Boeing C-17 Globemaster III

The Boeing C-17 Globemaster III is a large military transport aircraft. It was developed for the United States Air Force (USAF) from the 1980s to the early 1990s by McDonnell Douglas; the company later merged with Boeing. The C-17 is used for rapid strategic airlift of troops and cargo to main operating bases or forward operating bases throughout the world. It can also perform tactical airlift, medical evacuation and airdrop missions. The C-17 carries the name of two previous, but unrelated piston-engine, U.S. military cargo aircraft, the Douglas C-74 Globemaster and the Douglas C-124 Globemaster II. In addition to the U.S. Air Force, the C-17 is operated by the United Kingdom, Australia, Canada, Qatar, United Arab Emirates and NATO Heavy Airlift Wing.

Design

The C-17 is 174 feet (53 m) long and has a wingspan of about 170 feet (52 m). It can airlift cargo fairly close to a battle area. The size and weight of U.S. mechanized firepower and equipment have grown in recent decades from increased air mobility requirements, particularly for large or heavy non-palletized outsize cargo. The C-17 is powered by four Pratt & Whitney F117-PW-100 turbofan engines, which are based on the commercial Pratt and Whitney PW2040 used on the Boeing 757. Each engine is fully reversible and rated at 40,400 lbf (180 kN) of gross thrust. The thrust reversers direct engine exhaust air upwards and forward, reducing the chances of foreign object damage by ingestion of runway debris, and providing enough reverse thrust to back the aircraft up on the ground while taxiing. The thrust reversers can also be used in flight at idle-reverse for added drag in maximum-rate descents. The aircraft requires a crew of three (pilot, copilot, and loadmaster) for cargo operations. Cargo is loaded through a large aft ramp that accommodates rolling stock, such as a 69-ton (63-metric ton) M1 Abrams tank, other armored vehicles, trucks, and trailers, along with palletized cargo. The cargo compartment is 88 feet (26.82 m) long by 18 feet (5.49 m) wide by 12 feet 4 inches (3.76 m) high. The cargo floor has rollers for palletized cargo that can be flipped to provide a flat floor suitable for vehicles and other rolling stock. Maximum payload of the C-17 is 170,900 lb (77,500 kg), and its Maximum Takeoff Weight is 585,000 lb (265,350 kg). With a payload of 160,000 lb (72,600 kg) and an initial cruise altitude of 28,000 ft (8,500 m), the C-17 has an unrefueled range of about 2,400 nautical miles (4,400 km) on the first 71 aircraft, and 2,800 nautical miles (5,200 km) on all subsequent extended-range models that include sealed center wing bay as a fuel tank. Boeing informally calls these aircraft, the C-17 ER.[40] The C-17's cruise speed is about 450 knots (833 km/h) (0.76 Mach). The C-17 is designed to airdrop 102 paratroopers and their equipment. The U.S. Army BCT Ground Combat Vehicle is to be transported by the C-17. The C-17 is designed to operate from runways as short as 3,500 ft (1,064 m) and as narrow as 90 ft (27 m). In addition, the C-17 can operate from unpaved, unimproved runways (although with greater chance of damage to the aircraft). The thrust reversers can be used to back the aircraft and reverse direction on narrow taxiways using a three- (or more) point turn.

Development difficulties

A static test of the C-17 wing in October 1992 resulted in the wing failing at 128% of design limit load, which was below the 150% requirement. Both wings buckled rear to the front and failures occurred in stringers, spars and ribs. Some $100 million was spent to redesign the wing structure; the wing failed at 145% during a second test in September 1993. A careful review of the test data however, showed that the wing was not loaded correctly and did indeed meet the requirement. The C-17 received the "Globemaster III" name in early 1993. In late 1993, the Department of Defense gave the contractor two years to solve production and cost overrun problems or face termination of the contract after the delivery of the 40th aircraft. By accepting the 1993 terms, McDonnell Douglas incurred a loss of nearly US$1.5 billion on the development phase of the program. In April 1994, the C-17 program remained over budget, and did not meet weight, fuel burn, payload and range specifications. It also failed several key criteria during tests to evaluate its airworthiness. There were technical problems with mission software, landing gear, and so on. In May 1994, a proposal to cut the aircraft's production to as few as 32 aircraft emerged, but was rescinded. A July 1994 GAO document revealed that Air Force and DoD studies from 1986 and 1991 stated the C-17 could use 6,400 more runways outside the U.S. than the C-5, it was later discovered that this study had only considered the runway dimensions, but not their strength or Load Classification Numbers (LCN). The C-5 has a lower LCN, but the USAF classify both in the same broad Load Classification Group (LCG). When considering runway dimensions and their load ratings, the C-17's worldwide runway advantage over the C-5 shrank from 6,400 to 911 airfields. However, the C-17's ability to use lower quality, austere airfields was not considered. A January 1995 GAO report revealed that while the original C-17 budget was $41.8 billion for 210 aircraft, the 120 aircraft already ordered at that point had already cost $39.5 billion. In March 1994, the U.S. Army had decided it no longer needed the 60,000 lb (27,000 kg) Low Altitude Parachute Extraction System (LAPES) delivery with the C-17, feeling that the 42,000 lb (19,000 kg) capability of the C-130 was sufficient; C-17 testing was limited to this lower weight. Issues with airflow prevented the C-17 from meeting its airdrop requirements. A February 1997 GAO report revealed that a C-17 with a full payload could not land on 3,000 ft (910 m) wet runways; simulations suggested 5,000 ft (1,500 m) was required. The YC-15 was transferred to AMARC to be made flightworthy again for further flight tests for the C-17 program in March 1997. By the mid-1990s, most of the problems had been resolved. The first C-17 squadron was declared operational by the U.S. Air Force in January 1995. In 1996, DoD ordered another 80 aircraft for a total of 120. In 1997 McDonnell Douglas merged with its former competitor, Boeing. In April 1999, Boeing proposed to cut the price of the C-17 if the Air Force bought 60 more, and in August 2002, the order was increased to 180 aircraft.

Continued production

Due to a dwindling order backlog, Boeing was to deliver 13 C-17s in 2011. The company is transitioning to a lower production rate of 10 C-17s per year from a high of 16 per year to extend the production line through 2012 as it works to sign additional international orders. The C-17 production line was previously slated to be closed several times, but was extended due to new orders received. The C-17 workforce will be reduced by approximately 1,100 through the end of 2012, mostly through the elimination of a second shift at the C-17 final assembly plant in Long Beach. There have been 230 production C-17s delivered, including 210 to the USAF in April 2011. This does not include the "T-1" prototype, which is used by the USAF for testing and development. In January 2010, the USAF announced that it would end Boeing's performance-based logistics contracts to maintain the aircraft, which was a key source for projected profit growth for the company.

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