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.
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.
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.
Have Blue aircraft were built at Lockheed in only a few months. The
example was intended to evaluate the type's flying characteristics,
second was to evaluate the radar signature. In order to save some time
money, existing off-the-shelf components were used where feasible. The
were a pair of standard production non-afterburning General Electric
mounted in enclosures sitting atop the wings. The main landing gear was
from a Fairchild Republic A-10, and fly-by-wire components were
an F-16. The instrumentation and the ejection seat were taken from a
F-5. The Have Blue aircraft had the same general shape as that which
become familiar with the F-117A, except that the twin rudders were
forward of the exhaust ejectors and were angled inward rather than
inward cant was about 30 degrees.
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
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.
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.