Tag Archives: Allison Engineering Co. V-1710-39

29 December 1941

North American Aviation XP-51 Mustang 41-038 at Langley Field, Virginia, 29 December 1941. (NASA)

29 December 1941: The first North American Aviation XP-51 fighter prototype, Air Corps serial number 41-038, arrived at the National Advisory Committee for Aeronautics Langley Memorial Aeronautical Laboratory, Langley Field, Hampton, Virginia, for flight testing. This airplane was the fourth production Royal Air Force Mustang Mk.I, RAF serial AG348 (North American serial number 73-3101).

The test program resulted in an improved aileron design which significantly improved the Mustang’s maneuverability. The new aileron was used on all production models.

North American Aviation XP-51 41-038 at the NACA Langley Memorial Aeronautical Laboratory. (NASA)

41-038 was returned to Wright Field on 2 November 1942. The second XP-51, 41-039, arrived at Langley in March 1943 for continued testing.

The Mustang Mk.I (NAA Model NA-73) was a single-place, single-engine fighter of all metal construction. It was 32 feet, 3 inches (9.830 meters) long with a wingspan of 37 feet, ½-inch (11.290 meters) and overall height of 12 feet, 2½ inches (3.719 meters). The airplane’s empty weight was 6,280 pounds (25,848.6 kilograms) and loaded weight was 8,400 pounds (3,810.2 kilograms).

North American Aviation XP-51 41-038 at NACA Langley Memorial Aeronautical Laboratory, right profile. (NASA)

The Mustang Mk.I/XP-51 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 a compression ratio of 6.65:1 and 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 3 feet, ¾ inches (0.934 meters) high, 2 feet, 5-9/32 inches (0.744 meters) wide and 7 feet, 1-5/8 inches (2.175 meters) long. It had a dry weight of 1,310 pounds (594 kilograms).

North American Aviation XP-51 41-038 at NACA Langley Memorial Aeronautical Laboratory. (NASA)

The XP-51 tested at Wright Field had a maximum speed of 382.0 miles per hour (614.8 kilometers per hour) at 13,000 feet (3,962 meters) at wide open throttle, and cruise speed of 300 miles per hour (483 kilometers per hour).

Below 20,000 feet (6,096 meters), the Mustang was the fastest fighter in the world. The Mk.I was 30 m.p.h. (48 kilometers per hour) faster than its contemporary, the Curtiss P-40 Warhawk, though both used exactly the same engine. Below 15,000 feet (4,572 meters), the Mustang was also 30–35 m.p.h (48–56 km/h) faster than a Supermarine Spitfire, which was equipped with the more powerful Roll-Royce Merlin V-12.

The service ceiling was 30,800 feet (9,388 meters) and range was 750 miles (1,207 kilometers).

North American Aviation XP-51 41-038 at NACA Langley Memorial Aeronautical Laboratory, rear view. (NASA)

Armament consisted of two synchronized Browning AN-M2 .50-caliber machine guns mounted in the nose under the engine and firing through the propeller, and two more .50-caliber and four Browning .303 Mk.II machine guns in the wings.

North American Aviation XP-51 instrument panel. (U.S. Air Force)

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 Corps. These airplanes, assigned Air Corps 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.

North American XP-51 41-038 was transferred to the Smithsonian Institution National Air and Space Museum. It was restored in 1976. It is now in the collection of the EAA AirVenture Museum, Oshkosh, Wisconsin. It has a current FAA registration number, N51NA.

North American Aviation XP-51 41-038 in the collection of the Experimental Aircraft Association AirVenture Museum, Oshkosh, Wisconsin. (EAA AirVenture Museum)
North American Aviation XP-51 41-038 in the collection of the Experimental Aircraft Association AirVenture Museum, Oshkosh, Wisconsin. (EAA AirVenture Museum)

© 2018, Bryan R. Swopes

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20 November 1940

North American Aviation's NA-73X fighter prototype, engine idling, with Vance Breese in the cockpit at Mines Field, Los Angeles, 26 October 1941. (North American Aviation Inc.)
North American Aviation’s NA-73X fighter prototype, engine idling, with Vance Breese in the cockpit at Mines Field, Los Angeles, 26 October 1940. (North American Aviation Inc.)

20 November 1940: North American Aviation’s Chief Test Pilot, Paul Baird Balfour, made his first flight in the NA-73X, NX19998, prototype for a Royal Air Force fighter, the Mustang Mk.I.

Vance Breese was the free-lance test pilot who made the first seven flights in the new airplane. Breese claimed to have made a bet with North American executives that Balfour would crash the prototype on his first flight.

Paul B. Balfour (1908–1951). This is Balfour’s NAA employee file card. (North American Aviation Inc.)

This flight was scheduled to be a high speed test. Edgar Schmued, the designer, offered to show Balfour around the airplane. “Before this flight, I asked Balfour to get into the airplane and go through the routine of a takeoff and flight. He responded that one airplane is like another and he would not need the routine checkout.”

The ground crew started the NA-73X’s 1,150 horsepower Allison V-1710-39 liquid-cooled V-12 engine at 5:40 a.m. and let it warm up to normal operating temperature. When it was restarted just prior to Paul Balfour’s flight, “it was a little hard to start,” according to Olaf Anderson, the airplane’s mechanic.

The prototype Mustang, NA-73X, lies upside down in a plowed field, 20 November 1941. (North American Aviation Inc.)
The prototype Mustang, NA-73X, lies upside down in a plowed field, 20 November 1940. (North American Aviation Inc.)

Balfour took off from Mines Field at about 7:10 a.m. After about twelve minutes of flight, the Allison stopped running. Balfour was too far from Mines Field to make it back to the runway. He landed in a plowed field west of Lincoln Boulevard. When the tires hit the soft surface, the prototype flipped over. Balfour was not hurt and was able to crawl out of the upside-down wreck.

The Civil Aeronautics Board report described the damage as “engine housing broken, both wingtips damaged, tail surfaces damaged, top of fuselage damaged, and other miscellaneous damage.” The NA-73X had accumulated just 3 hours, 20 minutes of flight.

Vance Breese won his bet.

Paul Balfour was not injured in the crash landing, but the NA-73X prototype was significantly damaged. (North American Aviation Inc.)
Paul Balfour was not injured in the crash landing, but the NA-73X prototype was significantly damaged. (North American Aviation Inc.)

According to the C.A.B. investigation, the engine had stopped due to fuel starvation when Balfour neglected to select another tank.

The prototype was taken back to the factory and rebuilt. It would become the famous Mustang, one of the most significant aircraft of World War II.

Damage to the wingtips, tail surfaces, fuselage. (North American Aviation Inc.)
Damage to the wingtips, tail surfaces, fuselage. (North American Aviation Inc.)

Robert C. Chilton was hired as the new Chief Test Pilot. He would continue testing the Mustang developments throughout the war. Chilton made his first flight in NA-73X on 3 April 1941.

The Mustang prototype was hoisted out of the plowed field and taken back to the factory where it was rebuilt. (North American Aviation Inc.)
The Mustang prototype was hoisted out of the plowed field and taken back to the factory where it was rebuilt. (North American Aviation Inc.)

Paul Balfour continued to work for North American Aviation, testing the NA-40 and NA-40B prototypes and the B-25 Mitchell medium bomber. He later served in the United States Air Force.

Paul Baird Balfour was born 5 July 1908 in Washington State. He was the son of Fred Patrick Balfour and Edna May Baird Balfour. Balfour attended two years of college.

Paul Balfour entered the U.S. Army Air Corps (prior to 1930). He was stationed at Rockwell Field, San Diego, California.

Balfour married Martha Lillette Cushman of Coronado, California, at Yuma, Arizona, 6 June 1930.

Balfour began working as a test pilot for North American Aviation, Inc., 1 March 1936.

On 2 July 1938, he married Lois Tresa Watchman at Kingman, Arizona. They would have two children.

Paul B. Balfour, center, with a North American Aviation B-25 Mitchell medium bomber. (Photograph courtesy of Neil Corbett, Test and Research Pilots, Flight Test Engineers)
Paul B. Balfour, center, with a North American Aviation B-25 Mitchell medium bomber. (Photograph courtesy of Neil Corbett, Test and Research Pilots, Flight Test Engineers)

On 9 November 1951, Major Paul B. Balfour, U.S. Air Force, attached to the 1002nd Inspector General Group at Norton Air Force Base, California, was flying a North American VB-25J, 44-30955, a transport conversion of a B-25J-30-NC Mitchell medium bomber.

Shortly after takeoff, at about 10:00 a.m., the airplane developed engine trouble. Unable to return to Norton, Balfour attempted a belly landing at a small private airfield. Witness saw that the airplane’s left engine was idling, and its propeller was feathered. As he approached, the airplane was blocked by a windbreak of eucalyptus trees bordering U.S. Route 66. Balfour banked away from the trees but the B-25 crashed in an orange grove along Bloomington Avenue in Rialto, approximately 7 miles (11 kilometers) north of Norton.

Balfour, still buckled in his seat, was thrown clear of the burning wreck and landed in the street. One man on board was killed and two others seriously injured. Balfour died in a hospital three hours later. He was 41 years old. Major Balfour was buried at the Inglewood Park Cemetery, Inglewood, California.

Burning wing of North American VB-25J 44-30955, near Rialto, California, 9 November 1951.
Burning wing of North American VB-25J 44-30955, near Rialto, California, 9 November 1951.

© 2016, Bryan R. Swopes

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20 May 1941

NAA test pilot Robert C. Chilton stand on the wing of P-51B-10-NA 42-106435. (North American Aviation, Inc.)
North American Aviation test pilot Robert C. Chilton standing on the wing of P-51B-10-NA Mustang 42-106435. (North American Aviation, Inc.)

20 May 1941: North American Aviation, Inc., test pilot Robert Creed Chilton took the first XP-51 for its maiden flight at Mines Field, Los Angeles, California. The XP-51 was the fourth production Mustang Mk.I built for the Royal Air Force, (North American serial number 73-3101) and assigned registration number AG348 .

The Mustang was reassigned to the U.S. Army Air Force, designated as XP-51, serial number 41-038, and sent to Wright Field, Dayton, Ohio, for evaluation.

North American Aviation Mustang Mk.I AG348 at Mines Field, California, 1941. North American Aviation, Inc., photograph 73-0-9. (Ray Wagner Collection/SDASM)
North American Aviation Mustang Mk.I AG348, Mines Field, California, 1941. North American Aviation, Inc., photograph 73-0-10. (Ray Wagner Collection/SDASM)
North American Aviation Mustang Mk.I AG348 at Mines Field, California, 1941. North American Aviation, Inc., photograph. (Ray Wagner Collection/SDASM)

Later, the XP-51 was extensively tested by the National Advisory Committee for Aeronautics (N.A.C.A.) at the Langley Memorial Aeronautical Laboratory, Langley Field, Hampton, Virginia.

Today, the restored XP-51 is in the collection of the E.A.A. AirVenture Museum at Oshkosh, Wisconsin.

North American Aviation XP-51 41-038 at the NACA Langley Memorial Aeronautical Laboratory. (NASA LMAL 27030)
North American Aviation XP-51 41-038 at the NACA Langley Memorial Aeronautical Laboratory. (NASA)

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 XP-51 41-039 at NACA Langley. (NASA)
North American Aviation XP-51 41-039 at NACA Langley. (NASA)

The Mustang 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 with a compression ratio of 6.65:1. The -F3R had a Normal Power rating of 880 horsepower at 2,600 r.p.m., at Sea Level, and 1,000 horsepower at 2,600 r.p.m. at 11,000 feet (3,353 meters). It had a Takeoff and Military Power rating of 1,150 horsepower at 3,000 r.p.m., to 11,800 feet (3,597 meters). The engine 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 V-1710-F3R was 7 feet, 4.38 inches (2.245 meters) long, 3 feet, 0.54 inches (0.928 meters) high, and 2 feet, 5.29 (0.744 meters) wide. It weighed 1,310 pounds (594 kilograms).

The Mustang Mk.I had a maximum speed of 382 miles per hour (615 kilometers per hour) at 13,700 feet (4,176 meters), the Allison’s critical altitude, 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 XP-51 41-038 at NACA Langley Memorial Aeronautical Laboratory, right profile. (NASA LAML)
North American Aviation XP-51 41-038 at NACA Langley Memorial Aeronautical Laboratory, right profile. (NASA)

The Mustang Mk.I was armed with four air-cooled Browning .303 Mk.II aircraft 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 XP-51 41-038 at NACA Langley Memorial Aeronautical Laboroatory. (NASA LAML 27045)
North American Aviation XP-51 41-038 at NACA Langley Memorial Aeronautical Laboratory, right three-quarter view. (NASA)

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

The XP-51 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.

North American Aviation XP-51 41-038 at NACA Langley Memorial Aeronautical Laboratory, rear view. (NASA LMAL 27033)
North American Aviation XP-51 41-038 at NACA Langley Memorial Aeronautical Laboratory, rear view. (NASA)

Robert Creed Chilton was born 6 February 1912 at Eugene, Oregon, the third of five children of Leo Wesley Chilton, a physician, and Edith Gertrude Gray. He attended Boise High School in Idaho, graduating in 1931. Chilton participated in football, track and basketball, and also competed in the state music contest. After high school, Chilton attended the University of Oregon where he was a member of the Sigma Chi fraternity (ΣΧ). He was also a member of the Reserve Officers Training Corps (ROTC).

Bob Chilton enlisted as an Aviation Cadet in the U.S. Army Air Corps, 25 June 1937. He was trained as a fighter pilot at Randolph Field and Kelly Field in Texas, and was commissioned as a Second Lieutenant in 1938. Lieutenant Chilton was assigned to fly the Curtiss P-36 Hawk with the 79th Pursuit Squadron, 20th Pursuit Group, at Barksdale Field, Louisiana. Because of a medical condition, he was released from active duty, 1 April 1939.

At some time prior to 1940, Bob Chilton, married his first wife, Catherine. They lived in Santa Maria, California, where he worked as a pilot at the local airport.

In January 1941, Chilton went to work as a production test pilot for North American Aviation, Inc., Inglewood, California. After just a few months, he was assigned to the NA-73X.

Chilton married his second wife, Betty W. Shoemaker, 15 November 1951.

On 10 April 1952, Bob Chilton returned to active duty with the U.S. Air Force, with the rank of lieutenant colonel. He served as Chief of the Republic F-84 and F-105 Weapons System Project Office, Air Material Command, at Wright-Patterson Air Force Base, Dayton, Ohio, until 9 March 1957.

From 1958, Chilton was a vice president for Horkey-Moore Associates, an engineering research and development company in Torrance, California, founded by former North American aerodynamacist Edward J. Horkey. In 1961, he followed Horkey to the Space Equipment Corporation, parent company of Thompson Industries and Kerr Products, also located in Torrance. Chilton served as corporate secretary and contracts administrator.

Chilton married his third wife, Wilhelmina E. Redding (Billie E. Johnson) at Los Angeles, 26 July 1964. They divorced in 1972.

In 1965, Bob Chilton returned to North American Aviation as a flight test program manager. He retired in 1977.

Robert Creed Chilton died at Eugene, Oregon, 31 December 1994, at the age of 82 years.

North American Aviation XP-51 at Wright Field. (Charles M. Daniels Collection, San Diego Air & Space Museum Archives, Catalog #: 15_002838)

© 2018, Bryan R. Swopes

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