Flying sideways

DARPA has posted a video of the planned Oblique Flying Wing X-plane demonstrator on its website. The animation shows the tailless flying wing sweeping smoothly from 0 degrees to 65 degrees as it accelerates from Mach 0.6 to Mach 1.2.

It looks surprisingly real – down to the wobbly “camera” tracking – and deceptively simple. If it flies as planned in 2011, the OFW X-plane will be the first supersonic, tailless, variable-sweep flying wing – and making it fly will be far from easy.

X-factor – Northrop’s OFW demonstrator (DARPA photo)There is no guarantee it can be made to work, but if Northrop Grumman can successfully fly an OFW X-plane, it will give designers a new configuration option for future reconnaissance/strike aircraft that can loiter like a UAV, fly as far as a bomber and dash like a fighter.

The oblique flying wing concept has been around almost as long as the swept wing, and designers have been drawn repeatedly to its compelling efficiency and simplicity, but always have shied away from using the oblique wing because of its aerodynamic and control issues.

Earlier OFW X-plane concept with paired engines

A supersonic oblique flying wing or a tailless variable-sweep flying wing would be challenging in their own right, and the OFW X-plane will combine both. Previous oblique-wing flight tests have all been subsonic and have involved aircraft with tails, and in some cases fuselages.

The original – R T Jones’ oblique flying wing

Famed US aerodynamicist R T Jones first suggested in the late 1950s that asymmetrically swept, or oblique, wings offered advantages and calculated that an oblique flying wing offered the lowest supersonic drag.

But after a promising start, the idea languished, being picked up several times only to be put down again. NASA flew the AD-1 subsonic oblique-wing demonstrator 79 times between 1979 and 1982, but plans for a supersonic demonstrator never materialised.

Slow start – NASA Ames’ AD-1

The idea has never died because it offers a compelling combination of endurance, range and speed in a single aircraft. The question is whether it is feasible, and that is what DARPA intends to find out.

Like the swept wing and forward-swept wing before it, the oblique flying wing is a concept that has to be flown to be believed, and it shows that X-planes still have a pivotal role to play in proving the feasibility of new technologies and configurations.

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