Tuesday, May 22, 2012

Black Bullet

Jack Northrop had a knack for thinking outside the box...and coming up with radical, unusual aircraft designs. And not all of them worked...the XP-56 Black Bullet is a shining example of that kind of glorious "failure" that comes from pushing the envelope of design.

Our two "photos" today are morphs, glossy 8x10 press photos that are based on actual photographs of the aircraft, but which are heavily retouched by an artist. Keep in mind, this was war time, and the rules on releasing actual photos of cutting edge, experimental aircraft, were quite restrictive on what could actually be shown.

Ever obsessed with developing the flying wing aircraft design - and taking advantage of the reduction in aerodynamic drag that the elimination of the tail surfaces provided - Northrop envisioned an extremely fast, maneuverable fighter.

Both photos carry the identical mimeographed cut line pasted on the back, which reads, "Northrop Aircraft's XP-56 -- an extremely advanced pusher type pursuit plane, and the first of its type ever designed and built.  The streamlined nacelle, vertical fins above and below, and the absence of a conventional tail give the XP-56 a startling and unusual appearance." The images are also stamped as approved for publication by the War Department.

The source photo which the artist of the publicly released version
worked from shows the second XP-56 on jacks in a hangar at
Muroc. This photo is from the National Museum of the Air Force,
via Tony Landis' excellent book Experimental and Prototype
It didn't work out so good. The original design, which Northrop called the N2B, did not have the upper vertical stabilizer shown here, and directional stability on the first flights was severely lacking.

Jack's concept was actually designed around a proposed liquid-cooled 24-cylinder H-block engine, Pratt & Whitney's X-1800. When the engine builder gave up on that design, however, Northrop was forced to adapt the airframe's design to accommodate a very different engine shape, the air-cooled Pratt R-2800 radial engine, which was embedded in the fuselage right behind the cockpit. The engine drove two contra-rotating pusher props, and excessive flexing of the drive shafts caused additional problems.

The first of the two prototypes was destroyed while doing a high-speed taxi test on Muroc's lakebed, when the left tire disintegrated and the plane went out of control. The second prototype, 42-38353 and the aircraft shown here, took over testing. A number of design changes were made to try to improve the stability, including the addition of the upper vertical and the installation of an innovative flaperon system that was pneumatically actuated (by a system of bellows powered by air from the venturiis on the wingtips). First flight of 42-38353 was on March 23, 1944, but was very short, since the pilot experienced problems in pitch control, with the aircraft acting extremely nose-heavy. There were other problems, as well, including excessive fuel consumption and an inability to fly anywhere near the top speeds that the engineers expected.

To investigate the causes of these issues, NACA was asked to test the aircraft in their giant wind tunnel at Moffatt Field. However, higher priority projects pushed the XP-56's schedule to the right, so some additional tests were flown at Muroc. The handling qualities problems continued, and further testing was not deemed safe. The wind tunnel testing was delayed another year, and by this time the war was over and the age of jet aircraft was dawning. Ultimately, the Air Corps gave up and cancelled the program. The sole surviving XP-56 is stored awaiting restoration at the National Air and Space Museum.

Oh, and no, despite the name, the XP-56 was never painted black.

The mimeographed caption on the photo's back

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