One aircraft type in the X-series of experimental aircraft was the Northrop X-4. The X-4 Bantam made the maiden flight on 16^th December 1948 with company test pilot Charles Tucker at the controls. Designed and built specifically for NACA it was tasked with acquiring in-flight data on the stability and controllability of semi-tailless aircraft at high subsonic speeds and was powered by two Westinghouse XJ30 turbojet engines. Each of these was rated at 1,600 lb s t giving a performance of up to 620 mph and 40,000 ft altitude.

 Two examples of the X-4 were built and during the six-year programme these single-seat, low swept wing semi-tailless aircraft helped to demonstrate that tail surfaces ware important for proper control effectiveness in the transonic speed range. They were also extremely used in the investigation of problems unique to tailless aircraft at low speeds, such as longitudinal stability and control.

 Both still survive, the first (46-676) being at the USAF Academy in Colorado Springs whilst the second (46-677) is owned by the USAF museum. 

 Vac-form kit consisting of one white sheet of acetate with all the vac form parts on it. A separate canopy comes in clear but thick acetate. There are injection-moulded parts comprising of wheels, oleo legs and ejection seat. The main parts are the fuselage halves and three-piece wing i.e. the lower part moulded in one piece and two separate upper wing halves.

  A 4-view scale plan gives a clear indication of the shape of x-plane that the kit will take when assembled. I noted that the kit wing parts had a slightly more swept than the one shown on the drawing making it difficult to discern which was the correct one. Finally I opted for the kit shape to be correct after consulting several photos of the type. These also indicated that the nose wheel and leg needed to be replaced with a slightly larger combination.

 The kit major parts were first marked and cut from backing sheet by simple time-honoured method of scoring around the edges with a modelling knife, then breaking the parts away. The amount of rubbing-down required depended on the amount of edge or lip that is left. Rubbing down is followed on wing halves and checked against each opposing part for accurate match. I prefer dry rubbing but wet rubbing can also be used in the rubbing down process.

 The fuselage is also cut and sanded. The wheel wells were then cut at all three places and also the cockpit aperture was cut and shaped oval. The canopy itself, which is rather thick in section, was brought to fit using a new blade trimming little by little. The canopy was then placed aside to fit at a later stage. With the fuselage and wing parts prepared the fuselage interior detail was added. Wheel well detail was also added using channels shaped from stretch sprue. Cockpit was painted light grey with a black ejection seat, instrument panel and control column.

 The fuselage parts were cemented together using liquid cement and held together with pegs. The wing parts were also glued together. When these dried sufficiently the fuselage was checked and inserted at the space or gap left between the upper wings and more glue applied. These formed a complete fuselage and wings assembly. Checking the assembly from front the tail should look exactly perpendicular to the wings and not showing any tilt to the right or left. A small amount of filler is added at joining areas particularly the aft jet exhaust area. Two jet pipe pieces were added to the rear. These were cut to size from surplus ballpoint body. These were inserted inside the empty outlet allowing these to protrude 1mm at the rear before applying glue.

Turning to the underside of the model, the wheel wells are painted zinc chromate green and the undercarriage legs are then fixed. The nose wheel leg was made from plastic card and sprue glued together and filed to shape. The kit parts for the nose wheel well doors were too thick and I fashioned new ones from a thin sheet of plastic card, adding detail to the inner side of doors. The nose wheel itself was substituted from one in my spares box. Wing undercarriage legs also fitted and finally small details such as the nose and tail fin metal probes, rudder balance weights crew figure were all added at this stage and the model was now ready for paintwork.

Only two aircraft of the type were built however in spite of this the X-4 wore a variety of paint finishes. This goes from an overall orange scheme to an overall white one, another in NASA markings and there is also another interesting and colourful scheme worn by the X-4 accommodated at the USAF Academy museum in Colorado Springs. This was white finish with bright red stripes and USAF star and bars. I opted for this scheme in spite that it involved a lot of preparation. Model was first painted overall semi gloss white, allowed to dry overnight and then started the long process of masking to bring out the positions of the red stripes. As for decals I had to resort to Superscale sheet No 72-83, which had the star and bars; and Scale Master decal sheet SM-32B that had the right size of USAF letters.

 Not a simple quick build as the small size of kit may implicate, but all in all I thoroughly enjoyed making this model. It is not the type of kit for the impatient youngster but it is definitely recommended for those with experience of building vac-form kits. 

Scale Aircraft Modelling

Carmel J. Attard