Aviation Naval Warfare Land Systems Small Arms Space By Flag By Year By Tag

McDonnell Douglas YC-15

1976 COLD WAR X-PLANE

History

In the early 1970s, the United States Air Force (USAF) was actively looking for a replacement for their excellent and capable but aging Lockheed C-130 Hercules high-wing aircraft. Introduced in the mid-1950s, these aircraft were subsequently widely accepted and serviced around the world. The USAF developed the Advanced Medium STOL Transport (AMST) program around the new requirements, a fully modern, tactically oriented form of medium lift with better short/rough fields than the in-service propeller powered C- Performance 130 may provide.

Official requirements were established in 1968, and a Request for Proposal (RFP) was issued in 1972.

In the initial phase, industry players such as Bell, Boeing, Lockheed (with Rockwell North America) and McDonnell Douglas all responded. Boeing and McDonnell Douglas eventually emerged from this stage, each receiving contracts for two airworthy prototypes for testing and head-to-head competition.

They were designated Boeing "YC-14" (detailed elsewhere on this page) and McDonnell Douglas "YC-15".

Unlike Boeing's template, which relies on two engines mounted above the wing mainframe, the YC-15 uses a traditional four-engine layout with two paired nacelles below each wing panel. Like the YC-14 (as well as the C-130), the YC-15 uses a high-wing, straight-line (supercritical airfoil) main aircraft configuration to meet the lift, drag, and short-field performance required by the USAF.

Large double-slotted outer flaps The wing occupies a good length of the main aircraft span at the trailing edge of the wing and is designed to improve short take-off and landing (STOL) performance. The engines chosen for the design were 4 x Pratt & Whitney JT8D-17 turbojets, each rated at 15,500 pounds of thrust, already in production and service on commercial airliners at the time.

The fuselage is large, relatively short, and tubular. The raised tail will allow the loading dock to be lowered to accommodate cargo loads fairly easily. The fins are in a typical "T-shaped" arrangement, with the horizontal plane high above the vertical fins.

The tricycle landing gear (retractable) is used for ground operations, and the front wheels are a modified version of the same steering struts used in the DC-8 narrow-body airliner. Inside, the cockpit is taken from the proven McDonnell Douglas DC-10 wide-body airliner and adapted for military service.

The aerial refueling tank was from the attack aircraft Fairchild A-10 "Thunderbolt II", and other components were also borrowed from existing aircraft to speed development and minimize cost.

Two contracted YC-15s arrived as prototypes in 1975 and recorded their first flight on August 26, 1975 (the second prototype flew before the end of the year). Both planes were ahead of rival Boeing designs, which did not enter the air until the following year, and a formal competition between the two began in late 1976.

Due to the changing requirements of the USAF, the AMST program has suffered despite progress. Authorities ultimately agreed to continue to support C-130 production for the foreseeable future and recommitted to expanding the USAF's strategic transport capability, which extends the life of the Hercules aircraft to today (2018).

The AMST program ended in December 1979 with no winner selected, but the "C-X" program was created to now find a strategic transport aircraft - which eventually led to a larger version of the McDonnell Douglas YC-15 - and influenced The future Boeing C-17 Globemaster III swept-wing transport aircraft. The C-17 entered service in 1995 and has been in service to date (2018) with nearly 300 produced.

McDonnell Douglas eventually became a subsidiary of the Boeing Company brand, hence the official product name for the C-17.

The YC-15 was built with a crew of three deployed. It is capable of carrying up to 150 combat-ready troops or up to 78,000 pounds of cargo. Dimensions include a length of 124.2 feet, a wingspan of 110.3 feet and a height of 43.2 feet. Curb weight is 105,000 pounds and MTOW is 216,680 pounds.

Performance specs include a top speed of 590 mph, a cruising speed of 543 mph, a range of up to 3,000 miles, and a service ceiling of up to 30,000 feet.