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F-16XL
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The General Dynamics F-16XL is a derivative of the F-16 Fighting Falcon, with a cranked-arrow delta wing that is over twice the size of that of the standard F-16 wing. It was entered in the U.S. Air Force's Enhanced Tactical Fighter (ETF) competition but ultimately lost to the F-15E Strike Eagle. Several years after the prototypes were shelved, they were turned over to NASA for aeronautical study.
977, the F-16XL started out as the F-16 SCAMP (Supersonic Cruise and Maneuver Prototype) at General Dynamics Fort Worth.
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Encyclopedia
The General Dynamics F-16XL is a derivative of the F-16 Fighting Falcon, with a cranked-arrow delta wing that is over twice the size of that of the standard F-16 wing. It was entered in the U.S. Air Force's Enhanced Tactical Fighter (ETF) competition but ultimately lost to the F-15E Strike Eagle. Several years after the prototypes were shelved, they were turned over to NASA for aeronautical study.
Development
SCAMP
In 1977, the F-16XL started out as the F-16 SCAMP (Supersonic Cruise and Maneuver Prototype) at General Dynamics Fort Worth. Under the leadership of Harry Hillaker (father of the original F-16), the original goal of the program was to demonstrate the applicability of Supersonic transport technologies to military aircraft.
Working closely with NASA's Langley Research Center, the company invested significant Internal Research and Development (IRAD) funds for wind tunnel testing and that led to the Model 400. As seen in the supersonic wind tunnel model at right, the Model 400 featured all moving wing tips for roll control and an all moving vertical tail. These surfaces were actually the horizontal tail surfaces from the F-16A. These surfaces were later dropped as they did not provide adequate control at low speed, high angle of attack. Also, there would have been no provision for wing-tip mounted missiles. The main wing incorporated forebody strakes to enhance vortex generation for high angle of attack maneuverability, negative stability for improved subsonic lift and reduced supersonic drag. It was built around a 40" fuselage stretch. Both the large wing and fuselage stretch yielded a dramatic increase in range at all speeds. In 1979, with a strong positive response by the USAF, GD released the Model 400 for a company funded preliminary design effort.
Enhanced Tactical Fighter competition
In 1980, the USAF signed on as a partner, providing two early model F-16s for conversion (the third and fifth production airframes). In March 1981, the USAF announced the Enhanced Tactical Fighter program to procure a replacement for the F-111 'Aardvark'. The concept envisioned an aircraft capable of launching deep interdiction missions without requiring additional support in the form of fighter escort or jamming support. General Dynamics submitted the F-16XL, while McDonnell Douglas submitted a variant of the F-15 Eagle. In February 1984, the USAF awarded the ETF to McDonnell Douglas (which resulted in the F-15E Strike Eagle), and both F-16XL aircraft were returned to the Air Force and placed in storage.
NASA
In 1988, the two airplanes were taken out of storage and turned over to NASA for research. The first aircraft was fitted with an active suction titanium glove encasing the left wing and delivered to the Ames-Dryden Flight Research Facility at Edwards AFB. Designed and built by North American Aviation (a division of Rockwell International), the glove had laser-cut holes that were nominally 0.0025 in (0.0635 mm) diameter. Distance between holes varied between 0.010 and 0.055 in (0.25 and 1.40 mm) depending on the suction. The glove covered over five square feet (0.5 m²) of the wing. It was intended to suck away turbulent airflow over the wing, restoring laminar flow and reducing drag. The aircraft was also involved in testing sonic boom characteristics, takeoff performance, and engine noise, for NASA's civil transport program.
The second aircraft (a two seater) had its experimental engine replaced with a General Electric F110-129. It accidentally achieved supercruise, a design goal of the F-16XL that was never attained in ETF testing, when it reached Mach 1.1 at 20,000 feet (6 km) on full military power. It was mounted with a passive fiberglass and foam glove on the right wing to examine supersonic flow, and an active glove on the left wing. This second glove was composed of fiberglass and foam over a titanium skin, and covers 75% of the wing's surface and 60% of its leading edge. The active portion consists the middle two-thirds of the glove, with laser-drilled holes leading to cavities beneath the wing. It was designed collaboratively by Langley research center, Dryden, Rockwell, Boeing, and McDonnell Douglas. The glove is intended as a testbed for supersonic laminar flow.
At the conclusion of their test programs in 1999, both F-16XLs were placed into storage at NASA Dryden. In 2007, NASA approached Lockheed Martin to request a study into the feasibility and cost of returning F-16XL #1 to flight status and upgrading it with many of the improvements found in the USAF's Block 40 F-16s. As of July, 2007, the study is still underway, however in the meantime F-16XL #1 has been taxi tested at Dryden and given systems checks.
Project Management
The F-16XL flight project office was located at the NASA Dryden Flight Research Center, Edwards, CA. The NASA Langley Research Center, developed and coordinated F-16XL experiments. Project managers at Dryden were Marta Bohn-Meyer and Carol Reukauf.
Design
The wing and rear horizontal control surfaces were replaced with a cranked-arrow delta wing 120% larger than the original wing. Extensive use of carbon fiber composites allowed the savings of 600 lb (270 kg) of weight but the F-16XL was still 2,800 lb (1300 kg) heavier than the original F-16A.
Less noticeable is that the fuselage was lengthened by 56 inches (1.4 m) by the addition of 2 sections at the joints of the main fuselage sub-assemblies. With the new wing design, the tail section had to be canted up 3 degrees, and the ventral fins removed, to prevent them from striking the pavement during takeoff and landing. However, as the F-16XL exhibits greater stability than the native F-16, these changes were not detrimental to the handling of the aircraft.
These changes resulted in a 25% improvement in maximum lift-to-drag ratio in supersonic flight and 11% in subsonic flight, and a plane that reportedly handled much smoother at high speeds and low altitudes. The enlargements increased fuel capacity by 82%. The F-16XL could carry twice the ordnance of the F-16 and deliver it 40% further. The enlarged wing allowed a total of 27 hardpoints on the plane:
- 16 wing stations of capacity 750 lb (340 kg) each
- 4 semi-recessed AIM-120 AMRAAM stations under fuselage
- 2 wingtip stations
- 1 centerline station
- 2 wing "heavy/wet" stations
- 2 chin LANTIRN stations
However, the "heavy/wet" stations interfered with up to 4 wing stations
Specifications (F-16XL number 2)
From
See also
External links
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