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, 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’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 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.)
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.)
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.)
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)
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) west 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.
20 August 1944: At 16:26 hours, North American Aviation Mustang Mk.I AG346, assigned to No. 168 Squadron,¹ 39 (Reconnaissance) Wing, Second Tactical Air Force, Royal Air Force, took off from an advance airfield, B21, at Sainte-Honorine-des-Pertes, Normandy, France.
AG346 was the very first operational Mustang Mk.I. During this mission, it was hit by intense antiaircraft fire northeast of Gacé. The Mustang’s pilot, Flight Lieutenant Denis Clark, 119758, Royal Air Force Volunteer Reserve, bailed out. He landed safely, but was captured and taken to a German prisoner of war camp at Les Hogues, a small community east of Rouen.
Flight Lieutenant Clark, along with four other prisoners of war,² was shot and killed at the camp on the afternoon 25 August 1944. A Court of Enquiry held in August 1945 found that the five men had been murdered by SS-Obersturmfürer Eugen Gutemann. Gutemann had been captured in Italy on 28 April 1945 and was held as a prisoner of war by the American forces. It is not known if he was ever brought to trial.
Denis Clark was born 17 December 1918 at Stockton-on-Tees, County Durham, England. He was the son of Sydney Clark, an electrician in the chemical industry, and Minnie Gertrude Ritchie.
In 1939, Clark was employed as a civil service clerk. He resided at 3 Crayke Road in Stockton, with his parents and maternal grandmother.
He was married to Miss Beth Ayre of Seaton, County Durham, possibly in July 1942.
Clark entered the United States at Buffalo, New York, on 16 July 1941, having traveled from Toronto, Ontario, Canada. He was trained as a pilot at the Southern Aviation School, a military contract primary flight school in Camden, South Carolina, United States, beginning in July 1941. He was one of 297 RAF pilots to train there between 7 June 1941 and 16 February 1942.
Head stone of Flight Lieuetenant Denis Clark, RAFVR. (Find-a-Grave)
On 7 February 1942 Temporary Flight Sergeant Denis Clark 945260 was promoted to the rank of Pilot Officer on probation (Temporary) 119758.
On 1 October 1942, Pilot Officer (prob.) Denis Clark was promoted to Flying Officer on probation (war substantive).
Flying Officer Clark was later promoted to the rank of Flight Lieutenant. (Date not determined)
Flight Lieutenant Denis Clark, RAFVR, was buried at Les Hogues Communal Cemetery, along with the other four victims. His head stone is engraved
GREATER LOVE HATH NO MAN THAN THIS. THAT A MAN LAY DOWN HIS LIFE FOR HIS FRIEND.
On 10 September 1945 a warrant was issued as a gratuity for the representatives of deceased officers in the amount of £172/13/7.
North American Aviation Mustang Mk.I AG346 (s/n 73-3099) at Mines Field, California, Summer 1941. Note the short carburetor intake, and compare to the photograph below. (North American Aviation, Inc.)
The very first operational North American Mustang, AG346 (North American Aviation serial number 73-3099) was the second airplane to come off the assembly line at Inglewood, California. North American test pilot Robert Creed Chilton took it for its first flight 3 July 1941. It was the first Mustang Mk.I to be equipped with its full armament.
During flight testing of the first Mk.I, AG345, Chilton and other test pilots heard a banging sound. This was determined to be a resonance in the carburetor intake tract. Also, at high angles of attack, air flow into the intake was decreased. The intake was lengthened. The resonance stopped and air flow to the carburetor was improved.
After flight testing by North American’s test pilots and Royal Air Force fighter pilots Wing Commander Chris Clarkson and Squadron Leader Michael N. (“Red Knight”) Crossley, AG346 was disassembled and crated, then shipped from the port of Long Beach, California, through the Panama Canal and on to England, arriving at Liverpool, 24 October 1941. It was taken to the Lockheed facility at Speke Aerodrome (now, Liverpool John Lennon Airport, LPL) where it was reassembled and put through additional performance and flight tests. Up to 20,000 feet (6,096 meters), AG346 was faster than any other British fighter then in service. A Mk.II reflector gun sight was installed (the same type used in the Supermarine Spitfire), as well as a British VHF radio.
AG346 was publicly displayed for the British news media at Speke Aerodrome on 5 December 1941.
AG346 was then assigned to an operational RAF fighter squadron. It served with Nos. 225, 63 and 26 Squadrons before being assigned to No. 41 Operations Training Unit. AG346 was returned to operations with No. 16 Squadron, and finally, No. 168 Squadron.
North American Aviation Inc. Mustang Mk.I fighter, AG348, built for the Royal Air Force, at Mines Field, Los Angeles, California, 1941. North American Aviation, Inc., photograph. (Ray Wagner Collection/SDASM)
The Mustang Mk.I was a new fighter built by North American Aviation, Inc., for the Royal Air Force. The British Purchasing Commission asked North American Aviation in Los Angeles, California, to build additional Tomahawks (the RAF variant of the Curtiss-Wright P-40 Warhawk) under license from Curtiss-Wright.
North American countered with a proposal to design a completely new and superior fighter around the P-40’s liquid-cooled Allison V-12 engine, and to begin production in no more time than it would take to get a P-40 production line up and running. The Purchasing Commission agreed, and with a letter of understanding, North American began work on the NA-73X on 1 May 1940. They were to produce 320 fighters before 30 September 1941—approximately 50 per month—at a total price of $14,746,964.35.
Edgar Schmued with P-51-NA 41-37322 (Mustang Mk.IA) (San Diego Air and Space Museum Archives Catalog #: 02-S-00192)
Designed by a team led by Edgar Schmued, the prototype North American Aviation Model NA-73X, serial number 73-3097, registered NX19998, was completed 9 September 1940. After a delay waiting for the Allison V-1710 to arrive, the prototype made its first flight 26 October 1940 with free lance test pilot Vance Breese in the cockpit. This was only 179 days since work began on the project.
In a contract amendment dated 9 December 1940, the British Purchasing Commission directed that the NA-73 would be identified by the name, “Mustang.”
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).
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).
Allison V-1710-39 (F3R) V-12 aircraft engine.
This engine 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 AN-M2 .50-caliber machine guns, with one in each wing and two mounted in the nose under the engine and four Browning .303 Mk.II machine guns, two in each wing. The airplane carried 300 rounds of ammunition for each of the .50-caliber guns. Each of the inboard .303s were supplied with 932 rounds; and the outboard .303s, 814 rounds, each.³
The British would recommend that the Allison engine 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 85 years, the Mustang is one of the most recognizable of all airplanes.
Mustang Mk.I of No. 168 Squadron, Royal Air Force. (RAF)
¹ No. 168 Squadron was a reconnaissance unit. Its motto was Rerum cognoscere causas (“To know the cause of things”)
² Warrant Officer Griffin James Young R85855, Royal Canadian Air Force, a Spitfire pilot who had been shot down 13 August 1944; Lead Bombardier Jack Martin 976272, 65th Anti-Tank Unit (The Norfolk Yeomanry), Royal Artillery, captured 21 August; an unidentified Gunner, Royal Artillery; and Private Gordon Lafayette Bryant 6969514, 117th Infantry Regiment, 30th Infantry Division, United States Army.
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, North American serial number 73-3101.
