SR-71

"Behave or Be Careful"

A-12/SR-71 BLACKBIRD

The A-12/SR-71 is the fastest, highest flying, air-breathing aircraft in the world. It flies at mach 3.5 and above 80,000 feet. The SR-71 is affectionately called HABU (for a poisonous snake in Okinawa) [the A-12 aircraft was first deployed there] by the pilots who fly her.

Kelly Johnson started working on a mach three design in early 1957, and called the design Archangel. The design was for a mach 3 aircraft that flew between 90,000 and 95,000 feet. A development contract for an aircraft called A-12 was let to the Lockheed Skunk Works on August 29, 1959. The propulsion system dominated the design the engine nacelles were larger in diameter than the fuselage. The propulsion system consisted of three main components; the modified Pratt and Whitney J-58 engine; inlet and control system and self-actuating airframe mounted ejector nozzle. One of the stickiest problems of design was to try and build an aircraft with as small a radar cross section (RCS) as possible to prevent radar detection. The A-12 structure was comprised of 85% titanium and 15% composite materials. Never before had anyone anywhere tried to build an aircraft structure from titanium. Titanium parts are 30% lighter than the equivalent strength steel part, great strength properties at high temperatures, scratches easily, extremely hard to machine, and very costly due to world wide scarcity.

YF-12A INTERCEPTORS:

During the development of the A-12 the Air Force asked if the Skunk Works could modify several of the A-12s into a high altitude interceptor. Kelly said yes, that was not a problem that A-12 aircraft would be modified by installing the Hughes AN/ASG-18 fire control radar, design weapons bays to carry two Hughes GAR-9/AIM-47 missiles internally and space for a second seat for the fire control system operator. A ventral fin was attached under each nacelle and a folding ventral fin was mounted under the fuselage for added stability due to flight characteristics impacted by the revised nose and cockpit area to house the massive radar. This version was labeled AF-12 and later reidentified by the Air Force as YF-12.