Fighter Wing: A Guided Tour of an Air Force Combat Wing Page 7
In the 1970s, the Russians began to develop mobile ICBM systems that could shuttle around the vast spaces of the Soviet Union on special railroad trains or giant wheeled vehicles. The Soviets knew that every fixed missile silo could be pinpointed by satellite imagery and targeted for destruction; every Soviet ballistic missile submarine could be tracked by sonar arrays and trailed by a U.S./NATO attack boat; but what could you do to kill a mobile missile complex? The proposed U.S. solution was to hunt down the mobile missiles with an aircraft so revolutionary that nothing in the Soviet arsenal could touch it.
The first pre-production B-2A Spirit stealth bomber in front of its hangar at the Northrop Grumman factory at Palmdale, California. Craig E. Kaston
An invisible airplane that traveled at the speed of light, armed with precision “death ray” weapons, would have been ideal. But a subsonic airplane which was almost invisible to radar and IR sensors, carrying a few nuclear-tipped missiles, was sufficient if (and it was a big if) its development could be kept so secret that the other side would have no time, and no data, to develop effective countermeasures. Thus was born the B-2A Spirit. The origins of the B-2 design date back to experimental aircraft of the 1920s, when the visionary Horten brothers of Germany designed their first “flying wing” aircraft, without conventional tail surfaces and with a cockpit smoothly blended into the thickened wing section. Their goal was low drag (they were unaware as yet of the advantages of a low radar cross section). The problem with all-wing aircraft is that they are inherently less stable than the more normal kind with fuselages and tail sections; and crashes of various prototypes led to the shelving of the Hortens’ project (although a very ambitious twin-jet-powered version was under development at the end of the Second World War). In the 1940s, the brilliant and eccentric American engineer Jack Northrop designed the XB-35 heavy bomber, a propeller-driven flying wing, and later the YB-49, a promising eight-engined turbojet bomber (which compromised the purity of the design by adding four small vertical fins). Unfortunately, the manual flight controls of the time were inadequate to solve the inherent stability problems of pure flying wing designs, and the Air Force canceled the project. Despite the problems inherent in the flying wing design, it does have one undeniable characteristic: It is tough to see on radar. Thus, the stage was set for the development of the B-2.
Originally called the Advanced Technology Bomber (ATB), the B-2 began development in 1978 as a black program, which means that it was not published in the Air Force budget and its existence was revealed only to a limited circle of legislators. In 1981 the Northrop/Boeing team’s proposal was selected, and full-scale development of the new bomber followed. It took seven years, including a major redesign in the mid-1980s, when the USAF changed the original B-2 specification to include a low-level penetration capability. (Shortly before his death, under a special security dispensation, Jack Northrop was allowed to see a model of the B-2—the vindication of the idea he had championed four decades earlier.)
The first B-2 pre-production aircraft (known as Air Vehicle #1) was rolled out at Palmdale, California, on November 22nd, 1988, and the first flight was on July 17th, 1989. The first B-2A squadron (of eight aircraft) of the 509th Bombardment Wing at Whiteman AFB, Missouri, are scheduled to reach IOC (initial operation capability) in 1996. Given the official Air Force designation of Spirit, each aircraft will be named for a state; the first five are “Spirit of California,” “Spirit of Missouri,” “Spirit of Texas,” “Spirit of Washington,” and “Spirit of South Carolina.” General Mike Loh, the ACC commander, likes the designation because, like a ghost, the B-2 will be able to come and go without being seen.
A combination of several advanced technologies made the B-2 possible. Foremost among these was computer-aided design/computer-aided manufacturing, known as CAD/CAM in the aircraft industry. The F-117A had to employ awkwardly faceted flat surfaces, because this was the only solution available in the mid-1970s to the earlier-generation computer hardware and software on which it was designed (millions of radar cross section calculations were necessary to validate the design). The B-2, designed on vastly more powerful computer systems, could have smoothly contoured aerodynamic surfaces because, by that time, the billions of necessary calculations could be performed relatively quickly.
Moreover, the B-2 was the first modern aircraft to go into production without requiring a prototype, or even a development fixture. Designed with advanced three-dimensional CAD/CAM systems, which are used to fix parts, the B-2’s virtual development fixture allowed every component to be fit-checked before it was manufactured. As a result, when the first B-2s were assembled, something happened that was unprecedented in aviation history, possibly in the entire history of engineering development and manufacturing. Every part fit perfectly the first time, and the finished aircraft precisely matched its designed dimensions within a few millimeters over a span of 172 feet/52.4 meters.
The first pre-production B-2A Spirit bomber flies over Edwards AFB, California. Note the control surfaces (elevons and flaperons) along the trailing edge of the wing.
Craig E. Kaston
The B-2’s flight-control surfaces are unique. The outboard trailing edge of each wing tip consists of a pair of hinged “drag rudders,” moved by hydraulic actuators, with another set called “elevons” inboard of those. These surfaces take the place of the rudder, elevators, and ailerons on a conventional aircraft.
The B-2’s crew consists of a mission commander and pilot, who sit side by side on conventional ejection seats beneath blow-out panels overhead. The commander is in the right-hand (starboard) position, with the pilot on the left (port). Each crew station has four color multi-function displays and fighter-type control sticks, rather than the control yokes commonly used on large multi-engined aircraft. These controls feed into the quad-redundant fly-by-wire flight control system, which makes the Spirit very stable, but highly agile. (According to the test pilots, the B-2 flies “like a fighter” thanks to the agility of the fly-by-wire system.) The communications systems consist of a full array of HF/UHF/VHF radios, as well as a satellite communications terminal, all of which are controlled from a single data entry panel. Eventually, this will be fully compatible with the new MILSTAR communications satellites that are now coming online. The wraparound windows are very large, but there is no visibility aft, so the crew must rely on sophisticated tail-warning sensors to “check six.” The crew enters through a floor hatch with a retractable ladder that is just aft of the nose landing gear well. The traditional “alert” button is on the nose gear, though most experts agree that it will probably never be used by a B-2 crew.
The four General Electric F118-100 turbofan engines buried inside the wing are non-afterburning versions of the F101 used in the B-1B. Each engine is rated at 19,000 lb./8,600 kg. of thrust. To dissipate heat and hide the hot section from hostile IR tracking systems, the complex air intakes receive incoming air through an S-shaped turn, which shields the fan sections from the view of any hostile radar; then the unique V-shaped exhaust slots pass the exhaust gases across a long, wide, trough-shaped section of the upper wing.
While many details of the structure and materials of the B-2 will remain closely guarded secrets for years to come, published sources suggest that graphite-epoxy composites are used extensively. Even the paint requires unique new technology. Antennas are mounted flush with the skin; even the air-data sensors which stick out prominently on most fly-by-wire aircraft are flush-mounted on the leading edge of the B-2. The most conventional equipment is the main landing gear, derived from the Boeing 767 airliner, and the nose gear, from the Boeing 757.
With only one air-to-air refueling, a range of more than 10,000 nm./ 18,280 km. is possible. Endurance is thus limited only by crew fatigue, which is exceptionally low due to the high degree of onboard automation. In effect, with a minimum of tanker support, the B-2 can strike any target in the world and return to a base in the continental United States. The in-flight refueling receptacle on top of the c
rew compartment is concealed behind a retractable door of radar-absorbing material, and according to pilot reports, the B-2 is quite stable and has very pleasant flying qualities around tankers.
All weapons will be carried internally—an absolute requirement for any stealthy aircraft, since ordnance dangling on pylons increases the radar cross section dramatically. The two bomb bays, aft of the crew compartment, are designed to each accommodate an eight-round rotary launcher, or a conventional munitions module similar to those on the B-1B.
The Air Force plans to buy twenty B-2s by 1998 for $44 billion from Northrop Grumman Corp. of Los Angeles. Originally the service wanted 132 B-2s, but because of the plane’s high purchase price and the end of the Cold War, Congress limited the program. Though Northrop Grumman has proposed constructing an additional twenty aircraft by 2008 at a guaranteed fixed price of about $570 million each, the future of the program is highly uncertain. Nevertheless, the B-2A Spirit is the state of the art in strike aircraft, and probably will be well into the middle of the next century.
Lockheed Martin-Boeing F-22
It has been over twenty years since the current USAF air superiority fighter, the F-15 Eagle, first took wing in 1972. Those two decades have seen massive changes, both in the political makeup of the world and the nature of aviation technology. Thus, it is in that context that the Air Force is betting billions of dollars and the future of manned fighter aircraft on the Lockheed Martin-Boeing F-22 and its new Pratt & Whitney F119 engines. In 1984, the ATF specification called for a 50,000 lb./22,700 kg., $35 million aircraft (that’s in 1985 U.S. dollars) incorporating the latest advances in low-observable technologies and able to cruise at supersonic speed (the YF-22A demonstrated the ability to cruise at Mach 1.58 during the competitive fly-off, and to do so at altitudes in excess of 50,000 feet) to a combat radius of more than 800 nm./ 1,200 km. By 1986 the competition narrowed down to two teams, each of which would build and fly a pair of prototypes: the Lockheed-Boeing-General Dynamics YF-22 and the Northrop-McDonnell Douglas YF-23. Although the YF-23 had excellent performance, the Air Force decided in April 1991 to go with the superior agility of the YF-22. Under current plans, the Air Force will now buy 442 aircraft, with a first production aircraft flight scheduled early in 1997 and initial operational capability by 2004. Planned production will continue through 2011, with follow-on versions such as strike, SEAD (Suppression of Enemy Air Defenses), and reconnaissance coming afterwards as required.
One of the two YF-22 prototype aircraft flying over Edwards AFB during the advanced tactical fighter “fly-off.” Lockheed Martin
The Air Force views the mission of air superiority as instrumental for the success of other types of missions (deep strike, battlefield, interdiction, close air support, etc.). With the wide variety of current-generation fighters in the air forces of potential adversaries, as well as the potential sales of new-generation aircraft, the USAF will require a fighter able to engage and destroy any potential opponent at times and places of their choosing. The F-22 is designed to take the basic weapons/sensor load of the F-15C and repackage it into a stealthy platform capable of supersonic cruise. This combination of stealth and high cruise speed is designed to allow the F-22 to rapidly enter an area, establish air superiority, avoid enemy detection/engagement, and basically act like Ridley Scott’s Alien, so that the bad guys are too scared to even come up.
Lockheed Martin indicates that the F-22A/B will be a true stealth design, in the same class as the F-117A and the B-2A. Although the F-22 is essentially the same size as the F-15, over the frontal aspect its radar cross section is reportedly over one hundred times smaller! The structure of the F-22 will be composed of the following: 28% composites (carbon-carbon, thermoplastics, etc.), 37% titanium, 20% metal (aluminum and steel), and 15% “other” materials (kryptonite?). To reduce the weight of the aircraft and still provide strength, the structural members of the F-22 are of a mixed metal/composite design that minimizes the total RCS of the package. For example, two of every three wing spars are of composite construction, while every third one is titanium. Also, watch for a new paint which may have RAM properties as well. By the way, the “notch” in the leading edge of the wing is supposed to be a radar “trap” to catch and dissipate radar waves around the wing roots.
Even the engines are stealthy. Since the twin F119 power plants deliver enough dry thrust (i.e., without use of the afterburner) to allow the F-22 to cruise at supersonic speeds, its IR signature is significantly reduced over a conventional fighter aircraft traveling at the same speed. The Pratt & Whitney F119 (35,000 lb./15,909.1 kg. of thrust each) provides the F-22 with the performance of the F-15C (with the F100-PW-220 engine in full afterburner) while in military (dry) power. All this is done without a variable inlet ramp (to reduce the aircraft’s RCS) and with an engine that is stealthy by itself, unlike those on the F-117A, which require inlet screens. The inlet ducts are curved to hide the fan section of the engine from enemy radar, with RAM and other engineering tricks to further reduce this traditional radar trap. On most jet aircraft the exhaust nozzles are round; on the F-22 they are rectangular slots, with movable vanes that can deflect the exhaust—in effect “steering” the thrust vector. These “2-D” nozzles (up to +/-20° of vertical displacement from centerline) of the F119 improve aircraft agility and give the F-22 superb short-field takeoff-and-landing performance.
An F119 turbofan engine in a test stand, running at full afterburner. A pair of F119 engines will power the new F-22 fighter in the 21st century.
Pratt & Whitney-United Technologies
The cockpit will be an almost totally “glass” design (i.e., only MFDs), with only three analog instruments as emergency backups. No less than six multi-function displays of three sizes are arrayed for the pilot to configure as he or she pleases. The cockpit is a classic HOTAS design, with a wide-field-of-view holographic HUD. Also, a helmet-mounted sight for helping the pilots get weapons onto their targets is a likely upgrade. If the design for the F-22 works as planned, its flight envelope will vastly exceed that of any existing U.S. fighter, or even the MiG-29 or Su-27/35. Acceleration, rate of roll, and other control parameters are also planned to be superior on the F-22 when compared to existing designs. The quad-redundant, fly-by-wire flight control system is going to make the F-22 a true sustained 9-G airplane, able to rapidly turn and hold that load for as long as the pilot can stand it.
The F-22A/B will have the first fully integrated avionics suite ever flown on a combat aircraft. The Common Integrated Processor (CIP—the F-22 has two CIP bays, with room for a third) built by GM-Hughes is the core of the system and supports the Westinghouse-Texas Instruments APG-77 radar, the Lockheed Martin electronic warfare suite, and the TRW communications/ navigation/IFF subsystems. The electronics will be liquid-cooled, and they will run over one million lines of computer code. Total processing power for the F-22A/B with two CIP bays will be in the area of 700 Mips (700 million operations/sec—equivalent to four Cray supercomputers), with an expansion potential of something over 100% already planned into the design.
As for sensors, the new Westinghouse APG-77 radar is a wide field-of-view (over 120°) fixed phased array, which is virtually undetectable with conventional RWR systems. In fact, the APG-77 can probably be programmed to do virtually any kind of operation that a radar is capable of doing just by programming it with additional software and adding the necessary processor/memory capacity to the CIPs. Also, the F-22A/B will have an integrated countermeasures suite tied to the CIP bays. This will allow for rapid systems reprogramming in the event of a crisis, and should allow modifications to be handled quickly. The jammer/RWR antennas are contained in “smart skins” on the wing tips, with the communications, navigation, and IFF antennas in the leading edges of the wings.
The basic weapons package of the F-22 will be roughly similar to that of the F-15C, though it will develop in stages. The missiles will be fired off hydraulically extensible rail launchers out of three internal weapons bays (one on
either side, and one in the belly). Since opening a door to launch or fire a weapon may suddenly increase the RCS of the aircraft from certain angles, the designers have provided actuators that rapidly open and shut those doors, so that the exposure time is minimized. As an added stealth feature, the 20mm gun is buried deep in the right mid-fuselage area, and fires through a door that snaps open at the time of firing, then closes immediately after the last bullet passes. Also, in a non-stealth configuration, an additional eight air-to-air missiles can be carried on four wing pylons.
A mockup of the “glass” cockpit design of the new F-22 fighter. Note the use of computer-style multi-function displays instead of traditional dial or “strip” instruments. Lockheed Martin
The F-22 has been designed so that most of the access panels are at ground level, and require only eight more tools than are already in the standard kit of the F-15C. Also, the F-22 will require a bare minimum of ground support equipment, such as service carts and workstands. For example, the F-22 has its own onboard oxygen and inert-gas generators to supply the environmental control system for the pilot and to provide pressurization for the fuel system. Thus, maintenance hours per flight hour should be even less than the F-16 or A-10. There also will be a portable electronic maintenance aid, based around a handheld computer, which will plug into the aircraft, and a maintenance laptop computer, which will do all the diagnostic work on what needs to be replaced, filled, or whatever. One of the design goals was to increase sortie rates by achieving a fifteen-minute combat turnaround time—that’s to both refuel and re-arm!