MPM 1/72 Northrop XP-56 Black Bullet By Jim Schubert

History

Jack Northrop's first true "Flying Wing" was the N-1M of 1939, which led to the derivative N-9M series built as flying models 35% of the size of the projected B-35 bomber.  In 1940 the USAAF issued its famous - or infamous, depending on your point of view, Request For Data R-40C encouraging the development of unusual technology in fighter production.  R-40C ultimately yielded:

1.  Bell's XP-52, no name, a twin-boom, pusher layout, which was to have been powered by a Continental XIV-1430, an experimental inverted V-12.  It was never built and was canceled in favor of Bell's XP-59 (No; not the jet.).

2.  Vultee's XP-54 "Swoose Goose" twin-boom, pusher layout powered by a Pratt & Whitney X-1800 (H-2600) or Lycoming's XH-2470 24 cylinder liquid cooled "X" configuration engine.  Chosen as the winner of R-40C.  Two were built and flown.  A redesign - never built - using a Wright R-2160 engine, a 42 cylinder - six rows of seven cylinders - liquid cooled radial engine, was designated XP-68.

3.  Curtiss' XP-55 "Ascender" (in the field it was called the "Ass-Ender") canard, pusher layout powered by an Allison V-1710 engine.  Three were built and flown.

4.  Northrop's XP-56 "Black Bullet", the subject of this review.

5.  Bell's XP-59, no name, a revision of their XP-52.  None were built but in an effort to create confusion and help keep it a secret, Bell's jet "Airacomet" was given the same model designation.

6.  McDonnell's XP-67 "Moonbat", twin engined - two Continental XIV-1430s inverted V-12s - blended wing/body, tractor layout.  One built and flown.

7.  Republic's XP-69, no name, conventional tractor layout taildragger powered by a Wright R-2160 42 cylinder liquid cooled radial engine.  None built.

8.  General Motors Fisher Division's XP-75 "Eagle" conventional tractor layout taildragger powered by an Allison V-3420, which was in fact a "W" configuration, being essentially two V-1710s laid crank-to-crank on the same block like the Double Daimler DB610 in the Heinkel He 177 "Greif".  30 were committed to production, but only one was finished and flown.

None of these airplanes had their engines in the nose; they were either rear engined pushers or mid-engined tractors with extension shafts to nose mounted props.  All, save the two noted, had tricycle landing gear.

Northrop submitted his NS-2 design in response to R-40C and was awarded a contract for two prototypes.  This flying wing fighter had a very short monocoque fuselage and conventional wing and ventral fin structures of Heliarc welded magnesium.  In the early 1940s magnesium was not yet the critical war material that it would become by war's end.  The USAAF assigned the designation XP-56 and issued serials 41-786 and 42-38353 for the pair.  The type was nicknamed "Black Bullet".  The flying wing was controlled in pitch by trim-tabbed, mid-span "elevons" acting together.  In roll, the elevons acted differentially.  Yaw was controlled by wing tip mounted split-flap drag rudders; small yaw inputs were made via "trimmer" surfaces atop the wing forward of the "rudders".  A large ventral fin for directional stability also kept the tips of the pusher contra-props from striking the ground on take off and landing.  Landing flaps were fitted inboard on the wing T.E.  The pitch-down effect caused by lowering the flaps was countered by the elevons moving up for a pitch-up effect; this creates a lot of trim drag, but that's what you want when you're landing an otherwise very clean airplane.  The air-cooled 2000 HP twin row Pratt & Whitney R-2800-29 Double Wasp was installed amidships slightly aft of the CG and drove the three bladed contra-props via an extension shaft.  Engine cooling air was fed to the buried engine by large air inlets in the L.E. of each wing root.  A large engine driven fan mounted just ahead of the cowl flaps, running at more than prop shaft speed, assured a good flow of cooling air.  Cowl flaps, just forward of the props, controlled cooling airflow to maintain the best cylinder head temperatures.  The tricycle gear, although large and long legged, was otherwise conventional.  The fighter was to mount four .50 caliber machine guns and two 20mm cannon when fully developed.  No armament was ever fitted to either prototype although 41-786 had some provisions for armament built in.

I deduce from my reading that 41-786, initially, may have had no dorsal fin at all with the cockpit fairing arcing smoothly down to terminate just in front of the cowl flaps.  Can any reader comment on this and provide a photo, drawing or sketch?

At roll out 41-786 was painted O.D. over gray with white star in blue roundel insignia in four places.  Prior to its first flight the plane was repainted aluminum overall with yellow prop spinners (the kit's painting instructions don't mention the yellow spinners, but the color difference is evident from the different gray tones in contemporary B&W photos) and carried white star in blue roundel with white bars insignia, all outlined red, in four places. 

The first flight on September 6, 1943 at Muroc Dry Lake was made straight ahead at a height of about four feet and a speed of about 140 MPH and was followed, after a fast taxi back to the upwind starting point, by a similar flight.  After these two flights, test pilot Johnny Myers remarked on poor directional stability and control.  Before flight-testing resumed a small dorsal fin cap was added to improve directional stability.  On October 8 two high-speed taxi tests were followed by a short straight flight at a height of 10 to 15 feet.  Another high-speed taxi positioned the plane upwind for another low altitude straight-line flight.  On the return taxi at about 130 MPH the left main tire blew.  The resulting pitch-up caused the airplane to flip over backwards, slide upside down and tumble end-over-end across the dry lakebed.  The engine and propellers separated and were ejected from the tumbling mass of wreckage along with Johnny Myers still strapped in his seat.  Thanks to his polo helmet he suffered only minor injuries, but 41-786 was a write-off.

The second airplane, 42-38353, was rolled out in September of 1943 painted O.D. over gray with yellow fin tips carrying star and bar insignia no longer outlined in red.  The second plane differed from the first in having a tall dorsal fin in an attempt to improve directional stability and to improve pilot safety in a rollover.  The wing tips were changed to incorporate large venturiis feeding a bellows mechanism to boost rudder deployment to harmonize control loads.  A small wheel was added to the tip of the ventral fin to prevent the fin digging into the ground on over rotation during takeoff or landing.  The combination of the loss of 41-786, the type's poor handling, poor stability and, especially, the advent of jets led the USAAF to terminate the test program after ten flights, in which speeds up 300 MPH and an altitude of 2,500 feet were reached.  In 1946, 42-38353 was given to the nascent NASM collection.  In 1982 it was transferred to Northrop for restoration.  Does any reader know the status of this restoration?

The Kit

This kit, from which only 41-786 can be built, is typical of recent MPM offerings, which is to say it's quite good.  47 main parts, on two sprue trees, are well molded in light gray styrene with no sink marks, warpage or other distortions.  Interestingly the block of parts required to build 42-38353 have obviously been cut from one of the trees to ensure that you will buy another kit when MPM reissues this one as the second XP-56 prototype, 42-38353.  Five well molded resin parts are provided:  the cooling air inlet guide vanes, two gun fairing blisters and, what looks like, a radio box that fits under the rudder pedals.  I would have liked for the guide vanes to be deeper to provide a greater sense of depth in the intakes.  The parts map shows one injection molded clear styrene windscreen/hood unit but two were, in fact, provided.  The small, well printed, in perfect register, decal sheet provides all the markings for both of 41-786's color schemes.  The eight-page instruction folder is typical of current MPM practice and covers matters quite well.

The fuselage is split vertically and is provided with a reasonably detailed cockpit for a closed-hood model.  If you choose to open the right side hinged hood, you'll want to imagineer a more detailed cockpit.  I'm thinking a True-Details P-47 resin interior trimmed to fit would do the job nicely.  A separate, undetailed, nose wheel well is provided.  The deep section wings, incorporating undetailed separate wheel wells, are butt jointed to the fuselage.  The spinner for the contra-props is, unfortunately, molded in one piece locking you into a single position for the two props.  I'd cut the spinner and fit two concentric shafts to permit the two props to rotate independently.  Take care to assure the rear prop is left-handed and the front prop is right-handed when viewed from the rear.

Nit-Picks:  1.  The exhausts are very weakly modeled.  Study photos and drill out oval holes in the fuselage to accept short lengths of small diameter, thin walled tubing in nine places. 2.  The running lights are very weakly indicated on the separate wing tips. 3.  There is no tail running light blister on the T.E. of the short dorsal fin. 4.  The instructions show, graphically, that weight must be added in the forward fuselage to keep the model sitting on its nose wheel, but don't indicate how much weight. 5.  The inner cover doors for the main wheels are incorrectly scribed.  They should be the shape shown in the kit's painting guide.  These doors were only open whilst the main gear was in transit during retraction and extension. 6.  The previously mentioned lack of the yellow spinners on the overall painted-aluminum color scheme.  7.  MPM is still using those damned flimsy end-opening boxes.  All of these, save the last, are minor and easily dealt with by the average modeler.

Conclusion

Another winner from MPM for oddball airplane fans like me.  This is an extremely unusual subject, which no other manufacturer is likely to touch.  I believe we now have kits of six of Northrop's flying wings commonly available to us in 1/72 scale:  The N-9M from Sword; the XP-56 and the X-4 from MPM; the X/YB-35 and YB-49 from AMT and the B-2 from Testors.  Have I missed any?  (Planet Models has done the N1M in resin. Ed.) Now, Messrs. MPM, how about the N-1M, MX-324/334 and JB-1?

References

The Flying Wings of Jack Northrop:  G. Pope, J, Campbell & D. Campbell; Schiffer; Atglen, PA; 1994; ISBN 0-88740-597-5.   A good selection of 10 photos and one general arrangement drawing of the XP-56:  the best, albeit shallow, single source reference on all of Northrop's wings.

The Northrop Story:  R. S. Allen; Orion; New York; 1990; ISBN 0-517-56677-4.

Winged Wonders - The Story of the Flying Wings:  E. T. Woolridge; Smithsonian Press; Washington; 1983; ISBN 0-87474-966-2.

Northrop - An Aeronautical History:  Fred Anderson; Northrop; Century City, CA; 1976; Library of Congress #76-22294

Northrop Flying Wings:  Ed. Maloney; World War II Pubs.; Corona Del mar, CA; 1975; ISBN 0-915464-00-4.