The exclusive story of how a secret operation was funded to build three YF-12/SR-71 Blackbird aircraft, following the North American XF-108 Rapier cancellation.
The Lockheed YF-12 was an American Mach 3+ capable, high-altitude interceptor prototype, developed and manufactured by American aerospace company Lockheed Corporation.
The interceptor was developed during the late 1950s and early 1960s as a potential replacement for the F-106 Delta Dart interceptor for the United States Air Force (USAF). The YF-12 was a twin-seat version of the then-secret single-seat Lockheed A-12 reconnaissance aircraft operated by the Central Intelligence Agency (CIA); unlike the A-12, it was furnished with the Hughes AN/ASG-18 fire-control radar and could be armed with AIM-47 Falcon (GAR-9) air-to-air missiles. Its maiden flight was on 7 August 1963. Its existence was publicly revealed by President Lyndon B. Johnson on 24 February 1964; this move was to provide plausible deniability for the CIA-operated A-12 fleet, which closely resembled the prototype YF-12.
During the 1960s, the YF-12 underwent flight evaluations by the USAF, but funding to put it into operational use was not forthcoming partly due to the pressing demands of the Vietnam War and other military priorities. It set and held speed and altitude world records of over 2,000 miles per hour (3,200 km/h) and over 80,000 feet (24,000 m) (later surpassed by the closely related SR-71 Blackbird), and is the world's largest, heaviest, and fastest crewed interceptor. Following its retirement by the USAF, it served as a research aircraft for NASA for a time, which used it to develop several significant improvements in control for future supersonic aircraft.
In the late 1950s, the United States Air Force (USAF) sought a replacement for its F-106 Delta Dart interceptor. As part of the Long Range Interceptor Experimental (LRI-X) program, the North American XF-108 Rapier, an interceptor with Mach 3 speed, was selected. However, the F-108 program was canceled by the Department of Defense in September 1959. During this time, Lockheed's Skunk Works was developing the A-12 reconnaissance aircraft for the U.S. Central Intelligence Agency (CIA) under the Oxcart program. Kelly Johnson, the head of Skunk Works, proposed to build a version of the A-12 named AF-12 by the company; the USAF ordered three AF-12s in mid-1960.
Picture of the modified chine to accommodate the AN/ASG-18 radar
The AF-12s took the seventh through ninth slots on the A-12 assembly line; these were designated as YF-12A interceptors. The main changes involved modifying the A-12's nose by cutting back the chines to accommodate the huge Hughes AN/ASG-18 fire-control radar originally developed for the XF-108 with two infrared search and track sensors embedded in the chine leading edge, and the addition of the second cockpit for a crew member to operate the fire control radar for the air-to-air missile system. The modifications changed the aircraft's aerodynamics enough to require ventral fins to be mounted under the fuselage and engine nacelles to maintain stability. Three of the four bays previously used to house the A-12's reconnaissance equipment were converted to carry Hughes AIM-47 Falcon (GAR-9) missiles. One bay was used for fire control equipment.
Specifications (YF-12A)
Orthographically projected diagram of the Lockheed YF-12.
Data from Lockheed's SR-71 'Blackbird' Family
General characteristics
Crew: 2; pilot and fire control officer (FCO)
Length: 101 ft 8 in (30.97 m)
Wingspan: 55 ft 7 in (16.95 m)
Height: 18 ft 6 in (5.64 m)
Wing area: 1,795 sq ft (167 m2)
Aspect ratio: 1.7
Empty weight: 60,730 lb (27,604 kg)
Gross weight: 124,000 lb (56,200 kg)
Max takeoff weight: 140,000 lb (63,504 kg)
Powerplant: 2 × Pratt & Whitney J58 (JTD11D-20A) afterburning turbojet with compressor bleed bypass, 20,500 lbf (91 kN) thrust each dry, 31,500 lbf (140 kN) with afterburner
Performance
Maximum speed: 2,275 mph (3,661 km/h, 1,977 kn) at 80,000 ft (24,000 m)
Maximum speed: Mach 3.35
Combat range: 3,000 mi (4,800 km, 2,600 nmi)
Service ceiling: 90,000 ft (27,400 m)
Rate of climb: 11,820 ft/min (60 m/s)
Thrust/weight: 0.44
Armament
Missiles: 3× Hughes AIM-47A air-to-air missiles located internally in fuselage bays
Avionics
Hughes AN/ASG-18 look-down/shoot-down fire control radar
#YF12 #SR71 #aircraft
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