NASA AD-1

NASA AD-1 (Ames-Dryden-1) is a single-engine experimental aircraft from aviation history featuring wings that can be pivoted up to 60 degrees relative to the fuselage. This innovative design was developed by NASA’s Ames and Dryden (now Armstrong) Research Centers in the 1970s to test the low-speed behavior of the “oblique wing” concept. The aircraft’s primary objective was to improve fuel efficiency by positioning its wings at varying angles, thereby optimizing both takeoff and landing performance as well as cruise speed performance.

NASA AD-1 (NASA Video)

Development and Unique Design Features

The most distinctive feature of the AD-1 is its wings, which rotate around a single pivot point. This concept was proposed by NASA engineer Robert T. Jones to reduce aerodynamic drag at supersonic speeds and thereby achieve higher speeds and greater range with less fuel consumption. The project was launched in 1975 with a budget of $240,000 and was intended to serve as a low-cost research platform.

• Structural Materials and Lightweight Construction: To keep costs low, the fuselage and wings were constructed from glass fiber-reinforced plastic (GRP). This material choice maintained the aircraft’s empty weight at a remarkably light 1,450 pounds (approximately 658 kg). The aircraft was powered by two small Ames Industrial TRS-18 turbojet engines, each producing 220 pounds (approximately 99 kg) of thrust.
• Oblique Wing Mechanism: During takeoff and landing, the wings were held perpendicular to the fuselage at 0 degrees to maximize lift and control stability. As speed increased, an electrically controlled mechanism operated from the cockpit gradually pivoted the wings up to a maximum oblique angle of 60 degrees to minimize aerodynamic drag.

Flight Test Program and Obtained Data

The AD-1 completed a total of 79 flights between 1979 and 1982. This test program was designed to examine the effects of wing sweep angle on the aircraft’s control characteristics and performance.

• Test Phases: Flight tests progressed by incrementally increasing the wing sweep angle. Initial flights maintained the wings at 0 degrees; subsequent flights increased the angle to 20, 30, and 45 degrees. The final tests achieved the full 60-degree sweep angle.
• Findings: During flight tests, particularly at sweep angles above 45 degrees, the aircraft exhibited challenging control characteristics and complex aerodynamic interactions. It was documented that at high sweep angles the aircraft displayed asymmetric aerodynamic behavior and responded more sensitively to control inputs. These data were critical in understanding the potential challenges of the oblique wing concept at high speeds.
• Pilot Feedback: Feedback from test pilots Thomas C. McMurtry and Richard E. Gray indicated that control became increasingly difficult at low speeds, but that transitions in wing angle at high speeds were remarkably smooth.

Project Conclusion and Legacy

The AD-1 project concluded with its final flight in 1982. The project demonstrated the feasibility of the oblique wing concept at low speeds and provided valuable data on the aerodynamic and control challenges that arise at high speeds. The findings laid a foundation for future aircraft designs. Although plans were considered to modify an F-8 fighter jet for supersonic testing of the concept, these plans were later canceled. Today, the AD-1 aircraft is on display at the Dryden Flight Research Center at Edwards Air Force Base in California.