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Into Friendly Fire: the RP-63 "Pinball"

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Further testing went on by adding aluminium armour to the nose and vulnerable parts of an A-20 twin-engine bomber. The tests showed the frangible bullets were a success. However, a single-engine fighter was required to realistically simulate attacks by German or Japanese interceptors.

The Bell P-63 Kingcobra was chosen as a test-bed. Its performance was adequate and it was not being used by American forces in combat. This meant diverting a few airframes for testing would be less of a problem. Five P-63A-9 were taken off the production lines: serial numbers 24-69647, 42-69654, 42-69769, 42-69771 and 42-69801. They were redesignated RP-63A-11, “R” standing for Restricted (from combat use).

Extensive modifications were carried out. All armament was removed, as well as all internal armour. All forward surfaces were reskinned with heavy sheet metal. The rear part of the canopy glazing was covered with metal sheeting and heavy armoured glass was used for the rest of the glazing. All summed up, the added armour weighed some 1,487.7 lbs.

As it could not be covered with armour plating, it was thought the air scoop would be the most vulnerable part of the aircraft. Various designs were tested. The first prototype had a much smaller “clamshell” scoop, as well as the third and fifth prototypes. The second one had a flush scoop, while the fourth had a standard scoop.

RP-63 #42-69654 was the second RP-63A prototype, featuring the clamshell air scoop. (Photo: USAF).

In spite of the increased weight, performance of the RP-63 was similar to that of the P-63. The RP-63A-11 carried the same V-1710-93 engine as the P-63A-9, but was equipped with water injection. No external fuel could be carried as external fuel tanks would have been too vulnerable. Internal fuel capacity was raised to 126 gallons.

Among other important modifications was also the addition of 109 pressure-sensitive sensors which would record hits on the airframe. To tell students when they scored a hit, every recorded impact would flash a red light located in the propeller hub, where the 37 mm gun had been. As a result, the aircraft were quickly nicknamed “Pinballs”. A counter located in the cockpit would record the total number of hits.

Initial testing of the “Pinball” prototypes proved satisfactory. The handling of the airplane had been modified by the extra weight and its distribution, but these problems were easily ironed out. Nevertheless, future “jump” pilots were understandably uneasy with the idea of being shot at, even with frangible bullets.

Hank Rodrique was one of the pilots assigned to assist gunnery training at Harlingen. He recalls that Bell Aircraft Corporation sent one of its test pilots to demonstrate the Pinball in March 1945. During a staged demonstration, hundreds of frangible rounds were shot at the aircraft. Not a single round penetrated the armour. Instructions on how to handle the heavier aircraft were also given. To avoid “dropping like a rock”, Rodrique remembers that plenty of power had to be used at all times, right until the moment the airplane touched down. During the landing run, brakes had to be used judiciously, and aerodynamic drag was to be used as much as possible to slow the aircraft down.

With the frangible bullet and the RP-63 Pinball developed and proven, gunnery schools could now improve their training programs and put students in highly realistic combat conditions. An order for 95 RP-63A was placed. These aircraft bore the designation RP-63A-12, and carried serial numbers 42-69880 to 42-69974. They were similar to production P-63A-10 aircraft and used the clamshell type of air scoop. By April 1945, training with the Pinballs had begun in all gunnery schools.


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