-5 with STOL performance of C-130; required to operate from 915 m (3,000 ft) long and 18,3 m (60 ft) wide runways, complete 180° three-point turn in 25 m (82 ft) and reverse up 1 in 50 gradient when fully loaded using thrust reversers. Structure designed to survive battle damage and protect crew; essential line-replaceable units (LRU) to be replaceable in flight; rear loading ramp. Supercritical wing with 25° sweepback; 2.90 m (9.5 ft) high NASA winglets.
FLYING CONTROLS: Outboard ailerons and four spoilers per wing; four elevator sections; two-surface rudder split into upper and lower segments; full-span leading-edge slats; single-slotted Fowler flaps over about two-thirds of trailing-edge; small strakes under tail. Quadruple-redundant digital fly-by-wire flight control system, with mechanical backup.
STRUCTURE: Major subassemblies produced in new factory at Macon, Georgia; subcontractors include Beechcraft (composites winglets), Delco Electronics Corporation (mission computer and electronic display system), Grumman Aerostructures (composites ailerons, rudder and elevators), GEC Avionics (advanced head-up displays), Lockheed (wing components up to sixth aircraft only), LTV (vertical and horizontal stabilisers, engine nacelles and thrust reversers), Reynolds Metals Company (wing skins), CC Industries (wing spars and stringers), Kaman Aerospace (wing ribs and bulkheads), Plessey (fuel pumps), Pyrotector Division of Graviner Inc (smoke detection systems), General Electric (electronic flight control system), Honeywell (air data computer), Martin Marietta (tailcone), Heath Tecna (wing-to-fuselage fillet), Aerostructures Hamble (composite flap hinge fairing and trailing-edge panels) and Northwest Composites (main landing gear pod panels).
LANDING GEAR: Hydraulically retractable tricycle type, with free-fall emergency extension. Twin-wheel Menasco nose unit and two six-wheel main units, designed for sink rate of 4.57 m (15 ft)/s and suitable for operation from paved runways or unpaved strips. Mainwheel units, each consisting of two legs in tandem with three wheels on each leg, rotate 90° to retract into fairings on lower fuselage sides; Menasco nose leg retracts forwards. Allied Signal wheels and carbon brakes.
POWER PLANTS: Early aircraft will have four 185.5 kN (41,700 lb st) Pratt & Whitney F117-PW-100 turbofans with 181.0 kN (40,700 lb st) installed rating, pylon-mounted in individual underwing pods and each fitted with a directed-flow thrust reverser deployable both in flight and on the ground. Power plant contract open to competition for later C-17As. Provision for in-flight refuelling.
ACCOMMODATION: Normal flight crew of pilot and co-pilol, side by side on flight deck, plus a loadmastet in a station in the cargo hold. Provision for additional crew members if required for special missions. Access to flight deck via downward opening airstair door on port side of lower forward fuselage. Bunks for crew immediately aft of flight deck area; crew comfort station at forward end of cargo hold. Main cargo hold able 10 accommodate Army wheeled vehicles, including five-ton expandable vans in two rows, or three Jeeps side by side, or up to three AH-64A Apache attack helicopters, with straight-in loading via hydraulically actuated rear loading ramp which forms underside of rear fuselage when retracted. Alternatively, aircraft can be equipped as a troop transport, with rows of 27 stowable tip-up seats along each side wall and another 48 seats which can be erected along the centreline, or with litters for medical evacuation mission. Airdrop capability includes single platforms of up to 27,215 kg (60,000 lb), multiple platforms of up to 49,895 kg (110,000 lb), or up to 102 paratroops. Equipped tor low altitude parachute extraction system (LAPES) drops. The C-17A will be the only aircraft able to airdrop outsize firepower the size of the US Army's new infantry fighting vehicle; it will also be able to carry the M1 main battle tank in combination with other vehicles. The cargo handling system includes rails for airdrops and rails/rollers for normal cargo handling. Each row of rails/rollers can be converted quickly by a single loadmastet from one configuration to the other. Cargo tiedown rings, each stressed for 11,340 kg (25,000 lb) all over cargo floor at 61 cm (24 in) intervals. Three quick-erecting litter stanchions, each supporting four litters, permanently carried. Main access to cargo hold is via rear loading ramp, which is itself stressed for 18,145 kg (40,000 lb) of cargo. Underfuselage door aft of ramp moves upward inside fuselage to facilitate loading and unloading. Paratroop door at rear on each side; two ditching exits overhead, aft of the paratroop doors, and two overhead forward of the wing box.
SYSTEMS: Include Allied Signal computer controlled integrated environmental control system and cabin pressure control system; quad-redundant flight control and four independent 276 bar (4,000 lb sq/in) hydraulic systems; independent fuel feed systems; electrical system; Allied Signal GTCP331 APU (at front of starboard landing gear pod), operable in flight, provides auxiliary power for environmental control system, engine starting, and on-ground electronics requirements; onboard inert gas generating sysiem (OBIGGS) for the explosion protection system, pressurised by engine bleed air at 4.1 bars (60 lb/sq in) to produce NEA 4 gas and governed by a Gull Inc system controller; fire suppression system. All phases of cargo operation and configuration change capable of being handled by one loadmasler.
AVIONICS: General Electric digital fly-by-wire flight control system; Honeywell dual air data computers, with advanced digital avionics and four full-colour multifunction displays (MFDs), two GEC Avionics full flight regime head-up displays, plus integrated mission and communications keyboards (MCKs) and displays (MCDs). Primary flight data presented on HUD and a selectable mode for the MFD. Horizontal navigation situation, computer-generated flight plan and weather radar overlay selectable on MFD. Station keeping (SKE), engine and flight control configuration data available on MFDs. All frequency tuning for nav/com accomplished from glareshield control panel. MCDs have frequency and channel pre-storage facility and provide for flight plan entry manually or by preprogrammed cassette, permitting insertion of in-flight planning changes without disturbing ongoing navigation. All MCD information for flight and navigation monitoring is presented on the HUD and MFDs. Teledyne Controls warning and caution system. Master warning caution annunciator provides automatic monitoring of all main systems and provides visual alerts on glareshields, aural and voice alerts on intercom. Other equipment includes Allied Signal AN/APS-133[V] weather/mapping radar, Delco Electronics mission computer with MDC software; and electronic control sysiem. Hamilton Standard aircraft and propulsion dala management computer, General Dynamics automatic test equipment, and support equipment data acquisition and control system, LTV Sierra Research Division station keeping equipment, and Telephonic Corporation radio management system. Development of defensive electronic systems was authorised in 1988.