Yet, nothing helped. The two inlets on each A-12 never seemed to match.
This resulted in multiple unstarts on each flight. Even a special task force could not find a solution.
Finally, Johnson decided to scrap the existing pneumatic system and replace it with an electronic unit. Even this had problems. During a ground test, the pilot used the radio; this caused a false signal in the electronics and the spike retracted. Once the electronic interference problem was solved, the system proved far more effective, although at the price of much greater maintenance time. The electronic system was retrofitted to the existing aircraft and all new A-12s from Article 129 onward.
The unstart was only the most spectacular of the A-12's problems. The J58 engines' main shaft had to be redesigned to compensate for the high temperatures. The engine mounting points were also changed. The frictional heating raised the cockpit temperature to 130 degrees. On one flight, the control stick became so hot Park had to change hands to keep from burning himself. Changes in the air-conditioning system reduced the cockpit temperature to a 'warm but livable' level.[155]
Another change caused by the heat was in the A-12's finish. The prototype had flown in a bare-metal finish without any markings. By late 1963, the edges of the chines, the spikes, and the cockpit area were painted in a heat-resistant black paint. This reduced the internal heating of the airframe.
The aircraft also received a full set of national markings. Finding paint that could withstand exposure to high temperatures and fuel was, like everything about the plane, difficult.
A continuing problem was foreign-object damage. Nuts, bolts, clamps, and other debris were sometimes left in the nacelles during construction.
When the engines were run up, the debris would be sucked in and damage the engines.[156] In one case, an inspector's flashlight caused $250,000 damage. The engines would also suck rocks, asphalt pieces, and other debris off taxiways and runways.
Changes in procedures were made, such as cleaning the nacelles with 50-horsepower vacuums, then rolling them and listening for anything rattling around.[157] Taxiways and other areas were swept to remove any debris. After landing, covers were put on the inlets and locked with a 'great big pad-lock.' They would be unlocked only after the pilot was strapped in the cockpit for the next flight.[158]
Finally, after fifteen months of painful flight testing, the A-12 was ready to attempt Mach 3. The flight was made on July 20, 1963, by Lockheed test pilot Louis Schalk. Additional Mach 3 flights were made during the summer and fall.[159] In November, the design speed of Mach 3.2 was reached. It had taken sixty-six speed-buildup flights to go from Mach 2 to Mach 3.2.[160]
In these buildup flights, the peak speed was held only momentarily. The next step was sustained Mach 3 flight. This was much more demanding than a brief dash, as the heat would soak into the plane's structure. Lockheed test pilot James Eastham made the first sustained Mach 3 flight on February 3, 1964. The plan envisioned a peak speed of Mach 3.16, which would be held for ten minutes. Eastham began the speed run at 78,000 feet. By the end of the run, the A-12 had climbed to 83,000 feet. Eastham cut the throttles and landed at Groom Lake, the end of what seemed to be a completely successful flight. Lockheed's senior flight test engineer, Glen Fulkerson said, 'Turn it around, we'll fly it tomorrow.' But it would be another eight weeks before the A-12 would fly again.
During the postflight inspection, it was found that the plane had been 'burned to a crisp.' There had been an error in the air-speed system: rather than Mach 3.16, the plane had actually approached Mach 3.3. The heating had been far higher than predicted. The wiring had been damaged by 800-degree F temperatures. Nearly all the hydraulic fluid had been lost from the four flight-control systems — only one-half gallon remained out of the original seven and a half gallons. Eastham recalled years later, 'About fifteen more seconds at speed and I think I would have been out walking.'
The engineers did not know where the h y d r a u l i c fluid had gone. There were no leaks in the ground tests. Finally they used heat lamps to raise the temperature to 600 degrees F. As the joints expanded, the 3,300 psi hydraulic fluid literally flowed out. The plane was surrounded by smoke from the vaporizing fluid. Once the hydraulic system cooled, the leaks closed up.
The test pilots insisted a hydraulic fluid quantity gauge be added before another Mach 3 flight was made. Article 121 was fitted with the gauges (the only A-12 so equipped). After several maintenance flights, they were ready to try again.
The A-12 took off at first light with Eastham at the controls for a thirty-minute flight. During the Mach 3 run, no leaks appeared and the communications checks were successful. Eastham cut the throttles and descended toward a landing. As the A-12 turned onto the downwind leg, the left hydraulic system failed. Eastham thought, 'Oh boy, here we go again.'
Despite the failure, he landed successfully. A postflight inspection found that the brake manufacturer had put an aluminum plug in the hydraulic system. The high temperature and pressure had blown it out. At the next Monday morning technical meeting, Johnson asked, 'How the hell did a piece of aluminum get in this plane?'[161]
By the end of 1963, nine A-12s were at Groom Lake. They had also been joined by a derivative, the YF-12A interceptor. As the Oxcart program got under way, Johnson realized the basic A-12 airframe had a tremendous growth potential. The first derivative was to be an air-defense interceptor. The aircraft would use its Mach 3 speed to fly out to incoming Soviet bombers, which could then be destroyed well before they neared their targets.
This plane was the ultimate expression of a trend in fighter development under way since the early 1950s. The traditional fighter, with an emphasis on maneuverability, had been replaced by all-missile-armed interceptors.
They were not meant to attack other fighters, but rather large, nonmancu-vering bombers. It was widely accepted that any future war would be a nuclear 'high noon' with the Soviet Union. There would be no 'limited wars' such as Korea. Accordingly, fighter aircraft were oriented toward either nuclear delivery or interception. Ultimately, it was thought, manned aircraft would be replaced by guided missiles.
On March 16 and 17, 1960, Johnson had met in Washington, D.C., with Air Force Brig. Gen. Howell M. Estes Jr. and Courtlandt Perkins, Air Force Secretary for Research and Development, to discuss the interceptor. They were impressed and told Johnson to meet with Gen. Marvin Demler at Wright-Patterson Air Force Base. On October 31, 1960, Lockheed received a contract to build three of the Improved Manned Interceptors. The program was kept separate from the A-12. The planes were built in the same building that held the A-12 assembly line but were screened off to prevent anyone working on one project from knowing about the other.[162]
The A-12's nose and forward chines were cut back and replaced by a bulky-looking radome and two infrared scanners. The aircraft carried a Hughes pulse-doppler AN/ASG-18 radar and fire-control system; this could detect and track aircraft flying at low altitude and long range. The aircraft carried AIM-47 Falcon missiles with either a high-explosive or a low-yield nuclear warhead. The missile had a range of 120 miles and was carried internally. The fuselage underside was redesigned to accommodate the three missile bays. A second seat for a radar intercept officer (RIO) was added to the Q-bay behind the pilot's cockpit. The addition of the radome reduced high-speed stability, but this was corrected with the addition of two fins under the nacelles and a large retractable fin under the rear fuselage.[163]
In early January 1961, several months after the go-ahead was given for the interceptor, Johnson proposed two more A-12 derivatives — the B-12 strategic bomber and the R-12 reconnaissance aircraft. The B-12 design envisioned the nuclear weapons being carried in fuselage bays. The B-12 could carry four short-range attack missiles (SRAMs), six strike missiles, or twelve guided bombs. Targets would be picked up by radar in an A-12-like pointed nose. A second crewman would target the weapons. The B-12's mission would be 'cleanup' after the initial ICBM strike. Targets in Eastern Europe and the western Soviet Union could be hit, to include command posts, MiG 25 air bases, missile sites, submarine pens, and SAM sites. For the R-12 reconnaissance version, the weapons would be replaced by cameras, radar, and electronic intelligence (ELINT) equipment. To control the reconnaissance gear, a second crewman was added.
The R-12's wartime mission would be poststrike reconnaissance. Internal stowage of the weapons and reconnaissance equipment would keep weight down and preserve the low radar cross section. A pod, like that on the B-58, was not considered.
