Northrop research plane flies | Aviation Week, August 8, 1949


First flight photo of the Northrop X-4, subsonic research airplane, reveals flat underside and stubby fore-and-aft appearance. Although flying since June 7, 1949, this is first flight photo released. Craft is designed to test swept-wing tailless configuration at near- sonic speed and to determine handling characteristics of such types in the complex transonic zone. No. 2 airplane has now joined the prototype at Muroc for flight tests. Northrop test pilot Charles Tucker, former Thompson Race pilot, has handled all X-4 flying to date. Two 1600-lb.-thrust Westinghouse 19B turbojet units carry tiny craft to 650 mph. speed at 10,000 ft., its maximum design speed.