Mustang I

Mustang production begins

Reconnaissance missions


Serial numbers

3-Way drawings



Mustang production begins

After the quick development of the prototype by NAA, the first stage of production moved along at a slower rate. The second Mustang to be built was the first NA-73 production aircraft (AG345) and it did not fly until April 23rd , 1941, six months after NA-73X . It carried no weapons and was kept by NAA for testing, squawk fixing and development.

AG345, the first production Mustang (NAA)
AG345, the first production Mustang

The second production airplane (AG346) was the first aircraft with the full armament installed (four .30 caliber and four .50' caliber machine guns) and was crated up and shipped to England in September of 1941. The RAF received its first Mustang in Liverpool in October, 1941, about a year after the prototype's first flight. It made its first flight over British soil on October 24th, 1941. To make matters worse, 20 aircraft were lost at sea when the boat transporting them was sunk.

AG346 was fitted with a British VHF radio, had its gunsight and other incidental gear installed.

Mustang Is had the traditional British control stickOnce all of the British equipment was installed, the entire aircraft was ready to be evaluated at the Aeroplane & Armament Experimental Establishment at Boscombe Down and by the Air Fighting Development Unit at RAF Duxford. The newly-arrived Mustang was quickly recognized as being the best fighter aircraft yet to be delivered from the USA .

When the British performed tests on the Mustang I, they were very enthusiastic about its performance. Due to its advanced aerodynamics, it was a clear 30 mph faster than the P-40 and the Spitfire Mk VC, although it had the same Allison engine as the P-40, used the 3-blade Curtiss Electric propeller and weighed more than both the Spitfire and P-40. It flew 328mph at 13,000ft

It was also more maneuverable at low altitudes and handling proved to be excellent. The armament of four 0.50 inch and four 0.30 inch machine guns was heavy and effective. The range was nearly double that of any RAF single-engined fighter.

There were some points of concern however:

  • The cockpit layout differed from that of other RAF fighters
  • The 7.62 millimeter (0.30 caliber) machine guns used by the Mustang used ammunition incompatible with the standard British 7.9 millimeter (0.303 caliber) guns

Installation of an Allison engine (chin guns also are also visible)The most serious concern however was the engine. The Allison V-1710-39 (also known as -F3R) engine provided 1,150 horsepower. The Mustang suffered a rapid fall-off in performance at altitudes above 15,000 feet, caused by its low-altitude engine. Although the Allison did incorporate a gear-driven supercharger, it was, from the start, optimized for low-altitude operation. This was more than just a minor deficiency, since most aerial combat over Europe at that time was taking place at medium to high altitudes.

As a result, the Mustang was regarded underpowered, as it weighed a third more than a Spitfire, though as mentioned the flight tests showed it still had excellent performance at low altitude. Consequently, the new aircraft designated “Mustang I” was rejected by RAF Fighter Command and it was decided that it could be best used for low-level tactical reconnaissance and ground attack, where full advantage could be taken of its exceptional low-altitude performance.

The fourth aircraft (AG348) saw several changes made to the design:

•  The radiator scoop was enlarged to allow a better airflow into the radiator
Courtesy of In Action 45 - P-51 Mustang by Squadron/Signal Publications
•  It was the last Mustang with the short nose intake as the carburetor scoop on top of the nose was extended forward right up
to the spinner
Courtesy of In Action 45 - P-51 Mustang by Squadron/Signal Publications
•  The rounded racing-style windscreen was replaced by a 3-piece unit (the center piece being bulletproof glass)
Courtesy of In Action 45 - P-51 Mustang by Squadron/Signal Publications

AG348 also was the end of any hand-tooled parts. The production line was in business.

In December of 1940, the RAF had added another 300 aircraft on top of their initial order (RAF serials were AL958/AL999, AM100/AM257, and AP164/AP263). Still called Mustang I, the new NAA designation was NA-83. Improvements can only be found in the exhaust stacks design. The new stacks were flared from top to bottom versus the more streamlined initial version.

On January 28th , 1942, the aircraft arrived at the Air Fighting Development Unit (AFDU) at RAF Duxford to begin a complete evaluation. Most of the first 20 Mustangs to arrive in England were used for test and evaluation.

back to top - Next page

Copyright © 2007 Christophe Haentjens -