The Flying Pinball Machine

***image1***Arguably the worst American fighter of World War II was the Bell P-39 Aircobra, which combined inadequate performance – short range, slow rate of climb, low service ceiling and poor maneuverability – with poor handling. One aviation historian noted “it was the single exception to the rule that all U.S. WWII fighters had good, safe flight characteristics.”

When the United States sent P-39s to the RAF early in the war, it was immediately rejected despite Great Britain’s severe shortage of fighters. Unfortunately, a number of Army Air Force units had to use them in combat in the Pacific and North Africa – and suffered heavy losses – until they could be replaced by better aircraft.

Most P-39s were sent to the Soviet Union, where they were more successful (though stories persist of German fighter pilots specifically looking for Aircobras because they were easy kills).

Bell produced a follow-on to the P-39 with a number of modifications and renamed it the P-63 King Cobra. The modifications solved most of the handling problems but still left P-63’s performance inadequate, especially in range and at top speed. Many were sent to the Soviet Union, but structural problems appeared in the aircraft so deliveries were stopped.

This left the Army Air Force in late 1944 with a number of surplus new King Cobras whose performance was inadequate for combat, and this led to one of the most realistic, if bizarre, training programs ever instituted.

In an attempt to provide realistic training for bomber gunners, in 1944 professors at Duke University developed a frangible .50-caliber machine gun bullet made of a lead and graphite compound that would shatter harmlessly against armor plate.

With this bullet, it was decided to attempt to develop a training program to allow gunners to fire these bullets at a single-engine fighter simulating enemy fighter attacks. The P-63 was selected as the “target” aircraft; Bell added thick armored skin, covered the rear part of the canopy with metal sheeting and installed heavy armored glass for the rest of the canopy.

Along with the armor, engineers installed 109 sensors on the skin of the King Cobras; when a frangible round struck a sensor, it would shatter (hopefully) and transmit an electrical impulse that registered on a counter in the cockpit that recorded the total number of hits. This hit would also light a large, bright red bulb mounted on the P-63’s propeller spinner so the gunner knew he had hit his target.

Needless to say, the very appropriate name “Flying Pinball Machine” was quickly adopted.

Initial testing of the Pinball prototypes proved satisfactory, though the aircraft had to be handled carefully because of the extra weight. Soon, the Pinballs were in service – some painted bright orange. By April 1945, training with the Pinballs had begun and the gunnery schools could now put students in highly-realistic combat conditions.

On a typical mission, 12 students would take turns at firing at the Pinball aircraft. Each fired 2,000 frangible rounds at the P-63, but the Pinball was typically hit by only a dozen or so bullets per mission, which said something about the accuracy of bomber gunners.

While broadly successful, the Pinballs were not invulnerable. The air scoops occasionally ingested bullet fragments or entire bullets that would damage the oil and coolant radiators and overheat the engine. Additionally, Pinball pilots were uneasy with the idea of being shot at, even with frangible bullets, because only the forward parts of the aircraft were armored. Students were told to cease fire when the RP-63 broke off its attack and turned away, but occasionally a trigger-happy gunner kept firing and damaged the fighter.

The program was so successful that Bell engineers began work on a dedicated target plane version, the RP-63. It had additional lights added to the fuselage sides, back and on the outer wing upper surfaces to indicate hits more clearly to gunnery students. Armor plating was extended towards the rear of the fuselage, and an order for 450 RP-63Gs was placed, though only 30 were completed. At the end of the war, the Army Air Force Training Command turned its RP-63s over to the new Strategic Air Command to help train B-29 gunners, and they served until 1948.

While the “Flying Pinball” program now looks a bit humorous, it was significant as an attempt to provide truly realistic training for AAF aircrews. Had such a program been developed earlier in the war, it might have allowed American gunners to protect their bombers more effectively during the critical period of the air war over Germany in 1943.

Questions or comments, contact Dr. Michel at marshall.michel@ramstein.af.mil.