Lockheed A-12
| Lockheed A-12 Oxcart | |
|---|---|
 A-12 "Oxcart" (60-6932) in flight |
|
| Type: | Strategic altitude reconnaissance |
| Design country: | |
| Manufacturer: | |
| First flight: |
April 25, 1962 |
| Commissioning: |
1963 |
| Production time: |
1962 to 1964 |
| Number of pieces: |
13 + 2 carriers for D-21 drones |
The Lockheed A-12 Oxcart (English oxcart means "ox cart") was a reconnaissance aircraft made by the US American manufacturer Lockheed . It was developed on behalf of the Central Intelligence Agency (CIA) from the end of the 1950s by the Advanced Development Projects Unit , better known as Skunk works .
Clarence Johnson was the chief designer . The A-12 was made largely of titanium and measures were taken to reduce the radar reflective area . Together with the high speed of over Mach 3 , an aircraft was created that could carry out and survive manned reconnaissance flights over enemy airspace.
13 A-12s were built, 12 of them were operational, one was a training aircraft. The A-12 flew only 29 missions over Vietnam and Korea in 1967 and 1968 with the support of the United States Air Force and were then decommissioned in favor of the further development Lockheed SR-71 Blackbird .
history
Draft & tender
Shortly after the introduction of the Lockheed U-2 , the CIA had serious doubts about its ability to fly over the territory of the Soviet Union unscathed. Therefore, the companies Lockheed and Convair were contacted in early 1958 and asked for a concept for a high-flying high-speed reconnaissance aircraft. Lockheed already had experience building high-flying spy aircraft with the U-2, while Convair had already built the supersonic B-58 Hustler bomber . Other companies also participated. In addition to the designs by Lockheed and Convair, a proposal by Boeing and a design by the United States Navy were examined in September 1958 . Ultimately, however, only Lockheed and Convair stayed in the race. This resulted in a preliminary draft of the A-12 , known as the A-11 , on one side and FISH on the other. These two were rejected by the CIA in the summer of 1959. Lockheed's aircraft had too large a radar cross-section , the air-launched FISH could not be realized because the Air Force did not build the B-58B intended as a carrier aircraft .
As a result, both manufacturers improved their design again, Convair designed the self- launching Convair Kingfish , Lockheed the design A-12 . The two aircraft were presented to a commission made up of representatives from the Department of Defense , the Air Force and the CIA on August 20, 1959 . While Lockheed design easily had better performance and lower costs, which was stealth technology of KING FISH better. Ultimately, Lockheed was chosen because the U-2 was delivered on time and on budget, but Convair hadn't made it with the B-58. With the Skunk Works , Lockheed also had the experience and infrastructure to deal with secret projects, and with Clarence "Kelly" Johnson an experienced chief designer. The only requirement for Lockheed was the further reduction of the radar cross-section by 1960. This went hand in hand with the creation of the code name OXCART .
The improvements made, however, reduced the performance of the Lockheeds A-12 below the announced specifications, so that a subsequent weight reduction while increasing the fuel capacity was necessary. Johnson noted in the project log: “We have no performance margins left; so this project instead of being 10 times as hard as anything we have done, is 12 times as hard. This matches the design number and is obviously right "(Eng .:" We have no more performance reserves; instead of being ten times as difficult as everything we have built so far, this project is twelve times as difficult. That fits the project number and is so obviously correct ”).
On February 11, 1960, the contract for twelve aircraft was finally signed, the cost should amount to 96.9 million US dollars. However, since many new materials, above all titanium , were used, there was a clause in the contract that allowed a new estimate of the costs. This clause was used several times, and the costs were ultimately twice as high as intended.
construction
Construction of the first models to test aerodynamics and radar cross-section began in 1959. The A-12s were built by Lockheed in the halls of the Skunk Works in Burbank , California . The main material was titanium, Johnson decided to use the alloy B-120, which on the one hand had high strength and good heat resistance and was quite light, but on the other hand also very expensive.
August 1st, 1961 was targeted as the delivery date for the first machine. However, since there were problems both with the delivery of the required titanium and with the completion of the engines, this deadline could not be met. The Titanium Metals Corporation, as the supplier of the material, had problems supplying enough titanium in sufficient quality until 1961, so that up to 80% of the material had to be rejected beforehand. But even afterwards there were difficulties in production. Because of the high hardness of titanium, Lockheed had to abandon assembly line production and develop new tools for production.
Since the completion of the engines continued to be delayed, after the completion of the first airframes it was finally decided to temporarily deliver them with the older and far less powerful Pratt & Whitney J75 and to carry out the first test flights. That happened in February 1962.
The main problem with the development of the A-12 was the extremely high temperatures that the high speed brought with it. Parts of the aircraft's outer skin heated up to around 480 ° C (900 ° F ) at Mach 3 . All components had to be adapted to these high temperatures. Lockheed also required high temperature lubricants and hydraulic fluids for the A-12, which ultimately led to the development of synthetic alternatives.
The fuel used was PF-1 , which has a flash point of 60 ° C and a low vapor pressure . Triethylborane was used to ignite the engines and later the afterburner . The fuel was used to cool some components. In order to reduce the radar reflective surface of the afterburner flame, the cesium-containing additive A-50 was added to the fuel during use .
The thermal expansion caused leaks in the integral tanks again and again. These were lined with a sealing compound, which, however, was not particularly durable. The machines leaked permanently, which, however, did not pose a risk due to the low flammability of the fuel.
The windows for the camera bays were also subject to strong temperature fluctuations. In use, they were heated to 260 ° C (500 ° F) outside, while the air conditioning in the camera bay kept the temperature around 66 ° C (150 ° F). The glass had to retain its transparency and not loosen. Ultimately, as a subcontractor to PerkinElmer , Corning Glass Works developed a quartz glass that was ultrasonically welded to the fuselage and met all requirements.
Test flights
The A-12 test flights took place in secrecy at the remote base known as Area 51 on Groom Lake, Nevada . A runway with a length of around 2590 meters (8500 feet) was built there, as well as additional houses and hangars. Since the A-12 could not take off in Burbank due to the short runway, the wings were dismantled and the aircraft was trucked to Nevada, where it was reassembled. After a short, unofficial flight only a few kilometers long on April 25, 1962, the maiden flight took place on April 26. The first official flight in front of Air Force and CIA officers took place four days later and lasted around an hour. On May 2nd, the sound barrier was broken for the first time. Four more A-12s had been delivered by the end of the year, as well as ten of the planned Pratt & Whitney J58 engines . The first flight with two J58 took place on January 15, 1963. Since the test flights were to remain secret, the CIA and Air Force instructed all regional offices of the Federal Aviation Administration and the North American Aerospace Defense Command as early as 1962 to report radar contacts with unidentified, high-speed and high-flying objects only in writing and not to mention them by radio .
The aircraft remained a secret for 5 years, and even the type's operational category remained hidden. In the election year of 1964, the development, also known as the A-11, was revealed to the public, with the President and Secretary of Defense contradicting one another over the role of the aircraft. On February 29, 1964, President Johnson introduced the aircraft as a long-range fighter. Then a veil of secrets was drawn again, only to present the completely new version SR-71 as a strategic reconnaissance aircraft a short time later. On September 30, the YF-12A was presented again. In December 1964, the trade magazine Interavia finally reported that the first SR-71 version of the A-11 aircraft would be delivered in 1965.
By 1965, the major problems that had occurred particularly in the supersonic range had been eliminated; the first long-haul flight was therefore carried out on January 27th. In 100 minutes 2850 miles (around 4587 kilometers) were covered, a total of 75 minutes of the flight took place at Mach 3.1. On November 20, 1965, the acceptance flights took place, which were brought to a successful conclusion.
Calls
The A-12 was first relocated abroad in 1967. President Lyndon B. Johnson wanted more detailed information about the stationing of Soviet anti-aircraft missiles in Vietnam. The CIA suggested the use of the Lockheed A-12, and Johnson agreed. On May 22nd, the first aircraft arrived at Kadena Air Base in Japan. By May 27, two more aircraft reached Okinawa , the unit was declared operational on May 31 and also flew missions for the first time under the code name Operation Black Shield . During the Vietnam War, the A-12 flew over North Vietnam to photograph anti-aircraft missile positions. By the end of the year, 22 more missions had been flown over North Vietnam. The A-12s were repeatedly detected by the North Vietnamese radar and also attacked with anti-aircraft missiles. On October 30, 1967, a total of six surface-to-air missiles were fired at an A-12, three of which came close to the aircraft and a piece of a missile fairing penetrated the right wing of the A-12, but caused no harmful damage.
Six more flights followed in 1968. Two of these flights were not for Vietnam, but North Korea . Their aim was to confirm the takeover of the USS Pueblo (AGER-2) by North Korean naval forces. The pilot Frank Murray succeeded on January 26th.
Operations in the Middle East were also planned . The A-12 should operate from Upper Heyford , Oxfordshire or the Spanish Torrejón de Ardoz and fly over Spain and the Mediterranean to the area of operation. A planned flight route then led over northern Egypt, Israel, Lebanon, western Syria, southern Turkey and Crete.
The planning and monitoring of all operations took place at the CIA headquarters in Langley , Virginia . Since the A-12 often relied on air refueling during its operations , the CIA procured specially converted KC-135Q tanker aircraft from 1961 that could transport the fuel used.
End of the program
In the summer of 1968 the OXCART program was terminated. There were several reasons for this. The larger SR-71 could carry multiple sensor packages such as optical cameras, infrared cameras and high-resolution radar at the same time, while the A-12 could only carry one of these packages at a time. A big problem was that the A-12 missions required a lot more planning than the U-2s they were supposed to replace. A launch site and alternate airfields with long runways had to be found, and tankers with the special fuels used had to be provided. Ultimately, however, it was cost reasons that led to the termination of the OXCART program. Maintaining an A-12 and an SR-71 fleet side-by-side proved expensive, so the choice ultimately fell on the more versatile SR-71 Blackbird .
All A-12 aircraft used were ordered back from Kadena and mothballed in Burbank. The eight still existing machines could hardly serve as a spare parts store, since they were smaller than the Blackbirds , mainly the engines could continue to be used. Today all the remaining copies are on public display.
Follow-up projects
As a follow-up project under the code name ISINGLASS, a boost-glide aircraft reaching Mach 20 at a height of 60 km was proposed and examined by the McDonnell Aircraft Corporation . Since the advantage over spy satellites was small, the project was not pursued in 1967. Instead, the U-2R program, an enlarged version of the U-2 , was launched in September 1966 under the project name IDEALIST and twelve new aircraft were ordered.
Mission profile
As with the U-2, the task of the A-12 was to carry out reconnaissance high above the Soviet Union. The main area of application would have been strategic reconnaissance, i.e. taking pictures of bases and ICBMs. However, it became apparent as early as 1960 that it would probably never fulfill this task. On May 1st of that year the U-2 was shot down by Francis Gary Powers near Sverdlovsk . It was not certain that the much faster A-12 would have been able to escape the new Soviet missiles. But after the incident, the US and the Soviet Union signed an agreement not to operate manned spy flights over each other's territory.
Ultimately, the A-12 was used for tactical battlefield reconnaissance. The target area was flown over and photographed at the maximum speed of more than Mach 3. A one-way flight over the target territory in Vietnam only took around 12 minutes at these speeds.
variants
Two high-speed aircraft were developed from the A-12 OXCART for other purposes, which outwardly hardly differed from OXCART , but none of which was taken over into operational service.
YF-12
The first variant was the Lockheed YF-12 , an interceptor planned for the US Air Force that was supposed to intercept enemy bomber formations far off the coast. Three YF-12 prototypes were built, only one of which still exists.
M-21
Another offshoot was the carrier aircraft Lockheed M-21 for the D-21 - Drone (Project tagboard). It was supposed to bring the drone up to speed and altitude piggyback in order to then launch the D-21 drone at the border of the enemy airspace. Of two test aircraft, one was lost in an accident, which ultimately meant the end of the program. Before that, some D-21s were deployed over the People's Republic of China .
SR-71 Blackbird
Far better known and more successful, however, is the SR-71 Blackbird , which was used as the successor to the A-12 by the CIA and the US Air Force, but was also used by NASA as a test aircraft.
technology
Airframe
The fuselage of the A-12 was around 31 meters long, the wingspan was not quite 17 meters. The vertical stabilizers were just over 5.5 meters high. The total wing area was 170 m². A machine weighed 30,600 kilograms empty, then 53,000 kg when loaded. The roll and pitch control was carried out via elevons on the wing trailing edges.
The fuselage was largely made of titanium and was shaped according to the principles of continuous curvature to reduce the radar signature. Sharp kinks and edges are largely dispensed with, only the so-called "chin kink" remained, as this improved the lift and does not represent a right angle that would reflect a large part of the incident radar radiation back to the transmitter. Since early versions of the A-12 were not yet manufactured with a fuselage according to the continuous curvature, Johnson had to attach small, triangular additional pieces to the engine cowlings and wing noses , which could cover the edges. The vertical stabilizers of four aircraft were mostly made of heat-resistant non-metallic materials and inclined inward by 15 °.
The Pratt & Whitney J58 engines are built into fairings between the fuselage and wing tips so that they are clearly visible from the outside. The fairing is equipped with an extensive system for controlling the air flow to the engine, including the adjustable inlet cone, an air flap on the central body, which was in connection with the outside of the turbine cell, as well as additional air openings at the front and rear, as well as a suction air opening and a third additional air opening directly in front the nozzle. In addition, the outlet nozzle was adjustable, in the area of the cone there was a bleed air opening with which cooling air for the engine could be conveyed from the shock wave in the inlet cone.
The turbojet engine became a ramjet . Only through the ramjet function could the A-12 reach speeds of over Mach 3.
The avionics consisted of the usual instruments. In addition, an inertial navigation system was used for navigation .
As a special feature, gold-coated fuel tanks were also reported in Time magazine in 1964; the coating with gold, which conducts heat well, should therefore dissipate the heat.
Electronic countermeasures (ECM)
Although the radar reflection was reduced in the course of the A-12 program, Soviet radar was always able to detect the A-12. In order to detect enemy radar systems and to irritate anti-aircraft missiles , the A-12 therefore had an ECM system .
A system called BLUEDOG recorded the guidance signals transmitted in the L-band to a radar-guided S-75 anti-aircraft missile in an earlier phase of flight and then re-emitted the same guidance signals via a 20 kW transmitter as soon as the missile approached the A-12. As a result, the S-75 could no longer receive signals from the control system in the end phase of the flight and instead received the no longer current control signals from BLUEDOG. BLUEDOG was able to send wrong signals to 27 S-75s at the same time. Two systems were also used to detect radar radiation (PIN PEG) and to prevent radar measurements from sending false signals (BIG BLAST or MAD MOTH). BIG BLAST could be activated automatically by both BLUEDOG and PIN PEG and, as a noise jammer, sent interference signals with a power of 200 W in the S-band and 400 W in the C-band . The alternatively used MAD MOTH, however, works as a deceptive jammer , i.e. H. it generated false signals.
Sensors
Radio signal receiver
For telecommunications intelligence and signals intelligence , radio signals with frequencies between 50 MHz and 8 GHz with a bandwidth of 30 kHz were recorded in analog form. The broadband Crystal Video ELINT Receiver and Recorder used for this was manufactured by TRW Systems, Inc., which later became part of Northrop Grumman .
Cameras
As early as 1959, PerkinElmer , Eastman Kodak and Hycon entered a competition to develop the cameras. PerkinElmer then developed a camera called Type I. The stereo camera captured a 114 kilometer (71 mile) wide strip with a stereo overlap of around 30% using a 45 centimeter lens. The resolution was around 30 centimeters. A 6.6-inch film was used as the film, of which around 1,500 meters were on board. Kodak's Type II camera also took 30% stereo images of 97 kilometers (60 miles) wide strips, here with a 53 centimeter lens, which was sufficient for a resolution of the ground objects of around 43 centimeters. Around 2500 meters of 8-inch film were on board as footage. Hycon developed a camera based on the B camera successfully used in the U-2 . The 122-centimeter lens photographed 66 kilometers (41 miles) wide with a resolution of 20 centimeters on 9.5-inch film, of which there were over 3,600 meters on board.
Since all cameras had their advantages, all three proposals were accepted by the CIA and cameras were purchased for the A-12. In 1964 a fourth possible camera was added. Texas Instruments also adapted the FFD-4 thermal imaging camera developed for the U-2 for use in the A-12.
The films were developed in laboratories of the CIA and then evaluated by CIA employees.
radar
Instead of a camera could also with a side-looking 12 A- Radar ( Side Looking Airborne Radar be equipped) APQ-93rd The radar achieved a resolution of 4 m to 6 m and was able to scan and record an area of 35 km × 2500 km during a flight. The radar recordings were saved on film and evaluated with an optical correlator after the flight.
Pilots
The A-12 was piloted by a single pilot. For training purposes, the machine with the serial number 60-6927 had a second cockpit that could accommodate the flight instructor behind the actual pilot.
For safety reasons, the pilots wore a pressure suit with their own cooling, oxygen supply and pressure control.
Because the cockpit was fairly cramped, the pilots could not be taller than 6 feet (1.82 meters) and weigh less than 175 pounds (80 kilos). The CIA recruited the pilots from the US Air Force. After their selection by the CIA, they underwent another medical and psychological examination. Ten of the first eleven recruited pilots later rose to the rank of general .
Fleet overview
Inventory list
| Aircraft number | serial number | Starts | Flight hours | Whereabouts |
|---|---|---|---|---|
| 121 | 60-6924 | 332 | 418.2 | Blackbird Airpark in Palmdale, California |
| 122 | 60-6925 | 122 | 177.9 | Intrepid Sea-Air-Space Museum in New York City, New York |
| 123 | 60-6926 | 79 | 135.3 | Loss on May 24, 1963 |
| 124 | 60-6927 | 614 | 1076.4 | California Science Center in Los Angeles, California ("Titanium Goose" jet trainer) |
| 125 | 60-6928 | 202 | 334.9 | Loss on January 5, 1967 |
| 126 | 60-6929 | 105 | 169.2 | Loss on December 28, 1965 |
| 127 | 60-6930 | 258 | 499.2 | United States Space & Rocket Center in Huntsville, Alabama |
| 128 | 60-6931 | 232 | 453 | CIA headquarters in Langley, Virginia |
| 129 | 60-6932 | 268 | 409.9 | Loss on June 4, 1968 |
| 130 | 60-6933 | 217 | 406.3 | San Diego Aerospace Museum in Balboa Park, San Diego, California |
| 131 | 60-6937 | 177 | 345.8 | Southern Museum of Flight in Birmingham, Alabama. |
| 132 | 60-6938 | 197 | 369.9 | USS Alabama Battleship Museum in Mobile, Alabama |
| 133 | 60-6939 | 10 | 8.3 | Loss on July 9, 1964 |
| 134 | 60-6940 | 80 | 123 | (Lockheed M-21 / D-21), Museum of Flight in Seattle, Washington |
| 135 | 60-6941 | 95 | 152.7 | (Lockheed M-21 / D-21), lost July 30, 1966 |
Incidents
A total of six of the fifteen A-12s built were lost in accidents and two pilots died.
- On May 24, 1963, the aircraft with the registration number 60-6926 was the first to be lost. The pilot Ken Collins was on a flight to test the navigation system when the readings were obviously wrong, which caused the aircraft to stall . Collins was able to save himself with the ejection seat . To cover up the accident, it was stated that the crashed machine was a Republic F-105 Thunderchief . It was later found out that the cause of the instrument failure was an icing over of the pitot tube .
- On July 9, 1964, # 60-6939 crashed on approach when a valve for the control of the Elevons jammed. The pilot Bill Park was able to get out and survived the accident.
- On December 28, 1965 # 60-6929 also crashed. Only a few seconds after take off, the pilot Mel Vojvodich realized that he had no control over his A-12 and he got out; he was largely unharmed. The reason was the incorrect wiring of the stability augmentation system , which resulted in the pitch and yaw commands being executed incorrectly.
- On January 5, 1967, # 60-6928 was lost. After a fuel valve worked incorrectly, the A-12 ran out of fuel a few minutes before landing and the pilot Walter Ray had to get out of the vehicle using an ejector seat. However, since the mechanism that separates the seat from the pilot after disembarking failed, Ray was killed in the impact.
- On June 5, 1968, # 60-6932 crashed after taking off from Kadena. After the right engine had been changed, the flight should serve to check the new unit. 19 minutes after take-off, telemetry data from the aircraft initially showed extremely high temperatures in the engine and a drop in the flow of fuel into this engine. Then Kadena got the message that the aircraft had fallen below 68,500 feet. This was the last communication received from # 60-6932. The aircraft was written off as a total loss, the pilot Jack Weeks declared dead. The accident occurred between Okinawa and the Philippines over the South China Sea .
Technical specifications
| Parameter | Data |
|---|---|
| crew | 1 |
| length | 31.26 m |
| span | 16.97 m |
| Wing area | approx. 170 m² |
| Wing extension | 1.69 |
| Wing loading | 320 kg / m² (nominal) |
| height | 5.64 m |
| Empty mass | 30,600 kg |
| normal takeoff mass | approx. 53,000 kg |
| Top speed | Mach 3.35 (3,560 km / h) |
| Rate of climb | 60 m / s |
| Maximum altitude | approx. 29,000 m |
| Range | approx. 4,000 km (without refueling) |
| Armament | - |
| Engine | 2 × Pratt & Whitney J58 jet engines with afterburner and 144.57 kN each of thrust |
| Thrust-to-weight ratio | 0.56 (nominal) |
literature
- James Goodall: Lockheed's SR-71 "Blackbird" Family - A-12, F-12, D-21, SR-71. Midland 2003; ISBN 978-1-85780-138-5
- Jeannette Remak, Joe Ventolo Jr .: A-12 Blackbird Declassified. Zenith Press 2002; ISBN 978-0-7603-1000-7
Web links
- CIA document The U-2's Intended Successor: Project Oxcart, 1956-1968. released 1994
- Roadrunners Internationale with detailed information on A-12, U-2 and YF-12
- A-12 on the California Museum of Science and Industry pages . (engl.)
- LATimes report on Area 51 and OXCART (eng.)
Individual evidence
- ^ CIA document The U-2's Intended Successor: Project Oxcart, 1956–1968. Section The oxcart Contract , there quoted from "Archangel log", 21 January 1960 Johnson, (Engl.)
- ^ CIA document The U-2's Intended Successor: Project Oxcart, 1956–1968. Section The oxcart Contract (Engl.)
- ^ A b The A-11: New US Jet is Fastest and Highest , Time, March 13, 1964, p. 25
- ↑ America's fastest and most discussed military aircraft: YF-12A , Interavia No. 12/1964, p. 1806
- ^ CIA document The U-2's Intended Successor: Project Oxcart, 1956–1968. Section Summery of the OXCART Program (Engl.)
- ↑ A12 Oxcart Detachment on wvi.com (Engl.)
- ↑ A-12 OXCART Reconnaissance Aircraft Documentation, OXCART CONCEPTUAL ROUTE. CIA , Jan 1, 1991, archived from the original on Aug. 1, 2012 ; Retrieved December 30, 2009 .
- ↑ A-12 OXCART Reconnaissance Aircraft Documentation, Comparison of SR-71 and A-12 Aircraft. CIA , September 26, 1967, archived from the original on August 2, 2012 ; Retrieved January 1, 2010 .
- ↑ A-12 OXCART Reconnaissance Aircraft Documentation, Program Progress Report, Attachment II, ISING LASS. CIA , June 30, 1967, archived from the original on March 23, 2012 ; Retrieved January 2, 2010 .
- ↑ A-12 OXCART Reconnaissance Aircraft Documentation, Program Progress Report, Attachment II, IDEALIST. CIA , June 30, 1967, archived from the original on March 23, 2012 ; Retrieved January 2, 2010 .
- ^ CIA document The U-2's Intended Successor: Project Oxcart, 1956–1968. Section First A-12 deployment: Operation Black Shield (Engl.)
- ↑ D-21 Drone - Tagboard / Senior Bowl. (No longer available online.) In: spyflight.co.uk. Archived from the original on November 5, 2012 ; Retrieved February 19, 2013 .
- ↑ A-12 OXCART Reconnaissance Aircraft Documentation, PFIAB Submission from Deputy for Research and Development (OXCART, IDEALIST, ISINGLASS). CIA , July 10, 1967, archived from the original on July 31, 2012 ; Retrieved January 2, 2010 .
- ↑ A-12 OXCART Reconnaissance Aircraft Documentation, OXCART Facts, BLUEDOG. CIA Nov 16, 1972, archived from the original on Aug 2, 2012 ; Retrieved December 30, 2009 .
- ↑ A-12 OXCART Reconnaissance Aircraft Documentation, OXCART Facts, PIN PEG & BIG BLAST. CIA November 16, 1972, archived from the original on August 4, 2012 ; Retrieved December 30, 2009 .
- ↑ A-12 OXCART Reconnaissance Aircraft Documentation, OXCART Facts, OCART AVIONICS. CIA Nov 16, 1972, archived from the original on Aug 5, 2012 ; Retrieved December 30, 2009 .
- ↑ A-12 OXCART Reconnaissance Aircraft Documentation, OXCART Facts, System VI. CIA Nov 16, 1972, archived from the original on Aug 2, 2012 ; Retrieved December 30, 2009 .
- ↑ A-12 OXCART Reconnaissance Aircraft Documentation, OXCART Facts, Camera. CIA Nov 16, 1972, archived from the original on Aug 5, 2012 ; Retrieved December 30, 2009 .
- ↑ A-12 OXCART Reconnaissance Aircraft Documentation, Program Progress Report, Side Looking Radar system. CIA , July 31, 1967, archived from the original on August 1, 2012 ; Retrieved January 2, 2010 .
- ^ CIA document The U-2's Intended Successor: Project Oxcart, 1956–1968. Section Choosing Pilots for OXCART (Engl.)
- ↑ a b A-12, YF-12, SR-71 Blackbird crashes on area51specialprojects.com (engl.)
- ^ List of all USAF serial numbers 1960, with all A-12 ( Memento from January 31, 2012 in the Internet Archive )
