Northrop X-4 by Collectaire

1/48 scale
Kit No: 4840
Cost: $100.00
Decals: One version
Comments: Cast resin with white metal detail parts and vacuform canopy


The Northrop X-4 Bantam was a prototype small twin-jet aircraft manufactured by Northrop Corporation in 1948, specifically to test whether a swept-wing semi-tailless design was capable of operating effectively at speeds approaching Mach 1. Spawned in part by wartime research that led to the development of Nazi Germany’s Messerschmitt Me 163 Komet, as well as Northrop’s own previous flying wing designs of the 1940’s, the X-4 had no horizontal tail surfaces, depending instead on combined elevator and aileron control surfaces (called elevons) for control in pitch and roll attitudes, just as the Me 163 had. Some aeronautical engineers believed that eliminating the horizontal tail would do away with stability problems at high speeds resulting from the interaction of supersonic shock waves between the wings and the horizontal stabilizers, which were thought to be the cause of stability problems at transonic speeds up to Mach 0.9. The purpose of the X-4 was to put that concept to the test.

Northrop built two X-4s. Drawing on experience gleaned from Northrop’s earlier flying wing designs (the N-1M, the XB-35 and YB-49), these two aircraft provided a wealth of data for the U.S. Air Force and the National Advisory Committee on Aeronautics (NACA, the forerunner to NASA, National Aeronautics and Space Administration). The X-4 had a cutting edge design featuring a one-piece bubble canopy which opened upward on rear hinges, and provided pilots superb visibility not seen again until the introduction of General Dynamics’ F-16 in the 1970’s.

The No. 1 aircraft was first flown by Northrop on Dec. 16, 1948 at Muroc Dry Lake in the California desert. The second X-4 made its initial flight on June 7, 1949. The No. 1 aircraft proved mechanically unreliable and was grounded after its 10th flight to provide spare parts for the No. 2 aircraft. Aircraft No. 2 proved far more reliable, and Northrop made 20 test flights with it before handing it over to the Air Force and NACA after the 20th test flight on February 17, 1950. In the late summer of 1950, NACA conducted a further series of test flights with Air Force pilots at the controls, including Chuck Yeager, Frank Kendall Everest, Jr., and Jack Ridley, among others. Starting on September 28, 1950, NACA took over the test flight program itself.

The initial NACA X-4 flights, which continued from late 1950 through May of 1951, focused on the aircraft’s sensitivity in pitch. NACA pilots Griffith and Scott Crossfield noted that as the X-4’s speed approached Mach 0.88, it began a pitch oscillation of increasing severity, which was likened to driving on a washboard road. Increasing speeds also caused a tucking phenomena, in which the nose pitched down, a phenomenon also experienced by the Me 163A Anton prototypes in 1941. More seriously, the aircraft also showed a tendency to “hunt” about all three axes. This combined yaw, pitch and roll, which grew more severe as the speed increased, was a precursor to the inertial coupling which would become a major challenge in the years to come.

To correct the poor stability, project engineers decided to increase the flap/speed brake trailing edge thickness. Balsa wood strips were added between the flap/speed brake halves, causing them to remain open at a 5-degree angle. The first test of the blunt trailing edge was flown on 20 August 1951, by NACA pilot Walter Jones. A second test was made by Scott Crossfield in October. The results were positive, with Jones commenting that the X-4’s flight qualities had been greatly improved. The X-4 did not have pitch control problems up to a speed of Mach 0.92 — the fastest recorded flight it ever made, on January 24, 1951 with Scott Crossfield at the controls . The program ended in September 1953 with the 102nd and last flight of the No. 2 aircraft, after proving that swept wing aircraft without horizontal tails were not suitable for transonic flight (flight near the speed of sound). It was not until the development of computerized fly-by-wire systems that a design of this type was proven to be practical.

The No. 2 X-4 was used in the joint USAF/NACA program to explore stability problems near the speed of sound. Both aircraft survived the test program without serious incident. The No. 1 X-4 is displayed at the Air Force Academy. The No. 2 aircraft was transferred to the National Air museum shortly after the program ended. It was restored by the Western Museum of Flight in Hawthorne, California.


Span: 26 ft. 10 in.
Length: 23 ft. 3 in.
Height: 14 ft. 10 in.
Weight: 7,550 lbs. maximum
Armament: None
Engines: Two Westinghouse XJ-30 turbojet engines of 1,600 lbs. thrust each
Crew: One

Maximum speed: 640 mph
Cruising speed: 480 mph
Maximum endurance: 44 minutes
Service ceiling: 44,000 ft.

The Kit

Collectaire’s Northrop X-4 presents modelers with something extraordinary. First is the dramatic box art that is a hallmark of Collectaire kits, in this case a portrait of the X-4 in a near-vertical climb above what appears to be a remote airstrip (Muroc, circa 1948?). Then there are the trademark yellow labels on the kit on all sides save the bottom. The kit comes in a hard cardboard flip-up box, and the components are thickly wrapped in white tissue paper — packed by hand. The first such package holds a zip-lock bag containing the decals and two vacuform canopies. The second tissue-wrapped package contains two more zip-lock baggies, one holding 21 cast resin parts, the second containing 25 white metal parts. The wings and fuselage bear lightly engraved panel lines, and the nose section features realistically hollowed out jet intakes. Likewise, the tail section has detailed, hollowed out twin jet exhausts. The wheel wells for the main landing gear are deep and feature raised interior detail. The cockpit tub features thin sidewalls with good interior detail, but it could be a bit more crisp. The wheels of the main landing gear are realistically molded with clearly defined spokes, and the main landing gear themselves, like the nose gear, are well-detailed white metal parts. The cockpit features white metal parts for the pilot’s seat, instrument panel, and control column.

This is a limted run kit that will take a bit of work, but is in a scale large enough for the modeler to see the fruits of his labor once complete. The heart of the kit is the one-piece wing, which is molded so that it includes the center section of the fuselage. The nose and tail components — which given the overall size of the X-4 are relatively small in relation to the wing, the largest part of the airframe — must be cemented on with cyanaoacrylate glue, and some skillful puttying and seam-hiding will be required afterward. Although the white metal parts for the cockpit will add detail to the kit, a bit more more will be required if, for example, you want seat straps, as these are not molded onto the seat and not included separately. Photo-etch details or the old-fashioned method of masking tape, painted and perhaps treated with some sort of finish, will put a nice finishing touch on the cockpit. The decals are by Scalemaster (the high quality Invisa-Clear line) and provide the option for depicting the X-4 in either USAF or NACA markings, Aircraft No.1 (Serial No. 46-676) or No. 2 (Serial No. 46-677), respectively.


Make no mistake, this kit is pricey, but you get a high quality, and relatively rare, aircraft kit for your money. The only other option in 1/48 scale (or close to it) are the painted mahogany examples from the Phillipines for even more money. In 1/72 scale, MPM once put out a kit that is now out of production, but does not come close to the level of detail seen in Collectaire’s kit. Highly recommended.


  • National Museum of the United States Air Force
  • Photo File: Northrop X-4, International Masters Publishers AB. Aircraft of the World, Copyright 2007.


DAYTON, Ohio — Northrop X-4 at the National Museum of the United States Air Force. (U.S. Air Force photo)

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