A-36 Apache/Invader

Dive bomb Mustang

Design changes

Operational service

Specifications

Serial numbers

3-Way drawings

 

 

Dive bomb Mustang

Is was not untill after the attack on Pearl Harbor that the USAAF finally agreed to order the Mustang for its own use. There was one large problem however: the US military air fleet was expanding so fast there wasn't any money to buy more fighters for the moment.

Lt. Benjamin Kelsey had no funds left for development of fighter aircraft (or pursuit aircraft as they were also named, hence the prefix “P-“) so he came up with an idea to get the US involved in the design. NAA came up with a Mustang designed specifically for the attack role. Naming the aircraft A-36 (next logical designation of attack aircraft), Kelsey was able to utilize some funds allocated to ground attack aircraft.

Dive bombers were not popular at that time, but the Germans proved the value by such aircraft with their JU-87 Stuka. NAA designation of the type was “NA-97”.

On April 16th , 1942, the USAAF ordered 500 NA-97's. The A-36 carried different names throughout its lifetime. It was initially called “Apache” by the Army and was later called “Invader” following the invasion of Sicily . In practice the name “Mustang” was however generally applied by most people. Serial numbers for the A-36 were 42-83663 to 42-84162.

These were to be the first Mustangs to be specifically ordered for American service. The A-36A first flew on September 21st , 1942, with NAA test pilot Ben Chilton at the controls.

 

Design changes

The A-36 incorporated the following changes in design:

  • It was powered by an uprated Allison V-1710-87 (F21R) engine, rated at 1325 hp at 3000 feet.

  • The A-36A was stressed for high-speed dives resulting in the addition of a set of fence-like hydraulically-operated dive brakes.. These were located approximately at mid-chord on the top and bottom of each wing outboard of the guns. They resided resessed in the wings but could be openened to 90 degrees by a hydraulic jack to slow diving speeds down.
    In a vertical dive the A-36 reached speeds of over 500mph. Opening the dive brakes would slow them down to about 390mph. In practice the angle of dive was reduced to 70 degrees because the high stress of pull-out from a higher angle.
    Courtesy of In Action 45 - P-51 Mustang by Squadron/Signal Publications

  • The addidtion of 2 hard points under the wings for 500 pound bombs, 75 US Gallon (284 liter) fuel tanks or smoke curtain equipment. The hardpoints were close to the main gear to reduce stress.

  • The L-shaped pitot tube was replaced by a pitot boom on the wing's leading edge, near the wingtip (because of the bomb racks).

  • 2 landing/taxi lights which are located together in one housing on the leading edge of the left wing.

  • A fixed radiator intake scoop was used.
    Courtesy of In Action 45 - P-51 Mustang by Squadron/Signal Publications

  • The air filter was placed inside the carburetor scoop which resulted in a wider inlet.

  • Armament was changed to six .50 caliber guns, two in lower fuselage nose and four in the wings. The wing guns were moved closer to the main landing gear in order to minimize stress under taxi and takeoff. The nose guns were often deleted in the field to save weight.
    Courtesy of In Action 45 - P-51 Mustang by Squadron/Signal Publications

    Courtesy of In Action 45 - P-51 Mustang by Squadron/Signal Publications

The top speed of the A-36 was down to about 358 mph at 5,000 feet (without external stores), because of the added weight in the new design.

A single A-36A would be passed on to the British in March 1943. This one aircraft was designated in RAF service as the "Mustang I (Dive Bomber)". It had RAF serial number EW998. The British did not place any A-36 orders however.

A-36 Apache EW-998
EW-998 (42-83687) was the only A-36 delivered to the RAF.

Operational service

In the meantime, A-36As were pouring into North Africa by the hundreds, with a total of over 300 in action by May. The A-36A equipped the 27th and 86th Fighter Bomber Groups based in Sicily and in Italy . On June 7th , the USAAF performed its first combat mission with the Mustang, performing attacks on the Mediterranean island of Pantelleria , with the first sortie being flown on June 6th , 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 A-36 proved to be a good dive bomber as it was a very stable platform and very effective in ground strafing runs. Dive bombing was usually initiated at about 10,000 – 12,000 ft with a diving speed of around 250 – 300mph with diving brakes deployed. The bombs were dropped at about 3,000 ft and pullout was done at approximately 1,500 ft.

When not in the ground attack role, the A-36 was essentially a low-altitude P-51A and was used as a fighter. The A-36 scored 101 air-air victories during WWII. One of the pilots of the 27th Fighter Bomber Group, Lt. Michael T. Russo, became the only ace in the Allison-engined Mustang

Although it is often said that the A-36 was not particularly effective during combat, on 23,300 combat mission only 177 A-36s were lost. Keep in mind that they were almost constantly involved in low altitude fighting (often as low as 20 ft dodging trees, buildings, …) and were submitted to intense AA fire.

A-36 42-83671 (USAF)
A-36 with serial number 42-83671. Note the dual landing/taxi light and straight pitot-tube.

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 Apaches 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.

Back to top - Next page

Copyright © 2007 Christophe Haentjens - http://www.crazyhorseap.be