McDonnell Douglas YC-15

Information about McDonnell Douglas YC-15

YC-15
One of the YC-15 prototypes conducting flight testing, accompanied by an F-4 Phantom II.
TypeTactical airlifter
ManufacturerMcDonnell Douglas
Maiden flight1975-08-26
StatusRetired
Number built2
VariantsC-17 Globemaster III
The YC-15 was McDonnell Douglas' entrant into the U.S. Air Force's Advanced Medium STOL Transport (AMST) competition, to replace the C-130 Hercules as the USAF's standard STOL tactical transport. In the end neither aircraft was ordered into production, although the YC-15's basic design would be used to form the successful McDonnell Douglas C-17 of the 1990s.

History

In 1971 the USAF started work on a series of prototype proposals, which would lead to both the AMST project and the Light Weight Fighter. The official RFP was issued in January 1972, asking for operations into a 2,000 foot semi-prepared field at 500 nmi with a 27,000 lb payload in both directions with no refueling. For comparison, the C-130 of that era required about 4,000 ft for this load. Five companies submitted designs at this stage of the competition, Boeing with their Model 953 in March 1972. On 10 November 1972 the downselect was carried out, and Boeing and McDonnell Douglas won development contracts for two prototypes each.

McDonnell Douglas's design incorporated a supercritical wing, the result of NASA research carried out by the already famous Richard Whitcomb. This wing design dramatically lowers transonic wave drag by as much as 30% compared to more conventional profiles, while at the same time offering excellent low-speed lift. Most contemporary aircraft used swept wings to lower wave drag, but this led to poor low-speed handling, which made them unsuitable for STOL operations.

The design team also chose to use externally-blown flaps to increase lift. This system uses double-slotted flaps to direct part of the jet exhaust downwards, while the rest of the exhaust passed through the flap and then followed the downward curve due to the Coandă effect. Although the effects had been studied for some time at NASA, along with similar concepts, until the introduction of the turbofan the hot and concentrated exhaust of existing engines made the system difficult to use. By the time of the AMST project, engines had changed dramatically and now provided larger volumes of less-concentrated and much cooler air. For the YC-15 four small engines were used, versions of the Pratt & Whitney JT8D widely used on the Boeing 727 modified with an extra fan stage at the rear of the engine to increase the cool air flow.

Boeing's design was generally similar, and also utilized a supercritical wing. Where the two differed was in the placement of the engines. Boeing's design used "upper surface blowing" in place of the externally-blown flap (although it is in effect a subtype). This system allowed them to place two larger engines close to the wing root, using a diffuser to spread the exhaust over the upper surface. They felt this arrangement offered safety margins in case of an engine failure on one side, whereas the under-wing system on the YC-15 would lead to significant asymmetric lift.

Testing

Two YC-15s were built, one with a wingspan of 110 feet (#72-1876) and one with 132 feet (#72-1875). Both were 124 feet long and powered by four Pratt & Whitney JT8D-17 engines, each with 15,500 lbf (68.9 kN) thrust.

The first flight was August 26, 1975. The second prototype followed in December. They were tested for some time at McDonnell Douglas as the Boeing entry was not ready until almost a year later. In November 1976 both designs were transferred to Edwards Air Force Base for head-to-head testing, including lifting heavy loads like tanks and artillery from dirt airfields at Graham Ranch, off the end of Runway 22.

The YC-15s completed a 600 hour flight test program in 1977.Generally pilots favored the Boeing design, as its advanced flight control system made it fly like a fighter. After the flight test program, the two aircraft were stored at the AMARC. located at Davis-Monthan Air Force Base. One was subsequently displayed at the nearby Pima Air & Space Museum.

By this point the seeds of the AMST program's demise had already been sown. In March 1976 the Air Force Chief of Staff Gen. David C. Jones asked the Air Force Systems Command to see if it was possible to use a single model of the AMST for both strategic and tactical airlift roles, or alternately, if it was possible to develop non-STOL derivatives of the AMST for the strategic airlift role. This led to a series of studies which basically stated that such a modification was not easy, and would require major changes to either design to produce a much larger aircraft.

Enlarge picture
The C-17 Globemaster III, derived from the YC-15, shares a similar configuration, except for having swept wings.
Although the YC-14 and YC-15 both met or exceeded the specifications of the contest, the increasing importance of the strategic vs. tactical mission eventually led the Air Force to conclude that they were better off with an updated C-130 in the short term. The AMST program was canceled in 1979. In January 1979, the C-X Task Force formed to develop the required strategic aircraft. The C-X eventually became the C-17 Globemaster III, developed on the basis of the YC-15.

AMARC's YC-15, 72-1875, was later returned to flying status by McDonnell Douglas in 1996, and resumed flying in April 1997. The intention was to use the YC-15 to evaluate new technology for advanced tactical transports. After an engine failed, the aircraft was deemed too expensive to repair and was returned to storage.

Specifications

General characteristics

* Crew: 3* Capacity: Up to 150 troops or 78,000 lb of cargo

Performance

External links

Related content

Related development

Comparable aircraft

Designation sequence

See also

 •  • [ e]
McDonnell and McDonnell Douglas military aircraft
Fighters: XP-67 FH F2H XF-85 XF-88 F3H F-101 F-110 F-4 F-15 F/A-18 CF-188 YF-23 F/A-18E/F
Attack: AH AV-8 F-15E A-12 EA-18
Trainers: T-45
Transports: C-9 KC-10 YC-15 C-17
Helicopters: XHJH XH-20 XHCH XHRH AH-64
Drones: TD2D KDH
Experimental: XV-1 X-36 Bird of Prey -
Spacecraft: Mercury Gemini
 •  • [ e]
Lists relating to aviation
Timeline of aviation
Aircraft Aircraft manufacturers Aircraft engines Aircraft engine manufacturers Airports Airlines
Air forces Aircraft weapons Missiles Unmanned aerial vehicles (UAVs) Experimental aircraft
Notable incidents & accidents in: Military aviation Airliners General aviation Famous aviation-related deaths
Flight airspeed record Flight distance record Flight altitude record Flight endurance record Most produced aircraft
Type Fighter-bomber
Manufacturer McDonnell Douglas
(née McDonnell Aircraft)
Designed by David S. Lewis, Jr.
Maiden flight 27 May 1958
Introduction 30 December 1960
Status
..... Click the link for more information.
airlift is the organized delivery of supplies primarily via aircraft.

Airlifting consists of two distinct types, strategic airlifting and tactical airlifting. Typically, strategic airlifting involves moving materiel long distances (such as across or off the continent or
..... Click the link for more information.
An aerospace manufacturer is a company or individual involved in the various aspects of designing, building, testing, selling, and maintaining aircraft, aircraft parts, missiles, rockets, and/or spacecraft.
..... Click the link for more information.
McDonnell Douglas was a major American aerospace manufacturer and defense contractor, producing a number of famous commercial and military aircraft. It merged with Boeing in 1997 to form The Boeing Company.
..... Click the link for more information.
The maiden flight of an aircraft is the first occasion on which an aircraft leaves the ground of its own accord. This is similar to a ship's maiden voyage.

The first flight of a new aircraft type is always a historic occasion for the type.
..... Click the link for more information.
Type Strategic airlifter
Manufacturer McDonnell Douglas/Boeing
Maiden flight 15 September 1991
Introduction 14 July 1993
Status In service
Primary users United States Air Force
Royal Air Force
..... Click the link for more information.
McDonnell Douglas was a major American aerospace manufacturer and defense contractor, producing a number of famous commercial and military aircraft. It merged with Boeing in 1997 to form The Boeing Company.
..... Click the link for more information.
United States Air Force (USAF) is the aerial warfare branch of the United States armed forces and one of the seven uniformed services. Previously part of the United States Army, the USAF was formed as a separate branch of the military on September 18, 1947.
..... Click the link for more information.
Advanced Medium STOL Transport (AMST) project was intended to replace the Lockheed C-130 Hercules tactical transport in USAF service.

The project was given go-ahead in 1970. The Department of Defense submitted an RFP in 1972.
..... Click the link for more information.
Type STOL military transport aircraft
Manufacturer Lockheed Corporation
Maiden flight 1954-08-23
Introduction December 1956
Status In production
Primary users United States Air Force (514)
Royal Air Force (91)
..... Click the link for more information.
STOL is an acronym for Short Take-Off and Landing, a term used in the aircraft industry to describe aeroplanes with very short runway requirements.

The formal NATO definition (since 1964) is:


..... Click the link for more information.
Type Strategic airlifter
Manufacturer McDonnell Douglas/Boeing
Maiden flight 15 September 1991
Introduction 14 July 1993
Status In service
Primary users United States Air Force
Royal Air Force
..... Click the link for more information.
Lightweight Fighter (LWF) Program was a U.S. Air Force technology evaluation program initiated in the 1960s by a cabal of officers and defense analysts known as the "fighter mafia". It was spurred by then Maj.
..... Click the link for more information.
McDonnell Douglas was a major American aerospace manufacturer and defense contractor, producing a number of famous commercial and military aircraft. It merged with Boeing in 1997 to form The Boeing Company.
..... Click the link for more information.
supercritical airfoil is an airfoil designed, primarily, to delay the onset of wave drag in the transonic speed range. Supercritical airfoils are characterized by their flattened upper surface, highly cambered (curved) aft section, and greater leading edge radius as compared to
..... Click the link for more information.
National Aeronautics and Space Administration

NASA logo
Motto: For the Benefit of All[1]

NASA seal
Agency overview
Formed 29 July 1958

Headquarters Washington D.C.

Annual Budget $16.
..... Click the link for more information.
Richard T. Whitcomb (1921, Evanston, Illinois) is an aeronautical engineer who spent most of his career at the Langley Laboratory of the NACA and its successor organization, NASA.

In the 1950s, Whitcomb proposed the 'Area Rule'.
..... Click the link for more information.
Transonic is an aeronautics term referring to a range of velocities just below and above the speed of sound (about mach 0.8–1.2). It is defined as the range of speeds between the critical mach number, when some parts of the airflow over an aircraft become supersonic, and a
..... Click the link for more information.
Wave drag is an aerodynamics term that refers to a sudden and very powerful form of drag that appears on aircraft flying at high-subsonic and supersonic speeds.

Overview

Wave drag is caused by the formation of shock waves around the aircraft.
..... Click the link for more information.
swept-wing is a wing planform common on high-speed aircraft, with the wing swept back instead of being set at right angles to the fuselage. Forward sweep is also used on some aircraft.
..... Click the link for more information.
Blown flaps are a powered aerodynamic high-lift device on the wings of certain aircraft to improve the low-speed lift during takeoff and landing. The process is sometimes called a boundary layer control system (BLCS).
..... Click the link for more information.
Flap may refer to:
  • Flap (aircraft), a hinged surface on the trailing edge of an airplane wing
  • Flap, any hinged plate often used as a cover or a simple one-way valve

..... Click the link for more information.
turbofan is a type of jet engine, similar to a turbojet. It essentially consists of a ducted fan with a smaller diameter turbojet engine mounted behind it that powers the fan.
..... Click the link for more information.
Pratt & Whitney JT8D is a low-bypass (0.96 to 1) turbofan jet engine, introduced by Pratt & Whitney in February 1964 with the inaugural flight of Boeing's 727. It was a modification of the Pratt & Whitney J52 turbojet engine, which powered the US Navy A-6 Intruder attack aircraft.
..... Click the link for more information.
Type Airliner
Manufacturer Boeing Commercial Airplanes
Maiden flight 1963-02-09
Introduction 1964-02-01 with Eastern Air Lines
Status Out of production
Primary user FedEx
Produced 1963 - 1984
Number built
..... Click the link for more information.
Pratt & Whitney

Subsidiary of UTC
Founded 1860
Headquarters East Hartford, Connecticut

Key people Steven Finger, President
Industry Aerospace
Products Aircraft engines
Gas turbines
Spacecraft propulsion
Website Pratt & Whitney


..... Click the link for more information.
Pratt & Whitney JT8D is a low-bypass (0.96 to 1) turbofan jet engine, introduced by Pratt & Whitney in February 1964 with the inaugural flight of Boeing's 727. It was a modification of the Pratt & Whitney J52 turbojet engine, which powered the US Navy A-6 Intruder attack aircraft.
..... Click the link for more information.
A pound or pound-force (abbreviations: lb, lbf, or lbf) is a unit of force. Pound is also the name of a unit of mass. One pound-force is approximately equal to the gravitational force exerted on a mass of one avoirdupois pound on the
..... Click the link for more information.
August 26 is the 1st day of the year (2nd in leap years) in the Gregorian calendar. There are 0 days remaining.

Events

  • 55 BC - Julius Caesar invades Britain.

..... Click the link for more information.
1975 1976 1977 1978

19th Century · 20th century · 21st century
1940s 1950s 1960s 1970s 1980s 1990s 2000s
1972 1973 1974 1975
..... Click the link for more information.


This article is copied from an article on Wikipedia.org - the free encyclopedia created and edited by online user community. The text was not checked or edited by anyone on our staff. Although the vast majority of the wikipedia encyclopedia articles provide accurate and timely information please do not assume the accuracy of any particular article. This article is distributed under the terms of GNU Free Documentation License.