entire engine nacelle was nearly as long as a Republic P-47 Thunderbolt. Research showed that a force roughly equivalent to was generated by each engine exhaust during high speed cruise while at altitude. Each engine featured twin General Electric turbochargers at the rear of the nacelle and for brief bursts of additional power, water-methanol injection. The XF-12 was originally intended to use contra-rotating propellers similar to those used on the XF-11, However, due to delivery delays and reliability issues, they were never installed. They would have been twinned three-bladed propellers (rotating in opposite directions). As it was, the aircraft used standard four-bladed Curtiss Electric propellers. The only visible external difference between the first and second prototypes was the addition of cooling gills on the upper engine cowlings. The second prototype was fitted with the full reconnaissance equipment suite. Operational history The first prototype was damaged on 10 July 1947 while undergoing maximum landing weight tests when the right main gear was severed at the engine nacelle. After bouncing hard and staggering back into the air the test pilot climbed to a safe altitude where excess fuel was burnt off, to lighten the aircraft and reduce the risk of fire. The pilot landed on the left main gear and the nose wheel and despite losing as much speed as possible before the other wing dropped, the aircraft suffered significant damage. The wing spar was cracked, and engines and props needed to be replaced but it was repaired by Republic, and returned to service. When the U.S. Army Air Forces became the U.S. Air Force the XF-12 was later re-designated XR-12. Operation Birds Eye was conceived to demonstrate the XF-12's capabilities. On 1 September 1948, the second prototype departed the U.S. Air Force Flight Test Center at Muroc, California, and climbed west to its cruising altitude over the Pacific before heading east. It then photographed its entire flight path across the United States on 390 individual photos each covering , which were jointed to form a continuous print. They landed at Mitchel Field on Long Island, New York after six hours and 55 minutes at an average speed of . A photo was taken approximately every 66 seconds. The flight was featured in the 29 November 1948 issue of Life magazine and the filmstrip exhibited at the 1948 U.S. Air Force Association Convention in New York. The XF-12 program had already been