Only after Pearl Harbor did the US Army finally agree to order the Mustang for its own use. General H. H. "Hap" Arnold, Chief of Staff of the USAAF, was instrumental in breaking up the bureaucratic log-jam and getting the Army to relent and order the Mustang for its own use. On April 16, 1942, the Army finally ordered 500 NA-97s. The NA-97 was a ground attack version and was designated A-36A (in the attack series rather than the fighter series). Serial numbers were 42-83663/84162.
There is a considerable amount of confusion and misinformation about the correct name for the A-36. Names such as Invader and Apache have also been associated with the A-36, but the correct name is and always has been Mustang. There was a brief effort to change the name of the A-36 to Invader following the invasion of Sicily in order to distinguish it from the fighter versions in press coverage. The Army turned down the request, since they didn't want to reveal to the enemy that they were facing a dive bomber version of the fighter. In addition, the name Invader had already been assignated to the Douglas A-26. There is a persistent myth that the A-36 was initially called Apache, which was the name that the Army had initially assigned to the very early P-51. However, this story has no basis in fact, and was in fact a myth that originated in the 1980s.
The A-36A differed from previous Mustang versions in having a set of hydraulically-operated perforated door-type dive brakes mounted at approximately mid-chord on both the upper and lower wing surfaces outboard of the wing guns. The brakes were normally recessed into the wings, but were opened to 90 degrees by a hydraulic jack to hold diving speeds down to 250 mph. A rack was fitted under each wing for a 500-pound bombs, a 75 US gallon drop tank, or smoke-curtain equipment. A built-in armament of six 0.50-inch machine guns (two in lower fuselage nose, four in the wings) was fitted, however the two nose guns were often omitted in service. The wing guns were moved closer to the main landing gear strut in order to minimize stress under taxi and takeoff conditions. The engine was the Allison V-1710-87 (F21R), rated at 1325 hp at 3000 feet. Normal and maximum loaded weights rose to 8370 pounds and 10,700 pounds, and the maximum speed in clean condition fell to 356 mph at 5000 feet and 310 mph with the two 500-lb bombs fitted. With the bombs, range and service ceiling were 550 miles and 25,100 feet respectively.
The first A-36A flew on September 21, 1942. Deliveries of the A-36A were completed by the following March. The A-36A equipped the 27th and 86th Fighter Bomber Groups based in Sicily and in Italy. They initially were painted in olive-drab and light-gray finish and were painted with yellow wing bands and yellow circles around the national insignia. Both of these Groups arrived in North Africa in April of 1943 just after the end of the Tunisian campaign. They saw their first action during aerial attacks on the island of Pantelleria, with the first sortie being flown on June 6, 1943. The A-36A was involved in the taking of Monte Cassino, and participated in the sinking of the Italian liner Conte di Savoia.
The only other A-36 user was the 311th Fighter Bomber Group, based in India. It saw extensive use in the China-Burma-India theatre.
Several sources list the A-36 as not being particularly effective during combat. It seems that this is not strictly correct. Although losses during low-level attacks were rather high, the A-36 was actually a good dive bomber and it was a stable and effective ground strafer. The engine was very quiet, and it was often possible for an A-36 to get nearly on top of an enemy before he realized that an attack was imminent. Dive bombing was usually initiated from an altitude of 10,000 feet to 12,000 feet, with bombing speed held to around 300 mph by the dive brakes. The bombs were dropped at an altitude of 3000 feet, and pullout was at approximately 1500 feet. The A-36 was fairly rugged and easy to maintain in the field. The A-36 could consistently stay within 20 feet of the deck and could easily maneuver around trees, buildings, and other obstacles while strafing. The A-36A was able to take a considerable amount of battle damage and still return to base. Nevertheless, a total of 177 A-36As were lost in action.
The A-36s did not see very much air-to-air combat, since it was optimized for low-altitude operations and lost its effectiveness above 10,000 feet altitude. It was generally believed that the A-36 was no match for the Messerschmitt Bf 109 at high altitudes, and that it was therefore best for A-36 pilots to avoid such encounters if at all possible. If air-to-air combat was unavoidable, it was thought best to force the battle down to altitudes below 8000 feet, where maximum advantage could be taken of the A-36A's excellent low-altitude performance. Although it was not a fighter, the A-36 claimed 101 enemy aircraft destroyed in air-to-air combat. One of the pilots of the 27th Fighter Bomber Group, Lt Michael T. Russo, became the only ace in the Allison-engined Mustang, although several other of his colleagues did score victories as well.
A sort of urban legend has sprung up about the A-36A's dive brakes. According to some stories, the dive brakes of the A-36A were next to useless and were deliberately wired shut at the manufacturers so that they could not be used. This story is totally incorrect. On the contrary, the dive brakes proved to be quite effective in combat, and the aircraft was so stable with the dive brakes extended that bombing while in a dive was particularly accurate. The origin of this legend seems to have been in the United States, at a time before the A-36s first went overseas. It seems that A-36A pilots were told by their officers in the USA that their dive brakes would be all but useless in combat and it would be best if they simply wired them shut. This turned out to be incorrect, and the dive brakes were used to great effect throughout the Sicilian campaign and the Italian invasion.
One A-36A was supplied to the RAF in March of 1943 for experimental purposes. Its RAF serial number was EW998.
There are very few A-36As still surviving today. A-36A Ser No 42-83665 is on display at the WPAFB Museum in Dayton, Ohio. 42-83731 is with the Lone Star Flight Museum in Texas. 43-83738 is currently undergoing restoration as a P-51B at the Warhawk Air Museum in Boise, ID. Another A-36A is with the Collings Foundation, where it is undergoing restoration.
Serial numbers of the A-36 were 42-83663/84162.