F-117 Nighthawk

The Lockheed F-117 Nighthawk is a retired American single-seat, subsonic, twin-engined stealth attack aircraft built by Lockheed's Skunk Works division for the United States Air Force. It achieved initial operating capability in October 1983 and was the first operational aircraft designed around stealth technology. Officially designated a fighter, it was employed exclusively as a precision attack platform and was retired in 2008.

Development

Design work followed the Vietnam War and the 1973 Yom Kippur War, where Soviet-built SAMs inflicted heavy losses. Lockheed analyst Denys Overholser drew on Pyotr Ufimtsev's 1962 paper on edge-wave diffraction, which showed radar return depends on edge configuration rather than size. Lockheed's 1975 "Hopeless Diamond" model led to a 1976 DARPA contract for two Have Blue demonstrators, which used T-38A engines, F-16 fly-by-wire, A-10 landing gear and C-130 environmental systems, and were built for $35 million total. Have Blue first flew on 1 December 1977; both aircraft crashed, but the test data was positive. The production decision was taken on 1 November 1978 under the code name Senior Trend, with Ben Rich leading the programme and Alan Brown as project manager. The first of five YF-117A development aircraft, 79-10780, flew from Groom Lake, Nevada, on 18 June 1981. The first production aircraft was delivered in 1982. The USAF denied the type's existence until 10 November 1988. The last of 59 production F-117s was delivered on 3 July 1990.

Design

The faceted airframe of flat panels was derived from the "Echo" radar-cross-section program and yields an RCS of about 0.001 m². Almost one ton of radar-absorbent material was applied as flat sheets bonded with adhesive and gap-filling putty. Power comes from two non-afterburning General Electric F404-F1D2 turbofans of 9,040 lbf each, fitted with conductive mesh intake grilles and slit-shaped tailpipes that mix exhaust with ambient air. Maximum speed is Mach 0.92; service ceiling is 45,000 ft and range 930 nmi. The aircraft is unstable about all three axes and uses quadruple-redundant fly-by-wire controls, with systems derived from the F-16, B-52, F/A-18 and F-15E. No radar is fitted; navigation uses GPS and inertial systems, and targeting a thermal imaging infrared system with laser rangefinder/designator.

Armament

Two internal weapons bays each carry one hardpoint, for a total payload of 5,000 lb. Typical loads are GBU-10 or GBU-27 Paveway laser-guided bombs with Mk84, BLU-109 or BLU-116 warheads, GBU-12 with Mk82, and from 2006 the GBU-31 JDAM. The aircraft could also carry two B57 or B61 nuclear gravity bombs, with a cockpit panel for permissive action links, though it was never assigned a standing nuclear alert role.

Operational History

The fleet operated from Tonopah Test Range Airport under the 4450th Tactical Group, absorbed by the 37th Tactical Fighter Wing in 1989, then moved to Holloman AFB under the 49th Fighter Wing in 1992. The first combat mission was the 1989 invasion of Panama, bombing Rio Hato airfield. In the 1991 Gulf War, 42 F-117s flew about 1,300 sorties over 6,905 hours and dropped 2,077 bombs, including the Amiriyah shelter strike that killed at least 408 civilians. On 27 March 1999, 82-0806 was downed over Yugoslavia by an S-125 battery of the 3rd Battalion, 250th Air Defence Missile Brigade; the pilot ejected and was recovered. The type also flew in Operation Enduring Freedom in 2001 and opened Operation Iraqi Freedom in 2003 with EGBU-27 strikes on Dora Farms. Retirement ran from March 2007 to 11 August 2008, with most airframes placed in Type 1000 storage at Tonopah. Around 45 aircraft remain flyable for testing and aggressor training.

Variants

• YF-117A: Five full-scale development aircraft, the first flying in June 1981.
• F-117A: Production single-seat attack version, 59 built.
• F-117N Seahawk: Proposed carrier-capable variant with F414 engines, bubble canopy, revised wing and tail and optional hardpoints; not ordered.
• F-117B / A-F-117X: Land-based multirole proposal with afterburning engines, offered to the USAF and RAF; not ordered.