General Dynamics F-16XL
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The General Dynamics F-16XL is a derivative of the
F-16 Fighting Falcon The General Dynamics F-16 Fighting Falcon is a single-engine multirole fighter aircraft originally developed by General Dynamics for the United States Air Force (USAF). Designed as an air superiority day fighter, it evolved into a successful ...
, with a cranked-arrow delta wing. It was originally conceived as a technology demonstrator, later entered in the
United States Air Force The United States Air Force (USAF) is the air service branch of the United States Armed Forces, and is one of the eight uniformed services of the United States. Originally created on 1 August 1907, as a part of the United States Army Signal ...
's (USAF) Enhanced Tactical Fighter (ETF) competition but lost to the
F-15E Strike Eagle The McDonnell Douglas (now Boeing) F-15E Strike Eagle is an American all-weather multirole strike fighter derived from the McDonnell Douglas F-15 Eagle. The F-15E was designed in the 1980s for long-range, high-speed interdiction without rely ...
. Several years after the prototypes were shelved, they were turned over to
NASA The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research. NASA was established in 1958, succeeding t ...
for additional aeronautical research. Both aircraft are currently stored at
Edwards Air Force Base Edwards Air Force Base (AFB) is a United States Air Force installation in California. Most of the base sits in Kern County, but its eastern end is in San Bernardino County and a southern arm is in Los Angeles County. The hub of the base is E ...
.


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 be a quick project to demonstrate the applicability of
supersonic transport A supersonic transport (SST) or a supersonic airliner is a civilian supersonic aircraft designed to transport passengers at speeds greater than the speed of sound. To date, the only SSTs to see regular service have been Concorde and the Tupol ...
technologies to military aircraft. The big wing generated a lot of lift, and typical aerodynamic limitations of delta wings were overcome by the F-16's relaxed static stability. The F-16's electronic flight control system was tweaked to allow control at high angles of attack. The wing was also a big fuel tank which greatly increased range. The study went on for two years. The goal of the cranked arrow was to have a high sweep inboard panel for low drag at supersonic speeds, and a low sweep outboard panel to provide better handling and maneuverability at subsonic speeds. Working closely with NASA's
Langley Research Center The Langley Research Center (LaRC or NASA Langley), located in Hampton, Virginia, United States of America, is the oldest of NASA's field centers. It directly borders Langley Air Force Base and the Back River on the Chesapeake Bay. LaRC has fo ...
, the company invested significant Internal Research and Development (IRAD) funds for wind tunnel testing and that led to the Model 400. It 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 In fluid dynamics, angle of attack (AOA, α, or \alpha) is the angle between a reference line on a body (often the chord line of an airfoil) and the vector representing the relative motion between the body and the fluid through which it is m ...
maneuverability, negative stability for improved subsonic lift and reduced supersonic drag. It was built around a 40-inch 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 the third and fifth production F-16 airframes for conversion. These two airframes became the only examples of the F-16XL. In March 1981, the USAF announced the Enhanced Tactical Fighter (ETF) program to procure a replacement for the
F-111 Aardvark The General Dynamics F-111 Aardvark is a retired supersonic, medium-range, Multirole combat aircraft, multirole combat aircraft. Production variants of the F-111 had roles that included attack aircraft, ground attack (e.g. Air interdiction, i ...
. The concept envisioned an aircraft capable of launching deep
interdiction Interdiction is a military term for the act of delaying, disrupting, or destroying enemy forces or supplies en route to the battle area. A distinction is often made between strategic and tactical interdiction. The former refers to operations whose ...
missions without requiring additional support in the form of fighter escort or jamming support. Under the leadership of program director David Randall "Randy" Ken

General Dynamics submitted the F-16XL, while
McDonnell Douglas McDonnell Douglas was a major American aerospace manufacturing corporation and defense contractor, formed by the merger of McDonnell Aircraft and the Douglas Aircraft Company in 1967. Between then and its own merger with Boeing in 1997, it produ ...
submitted a variant of the F-15 Eagle. Though the two aircraft were competing for the same role, they were fairly different in design approach. The F-15E is basically an F-15D two-seat trainer with the back-seat station modified to support ground-attack instruments, while the F-16XL has major structural and aerodynamic differences from the original F-16. As such, the XL would have required much more effort, time and money to put into full production. Additionally, the Strike Eagle has two engines, which gives it more thrust and capacity to carry more weapons and/or armor. Furthermore, engine redundancy can be very useful for an aircraft whose mission involves operating within the reach of
anti-aircraft artillery Anti-aircraft warfare, counter-air or air defence forces is the battlespace response to aerial warfare, defined by NATO as "all measures designed to nullify or reduce the effectiveness of hostile air action".AAP-6 It includes surface based, ...
and
surface-to-air missile A surface-to-air missile (SAM), also known as a ground-to-air missile (GTAM) or surface-to-air guided weapon (SAGW), is a missile designed to be launched from the ground to destroy aircraft or other missiles. It is one type of anti-aircraft syst ...
s, in addition to the standard threats of
fighter aircraft Fighter aircraft are fixed-wing military aircraft designed primarily for air-to-air combat. In military conflict, the role of fighter aircraft is to establish air superiority of the battlespace. Domination of the airspace above a battlefield ...
and
interceptors An interceptor aircraft, or simply interceptor, is a type of fighter aircraft designed specifically for the defensive interception role against an attacking enemy aircraft, particularly bombers and reconnaissance aircraft. Aircraft that are c ...
. In February 1984, the USAF awarded the ETF contract to McDonnell Douglas. The two F-16XLs were returned to the Air Force and placed in storage at Edwards Air Force Base, Mojave, California. Had General Dynamics won the ETF competition, the F-16XL would have gone into production as the F-16E/F (E for single seat, F for two seat trainer).


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 (1,300 kg) heavier than the original F-16A. Less noticeable is that the fuselage was lengthened by 56 in (1.4 m) by the addition of two sections at the joints of the main fuselage sub-assemblies. With the new wing design, the tail section had to be canted up 3°, 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 aerodynamics, the lift-to-drag ratio (or L/D ratio) is the lift generated by an aerodynamic body such as an aerofoil or aircraft, divided by the aerodynamic drag caused by moving through air. It describes the aerodynamic efficiency under give ...
in supersonic flight and 11% in subsonic flight, and a plane that reportedly handled much more smoothly 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% farther. The enlarged wing allowed a total of 27 hardpoints: * 16 wing stations of capacity 750 lb (340 kg) each * 4 semi-recessed
AIM-120 AMRAAM The AIM-120 Advanced Medium-Range Air-to-Air Missile, or AMRAAM (pronounced ), is an American beyond-visual-range air-to-air missile (BVRAAM) capable of all-weather day-and-night operations. It is 7 inches (18 cm) in diameter, and employs ...
stations under fuselage * 2 wingtip stations * 1 centerline station * 2 wing "heavy/wet" stations * 2 chin
LANTIRN LANTIRN (Low Altitude Navigation and Targeting Infrared for Night) is a combined navigation and targeting pod system for use on the United States Air Force fighter aircraft—the F-15E Strike Eagle and F-16 Fighting Falcon (Block 40/42 C & D mo ...
stations However, the "heavy/wet" stations interfered with up to four wing stations.


Operational history


NASA testing

In 1988, the two aircraft 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 Edwards Air Force Base (AFB) is a United States Air Force installation in California. Most of the base sits in Kern County, but its eastern end is in San Bernardino County and a southern arm is in Los Angeles County. The hub of the base is Ed ...
. Designed and built by
North American Aviation North American Aviation (NAA) was a major American aerospace manufacturer that designed and built several notable aircraft and spacecraft. Its products included: the T-6 Texan trainer, the P-51 Mustang fighter, the B-25 Mitchell bomber, the F ...
(a division of
Rockwell International Rockwell International was a major American manufacturing conglomerate involved in aircraft, the space industry, defense and commercial electronics, components in the automotive industry, printing presses, avionics and industrial products. R ...
), 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 5 ft² (0.5 m²) of the wing. It was intended to suck away turbulent airflow over the wing, restoring
laminar flow In fluid dynamics, laminar flow is characterized by fluid particles following smooth paths in layers, with each layer moving smoothly past the adjacent layers with little or no mixing. At low velocities, the fluid tends to flow without lateral mi ...
and reducing drag. The aircraft was also involved in testing
sonic boom A sonic boom is a sound associated with shock waves created when an object travels through the air faster than the speed of sound. Sonic booms generate enormous amounts of sound energy, sounding similar to an explosion or a thunderclap to t ...
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 Supercruise is sustained supersonic flight of a supersonic aircraft with a useful cargo, passenger, or weapons load without using afterburner (also known as "reheat"). Many supersonic military aircraft are not capable of supercruise and can only m ...
, a design goal of the F-16XL that was never attained in ETF testing, when it reached Mach 1.1 at 20,000 ft (6,096 m) 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. The F-16XL flight project office was located at the NASA
Dryden Flight Research Center The NASA Neil A. Armstrong Flight Research Center (AFRC) is an aeronautical research center operated by NASA. Its primary campus is located inside Edwards Air Force Base in California and is considered NASA's premier site for aeronautical rese ...
, Edwards AFB, CA. The NASA
Langley Research Center The Langley Research Center (LaRC or NASA Langley), located in Hampton, Virginia, United States of America, is the oldest of NASA's field centers. It directly borders Langley Air Force Base and the Back River on the Chesapeake Bay. LaRC has fo ...
, developed and coordinated F-16XL experiments. 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 F-16 Block 40. This was studied while F-16XL #1 was taxi tested at Dryden and given systems checks. However, both F-16XLs were retired in 2009 and stored at Edwards AFB.


Aircraft on Display

;F-16XL * 75-0747 – Museum Air Park, Air Force Flight Center Museum,
Edwards AFB Edwards Air Force Base (AFB) is a United States Air Force installation in California. Most of the base sits in Kern County, but its eastern end is in San Bernardino County and a southern arm is in Los Angeles County. The hub of the base is Ed ...
,
California California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...
. * 75-0749 – in storage at the Air Force Flight Center Museum,
Edwards AFB Edwards Air Force Base (AFB) is a United States Air Force installation in California. Most of the base sits in Kern County, but its eastern end is in San Bernardino County and a southern arm is in Los Angeles County. The hub of the base is Ed ...
,
California California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...
.


Specifications (F-16XL number 2)


See also


References


Citations


Bibliography

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External links

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photo gallery number 2
* . * . * . * . * * {{F-16 Fighting Falcon variants Tailless delta-wing aircraft
F-16XL The General Dynamics F-16XL is a derivative of the F-16 Fighting Falcon, with a cranked-arrow delta wing. It was originally conceived as a technology demonstrator, later entered in the United States Air Force's (USAF) Enhanced Tactical Fighter ...
NASA aircraft
General Dynamics F-16XL The General Dynamics F-16XL is a derivative of the General Dynamics F-16 Fighting Falcon, F-16 Fighting Falcon, with a Cranked arrow, cranked-arrow delta wing. It was originally conceived as a technology demonstrator, later entered in the Unite ...
Single-engined jet aircraft Relaxed-stability aircraft Aircraft first flown in 1982