In 1968, the U. S. Air Force issued a Request for Proposals for an Advanced Medium Short Takeoff and Landing Transport (AMST) “with an eye toward replacing” the Lockheed C-130. Both Boeing and McDonnell Douglas won development contracts to produce prototype aircraft. Boeing’s aircraft was the YC-14 and McDonnell Douglas developed the YC-15.
The YC-15 Was Officially a No-Go
Following the first flights and 600 hours of flight-testing the prototypes, the Air Force selected neither the YC-14 nor the YC-15, and the Air Force/DoD canceled the AMST program.
After cancellation of the program, one of the YC-14 and the two YC-15 aircraft were sent to the Aerospace Maintenance and Regeneration Center (AMARC), now the Aerospace Maintenance and Regeneration Group (AMARG)—often called The Boneyard—at Davis–Monthan Air Force Base. This is where aircraft go to be cannibalized for parts and/or eventually broken down and their structural material recycled. The second YC-14 is on display at the Pima Air Museum.
YC-15 Whet The Appetite For A Strategic Airlifter With C-130-like Qualities
Following the cancellation of the initial AMST program, the Air Force/DoD determined that what they really needed was a heavy lift aircraft capable of transporting a main battle tank or 100 fully equipped soldiers over long distances to unimproved airstrips. The DoD changed the program requirements, but the Air Force had been impressed with many aspects of the YC-15’s capabilities and technologies, and it became the model from which the future heavy-lift aircraft would eventually evolve.
Two YC-15s were built. One (#72-1876) had a wingspan of 110 fee, while the other (#72-1875) had a wingspan of 132 feet. Both were 124 feet long and were powered by four Pratt & Whitney JT8D-17 engines.
Specifically, the YC-15 demonstrated several new approaches to improved performance, including externally blown flaps that used double-slotted flaps to direct a portion of the jet exhaust downwards. The rest of the airflow/exhaust passed through and downward over the flaps producing the Coanda effect. It was also the first military aircraft with a supercritical airfoil.
McDonnell Douglas YC-15 Prototype Specifications
| YC-15 First flight | Aug. 26, 1975 |
| Model number | YC-15 |
| Wingspan | 110 feet and 132 feet |
| Length | 124 feet |
| Height | 43 feet 4 inches |
| Gross weight | 219,180 pounds |
| Cruising speed | 535 mph |
| Range | 460 miles STOL with 27,000-pound payload; 2,292 miles conventional with 38,000-pound payload |
| Power plant | Four 15,500-pound-thrust Pratt & Whitney JT8D-209 Turbofan engines |
| Accommodation | Three crew, 150 troops or 27,000 pounds of cargo (STOL) or 69,000 pounds of cargo (conventional) |
A New Re-Focused Program Based On Previous Work
The new AMST program required the ability to operate from short, semi-prepared airstrips; lift a 27,000-pound payload; and have a 460-mile tactical operating radius.
Although not selected as part of the original AMST program, the YC-15’s basic design would be used to guide the development of the successful McDonnell Douglas (later Boeing) C-17 Globemaster III.
In 1968, the AMST program appeared in another RFP bundled with a solicitation for a Lightweight Fighter. The transport part of this two-part program became the C-X program for an enlarged YC-15-type aircraft with the ability to operate from semi-prepared airstrips no longer than 2000 feet, lift a 27,000-pound payload, and have a 460 mile operating radius.
McD’s Proposal Was an Upscaled and Improved YC-15
This aircraft would become the C-17 Globemaster III that could haul a main battle tank or equivalent mass of military hardware and supplies or 100-plus fully equipped soldiers and deliver them to minimally prepared airstrips.
In 1980, the USAF issued the new mission requirements and a new Request for Proposals for a an aircraft to meet the revised strategic mission requirements. Based on the earlier AMST program, the Air Force Systems Command wanted to use a single model aircraft for both tactical and strategic airlift. That means the aircraft had to be able to a carry a main battle tank or equivalent mass of military hardware, or more than 100 fully equipped soldiers and deliver them to unpaved forward airstrips—from home base to the battle front.
Proposals Were Made By Many But McDonnell Douglas’ Won
Proposers included Boeing offering a three-engine version of the YC-14 submitted for the former AMST program, and Lockheed submitting two proposals, one based the C-5 Galaxy, and another developed from the C-141. McDonnell Douglas elected to build a new aircraft, but with many of the positive capabilities and lessons-learned from of the earlier YC-15 AMST offering.
In 1981, the contract was awarded to McDonnell Douglas to build its aircraft, designated C-17.
1997 was a landmark year for the C-17: its parent company, McDonnell Douglas was merged into Boeing Aircraft. Production of the C-17 continued until 2015.
The C-17A Globemaster III
McDonnell Douglas experienced a number of growing pains developing the C-17, but by 1995, the Globemaster was declared operational, and the Air Force ended up buying over 200 of them. As of 2015, a total of 279 aircraft had been produced.
General characteristics of the C-17
| C-17A First flight | September 15, 1991, from the Long Beach, California airport. |
| Model number | C-17 Globemaster III |
| Minimum Crew | 3: two pilots and the loadmaster |
| Wingspan | 169 feet, 9.6 in. |
| Wing Area | 3,800 sq. ft. |
| Wing Sweep Angle | 25 degrees |
| Length | 174 feet |
| Height (Tail) | 55 feet 1 inch |
| Fuselage Diameter | 22.5 ft |
| Flight Control System | Quadruple-redundant electronic flight controls with mechanical backup system |
| Empty weight | 252,800 lb. (128,140 kg) |
| Mission | Tactical airlift, troops and/or military equipment, airdrop missions, medical transport of litter and ambulatory patients |
| Max Takeoff Weight | 585,000 lb. |
| Cruising speed | 550 mph (max cruising speed: 590 mph) |
| Service Ceiling | Service ceiling: 30,000 ft (9,100 m) |
| Range | 460 miles STOL with 27,000-pound payload. 2,292 miles Conventional with 38,000-pound payload |
| Power plant | 4 × Pratt & Whitney F117-PW-100 turbofan engines; 40,440 lbf thrust each |
| Max Payload – Tactical | 102 troops or 27,000 pounds of cargo (STOL) or 69,000 pounds of cargo (conventional) |
| Landing | Runways as short as 3500 feet |
| Maneuverability | Three-point turn using reverse thrusters on runways 90 feet wide. |
Additional Facts and Capabilities of the C-17
The C-17 has developed an international following and is currently serving in at least nine countries including Australia, Canada, India, Kuwait, European Union, Qatar, United Arab Emirates, the United Kingdom, in addition the USAF.
Each engine is rated at 40,440 pounds of thrust and includes thrust reversers that direct the flow of air upward and forward. A fully-loaded aircraft on the ground can use its thrust reversers to back up. For an aircraft as massive as the C-17, that’s impressive.
Not only can the C-17 back up using reverse thrust, but it can also make a pivot-turn in the middle of a runway by using reverse thrust on one side and positive thrust on the other.
The 35-degree swept back wings have a supercritical airfoil that enhances aerodynamic efficiency and reduce drag.
More C-17 Facts:
The C-17 has been involved in every major worldwide operation since the 1990s, dropping cargo or assisting other branches of the military. The Globemaster III’s resume includes a history of both combat performance and humanitarian aid. The C-17 flew critical supply missions in response to massive flooding in Puerto Rico; delivering food and critical relief supplies to Haiti; and delivering a fire truck for emergency responders in Guatemala, to name only a few such missions.
The C-17 has broken more than 20 records for oversized payloads and was awarded the prestigious Collier Trophy.
The first operational mission transporting paratroopers occurred in 2003 when C-17s deployed 1000 paratroopers into Northern Iraq.
A C-17 accompanies Air Force One to transport the President’s car and vehicles for security personnel.
The C-17 is operated by Australia, Canada, India, NATO, Kuwait, Qatar, United Arab Emirates, United Kingdom, and the United States
The C-17 Globemaster III has become something of a cinema star appearing in a number of films and television series including Iron Man, Godzilla, and American Sniper, as well as on TV including in Seal Team, Hawaii Five-O, and Marvel: Agents of S.H.I.E.L.D.
Outlook For The C-17
The C-17 Globemaster III is expected to remain in service with the USAF through 2040. And it is likely to be operating somewhere for many years into the future.
