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F-117 History

Project Harvey

In 1975, Ed Martin and Ben Rich solicited the help of five engineers from Lockheed's Advanced Design and Skunk Works Engineers to help prepare a proposal for the Experimental Survivable Testbed (XST) program using discretionary funds.  This Lockheed XST Program was named "Project Harvey" after the 1950 movie titled Harvey, staring James Stewart, about an invisible six foot rabbit that could only be seen by one person, Stewart.  Dick Scherrer was the Project Harvey Program Manager and Leo Celniker was the Proposal Manager for the XST proposal.  The product of Project Harvey was the Hopeless Diamond.

Hopeless Diamond

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. The surfaces were arranged in such a way that the vast majority of the radar incident on the aircraft 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. 


James Clerk Maxwell, a Scottish physicist, has derived a set of equations that could predict how a body of a given shape would scatter, or reflect, electromagnetic radiation. Two Skunk Works engineers cracked Maxwell's ciphers in 1975. Veteran designer Bill Schroeder sketched a flyable, controllable aircraft with no curved surfaces at all, except for small-radius, straight edges to its wings and tail surfaces. It was as if a diamond had been cut to the shape of an aircraft, and the technique came to be called "faceting". Schroeder took the problem to Dennis Overholser, a software engineer. Using a Cray computer, Overholser developed a program that could model the scattering from Schroeder's new faceted shapes, and predict their Radar Cross Section (RCS), in a reasonable amount of time.  Because Denny's early work was totally funded with Lockheed funds, the computer program and the faceted designs belonged to Lockheed.  Lockheed owns the patent for the faceted designs.  From the computer program, the Skunk Works engineers created a ten-foot wooden model dubbed the "Hopeless Diamond". The model was taken to an outdoor radar test range on the Mojave Desert near Palmdale. The model was mounted on a 12-foot high pole, and the radar dish zeroed in from about 1,500 feet away. The site radar operator could not see the model on the radar, until a black bird landed right on top of the Hopeless Diamond. The radar was only picking up the bird....

In March 1976, the Skunk Works built a model out of wood, all flat panels, thirty-eight feet long, and painted black. It was hauled to White Sands New Mexico for competition against Northrop's candidate. The Skunk Works model had a lower RCS than the pole it was mounted on so Lockheed built a new pole. In April 1976, Lockheed won the competition and the "Have Blue" program was born.  Lockheed was the winner, not only because the Hopeless Diamond's low RCS, but also because Lockheed has a computer model which could predict the signature - something that the competition did not have.

Have Blue

The F-117A was the first warplane to be specifically designed from the outset for low radar observability.  Lockheed Advanced Development Projects (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.

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, no one 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 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 ejection 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 ejection seat was provided. The Have Blue aircraft employed V-type windshields (similar to those of the F-102/F-106). No weapons bay or any sort of tactical equipment was fitted. 

The Have Blue aircraft were equipped with fly-by-wire (FBW) flight controls that 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 that 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 Building 83C, Burbank, California. Neither aircraft ever received an official DoD designation, nor did they get a USAF serial number.  However, Lockheed did give the aircraft its own manufacturer's serial numbers, 1001 and 1002.


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), with veteran Lockheed test pilot William M. "Bill" Park at the controls. At an early stage, Lt. Col. Norman Kenneth “Ken” Dyson of the USAF assisted Bill Park in the flight test program. 

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.

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 could 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. 

Application of the RAM proved to be 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 were 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. No further Have Blue aircraft were built, since the general concept had been proven.

 

F-117 History

The gain of valuable engineering data during the Have Blue flight test program led to a Full Scale Development (FSD) decision by the Air Force and contract award to the Lockheed Skunk Works on November 16, 1978. The original order was for five FSD test aircraft and 15 production articles. The initial F-117 delivered in June 1981 and subsequent production lots of varying quantities yielded a total of 64 aircraft built through July 1990. As of May 2001, 51 production and 3 FSD test aircraft are still active. 


Streamlined management by Aeronautical Systems Center, Wright-Patterson AFB, Ohio, in close coordination with the Skunk Works, combined breakthrough stealth technology with concurrent development and production. The result of this effort, shrouded in secrecy rivaling that of the Manhattan Project to develop the atomic bomb, was declaration of Initial Operating Capability (IOC) after delivery of the fourteenth F-117 in October 1983. Incredibly, IOC occurred in just under five years after production go ahead, about half the time for most programs. 

Beginning in 1982, the 4450th Tactical Group operated the F-117 through the first years of its existence at the Tonopah Test Range. This covert facility in central Nevada at the north end of the Nellis complex, enabled the concurrent development and production of the F-117 to continue far from the prying eyes of the media. By late 1989, as the F-117 was reaching maturity and now a publicly acknowledged program, the Air Force wanted to redefine its operating command to a combat unit versus a test organization as was the 4450th TG’s heritage. In October 1989, the 4450th was deactivated and became the 37th Tactical Fighter Wing, which continued to operate the F-117 through its first combat employments. 

In venturing out of the “Black World” following the successful Desert Storm campaign, the F-117’s transition to conventional base operations was a natural progression to fully integrate this new and very effective tool into the Air Force arsenal. By mid 1992, the F-117 Wing transferred operations to Holloman Air Force Base in Alamogordo NM. At the same time, it was also redesignated the 49th Fighter Wing, carrying on the proud heritage of 43 Air Aces from the Second World War.

F-117A CLIMATIC TEST

Following acknowledgement of the existence of the F-117A aircraft in November 1988, efforts were begun to assimilate its unique capabilities into the national integrated air defense system. Because no operational environment specification existed for the aircraft, a decision was made to subject it to climatic testing to determine how the aircraft and its systems would perform if it were required to be operated and maintained outside of its normal hangar sheltered environment. Responsibility for the test was assigned to the 6510th Test Wing at Edwards AFB, CA, and a full range of climatic testing per provisions of MIL SPEC 210 was selected. Planning, publication of a formal test plan, and support contracting occurred from February of 1990 through March 1991.

Aircraft 824 had undergone installation of all scheduled Depot and Field modifications by April 1991. Considered to be typical and representative of the rest of the operational fleet, it was selected for the test, and was flown from PS-66 to the Climatic Test Chamber at Eglin AFB, FL on July 9th, 1991. The aircraft was prepped and then installed in the Chamber using special fixtures and tooling designed to allow simulation of conditions in flight. Testing began under cold weather conditions (-40 F ambient) on July 15th 1991, and continued through conditions of snow loading, blowing snow, hail, freezing rain, ice and fog, hot weather (140 F ambient), water intrusion testing, and concluded in January 1992 with tropical rain and human factors evaluations. Cold soaks to -60 F and 160 F were also included. A typical mission "flown" included pre-flight, pilot ingress, APU and engine start, full power takeoff, cruise, systems operation and weapon delivery, landing, pilot egress, and post flight inspection. Aircraft maintenance was performed and evaluated throughout the testing sequence.

Support for this test was provided by all agencies associated with the aircraft at that time. Program oversight and funding were provided by SPO at Wright Patterson AFB, test direction, control and instrumentation by the 6510th Test Wing at Edwards AFB, logistics support, failure analysis, and component spares by SM-ALC/QL at Mc McClellan AFB and the Skunk works at Burbank. Pilots, maintenance, and security personnel were provided jointly by the 37th TFW at PS-66 and the CTF on a rotational basis, and test facilities and support equipment by the Climatic Test Organization at Eglin AFB. To expedite resolution of problems encountered, direct on-site engineering support and liaison was provided throughout the test by a single FSR from the Skunk Works.

The Climatic Test was successfully completed in early January 1992, and Aircraft 824 was removed from the test chamber. It was inspected, pre-flighted, and returned to home base shortly thereafter. Several improvements to aircraft systems were ultimately incorporated as a result of analysis of test data collected. A final tribute to the F-117A design is that it is one of the very few Aircraft to undergo climatic testing and return home under its own power.