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. Note the increased length of the carburetor intake. (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

20 May 1937

Amelia Earhart with her Lockheed Electra 10E, NR16020.

Leg 1: After her Lockheed Electra 10E Special, NR16020, was repaired by Lockheed following a takeoff accident at Wheeler Field, Oahu, in March, Amelia Earhart repositioned it to Oakland Municipal Airport to begin her second attempt to fly around the world. Because of changing weather patterns since the earlier attempt, this time her route will be eastward.

Great Circle route between Oakland Airport and Union Air Terminal. (Great Circle Mapper)

On 20 May 1937, without any public notice, Earhart and her navigator, Captain Frederick J. Noonan, left Oakland, California, on the first leg of the trip: 283 nautical miles (325 miles (523 kilometers) to Union Air Terminal, Burbank, California (now, Hollywood Burbank Airport—BUR), where the airplane was manufactured and repaired. They arrived at about 6:00 p.m. and remained there over night.

“The rebuilt Electra came out of the Lockheed plant on May 19. Two days later we flew it to Oakland. . .  As that time we had made no announcement of my decision to reverse the direction of the flight. It seemed sensible to slip away as quietly as we could. While I was actually heading for Miami, with hope of keeping on from there eastward, technically the journey from Burbank across the country was a shake-down flight. If difficulties developed we would bring the ship back to the Lockheed plant for further adjustments.”

—Amelia Earhart

Amelia Earhart in the cockpit of her Electra. (Rudy Arnold Collection)

© 2018, Bryan R. Swopes

20–21 May 1932

Amelia Earhart at Harbor Grace, Newfoundland, 20 May 1932. Photographer: Ernest Maunder. Courtesy of Library and Archives Canada (PA-057854).
Amelia Earhart at Harbor Grace, Newfoundland, 20 May 1932. Photographer: Ernest Maunder. Courtesy of Library and Archives Canada (PA-057854).

20 May 1932: At 7:12 p.m., local, aviatrix Amelia Earhart departed Harbor Grace, Newfoundland, on a solo transoceanic flight. Her airplane was a modified single-engine Lockheed Model 5B Vega, registration NR7952.

Her plan was to fly all the way to Paris, but after her altimeter had failed, encountering adverse weather, including heavy icing and fog, a fuel leak, and a damaged exhaust manifold, Earhart landed in a field at Culmore, Northern Ireland. The distance flown was 2,026 miles (3,260.5 kilometers). Her elapsed time was 14 hours, 56 minutes.

A lone, astonished farmer saw her land.

Amelia cut the switches, climbed out of the plane, and, as the man approached the plane, called out, “Where am I?”

Danny McCallion replied obligingly and with excruciating accuracy. “In Gallegher’s pasture.”

The Sound of Wings by Mary S. Lovell, St. Martin’s Press, New York, 1989, Chapter Fifteen at Page 183.

Amelia Earhart with her Lockheed Vega 5B, NR7952, at Culmore, North Ireland after her solo transatlantic flight, 21 May 1932. (National Library of Ireland)

Though she didn’t make it all the way to Paris, she was the first woman—and only the second person, after Charles A. Lindbergh—to fly solo across the Atlantic Ocean. Lindbergh’s flight was on the same date, five years earlier.

Great Circle route between Harbour Grace Airport, Newfoundland, and Londonderry Airport, near Culmore, Northern Ireland. 1,754 nautical miles (2,019 statute miles/3,249 kilometers). (Great Circle Mapper)

In an unusual move, Amelia Earhart, a civilian, was awarded the United States military’s Distinguished Flying Cross by Patrick J. Hurley, Secretary of War, 18 July 1932.

Amelia Earhart’s Distinguished Flying Cross certificate signed by Patrick J. Hurley, Secretary of War.

Built by the Lockheed Aircraft Company in December 1928, the Vega is a single-engine high-wing monoplane designed to carry a pilot and up to seven passengers. The fuselage was molded laminated plywood monocoque construction and the wing was cantilevered wood. The Vega 5B is 27 feet, 6 inches (8.382 meters) long with a wingspan of 41 feet (12.497 meters) and overall height of 8 feet, 2 inches (2.489 meters).

Amelia Earhart stands in front of her Lockheed Model 5B Vega, NR7952, at Union Airport, 1932. Left to right, Earhart; Lockheed founder Allan Loughead; Paul Mantz; and Lockheed president Lloyd Stearman. (Philip S. Dockter/Valley Relics Museum)

Earhart’s Vega, serial number 22, was certified by the Department of Commerce, 17 September 1931, with its empty weight increased 220 pounds (99.8 kilograms) to 2,695 pounds (1,222.4 kilograms) and maximum gross weight of 4,375 pounds (1984.5 kilograms).

Aircraft Registration Certificate, Lockheed Vega, serial number 22, NC7952, 1928.

NR7952 was modified at the Fokker Aircraft Corporation of America factory in Teterboro, New Jersey, to increase the fuel capacity to 420 gallons (1,589.9 liters). While it was there, Earhart’s mechanic, Eddie Gorski, replaced the original Pratt & Whitney Wasp B engine with a new Wasp C, an air-cooled, supercharged 1,343.804-cubic-inch-displacement (22.021 liter) nine cylinder radial engine with a compression ration of 5.25:1. The Wasp C was rated at 420 horsepower at 2,000 r.p.m. at Sea Level, burning 58 octane gasoline.¹ It was a direct-drive engine, and turned a two-bladed Hamilton Standard controllable-pitch propeller. The Wasp C was 3 feet, 6.63 inches (1.083 meters) long, 4 feet, 3.44 inches (1.307 meters) in diameter and weighed 745 pounds (338 kilograms).

The standard Vega 5 had a cruising speed of 165 miles per hour (265.5 kilometers per hour) and maximum speed of 185 miles per hour (297.7 kilometers per hour). The service ceiling was 15,000 feet (4,572 meters). Range with standard fuel tanks was 725 miles (1,166.8 kilometers).

Amelia Earhart disappeared in 1937 while attempting to fly around the world. Her Lockheed Model 5B Vega, NR7952, is in the collection of the Smithsonian Institution National Air and Space Museum.

Amelia Earhart's Lockheed Vega 5b, NR7952, at the Smithsonian Institution National Air and Space Museum.
Amelia Earhart’s Lockheed Model 5B Vega, NR7952, at the Smithsonian Institution National Air and Space Museum. (NASM)

¹ The Pratt & Whitney Wasp C was also used by the U.S. Army and Navy, designated R-1340-7. It was rated at 450 horsepower at 2,100 r.p.m. at Sea Level.

© 2019, Bryan R. Swopes

Charles A. Lindbergh’s Ryan NYP, NX211, “Spirit of St. Louis”

Charles A. Lindbergh and the Spirit of St. Louis over San Diego Bay. Photograph by H.A. Erickson. (San Diego Air and Space Museum)

On 25 February 1927, Charles A. Lindbergh, backed by a group of St. Louis, Missouri, businessmen, contracted the Ryan Airlines Company to build an airplane for the purpose of flying across the Atlantic Ocean from New York to Paris. The agreed price was $10,580. 63 days later, 28 April, Lindbergh made the first flight of the Ryan NYP at Dutch Flats, a short distance from the factory on Juniper Street.

Ryan airplane factory at the foot of Juniper Street, San Diego, California. (Donald A. Hall Photograph & Document Collection)
Ryan airplane factory at the foot of Juniper Street, San Diego, California. (Donald A. Hall Photograph & Document Collection)

The Ryan NYP is a single-place, single-engine, strut-braced high-wing monoplane with fixed landing gear and tail skid, built at the Ryan Airlines Company factory, San Diego, California. Although it was based on the earlier Ryan M-2, Spirit of St. Louis was a complete redesign, with longer wings and fuselage. The ailerons are smaller. The airplane has no serial number and was not issued a type certificate by the Civil Aeronautics Authority. It was assigned an experimental registration number, NX211.

Spirit of St. Louis is 27 feet, 8 inches (8.433 meters) long with a wingspan of 46 feet, 0 inches (14.021 meters) and height of 9 feet, 10 inches (2.997 meters). The wing has a chord of 7 feet, 0 inches (2.134 meters) and area of 319 square feet (29.636 square meters). There is no dihedral or sweep. The airfoil is the Clark Y, with a cambered upper surface, while the lower surface is flat from aft of the wing’s forward spar.

The fuselage and tail surfaces are constructed of welded tubular SAE 1020 steel framework covered with doped linen fabric. The wing was built as a single unit with wooden spars and ribs. The leading edge is covered in plywood and the entire wing with doped fabric. The rib spacing is 11 inches (27.94 centimeters). The horizontal stabilizer is adjustable from the cockpit to control trim as the fuel load decreased.

Welded tubular steel framework fuselage of the Spirit of St. Louis. (Donald A. Hall)
Welded SAE 1020 tubular steel framework fuselage of the Spirit of St. Louis. (Donald A. Hall Photograph & Document Collection)
This photograph shows the wooden structure of the wing and welded tubular framework of the fuselage of Spirit of St. Louis. The forward fuselage fuel tank is in place. (Donald A. Hall)
This photograph shows the complex wooden structure of the wing and welded tubular framework of the fuselage of Spirit of St. Louis. The 310 gallon (1,174.5 liter) main fuel tank is in place. The flat lower surface of the wing is the primary characteristic of the Clark Y airfoil. (Donald A. Hall Photograph & Document Collection)

The split-axle main landing gear uses bungee cords for shock absorption. B.F. Goodrich pneumatic tires are mounted on 21 inch × 4 inch (533 millimeter × 102 millimeter) wire-spoked wheels. The struts were designed for a load factor of 4 and allow 6½ inches (165 millimeters) of vertical motion. The wheels can spread to absorb impacts. The tail skid is heat-treated chrome moly tubing.

This photograph shows the forward 86-gallon fuel tank and 25 gallon lubricating oil tank in the nose of Spirit of St. Louis. The Wright J-5C Whirlwind has been installed. (Donald A. Hall)
This photograph shows the forward 86 gallon (325.6 liter) fuel tank and 25 gallon (94.6 liter) lubricating oil tank in the nose of Spirit of St. Louis. The Wright J-5C Whirlwind radial engine has been installed. The bungee cord suspension of the main landing gear is also visible. (Donald A. Hall Photograph & Document Collection)

The main fuel tank and lubricating oil tank were placed in front of the cockpit for safety reasons, but this eliminated any forward view for the pilot. A small retractable periscope with a 3 inch × 5 inch (76 × 127 millimeters) viewing area in the instrument panel could be extended through the left side of the fuselage.

Spirit of St. Louis was powered by an air-cooled, normally-aspirated 787.26-cubic-inch-displacement (12.901 liter) Wright Aeronautical Corporation Model J-5C Whirlwind nine-cylinder radial engine, serial number 7331. This was a direct-drive engine with a compression ratio of 5.1:1. The engine was assembled by Thomas W. Rutledge at the Wright factory in Paterson, New Jersey, and was completed 1 April 1927.

Charles Lindbergh works on the Wright Model J-5C Whirlwind installed on the Spirit of St. Louis. (Library of Congress)

The J-5 was built with a cylindrical cast aluminum crankcase and steel cylinder barrels with integral cooling fins. The cylinder head was cast aluminum with a hemispherical combustion chamber, which allowed larger valves and improved combustion efficiency. There were two valves per cylinder, actuated by pushrods and rocker arms.

The Wright J-5C was rated at 200 horsepower at 1,800 r.p.m., and 220 horsepower at 2,000 r.p.m. The engine was 2 feet, 10 inches (0.864 meters) long and 3 feet, 9 inches (1.143 meters) in diameter. It weighed 508 pounds (230.4 kilograms).

During 50-hour endurance tests, the J-5C produced 216 horsepower at 1,837 r.p.m., and 238 horsepower at 1,970 r.p.m. It averaged 223 horsepower during a 100-hour, full-throttle test conducted by the U.S. Navy in May 1927. An overload test run with an external supercharger produced 295 horsepower at 2,150 r.p.m. for 50 hours.

The engine drove a two-bladed Standard Steel Propeller Co. adjustable-pitch propeller with a diameter of 8 feet, 9 inches (2.667 meters). The drop-forged solid Duralumin blades attached to a steel hub. The pitch of the propeller blades could be set prior to flight. Spirit of St. Louis‘ blades were set to 16¼ inches (41.275 centimeters). (This is the distance that the propeller would travel forward during one revolution.)

Instrument panel and fuel manifold
Instrument panel and fuel manifold. (Donald A. Hall Photograph & Document Collection)

The airplane’s Instrument panel included a Waltham Watch Company Eight-Day Clock and a Pioneer Instrument Company Earth Inductor Compass.

A barograph was carried on board to certify the non-stop flight for the Fédération Aéronautique Internationale.

Ryan NYP N-X-211, Spirit of St. Louis, front view, at Dutch Flats, San Diego, California, 28 April 1927. (Donald A. Hall Collection)
Ryan NYP N-X-211, Spirit of St. Louis, front view, at Dutch Flats, San Diego, California, 28 April 1927. (Donald A. Hall Photograph & Document Collection)

During flight testing at San Diego, the maximum speed of Spirit of St. Louis was found to be 120.0 miles per hour (193.1 kilometers per hour) at full load, increasing to 124.5 miles per hour (200.4 kilometers per hour) when lightly loaded. It reached 129 miles per hour (207.6 kilometers per hour) over a 3-kilometer course, when the fuel load was just 25 gallons (95 liters). The Ryan’s best economic speed was 97 miles per hour (156.1 kilometers per hour) at full load, and 67 miles per hour (107.8 kilometers per hour), light. Under ideal conditions, the airplane had a maximum range of 4,110 miles (6,614 kilometers).

The Ryan NYP N-X-211, Spirit of St. Louis, right front quarter view, at Dutch Flats, San Diego, California. (Donald A. Hall Collection)
The Ryan NYP N-X-211, Spirit of St. Louis, right front quarter view, at Dutch Flats, San Diego, California. (Donald A. Hall Photograph & Document Collection)
Ryan NYP N-X-211, Spirit of St. Louis, right side view, at Dutch Flats, San Diego, California, 28 April 1927. (Donald A. Hall Collection)
Ryan NYP N-X-211, Spirit of St. Louis, right side view, at Dutch Flats, San Diego, California, 28 April 1927. (Donald A. Hall Photograph & Document Collection)

Spirit if St. Louis has an empty weight of 2,150 pounds (975 kilograms). When in departed San Diego on 10 May 1927, it was overloaded with an additional 25 gallons (94.6 liters) of gasoline, bringing the total gross weight at takeoff to 5,250 pounds (2,381 kilograms). (The density of California gasoline was 6.12 pounds per gallon/0.73 kilograms per litre.)

Donald A. Hall, designer of the Ryan NYP, Spirit of St. Louis, at work in his office at the Ryan Airlines, Inc., factory, San Diego, CA, 1927. (Donald A Hall Collection)

Designer Donald A. Hall estimated that the Ryan NYP required 850 engineering man hours and 3,000 construction man hours.

Spirit of St. Louis made 174 flights, with a total duration of 489 hours, 28 minutes. NX211 last made its final flight 30 April 1928, from St. Louis, Missouri, to Bolling Field, Washington, D.C., where Charles A. Lindbergh presented it to the Smithsonian Institution. Its registration was cancelled 2 June 1928.

The Ryan NYP Spirit of St. Louis, NX211, on display at the Smithsonian Institution National Air and Space Museum
The Ryan NYP Spirit of St. Louis, NX211, on display at the Smithsonian Institution National Air and Space Museum (NASM)

© 2018, Bryan R. Swopes

20 May 1927

Charles A. Lindbergh and the Spirit of St. Louis. (Hulton Archive/Getty Images)

20 May 1927, 7:51:30 a.m. Eastern Daylight Time (11:51:30 G.M.T.): In his effort to advance the Art and Science of Aviation, to win the $25,000 Orteig Prize, to fly from New York to Paris, 25-year-old aviator Charles A. Lindbergh takes off from Roosevelt Field, Long Island, New York, United States of America, and heads north-eastward over the Atlantic Ocean on his solo, record-breaking flight to Paris, France, and into History.

The Spirit of St. Louis is pushed into position for takeoff at Roosevelt Field, 20 May 1927. (Underwood and Underwood. National Air and Space Museum Archives, Smithsonian Institution)
The Spirit of St. Louis is pushed into position for takeoff at Roosevelt Field, 20 May 1927. (Underwood and Underwood, National Air and Space Museum Archives, Smithsonian Institution)
Lindbergh taxis away from the crowd of spectators.

“I buckle my safety belt, pull goggles down over my eyes, turn to the men at the blocks, and nod.”

The Spirit of St. Louis, by Charles A. Lindbergh, Charles Scribner’s Sons, 1953, at Page 185.

Spirit of St. Louis begins its takeoff run at Roosevelt Field, Long Island, New York, 20 May 1927.

As he circles to gain altitude after takeoff, Lindbergh scans his instruments.

“On the instrument board in front of me, the earth-inductor compass needle leans steeply to the right. I bank cautiously northward until it rises to the center line — 65 degrees — the compass heading for the first 100-mile segment of my great-circle route to France and Paris. It’s 7:54 a.m. Eastern daylight time.”

— The Spirit of St. Louis, by Charles A. Lindbergh, Charles Scribner’s Sons, 1953, at Page 189.

Great Circle route from the location of the former Roosevelt Field to Le Bourget, Paris: 3,145 nautical miles (3,619 statute miles/5,825 kilometers). (Great Circle Mapper)

© 2019, Bryan R. Swopes