LOCKHEED F117 NIGHTHAWK STEALTH FIGHTER PAUL F. CRICKMORE © Osprey Publishing • www.ospreypublishing.com AIR VANGUARD 16 LOCKHEED F117 NIGHTHAWK STEALTH FIGHTER PAUL F. CRICKMORE © Osprey Publishing • www.ospreypublishing.com CONTENTS INTRODUCTION 4 DESIGN AND DEVELOPMENT 5 (cid:423)(cid:1) Have Blue (cid:423)(cid:1) Senior Trend (cid:423)(cid:1) Flight-testing TECHNICAL SPECIFICATIONS 27 (cid:423)(cid:1) Stealth features (cid:423)(cid:1) Other considerations (cid:423)(cid:1) Operational analysis (cid:423)(cid:1) Powerplant (cid:423)(cid:1) Fuel and oil system (cid:423)(cid:1) Ignition system (cid:423)(cid:1) Hydraulics (cid:423)(cid:1) Electrical system (cid:423)(cid:1) Flight control system (cid:423)(cid:1) Autopilot (cid:423)(cid:1) Flight instruments (cid:423)(cid:1) Displays (cid:423)(cid:1) Avionics integration (cid:423)(cid:1) Antenna systems (cid:423)(cid:1) Environmental control system (cid:423)(cid:1) Oxygen system (cid:423)(cid:1) Ejection seat (cid:423)(cid:1) Updates (cid:423)(cid:1) Weapons systems OPERATIONAL HISTORY 45 (cid:423)(cid:1) The Tonopah years (cid:423)(cid:1) First losses (cid:423)(cid:1) Operation Just Cause  (cid:423)(cid:1) Operation Desert Storm  (cid:423)(cid:1) The move to Holloman (cid:423)(cid:1) The Balkans (cid:423)(cid:1) Operations Iraqi Freedom and Enduring Freedom  THE PROGRAM SHUTDOWN 61 (cid:423)(cid:1) Conclusion BIBLIOGRAPHY 63 INDEX  64 © Osprey Publishing • www.ospreypublishing.com LOCKHEED F117 NIGHTHAWK STEALTH FIGHTER INTRODUCTION Although universally known as “the Stealth Fighter,” Lockheed’s F-117 was an attack aircraft. Designed within the legendary Skunk Works primarily by electronic engineers, radically new solutions had to be developed to enable the aircraft to evade radar detection and interception. The enormity of the challenge is neatly conceptualized by the radar equation, which basically states that “radar detection range is proportional to the fourth root of the targets’ radar cross section (RCS).” In other words, to reduce the detection range of an aircraft by a factor of ten, it is necessary to reduce its RCS by a factor of 10,000 or 40 dBs. Having successfully vaulted such a monumental hurdle, when the F-117 was deployed in combat, together with its weapons delivery system it achieved a consistent – almost eye-watering – level of success, the like of which had never before been attained by any other previous combat aircraft. Indeed, so deadly accurate was this weapons platform, it enabled US Air Force (USAF) planners to confidently utilize the aircraft against some of the world’s most highly defended targets to perform a “surgical strike” – destroying the target without other areas incurring collateral damage. Perhaps not surprisingly, the F-117 and its forerunners were developed in the “Black World” and flight-tested at the hot, highly classified desert test site known as Area 51. When, finally, the basic shape of the much speculated F-19 stealth fighter was revealed to the public by Assistant Defense Secretary J. Daniel Howard during a Pentagon press conference on November 10, 1988, the grainy photograph depicted a black, stubby, angular aircraft, whose shape was more akin to a lifting body or something that Darth Vader might have flown in a sequence from Star Wars. It certainly bore no resemblance whatsoever to the curves and blended body of what was supposedly an accurate representation of the aircraft available for model enthusiasts to purchase in the form of a plastic construction kit. The security clearance necessary to access information relating to the Have Blue proof of concept (or demonstrator) vehicles and the follow-on Senior Trend program (the equally classified code name for the F-117) was categorized as top secret/sensitive compartmented information (TS/SCI), and it was spectacularly successful in keeping both programs under wraps. When Lockheed test pilot Dave Ferguson first saw the highly faceted, unconventional, “slab-sided” aircraft, he asked Dick Cantrell how airframe ice encrustation might affect the aircraft’s aerodynamics. The program’s chief aerodynamicist dryly replied, “Probably improve it.” 4 © Osprey Publishing • www.ospreypublishing.com When Ben Rich became president of the Skunk Works on January 17, 1975, Lockheed faced financial losses amounting to $2 billion. Selling the U-2R concept to the USAF, together with his strident support of Have Blue and the F-117 program, undoubtedly played a major role in turning around the company’s fortunes. (Lockheed Martin)  The less-than-spectacular combat debut of the F-117 during Operation Just Cause – the US invasion and subsequent ousting of General Manuel Noriega from Panama – was more than compensated for just 15 months later, on January 17, 1991. On this date, during the opening phase of Operation Desert Storm (the expulsion of Saddam Hussein’s occupying forces from Kuwait), the first laser-guided bombs dropped from F-117s slammed into their targets with devastating accuracy. Some of the infrared footage of these strikes, recorded in each aircraft for subsequent analysis by pilots and intelligence specialists, was made available to the media, and became a source of fascinating viewing during news bulletins throughout the world. The 43-day campaign proved beyond a shadow of a doubt the effectiveness of stealth technology as applied to the F-117 when, despite flying hundreds of sorties against the most heavily defended targets in Iraq, not a single one of these ungainly looking aircraft was shot down or even hit. DESIGN AND DEVELOPMENT Air battles fought by the United States during the Vietnam War, together with losses suffered by Israel during the so-called Yom Kippur War of 1973, were responsible for the Defense Advanced Research Projects Agency (DARPA) initiating conceptual studies into developing a manned aircraft with a sufficiently low RCS to defeat modern air-defense systems. Consequently, in 1974 Ken Perko of the Tactical Technology Office (TTO) at DARPA requested submissions from Northrop, McDonnell Douglas, General Dynamics, Fairchild, and Grumman, under the code name Project Harvey (derived from an old movie starring James Stewart and “featuring” an invisible ten-foot rabbit named Harvey), addressing two considerations. Firstly, what were the signature thresholds that an aircraft would need to achieve to become essentially undetectable at an operationally useful range? Secondly, did the relevant companies possess the capabilities to design and produce an aircraft with the necessary low signatures? 5 © Osprey Publishing • www.ospreypublishing.com Fairchild and Grumman declined the invitation to participate, while General Dynamics emphasized the continued need for electronic countermeasures. However, the submissions from McDonnell Douglas and Northrop demonstrated both a grasp of the problem and a degree of technical capability for developing an aircraft with a reduced signature. Consequently, both companies were awarded contracts worth approximately $100,000 each during the closing months of 1974 to conduct further studies. Radar experts from the Hughes Aircraft Company were also involved, their role being to identify and verify appropriate RCS thresholds. At this early stage the studies were only classified as “Confidential.” Bill Elsner was the primary USAF technical expert on the program, and by the beginning of 1975 McDonnell Douglas had identified likely RCS thresholds that could produce an operational advantage. In the spring, these were confirmed by Hughes and were established by DARPA as goals for the program. DARPA then challenged the participants to find ways of achieving them. Lockheed had not been one of the five original companies approached by DARPA, simply because it had not produced a fighter for nearly ten years. This, however, was about to change. Whilst networking his contacts at the Pentagon and Wright-Patterson Air Force Base (AFB), Ed Martin, Lockheed California Company’s Director for Science and Engineering, was made aware of the study. He flagged this to Ben Rich, who at this time was deputy to the Skunk Works’ legendary president Clarence L. “Kelly” Johnson. The two men then briefed Johnson, who in turn obtained a letter from the Central Intelligence Agency (CIA), granting the Skunk Works permission to discuss with DARPA the low observable (LO) characteristics of their earlier A-12 and D-21 drone program. Rich and Martin presented this data to Ken Perko and Doctor George Heilmeier, the head of DARPA, and formally requested entry into the competition. However, Heilmeier explained that two $100,000 contracts had already been awarded and there was no more cash available. Drawing upon his negotiation skills, Rich convinced the DARPA boss to allow Lockheed into the competition without a government contract – a move that ultimately paid a handsome dividend. The Skunk Works team were then given access to technical reports already provided to the other participants, and the first step that would culminate in a revolutionary aircraft was taken. Within the Skunk Works team, Denys Overholser recalls his boss, Dick Scherrer, asking him one day, “How do we shape something to make it invisible to radar?” Overholser’s reply was, “Well, it's simple, you just make F117 PROFILES A 1: The Have Blue prototype HB1001 (known in-house as Blue 1) had a unique camouflage pattern applied at Burbank before being disassembled and flown via C-5 Galaxy to the test site at Area 51. 2: The second Have Blue aircraft, HB1002, first flew on July 20, 1978. It was flown primarily to enable various air- and ground-based radars to gather RCS data. It completed 52 sorties before crashing on July 11, 1979. 3: The F-117 prototype aircraft 780 sported an unusual camouflage pattern for its first ten test flights, before being painted light gray for over a year. 4: When aircraft 781 completed its flight-test career, it was bead-blasted of all its classified, radar-absorbent coatings, and generally stripped out inside, before undergoing a functional check flight (as depicted here). It was then delivered to the US Air Force Museum, where it received a coat of standard black paint before being put on display. 6 © Osprey Publishing • www.ospreypublishing.com 1 2 3 4 7 © Osprey Publishing • www.ospreypublishing.com In just five weeks, Denys Overholser and his two engineers developed the Echo 1 computer program that enabled accurate RCS predictions of prospective design submissions to be evaluated. (Lockheed Martin) it out of flat surfaces, and you tilt those flat surfaces over, sweeping the edges away from the radar view angle, and that way you basically cause the energy to reflect away from the radar, thus limiting the magnitude of the return.” The framework for such radical thinking had its roots in discussions that Overholser had had years earlier with his then-boss Bill Schroeder. Schroeder, a brilliant mathematician, had been employed by Johnson to resolve analytical problems, and had trained Overholser. During the course of discussing the mathematics and physics of optical scattering, the two had concluded that detectable signatures could be minimized by utilizing a shape composed of the smallest number of properly orientated flat panels. In addition, Schroeder believed that he could develop and resolve a mathematical equation capable of calculating analytically the reflection from a triangular flat panel; this in turn could be applied in a calculation relating to RCS. With input from Overholser, Scherrer drew a preliminary low-RCS shape based upon a faceted delta wing. By April, Bill Schroeder had been brought into the team and set about completing solutions to RCS equations that would enable the group eventually to predict results. Kenneth Watson was appointed Senior Lead Aircraft Designer, tasked with positioning all systems inside the “shell” that Scherrer and Overholser were designing. As Schroeder's mathematical computations became available, Overholser and his team of two engineers then used these to write the computer program that could evaluate the RCS of prospective design submissions nominated by Dick Scherrer. Overholser and his team worked night and day, and in just five weeks produced an RCS prediction program known as Echo 1. However, as tests continued, it became apparent that the edge contributions calculated by Echo 1 were not accurate, due to a phenomenon known as diffraction. 8 © Osprey Publishing • www.ospreypublishing.com Incredibly, a solution to this problem was provided by a Soviet scientist. The Skunk Works team were made aware of an article entitled “Method of Edge Waves in the Physical Theory of Diffraction,” published in an unclassified technical paper by Pyotr Ufimtsev (Chief Scientist at the Moscow Institute of Radio Engineering), which had been translated by Air Force Systems Command's Foreign Technology Division in 1971. Overholser was able to incorporate elements of its theory into a refined version of the Echo 1 program and use this to mathematically evaluate over 20 designs to identify the one with the smallest RCS. The faceted delta wing design had more than its share of sceptics within the Skunk Works. Some in aerodynamics referred to the shape as “the Hopeless Diamond.” Two one-third-scale wooden models of the Hopeless Diamond were constructed. One was used by the aerodynamists in wind tunnel tests, and the other was coated with metal foil to provide a conductive surface and used to measure RCS values in Lockheed's anechoic chamber. The first series of tests were conducted in June 1975, and they demonstrated that the RCS “spikes” matched precisely those predicted by Echo 1. The model was then moved outdoors to the Gray Butte Radar Test Range which boasted improved capabilities and enabled the team to measure even lower RCS values. Yet again, these test results conformed well to Echo 1 predictions, creating greater levels of confidence in both the computer program and the faceted design concept. The Northrop full-scale model demonstrator undertaking RCS tests during Phase 1 of the Experimental Survivable Testbed (XST) program at the USAF RATSCAT facility at White Sands, New Mexico in February 1976. (Northrop via Tony Landis) 9 © Osprey Publishing • www.ospreypublishing.com To improve the vehicle’s lift-to-drag ratio, the section outboard the engine inlets was thinned, resulting in the semblance of wings. These were eventually extended outward, changing the planform from the original diamond shape to a notched-out delta. The trailing edge sweep was increased to 48 degrees to ensure that the signature spike, associated with the trailing edge, fell outside the frontal sector. To minimize “nose-on” detection, inboard canted tail surfaces were also added. Two proposals were submitted to DARPA from Lockheed. One included the predicted and measured signature data for the Hopeless Diamond; the other provided the predicted data for an air vehicle of flyable configuration. This came about in response to DARPA issuing proposals to the three competitors for what was to become known as the Experimental Survivable Testbed (XST) program. This was informally requested in the late summer of 1975 and responses were due in August or September; the signature goals therein were those laid down in the earlier 1974/1975 directive. Northrop’s XST entry was similar in appearance to that of Lockheed’s. Its design had been developed from a computer program called GENSCAT, which also had its origins in mathematical equations associated with the physics of optics. Like Lockheed, Northrop used both computer modeling and the Gray Butte Range (near Palmdale, California) to test and evaluate their design. By the summer of 1975 they, too, had reliable indications that their design would achieve the RCS goals set earlier. Having been the first to determine what the RCS thresholds for the competition were likely to be, McDonnell Douglas were unable to design an aircraft that could achieve anything like those goals. With RCS results coming from both Lockheed and Northrop verging on the revolutionary, Ken Perko called a meeting within DARPA to determine the program's future direction. It was decided that the program should be developed still further, into a full-scale, flight-test demonstration, consisting of two phases. Phase 1 would culminate in a ground RCS evaluation of large-scale models. Following this, one contractor would be selected to proceed with Phase 2, the construction and flight-testing of two demonstration vehicles. The estimated cost for the XST program was $36 million and this would be borne by and split between the successful contractor, a reluctant USAF, and DARPA. The latter would contribute marginally more, thereby retaining program management control. By August 1975 funding arrangements were completed and on November 1, Lockheed and Northrop were awarded contracts of $1.5 million each to conduct Phase 1 of the XST program. The two companies were each given just four months to complete the initial phase of the competition, which involved the construction of full-scale, wooden test models. These would then be evaluated at the Air Force’s radar target scatter (RATSCAT) test range, located at White Sands, New Mexico. It was already apparent that the RCS results achieved by both participating companies were unlike anything obtained before, and it became necessary to develop a new, lower-signature pylon so that returns from the pylon did not impinge upon results from the test models. The Lockheed model was hauled by truck to RATSCAT for testing in March. Throughout the tests the competing contractors and their models were kept in isolation from one another, billeted in temporary quarters affording each independent access to the range. In early April 1976 Lockheed received word that they had officially won Phase 1 of the competition. 10 © Osprey Publishing • www.ospreypublishing.com