Fortunately, the program was dropped before it got to the stage of actually configuring one of NASA’s F-8s with an oblique wing. Aesthetically, it would have been a truly horrible thing to do to the “last of the gunfighters!”
The F-8 Crusader was one of the most effective fighters of the post-World War II period, characterized by its streamlined design, which included a gaping jet intake located beneath the fuselage and a variable-incidence wing that could be elevated to allow the aircraft to take off and land at low speeds while ensuring excellent visibility for the pilot. At a time when fighter pilots were increasingly depending on missiles, the Crusader still featured 20mm cannons, leading its pilots to refer to it as the “Last of the Gunfighters.”
Crusaders carried out their inaugural combat operations in October 1962, employing cameras instead of armaments for photo-reconnaissance flights over Cuba during the Cuban Missile Crisis. F-8s logged these missions as well, along with strike and combat air patrol operations throughout the Vietnam War, with Crusader pilots recognized for shooting down eighteen enemy MiGs in aerial engagements.
Several adapted F-8 aircraft were used by NASA during the early 1970s, demonstrating the effectiveness of digital fly-by-wire technology (leveraging data-processing systems modified from the Apollo Guidance Computer), as well as the design of supercritical wings.
An F-8 was almost used as a test aircraft for the Oblique Wing concept too, as Rear Admiral Paul T. Gillcrist explains in his book Crusader!: Last of the Gunfighters: ‘He had two strikes against him when he walked through the door of my office in the Pentagon. He was an acquaintance, not a friend, a retired Crystal City Rear Admiral who admitted to being employed by Rockwell International and who was looking for a small amount (10 million dollars) of research and development money to develop the concept of the oblique wing. My office, Director, Aviation Plans and Programs (OP-50), had something to say about how and where Navy R&D dollars were spent. But the artist’s sketch he carried was the thing that did him in. And the sad thing is that he didn’t even know it!
‘Not surprisingly, the airframe of choice for the test bed for the oblique wing was the F-8. For the same reason as the supercritical wing flight test program (ease of removal and reinstallation of the wing), the F-8 was chosen. The concept of the oblique wing was new then, in 1982, and it is, I believe, an offshoot of the X-wing concept. The wing pivots around the vertical axis, the tip of the left wing, for example, would sweep aft while the tip of the right wing swept forward. It achieves the same effect as wing sweeping in the conventional sense with a greatly diminished engineering penalty in terms of weight, complexity, and cost. Its only problems are that it looks like hell, it is asymmetric, and it is terribly unconventional.
‘He must have caught me in a weak moment because I agreed to “donate” the dollars, which I then had to steal from another funded program. My staff was furious at me… but then, that was not a new circumstance. The Navy money, along with a Defense Advanced Research Projects Agency (DARPA) contribution, permitted initial work to proceed at the National Aeronautics and Space Administration (NASA) Hugh L. Dryden Flight Research Facility at Edwards Air Force Base in California.
‘A remotely piloted vehicle (RPV), called the AD-1 Low-Speed Oblique-Wing Research Aircraft, was built as a proof-of-concept and flown successfully. Wind tunnel tests had shown potential performance benefits transonically and supersonically when an oblique-wing aircraft was compared with an equivalent variable sweep aircraft. ‘The approach was to build a small, low-cost manned research vehicle. NASA contracted to build a foam-and-fiberglass piloted via aircraft powered by two ducted fan turbine engines. This low-cost, low-speed, manned vehicle made significant contributions to oblique wing technology. Probably more significant than the stability for and control data that were gathered in this project were the handling qualities data obtained.
‘Pilots flew the aircraft to wing-skew angles of 60 degrees in the cruise configuration and landed at angles of up to 45 degrees. This unaugmented aircraft provided valuable information on the effects of cross-coupling on handling qualities. Although skew effects were most dramatic during the first 45 degrees of skew angle, pilots found cross-coupling effects fairly minor in this regime. Between 45 and 60 degrees, however, the cross-coupling effects became significant in maneuvering flight.
‘The AD-1 showed that the return on investment can be very high for small and inexpensive flight research vehicles. Although very limited in scope, such vehicles can address specific flight regimes, flight configurations, and flight dynamics issues, and provide a credible database that includes data on pilot-vehicle interface as well as stability and control characteristics. The data from the AD-1 program represents the predominant source of flight data for skew-wing technology in the low-speed flight regime.
‘Fortunately, the program was dropped before it got to the stage of actually configuring one of NASA’s F-8s with an oblique wing. Ascetically, it would have been a truly horrible thing to do to the “last of the gunfighters!”’
Crusader!: Last of the Gunfighters is published by Schiffer Publishing and is available to order here.
Photo by NASA and Secret Projects Forum
