Although the Lockheed F-117A stealth fighter is almost certainly NOT in the original fighter sequence of designations, the end of this particular sequence is perhaps most apt for a discussion of this unusual warplane, most of the details of which are still highly classified.
The F-117A was the first warplane to be specifically designed from the outset for low radar observability. The Lockheed Advanced Development Company (better known as the "Skunk Works") began working on stealth as far back as the late 1950s, and low radar observability had played a role in the design of the A-12/YF-12/SR-71 series of Mach 3+ aircraft.
During 1975, Skunk Work engineers began working on an aircraft which would have a greatly reduced radar cross section that would make it all but invisible to enemy radars, but would nevertheless still be able to fly and carry out its combat mission. The technique that they came up with was known as faceting, in which the ordinarily smooth surface of the airframe is broken up into a series of trapezoidal or triangular flat surfaces arranged in such a way that the vast majority of the radar incident on the aircraft from a source will be scattered away from the aircraft at odd angles, leaving very little to be reflected directly back into the receiver. An additional reduction in radar cross section was to be obtained by covering the entire surface of the aircraft with radar absorbent material (RAM). One of the disadvantages involved in the use of faceting on aerodynamic surfaces was that it tended to produce an aircraft which was inherently unstable about all three axes --- pitch, roll, and yaw.
In early 1977, Lockheed received a contract from the Defense Advanced Research Projects Agency (DARPA) for the construction of two 60-percent scale flyable test aircraft under a project named Have Blue. The name Have Blue seems to have no specific meaning, probably having been chosen at random from an approved list of secret project names. Shortly after the Have Blue contract was let, the project was transferred over to Air Force System Command control and became highly "black", with all information about it being highly classified and restricted to those with a need to know. Outside of a few people at Lockheed and the Defense Department, noone knew that Have Blue even existed.
The two Have Blue aircraft were built at Lockheed in only a few months. The first example was intended to evaluate the type's flying characteristics, whereas the second was to evaluate the radar signature. In order to save some time and some money, existing off-the-shelf components were used where feasible. The engines were a pair of standard production non-afterburning General Electric J85s, mounted in enclosures sitting atop the wings. The main landing gear was taken from a Fairchild Republic A-10, and fly-by-wire components were scavenged from an F-16. The instrumentation and the ejector seat were taken from a Northrop F-5. The Have Blue aircraft had the same general shape as that which would later become familiar with the F-117A, except that the twin rudders were located forward of the exhaust ejectors and were angled inward rather than outward. The inward cant was about 30 degrees. The leading edge of the semi-delta wing was swept back at 72.5 degrees. The wing featured two inboard trailing edge elevons for pitch and roll control. Four spoilers (two on top of the wing and two on the bottom) were mounted just forward of the elevons. There were no flaps or speed brakes. The wing trailing edge was less deeply notched than that of the F-117A. A single cockpit with an ejector seat was provided. The Have Blue aircraft employed V-type windshields (similar to those of the F-102/F-106). No weapons bay nor any sort of tactical equipment at all was fitted. The Have Blue aircraft were equipped with fly-by-wire (FBW) flight controls which were adapted from the F-16 system. However, the system had to be modified to handle an aircraft that was unstable about all three axes (the F-16 is unstable only about the pitch axis). The problem of designing a stealthy system for airspeed measurement had not yet been solved, and the aircraft were equipped with a conventional pitot tube which was retracted when they were being tested for radar reflections. The inertial navigation system provided enough speed data for test purposes when the probe was retracted.
Two prototypes were built at a cost of $37 million for both aircraft. Lockheed workers assembled the two Have Blue aircraft in a cordoned-off area in Lockheed's Plant 10 facility housed at the USAF Plant 42 in Palmdale, California. Neither aircraft ever received an official DoD designation, or did they get a USAF serial number. However, Lockheed did give the aircraft its own manufacturer's serial numbers --- 1001 and 1002, meaning Plant 10, aircraft numbers 1 and 2.
The first example (1001) was finished in November of 1977. In order to keep the project away from prying eyes, the Have Blue prototype was shipped out to the Groom Lake Test Facility in Nevada in high secrecy for the test flights. Groom Lake is located in a particularly remote area of the Nellis test range complex, and is a good location for the testing of secret aircraft. A camouflage paint scheme was applied to make it hard for unwanted observers at Groom Lake to determine the aircraft's shape.
The first flight of the Have Blue took place in January or February of 1978 (the exact date is still classified), veteran Lockheed test pilot William M. "Bill" Park being at the controls. At an early stage, Bill Park was assisted in the flight test program by Lt. Col. Norman Kenneth "Ken" Dyson of the USAF.
Flight test of the Have Blue initially went fairly smoothly, and the fly-by-wire system functioned well. The landing speed was quite high (160 knots), as expected because of the lack of flaps or speed brakes. However, on May 4, 1978, Have Blue prototype number 1001 was landing after a routine test flight when it hit the ground excessively hard, jamming the right main landing gear in a semi-retracted position. Pilot Bill Park pulled the aircraft back into the air, and repeatedly tried to shake the gear back down again. After his third attempt failed, he was ordered to take the aircraft up to 10,000 feet and eject. Park ejected successfully, but he hit his head and was knocked unconscious. Since he was unable to control his parachute during descent or landing, his back was severely injured on impact. He survived, but was forced to retire from flying. The Have Blue aircraft was destroyed in the crash. The wreckage was secretely buried somewhere on the Nellis test range complex.
Have Blue 1002 arrived at Groom Lake shortly after the loss of number 1. It took to the air for the first time in June of 1978, Lt.Col. Ken Dyson being at the controls. From mid-1978 until early 1980, Lt.Col. Dyson flew more than 65 test sorties, testing the response of the aircraft to various types of radar threats. The Have Blue prototype 1002 proved to be essentially undetectable by all airborne radars except the Boeing E-3 AWACS, which c ould only acquire the aircraft at short ranges. Most ground-based missile tracking radars could detect the Have Blue only after it was well inside the minimum range for the surface-to-air missiles with which they were associated. Neither ground-based radars nor air-to-air missile guidance radars could lock onto the aircraft. It was found that the best tactic to avoid radar detection was to approach the radar site head on, presenting the Have Blue's small nose-on signature.
It was found that the application of the RAM was rather tricky, and that ground crews had to be careful to seal all joints thoroughly before each flight. RAM came in linoleum-like sheets which was cut to shape and bonded to the skin to cover large areas. Doors and access panels had to be carefully checked and adjusted for a tight fit between flights and all gaps had to be filled in with conductive tape and then covered over with RAM. Paint-type RAM was available, but it had to be built up by hand, coat by coat. Even the gaps around the canopy and the fuel-filler door had to be filled with paint-type RAM before each flight. Ground crews had to even make sure that all surface screws were completely tight, since even one loose screw for an access panel could make the aircraft show up like a "barn door coming over the horizon" during radar signature tests. Have Blue number 1002 was lost in July of 1979. During its 52nd flight, with Lt.Col. Dyson at the controls, one of its J85 engines caught fire. The subsequent fire got so intense that the hydraulic fluid lines were burned through. Lt.Col. Dyson was forced to eject, and 1002 was a total loss. It too was secretely buried somewhere on the Nellis test range complex. No further Have Blue aircraft were built, since the general concept had been proven.
Specification of the Have Blue (approximate):
Two non-afterburning General Electric J85 turbojets. Maximum speed: 600 mph at sea level. Dimensions: wingspan 22 feet 0 inches, length 38 feet 0 inches, height 7 feet 6 inches. Gross weight 12,000 pounds. No armament was carried. Most other details are still classified.