Northrop Grumman's proposed Oblique Flying Wing X-plane demonstrator. Image copyright Northrop Grumman.

Oblique Flying Wing
Tech Level: 13

One of the more unusual aircraft designs ever proposed, an Oblique Flying Wing (OFW) is composed almost entirely of a single wing and one or more jet engines. That in itself is not so odd, as there have been many flying wing vehicles in both practical use and as test models throughout the last seventy years or so. However, in supersonic flight, one tip of the Oblique Flying Wing is designed to sweep back while the other is angled forward. In other words, the wing flies forward with its body angled asymmetrically into its direction of flight.

Experiments with oblique wing flight go back to the 1940s, and in the last 30 years NASA has created a number of experimental aircraft of varying sizes and designs to test the soundness of the concept. Northrop-Grumman in cooperation with DARPA was building an experimental OFW X-plane in order to more fully test the concept, but the project was canceled in 2008. However, the concept seems sound, and work on it may one day be revived.

The principles is the same as that with swept-wing jets. In subsonic flight, traditional straight wings work best at providing efficient lift and stability while in flight. However, as one approaches the speed of sound and beyond, shockwaves generated by the supersonic airflow over the wings produce ever increasing drag and stability problems. For these velocities, you need a different kind of wing shape that can minimize these detrimental shockwaves, namely the more severe angles of swept-wing jets such as the Concorde or the F-18.

There have been many compromise wing designs over the years, trying to incorporate efficient lift and stability for vehicles at both low and high speed. Some vehicles, such as the F-14 Tomcat, use ‘variable geometry’ wings, which means it can physically shift its wings further back at an angle the faster it goes, allowing for better flight characteristics at all speeds.

The OFW uses the same principles as the variable geometry wing, only as its entire body is its lifting surface, it sweeps its full-vehicle wing back at supersonic velocities so that one tip is angled forward and the other back, allowing it to fly asymmetrically. At subsonic speeds it would fly with its body-wing perpendicular to its direction of flight like a traditional airplane, and then sweep its body-wing back at an angle the faster it goes.

The engines the OFW mounts are gimballed to allow them to stay oriented in the proper direction of flight no matter how much the wing sweeps forward or back. They are also placed strategically on the body to act somewhat as rudders to help with stability. Some early OFW test models had one or more vertical fins on the trailing wing edge to help with stability; the tailless Northrop-Grumman version eschewed these for sophisticated computer controls similar to those used in the B-2 bomber, also a tailless flying wing.

Ideally, an OFW would be a very efficient vehicle from low up to hypersonic speeds, allowing it much greater fuel economy, range, and endurance at all stages of flight than most other transonic aircraft. It was these capabilities that made it very attractive as an Air Force project. It would have been capable of a high speed supersonic dash to its target area, and then could loiter over it for a potentially long time. This would make them ideal for use as recon UAVs (Unmanned Aerial Vehicles), similar to the Global Hawk, but could reach the target area and begin surveillance or execute a tactical strike much faster. They could also be used for manned fighting vehicles, though that capability is probably considerably farther off than their potential use as drones.







Article added 2/2/10