Tag Archives: Allison V-1710-39

9 September 1940

North American Aviation NA-73X prototype, NX19998, at Mines Field, California, 9 September 1940. (North American Aviation, Inc.)

9 September 1940: North American Aviation completed assembly of the NA-73X, the first prototype of the new Mustang Mk.I fighter for the Royal Air Force. This was just 117 days after the British Purchasing Commission had authorized the construction of the prototype. The airplane was designed by a team led by Edgar Schmued. The 1,150-horsepower Allison V-12 engine had not yet arrived, so the NA-73X was photographed with dummy exhaust stacks. The prototype’s company serial number was 73-3097. It had been assigned a civil experimental registration number, NX19998.

The NA-73X was a single-seat, single-engine, low wing monoplane with retractable landing gear. It was primarily of metal construction, though the flight control surfaces were fabric covered. The airplane was designed for the maximum reduction in aerodynamic drag.  The Mustang was the first airplane to use a laminar-flow wing. The fuselage panels were precisely designed and very smooth. Flush riveting was used. The coolant radiator with its intake and exhaust ducts was located behind and below the cockpit. As cooling air passed through the radiator it was heated and expanded, so that as it exited, it actually produced some thrust.

The prototype was 32 feet, 2⅝ inches (9.820 meters) long, with a wing span of 37 feet, 5/16 inch (11.286 meters). Empty weight of the NA-73X was 6,278 pounds (2,848 kilograms) and normal takeoff weight was 7,965 pounds (3,613 kilograms).

Aeronautical Engineer Edgar Schmued with a North American P-51-2-NA (Mustang Mk.IA), 41-37322. (San Diego Air and Space Museum Archives)

The NA-73X was powered by a liquid-cooled, supercharged, 1,710.60-cubic-inch-displacement (28.032 liter) Allison Engineering Company V-1710-F3R (V-1710-39) single overhead cam 60° V-12 engine, with four valves per cylinder and a compression ratio of 6.65:1. It used a single-stage, single-speed supercharger. This was a right-hand tractor engine (the V-1710 was built in both right-hand and left-hand configurations) which drove a 10 foot, 6 inch (3.200 meter) diameter, three-bladed, Curtiss Electric constant-speed propeller through a 2.00:1 gear reduction.

The V-1710-39 had a Normal Power rating of 880 horsepower at 2,600 r.p.m. at Sea Level; Take Off Power rating of 1,150 horsepower at 3,000 r.p.m. at Sea Level, with 44.5 inches of manifold pressure (1.51 Bar), 5 minute limit; and a War Emergency Power rating of 1,490 horsepower at 3,000 r.p.m., with 56 inches of manifold pressure (1.90 Bar). The V-1710-F3R was 7 feet, 4.38 inches (2.245 meters) long, 3 feet, 0.64 inches (0.931 meters) high, and 2 feet, 5.29 inches (0.744 meters) wide. It had a dry weight of 1,310 pounds (594 kilograms).

U.S. Army Air Corps flight tests of the fully-armed production Mustang Mk.I (XP-51 41-038), equipped with the V-1710-39 and a 10 foot, 9-inch (3.277 meters) diameter Curtiss Electric propeller, resulted in a maximum speed of 382.0 miles per hour (614.8 kilometers per hour) at 13,000 feet (3,962 meters). The service ceiling was 30,800 feet (9,388 meters) and the absolute ceiling was 31,900 feet (9,723 meters).

The Curtiss P-40D Warhawk used the same Allison V-1710-39 engine as the XP-51, as well as a three-bladed Curtiss Electric propeller. During performance testing at Wright Field, a P-40D, Air Corps serial number 40-362, weighing 7,740 pounds (3,511 kilograms), reached a maximum speed of 354 miles per hour (570 kilometers per hour) at 15,175 feet (4,625 meters). Although the Mustang’s test weight was 194 pounds (88 kilograms) heavier, at 7,934 pounds (3,599 kilograms), the Mustang was 28 miles per hour (45 kilometers per hour) faster than the Warhawk. This demonstrates the effectiveness of the Mustang’s exceptionally clean design.

Only one NA-73X was built. It made its first flight 26 October 1940 with test pilot Vance Breese. The prototype suffered significant damage when it overturned during a forced landing, 20 November 1941. NX19998 was repaired and flight testing resumed. The prototype’s final disposition is not known.

Originally ordered by Great Britain, the Mustang became the legendary U.S. Army Air Corps P-51 Mustang. A total of 15,486 Mustangs were built by North American Aviation at Inglewood, California and Dallas, Texas. Another 200 were built in Australia by the Commonwealth Aircraft Corporation.

The P-51 remained in service with the U.S. Air Force until 27 January 1957 when the last one, F-51D-30-NA 44-74936, was retired from the 167th Fighter Squadron, West Virginia Air National Guard. It was then transferred to the National Museum of the United States Air Force at Wright-Patterson Air Force Base, where it is on display.

North American Aviation NA-73X prototype, left front quarter view. (North American Aviation, Inc.)
North American Aviation NA-73X prototype, NX19998, left front quarter view. (North American Aviation, Inc.)

© 2017, Bryan R. Swopes

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20 August 1944

North American Aviation Mustang Mk.I AG346 at Speke Aerodrome, Liverpool, England, November 1941. © IWM (ATP 10608C)

20 August 1944: Mustang Mk.I AG346, while flying with No. 168 Squadron, Second Tactical Air Force, Royal Air Force, from a forward airfield at Sainte-Honorine-des-Pertes, Normandy, France, was shot down near Gacé by antiaircraft fire.

The very first operational North American Mustang, AG346 (North American serial number 73-3099) was the second airplane to come off the assembly line at Inglewood, California.

After flight testing by North American’s test pilots and Royal Air Force fighter pilots Chris Clarkson and Michael “Red Knight” Crossley, AG346 was crated and then shipped to England, arriving at Liverpool, 24 October 1941. It was taken to the Lockheed facility at Speke Aerodrome (now, Liverpool John Lennon Airport) where it was reassembled and put through additional performance and flight tests.

AG346 was then assigned to an operational RAF fighter squadron. AG346 served with Nos. 225, 63 and 26 Squadrons before being assigned to No. 41 Operations Training Unit. It was returned to operations with No 16 Squadron, and finally, No. 168 Squadron.

A North American Aviation Mustang Mk.I of No. 168 Squadron banking over Pierrefitte-en-Cinglais in Normandy on a tactical reconnaissance sortie, August 1944. Allied tanks can be seen on the road below. © IWM (C 4559)

The Mustang Mk.I was a new fighter built by North American for the Royal Air Force. The Royal Air Force had contracted with NAA to design and build a new fighter with an Allison V-1710 supercharged 12-cylinder engine producing 1,200 horsepower. The first order from the British Purchasing Commission was for 320 airplanes, and a second order for another 300 soon followed.

The Mustang Mk.I (NAA Model NA-73) was a single-place, single engine fighter primarily of metal construction with fabric control surfaces. It was 32 feet, 3 inches (9.830 meters) long with a wingspan of 37 feet, 5/16-inches (11.373 meters) and height of 12 feet, 2½ inches (3.721 meters). The airplane’s empty weight was 6,280 pounds (2,849 kilograms) and loaded weight was 8,400 pounds (3,810 kilograms).

North American Aviation Inc. Mustang Mk.I fighter built for the Royal Air Force.

The Mustang Mk.I was powered by a liquid-cooled, supercharged 1,710.597-cubic-inch-displacement (28.032 liter) Allison Engineering Company V-1710-F3R (V-1710-39) single overhead camshaft (SOHC) 60° V-12 engine with four valves per cylinder and a compression ratio of 6.65:1. The engine had a takeoff rating of 1,150 horsepower at 3,000 r.p.m. at Sea Level with 45.5 inches of manifold pressure (1.51 Bar), and a war emergency rating of 1,490 horsepower with 56 inches of manifold pressure (1.90 Bar). The Allison drove a 10 foot, 9 inch (3.277 meter) diameter, three-bladed, Curtiss Electric constant-speed propeller through a 2.00:1 gear reduction. The V-1710-39 was 7 feet, 4.38 inches (2.245 meters) long, 3 feet, 0.54 inches (0.928 meters) high, and 2 feet, 5.29 inches (0.744 meters) wide. It weighed 1,310 pounds (594 kilograms).

This gave the Mustang Mk.I a maximum speed of 382 miles per hour (615 kilometers per hour) and cruise speed of 300 miles per hour (483 kilometers per hour). The service ceiling was 30,800 feet (9,388 meters) and range was 750 miles (1,207 kilometers).

North American Aviation Mustang Mk.I AG365 of the Air Fighting Development Unit at Duxford, Cambridgeshire, February 1942. © IWM (CH17966)

The Mustang Mk.I was equipped with four Browning .303 Mk.II machine guns, two in each wing, and four Browning AN-M2 .50-caliber machine guns, with one in each wing and two mounted in the nose under the engine.

The British would recommend that the Allison be replaced by the Rolls Royce Merlin V-12. This became the Mustang Mk.III and the U.S.A.A.F. P-51B. Eventually, over 15,000 Mustangs were built, and it was a highly successful combat aircraft. Today, after 70 years, the Mustang is one of the most recognizeable of all airplanes.

AG346 was the first one to go to war.

No. 168 Squadron was a reconnaissance unit. Its motto was Rerum cognoscere causas (“To know the cause of things”)

Mustang Mk.1 of No. 168 Squadron, Royal Air Force. (RAF)
Mustang Mk.I of No. 168 Squadron, Royal Air Force. (RAF)

© 2017, Bryan R. Swopes

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23 April 1941

North American Aviation Mustang Mk.I AG348, prior to camouflage paint. (North American Aviation Inc.)
North American Aviation Mustang Mk.I AG345, c/n 73-3098, prior to camouflage paint. Note the short carburetor air intake compared to the photograph below. (North American Aviation Inc.)

23 April 1941: At North American Aviation’s Inglewood, California factory, test pilot Louis S. Wait takes the very first production Mustang Mk.I, AG345, (c/n 73-3098) for its first flight. The Royal Air Force had contracted with NAA to design and build a new fighter with an Allison V-1710 supercharged 12-cylinder engine producing 1,200 horsepower. The first order from the British Purchasing Commission was for 320 airplanes, and a second order for another 300 soon followed.

The Mustang Mk.I (NAA Model NA-73) was a single-place, single engine fighter primarily of metal construction with fabric control surfaces. It was 32 feet, 3 inches (9.830 meters) long with a wingspan of 37 feet, 5/16-inches (11.373 meters) and height of 12 feet, 2½ inches (3.721 meters). The airplane’s empty weight was 6,280 pounds (2,849 kilograms) and loaded weight was 8,400 pounds (3,810 kilograms).

North American Aviation Mustang Mk.I AG345 (North American Aviation Inc.)
North American Aviation Mustang Mk.I AG345 (North American Aviation Inc.)

The Mustang Mk.I was powered by a liquid-cooled, supercharged 1,710.597-cubic-inch-displacement (28.032 liter) Allison Engineering Company V-1710-F3R (V-1710-39) single overhead cam (SOHC) 60° V-12 engine which turned a 10 foot, 9 inch (3.277 meter) diameter, three-bladed, Curtiss Electric constant-speed propeller through a 2.00:1 gear reduction. The engine had a takeoff rating of 1,150 horsepower at 3,000 r.p.m. at Sea Level with 45.5 inches of manifold pressure (1.51 Bar), and a war emergency rating of 1,490 horsepower with 56 inches of manifold pressure (1.90 Bar).

This gave the Mustang Mk.I a maximum speed of 382 miles per hour (615 kilometers per hour) and cruise speed of 300 miles per hour (483 kilometers per hour). The service ceiling was 30,800 feet (9,388 meters) and range was 750 miles (1,207 kilometers).

The Mustang Mk.I was equipped with four Browning .303 Mk.II machine guns, two in each wing, and four Browning AN-M2 .50-caliber machine guns, with one in each wing and two mounted in the nose under the engine.

North American Aviation Mustang Mk.I AG345 (c/n 73-3098), front. (North American Aviation Inc.)
North American Aviation Mustang Mk.I AG345 (c/n 73-3098), front. (North American Aviation Inc.)

The Mk.I was 30 m.p.h. (48 kilometers per hour) faster than its contemporary, the Curtiss P-40 Warhawk, though both used the same engine. Below 15,000 feet (4,572 meters), the Mustang was also 30–35 m.p.h (48–56 kilometers per hour) faster than a Supermarine Spitfire, which had the more powerful Roll-Royce Merlin V-12.

Two Mustang Mk.Is, AG348 and AG354, were taken from the first RAF production order and sent to Wright Field for testing by the U.S. Army Air Force. These airplanes, assigned serial numbers 41-038 and 41-039, were designated XP-51. They would be developed into the legendary P-51 Mustang. In production from 1941 to 1945, a total of 16,766 Mustangs of all variants were built.

AG345 was retained by North American Aviation for long term testing. It was stricken off charge 3 December 1946.

North American Aviation Mustang Mk.I AG345, the first production airplane built for the Royal Air Force. (North American Aviation, Inc.)
North American Aviation Mustang Mk.I AG345, the first production airplane built for the Royal Air Force. (North American Aviation, Inc.)

© 2017, Bryan R. Swopes

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