McDonnell Douglas YC-15

McDonnell Douglas YC-15
Name	YC-15
Caption	The first YC-15 prototype during flight testing.
Type	STOL tactical airlifter
National origin	United States
Manufacturer	McDonnell Douglas
First flight	26 August 1975
Status	Experimental prototype
Primary user	United States Air Force
Developed into	Boeing C-17 Globemaster III

McDonnell Douglas YC-15 was a prototype STOL tactical airlifter designed and built by McDonnell Douglas for the United States Air Force's Advanced Medium STOL Transport (AMST) competition in the 1970s. It was developed to replace the aging Lockheed C-130 Hercules with an aircraft capable of operating from short, austere airstrips close to front lines. Although the program was ultimately canceled, the YC-15's pioneering technologies directly influenced the design of the later and highly successful Boeing C-17 Globemaster III.

Development and design

The YC-15 was developed in response to the United States Air Force's AMST request for proposal issued in 1972, which sought a new-generation tactical transport. McDonnell Douglas competed against Boeing, which produced the rival Boeing YC-14. The design centered on achieving exceptional STOL performance through the use of an externally blown flap (EBF) system, where engine exhaust was directed over large, complex double-slotted flaps to dramatically increase lift. The aircraft was powered by four Pratt & Whitney JT8D-17 turbofan engines, a significant departure from the turboprops used on the Lockheed C-130 Hercules. Its high-wing configuration and rear loading ramp were optimized for rapid cargo handling, and it featured advanced fly-by-wire controls for its spoilers. The design team, led by key engineers from McDonnell Douglas, aimed to carry a 27,000-pound payload in and out of unimproved airstrips as short as 2,000 feet.

Operational history

The first of two YC-15 prototypes (serial numbers 72-1875 and 72-1876) made its maiden flight from Long Beach, California on 26 August 1975. Both aircraft underwent extensive flight testing at Edwards Air Force Base, demonstrating remarkable capabilities, including the ability to land and take off in under 2,000 feet while carrying significant payloads. The prototypes were evaluated alongside the Boeing YC-14 by the United States Air Force's 417th Flight Test Squadron. Despite successfully meeting or exceeding many AMST requirements, the program was canceled in 1979 due to shifting United States Department of Defense priorities, which favored longer-range strategic airlift over dedicated tactical transports. The aircraft continued to be used for various research roles by McDonnell Douglas and NASA into the early 1980s.

Specifications (YC-15)

* **Crew:** 3 * **Capacity:** 150 troops or 27,000 lb (12,247 kg) payload * **Length:** 124 ft 3 in (37.9 m) * **Wingspan:** 110 ft 4 in (33.6 m) * **Height:** 43 ft 4 in (13.2 m) * **Empty weight:** 105,000 lb (47,627 kg) * **Max takeoff weight:** 216,680 lb (98,285 kg) * **Powerplant:** 4 × Pratt & Whitney JT8D-17 turbofan engines, 16,000 lbf (71 kN) thrust each * **Maximum speed:** 346 kn (398 mph, 641 km/h) at 15,000 ft * **Cruise speed:** 300 kn (345 mph, 556 km/h) * **Range:** 2,990 nmi (3,440 mi, 5,540 km) with 27,000 lb payload * **Service ceiling:** 30,000 ft (9,100 m) * **Takeoff distance:** 2,100 ft (640 m) at max gross weight

Variants

Only the two original prototypes were constructed. There were no production variants of the YC-15. However, the fundamental design and technologies were resurrected in the 1980s for the C-17 Globemaster III program, which scaled up the YC-15 concept into a strategic airlifter with retained tactical capabilities. The Boeing C-17 Globemaster III is considered the direct, albeit much larger and more advanced, descendant of the YC-15.

Aircraft on display

* **72-1875:** The first prototype is on permanent display at the Museum of Aviation at Robins Air Force Base in Warner Robins, Georgia. * **72-1876:** The second prototype was stored for many years at the AMARC facility at Davis–Monthan Air Force Base in Tucson, Arizona, and was later moved to Wright-Patterson Air Force Base in Ohio for potential restoration and display.

Legacy and influence

Although the AMST program was canceled, the YC-15 proved the viability of using externally blown flaps and high-bypass turbofan engines for STOL military airlift. The data and experience gained were instrumental when McDonnell Douglas (later Boeing) developed the Boeing C-17 Globemaster III, one of the most successful military transport aircraft in history. The YC-15 thus served as a crucial technological bridge between the Lockheed C-130 Hercules and the modern global airlift capability represented by the C-17. Its innovative systems influenced subsequent aerospace research at NASA and within the United States Air Force.

Category:United States military transport aircraft 1970–1979 Category:McDonnell Douglas aircraft Category:Four-engined turbofan aircraft Category:STOL aircraft