NASA 

National Aeronautics and

Facts

Space Administration

Dryden Flight Research Center 

P.O. Box 273

Edwards, California 93523 

Voice 661-258-3449 

FAX 661-258-3566 

pao@dfrc.nasa.gov FS-2002-09-047 DFRC 

THE LOCKHEED YF-12 

YF-12 in flight. (NASA photo EC72-3150) 

The YF-12 "Blackbird" was an experimental fighter-interceptor version of the Lockheed A-12 reconnaissance aircraft. In 

Air Force flight tests on May 1, 1965, the YF-12 set a speed record of 2,070.101 mph and an altitude record of 80,257.65 

feet. First publicly displayed at Edwards Air Force Base in 1964, the YF-12 was never adopted by the military as an 

operational aircraft. It was, however, a precursor to the SR-71 Blackbird reconnaissance plane. 

Two YF-12s were flown in a joint Air Force-NASA research program at the NASA Flight Research Center (after 1976, 

the NASA Dryden Flight Research Center) between 1969 and 1979. A third shared plane, piloted primarily by the Air 

Force, was lost to an in-flight fire in 1971. 

The YF-12 allowed NASA researchers at all four of the agency's aeronautical centers (Langley, Lewis [now Glenn], and 

Ames as well as the Flight Research Center) to study the thermal, structural, and aerodynamic effects of sustained, highaltitude, Mach 3 flight. Painted flat black, the YF-12 was fabricated primarily from titanium alloy, which enabled it to 

withstand skin temperatures of over 500o F. 

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Work on the YF-12 began in secret in the late 1950s at the 

Lockheed Advanced Development Projects office, better as 

known the "Skunk Works," in Burbank, Calif. Flight data 

remained classified long after President Lyndon Johnson 

announced the plane's existence on Feb. 29, 1964. After the 

announcement, the plane received the Air Force designation YF-12A. 

(The "Skunk Works" was the unofficial designation of 

Lockheed's secret development entity in Burbank. It was 

located near a plastics plant that exuded a rather strong 

odor. Since the engineers were also brewing up their secret 

designs, the "Skonk Works" in Al Capp's comic strip "L'il 

Abner," where Kickapoo Joy Juice was made, seemed an 

appropriate designation. However, it was changed to Skunk 

Works to avoid plagiarism.) 

Although it yielded large amounts of research data, the YF12 program was terminated in the late 1970s when NASA's 

research agenda shifted from speed to efficiency. During its 

nine-year life, the YF-12 research program logged 297 

flights in the joint NASA-Air Force program and approximately 450 flight hours. 

Only one YF-12 remains in existence. It is displayed at the 

U.S. Air Force Museum at Wright-Patterson Air Force

Base in Dayton, Ohio. 

The Development of the “Blackbirds” 

In 1959, Lockheed began work on the design of a longrange, high-altitude plane, then known as the A-11. It was a 

Cold War project. Heading the project team was Clarence 

“Kelly” Johnson, Lockheed’s Vice President for Advanced 

Development Projects. Johnson had previously led the 

development of the U-2 spy plane. Five years after work 

began on the A-11, on February 29, 1964, President 

Lyndon Johnson told reporters that the aircraft (by that time 

modified to the A-12 production version with a reduced 

radar cross section) had attained speeds of over 2,000 mph 

and altitudes of more than 70,000 feet in tests at Edwards 

Air Force Base. 

The Air Force YF-12 flight test program lasted until 1966 

and was assigned to the 4786th Test Squadron at Edwards. 

The team of Col. Robert L. Stephens and Lt. Col. Daniel 

Andre took the plane to the record altitude and speed noted 

above. 

On July 24, 1964, President Johnson announced that 

Lockheed was also developing “a long-range advanced 

strategic reconnaissance plane for military use, capable of 

world-wide reconnaissance for military operations.” That 

plane, the SR-71, was a modified version of the YF-12. 

Although heavier than the YF-12, the SR-71 “spy plane” 

had a longer range and was capable of strategic surveillance. This spy plane was adopted by the military and the 

YF-12 was not. Usurped by a demand for its successor’s 

capabilities, the experimental YF-12’s were essentially 

shelved until 1969, when two of them were deployed as 

research vehicles at the NASA Flight Research Center. 

Program Managers 

Engineer Gene Matranga led a NASA research team that 

had begun studying Blackbird data in 1967. He continued 

to manage the project after the planes were acquired by 

NASA and the YF-12 project was formally initiated in 

1969. In its later years, the YF-12 program had two other 

NASA managers, Ming Tang and Berwin Kock. 

NASA YF-12 Crews 

The YF-12 carried a crew of two - a pilot and a flight 

engineer (in Air Force parlance and practice, a fire control 

officer). Research pilots Fitzhugh Fulton and Donald 

Mallick flew NASA's YF-12 flights at the NASA Flight 

Research Center from 1970 to 1979, with several other 

pilots performing familiarization and a few research flights. 

The flight engineers on NASA's YF-12 crews were Victor 

Horton and Ray Young. Air Force crews also conducted 

testing. 

Under its research agreement with NASA, the Air Force 

provided the agency with two YF-12As in 1969. On June 

24, 1971, one of the planes experienced an in-flight fuel 

line failure that led to a fire in the right engine. Unable to 

save the smoking aircraft, Air Force pilot Lt. Col. Ronald 

Layton and fire control officer Major Billy A. Curtis 

ejected and were not injured, but the YF-12A was lost in a 

fiery explosion in the desert. The plane was replaced by a 

"YF-12C." The YF-12C (so-called) differed from the YF12A in that the A-model had a round nose while the Cmodel had its chine carried forward to the nose of the 

airplane (see three-views below). There were other differences in internal and external configuration, but the two 

aircraft shared common inlet designs, structural concepts, 

and subsystems. 

In fact, the "YF-12C" was a then-secret SR-71A (serial no. 

64-17951) given the NASA tail no. 60-6937. The reason for

this bit of subterfuge lay in the fact that NASA, while

flying the YF-12A interceptor version of the aircraft, was

not allowed to possess the strategic reconnaissance version

for some time. The bogus tail number actually belonged to

a Lockheed A-12 (serial no. 60-6937), but the existence of

the A-12 remained classified until 1982. The tail number

06937 was selected because it followed in the sequence of

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tail numbers assigned to the three existing YF-12A aircraft: 

06934, 06935, and 06936. 

The History of NASA’s YF-12 project 

On July 18, 1969, NASA and the Air Force announced 

joint involvement in a YF-12 research program. The 

agendas differed, with the Air Force focusing on combat 

“YF-12C” (foreground) and YF-12A in flight. (NASA photo 

ECN-4775) 

research and NASA engineers initially focusing on a study 

of flight loads and structural heating. Much of the NASA 

research was concerned with the viability and development 

of supersonic cruise aircraft. Two YF-12As (tail numbers 

935 and 936) were removed from Air Force storage for the 

program. On December 11, 1969, 935 successfully made its 

first flight as a NASA-USAF research plane and inaugurated the program. On June 24, 1971, 936 experienced the 

fuel line failure described above. 

Unless grounded for maintenance or modification, the YF12s flew nearly every week for most of the program's 

lifespan. The fiery end of 936 on the desert floor was the 

program's only crash, but flight crews were forced to make 

emergency landings at least twice because of in-flight 

problems. The planes were also prone to an airflow problem involving the engine inlets called an "unstart," which 

caused a thrust imbalance and resulted in violent yawing. 

The YF-12's ability to sustain a cruise speed of greater than 

Mach 3 allowed NASA to expand its research capabilities. 

A large amount of flight research was performed in aerodynamics, propulsion, controls, structures, subsystems and 

other areas such as the physics of the upper atmosphere, 

noise tests and measurements, and handling qualities. The 

YF-12 flight research data was augmented by a series of 

wind tunnel tests, laboratory experiments, and analyses. As 

a result, the combined ground/flight research generated vast 

amounts of information that was later incorporated into the 

design of other supersonic aircraft. The program yielded 

over 125 technical reports. 

YF-12 flight tests included propulsion studies, investigations of a flight path oscillation known as phugoid, studies 

of the plane's loads and handling capabilities, and performance tests that involved flights with the ventral fin 

removed. Other research included the use of attached vanes 

to investigate airflow and wind gusts, studies of jet wake 

dispersion, engine stalls, elevation-hold at high Mach 

speeds, boundary layer noise, and the effect of a boattail 

design on drag. 

The program was ordered terminated in 1977, but NASA 

used some residual funding to keep the project alive into 

1979. Plane 935 made its last NASA flight on October 31, 

1979. On November 7, 1979, it was ferried by an Air Force 

crew to the Air Force Museum at Wright-Patterson Air 

Force Base in Dayton, Ohio. 

The Cold Wall 

Because air friction subjected the plane to extreme heat 

during flight, the YF-12 was also used to study hightemperature phenomena unrelated to the plane itself. 

Perhaps the most significant of these studies was the Cold 

Wall Experiment, which involved exposing a cooled 

cylinder to the friction and heat of a Mach 3 environment. 

The cylinder, which was hollow, equipped with sensors, 

and mounted beneath the aircraft, was cooled with liquid 

nitrogen and insulated from the heat that was generated 

during flight. When the plane neared Mach 3, a primer cord 

YF-12A 06935 with insulated hollow cylinder used on the Cold 

Wall Experiment. (NASA photo ECN-4777) 

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was used to blow the insulation from the frigid cylinder. 

Temperature, pressures, and friction readings from the 

cylinder in flight were compared with information developed from theoretical analysis and wind-tunnel simulation. 

The findings were a major achievement in fluid dynamics 

research. 

Thermal Loads Research 

To measure the thermal loads on the YF-12 required some 

extraordinary ground tests. At the supersonic speeds the 

aircraft achieved, high temperatures produced by friction 

with the atmosphere made it difficult to separate the 

aerodynamic from the purely thermal effects upon the 

airplane. As a result, the Flight Research Center conducted 

one of the most complex series of tests ever done on an 

aircraft, combining flight and ground-facility techniques 

and resources. In the Thermal Loads Facility a YF-12A 

Mach 3 heating simulation collected an enormous data 

base. This led to methods for separating the aerodynamic 

and thermal forces operating on an aircraft - a capability 

that will be of great importance for the design, structural 

integrity, and safety of future supersonic and hypersonic 

aircraft. 

Remarkably, this research still supports one of the ten goals 

of NASA's Office of Aeronautics and Space Transportation 

Technology by providing design tools for the next generation of aircraft. In addition, with respect to the YF-12A 

alone, the thermal calibration on the ground corrected highMach-number loads data for adverse thermal effects, which 

frequently proved to be large and were always significant. 

YF-12 forebody heater undergoing a lamp check in the Thermal 

Loads Facility.(NASA photo EC71 2789) 

Specifications 

The YF-12A (tail number 935, serial number 60-6935) has 

a wingspan of about 55 feet 6 inches. and a length of about 

101 feet 8 inches. It is roughly 18 feet 4 inches high. The 

plane's maximum loaded weight was 127,000 pounds. 

It derived its power from two Pratt & Whitney J58s, each 

with 32,000 pounds of thrust (as rated at sea level) with 

afterburners. However, a significant portion of the thrust as 

the aircraft neared Mach 3 speeds came from the supersonic shock wave captured within each engine inlet and 

exited through the engine nozzles. 

The YF-12 carried a two-person crew, had a maximum 

Three-view of YF-12A. 

Three-view of “YF-12C.” 

speed of Mach 3.2 and a range of more than 2,000 miles. 

Its service ceiling was above 80,000 feet. 

Pilots in the Joint NASA/USAF Program 

Maj. William J. Campbell, USAF 

William H. Dana, NASA Dryden Flight Research 

Center (DFRC) 

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Einar K. Enevoldson, NASA DFRC Francillon, Rene J. Lockheed Aircraft since 1913. 

Maj. Mervin L. Evenson, USAF Annapolis, MD : Naval Institute Press, 1987. 

Fitzhugh L. Fulton, NASA DFRC 

Stephen D. Ishmael, NASA DFRC Hallion, Richard. On the Frontier : Flight Research at 

Lt. Col. Calvin F. Jewett, USAF Dryden, 1946-1981. Washington, DC : NASA SPGary E. Krier, NASA DFRC 4303, 1984. 

Lt. Col. Ronald J. Layton, USAF 

Donald L. Mallick, NASA DFRC Jane’s All the World’s Aircraft, 1970-1971. John W. R. 

John A. Manke, NASA DFRC Taylor, ed. New York: McGraw-Hill. 

Thomas C. McMurtry, NASA DFRC 

Col. Joseph W. Rogers, USAF Jenkins, Dennis R. Lockheed SR-71/YF-12 Blackbirds. 

Col. Hugh C. Slater, USAF North Branch, MN: Specialty Press, 1997. 

Col. James V. Sullivan, USAF 

Michael R. Swann, NASA DFRC Kock, Berwin M. “Overview of the NASA YF-12 

Program,” YF-12 Experiments Symposium, Vol. 

Fire Control Officers/Test Engineers and Affiliation 1. 3 vols.; Washington, DC: NASA CP-2054,

1978.

Lorenzo C. Barnett, NASA DFRC 

Maj. Billy A. Curtis, USAF Quinn, Robert D. and Frank V. Olinger. “Flight 

Maj. William J. Frazier, USAF Temperatures and Thermal Simulation RequireMaj. Gary I Heidelbaugh, USAF ments,” NASA YF-12 Flight Loads Program. 

Victor W. Horton, NASA DFRC Washington, DC: NASA TM X-3061, 1974, pp. 

Col. R. Uppstrom, USAF 145-183.

Maj. Sammel M. Ursini, USAF 

William R. Young, NASA DFRC The US Air Force Museum http://www.wpafb.af.mil/ 

museum/an12.htm 

Sources 

Wallace, Lane E. Flights of Discovery : 50 years at the 

The Dryden Historical Reference Collection, including NASA Dryden Flight Research Center . Washinga flight log compiled by Peter Merlin. ton, DC : NASA SP-4309, 1996. 

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