Tag Archives: Pratt & Whitney Twin Wasp S1B3-G

15 October 1937

Boeing XB-15 takes off on its first flight, Boeing Field, 15 October 1937. (U.S. Air Force)

15 October 1937: Free-lance test pilot Edmund Turney (“Eddie”) Allen made the first flight of the prototype Boeing XB-15, 35-277, at Boeing Field, Seattle, Washington.

The Boeing Model 294, designated XB-15 by the Air Corps, was an experimental airplane designed to determine if a bomber with a 5,000 mile range was possible. It was designed at the same time as the Model 299 (XB-17), which had the advantage of lessons learned by the XB-15 design team. The XB-15 was larger and more complex than the XB-17 and took longer to complete. It first flew more than two years after the prototype B-17.

A large scale model of the Boeing XB-15 in the NACA Full Scale Tunnel, 6 May 1936. (NASA)

Designers had planned to use an experimental 3,421.19-cubic-inch-displacement (56.063 liter) liquid-cooled, supercharged and turbosupercharged Allison V-3420 twenty-four cylinder, four-bank “double V” engine which produced a maximum of  2,885 horsepower at 3,000 r.p.m. The engine was not available in time, however, and four air-cooled Pratt & Whitney R-1830 (Twin Wasp) engines were used instead. With one-third the horsepower, this substitution left the experimental bomber hopelessly underpowered as a combat aircraft.

Boeing XB-15 35-277. (U.S. Air Force)
Boeing XB-15 35-277. (U.S. Air Force)
Boeing XB-15 35-277. (U.S. Air Force)

The XB-15 was a very large four-engine mid-wing monoplane with retractable landing gear. It was of aluminum monocoque construction with fabric-covered flight control surfaces. The XB-15 had a ten-man crew which worked in shifts on long duration flights.

Boeing XB-15 35-277

The prototype bomber was 87 feet, 7 inches (26.695 meters) long with a wingspan of 149 feet (45.415 meters) and overall height of 18 feet, 1 inch (5.512 meters). The airplane had an empty weight of 37,709 pounds (17,105 kilograms) and maximum takeoff weight of 70,706 pounds (32,072 kilograms)—later increased to 92,000 pounds (41,730 kilograms).

As built, the XB-15 was powered by four air-cooled, supercharged, 1,829.39-cubic-inch-displacement (29.978 liter) Pratt & Whitney Twin Wasp S1B3-G (R-1830-11) two-row 14-cylinder radial engines, rated at 850 horsepower at 2,450 r.p.m. at 5,000 feet (1,524 meters), and 1,000 horsepower at 2,600 r.p.m. for take off. The engines turned three-bladed controllable-pitch propellers through a 3:2 gear reduction. The R-1830-11 was 4 feet, 8.66 inches (1.439 meters) long with a diameter of 4 feet, 0.00 inches (1.219 meters), and weighed 1,320 pounds (599 kilograms).

These gave the experimental airplane a maximum speed of 197 miles per hour (317 kilometers per hour) at 5,000 feet (1,524 meters) and a cruise speed of 152 miles per hour (245 kilometers per hour) at 6,000 feet (1,829 meters). The service ceiling was 18,900 feet (5,761 meters) and maximum range was 5,130 miles (8,256 kilometers).

The Boeing XB-15 experimental long-range heavy bomber flies in formation with a Boeing YP-29 pursuit. (U.S. Air Force)

The bomber could carry a maximum of 12,000 pounds (5,443 kilograms) of bombs in its internal bomb bay, and was armed with three .30-caliber and three .50-caliber machine guns for defense.

Only one XB-15 was built. During World War II it was converted to a transport and redesignated XC-105. In 1945 it was stripped and abandoned at Albrook Field, Territory of the Canal Zone, Panama.

The XB-15 set several Fédération Aéronautique Internationale (FAI) world records:  On 30 July 1939, the XB-15 carried 14,135 kilograms (31,162 pounds) to an altitude of 2,000 meters (6,562 feet) over Fairfield, Ohio.¹ The same flight set a second record by carrying 10,000 kilograms (22,046 pounds) to an altitude of 8,228 feet (2,508 meters).² On 2 August 1939, the XB-15 set a World Record for Speed Over a Closed Circuit of 5000 Kilometers With 2000 Kilogram Payload, at an average speed of 267.67 kilometers per hour (166.32 miles per hour).³

Boeing XB-15 35-277. (LIFE Magazine)

¹ FAI Record File Number 8739

² FAI Record File Number 8740

³ FAI Record File Number 10865

© 2017, Bryan R. Swopes

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21 September 1937

Jackie Cochran sits in the cockpit of the Seversky SEV-S1, NR18Y. Note how the landing gear retracts straight to the rear in this early version. It would be modified to retract inward to the airplane’s centerline, and more effectively streamlined in the future.

21 September 1937: Jackie Cochran flew a Seversky Aircraft Corporation SEV-S1, civil registration NR18Y, over a 3 kilometer course at Detroit Wayne County Airport, Romulus, Michigan, averaging 470.40 kilometers per hour (292.29 miles per hour). This was a new Fédération Aéronautique Internationale (FAI) speed record.¹

The Seversky SEV-S1 Executive was an improved version of the P-35 fighter, which was the first U.S. Army Air Corps single engine airplane to feature all-metal construction, an enclosed cockpit and retractable landing gear. It was designed by Major Alexander P. de Seversky. The airplane had been built as the SEV-2XP, a two-place monoplane with fixed landing gear, powered by an air-cooled, supercharged 1,666.860-cubic-inch-displacement (27.315 liter) Wright Aeronautical Division GR1670 two-row, 14-cylinder radial engine. The GR1670A1 had a compression ratio of 6.75:1 and was rated at 775 horsepower at 2,400 r.p.m., and 830 horsepower at 2,400 r.p.m. for takeoff. The GR1670B2C had a compression ratio of 7.0:1 and was rated at 750 horsepower at 2,500 r.p.m., and 850 horsepower at 2,600 r.p.m., for takeoff. These were developmental engines. Both variants had a propeller gear reduction ratio of 16:11. The SEV-2XP was to be a second entry, along with the SEV-1XP, to enter a fly-off at Wright Field. When it was damaged, though, it was rebuilt as a single place airplane with retractable landing gear and a 1,000-horsepower Wright Cyclone GR-1820G4 nine-cylinder engine, and designated SEV-1XP.

 The Seversky's passenger compartment was accessed through a hatch on the right side of the fuselage. (San Diego Air and Space Museum Archives) Jackie Cochran in the cockpit of the Seversky SEV-2S Executive, NR18Y. Note the passenger windows below and behind the cockpit. (San Diego Air and Space Museum Archives)
The Seversky’s passenger compartment was accessed through a hatch on the right side of the fuselage. (San Diego Air and Space Museum Archives)

After the Air Corps demonstrations, which resulted in an order for 100 P-35s, NX18Y was again repowered, this time with an air-cooled, supercharged, 1,829.39-cubic-inch-displacement (29.978 liter) Pratt & Whitney Twin Wasp S1B3-G (R-1830-11) two-row 14-cylinder radial engine with a compression ratio of 6.7:1. The R-1830-11 was rated at 850 horsepower at 2,450 r.p.m. at 5,000 feet (1,524 meters), and 1,000 horsepower at 2,600 r.p.m. for take off, burning 87-octane gasoline. The engine turned a three-bladed Hamilton-Standard controllable-pitch propeller through a 3:2 gear reduction. The R-1830-11 was 4 feet, 8.66 inches (1.439 meters) long with a diameter of 4 feet, 0.00 inches (1.219 meters), and weighed 1,320 pounds (599 kilograms).

With the R-1830, NR18Y was again redesignated SEV-S1. It was flown by Seversky’s chief test pilot, Frank Sinclair, at the 1937 National Air Races and the Bendix Trophy Race.

Major Alexander P. de Seversky and Jackie Cochran with a Seversky monoplane, circa 1937.
Major Alexander P. de Seversky and Jackie Cochran with a Seversky monoplane, circa 1937.

¹ FAI Record File Number 12026

© 2017, Bryan R. Swopes

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15 September 1939

Jackie Cochran with her record-setting Seversky AP-7A, NX1384. (FAI)

15 September 1939: Jackie Cochran set a Fédération Aéronautique Internationale (FAI) World Speed Record flying a Seversky AP-7A, civil registration NX1384, over a 1,000 kilometer course, from Burbank to San Francisco and back to Burbank. Her average speed was 492.34 kilometers per hour (305.93 miles per hour).¹

Jackie Cochran with the Seversky AP-7A, NX1384. Her racing number, 13, has not yet been painted on the fuselage. (San Diego Air and Space Museum Archive)
Jackie Cochran with the Seversky AP-7A, NX1384. Her racing number, 13, has not yet been painted on the fuselage. (San Diego Air and Space Museum Archive)

The Seversky AP-7 was an improved civil version of the Seversky P-35 fighter, which was the first U.S. Army Air Corps single engine airplane to feature all-metal construction, an enclosed cockpit and retractable landing gear. It was designed by Major Alexander Nikolaievich Prokofiev de Seversky, a World War I Russian fighter ace.

Cochran’s AP-7A was a specially-built racer, modified from the original AP-7 with a new-thinner wing and different landing gear arrangement. It was powered by a an air-cooled, supercharged, 1,829.39-cubic-inch-displacement (29.978 liter) Pratt & Whitney Twin Wasp S1B3-G (R-1830-11) two-row 14-cylinder radial engine rated at 850 horsepower at 2,450 r.p.m. at 5,000 feet (1,524 meters), and 1,000 horsepower at 2,600 r.p.m. for take off. The engine turned a three-bladed Hamilton-Standard controllable-pitch propeller through a 3:2 gear reduction. The R-1830-11 was 4 feet, 8.66 inches (1.439 meters) long with a diameter of 4 feet, 0.00 inches (1.219 meters), and weighed 1,320 pounds (599 kilograms).

This is the same airplane in which she won the 1938 Bendix Trophy.

Jackie Cochran's Seversky AP-7, NX1384, at the Union Air Terminal, Burbank, California, September 1938.
Jackie Cochran’s Seversky AP-7A, NX1384. (Unattributed)

¹ FAI Record File Number 12027

© 2017, Bryan R. Swopes

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1 September 1938

Seversky AP-7 NX1384, c/n 145. (San Diego Air and Space Museum Archives)
Seversky AP-7 NX1384, c/n 145. (San Diego Air and Space Museum Archives)

1 September 1938: Jackie Cochran departed the Lockheed Air Terminal, Burbank California, at 3:00 a.m., flying her Seversky AP-7, NX1384, c/n 145. Her destination was Cleveland, Ohio, the finish line for the Bendix Trophy Race,  2,042 miles (3,286 kilometers) away.

Jackie Cochran steps out of her Seversky AP-7 at Cleveland, Ohio, after winning the 1938 Bendix Trophy Race.

NX1384 was built especially for Jackie Cochran, and had been flown from the factory to Burbank by Major de Seversky just two days earlier. His flight set an East-to-West Transcontinental Speed Record of 10 hours, 2 minutes, 55.7 seconds.

The specially built AP-7 racer was an improved version of Major Alexander Nikolaievich Prokofiev de Seversky’s P-35A fighter, which was the U.S. Army Air Corps’ first all-metal single-engine airplane with an enclosed cockpit and retractable landing gear. Cochran’s AP-7 was powered by an air-cooled, supercharged, 1,829.39-cubic-inch-displacement (29.978 liter) Pratt & Whitney Twin Wasp S1B3-G (R-1830-11) two-row 14-cylinder radial engine rated at 850 horsepower at 2,450 r.p.m. at 5,000 feet (1,524 meters), and 1,000 horsepower at 2,600 r.p.m. for take off. The engine turned a three-bladed Hamilton-Standard controllable-pitch propeller through a 3:2 gear reduction. The R-1830-11 was 4 feet, 8.66 inches (1.439 meters) long with a diameter of 4 feet, 0.00 inches (1.219 meters), and weighed 1,320 pounds (599 kilograms).

Jackie Cochran paints her race number, 13, of the fuselage of her Seversky AP-7. (Unattributed)
Jackie Cochran paints her race number, 13, of the fuselage of her Seversky AP-7 at Burbank, California. (Unattributed)

“Finally the P-35 arrived. I decided that I didn’t want to take it into the air for a test even if I could. The racing officials impounded it because it was a prototype and there was some kind of rule about untested planes. I would test it en route. . . Finally, I got to sit in the cockpit. I began to study all the instruments by the hour. I can almost see them still.

 “There are about a hundred or more buttons, levers, and other gadgets to push, pull or twirl. . .  I close my eyes and reach for everything in the dark. And I keep at this until I can get to them blindfolded and with no false moves. . . 

“I finally see Cleveland. . . (a)nd am going so fast that I pass the airport and come in from the wrong side. . . Have I won? The crowds are cheering. It’s a standing ovation. . . I have won the Bendix.”

Vincent Bendix congratulates Jackie Cochran on winning the 1938 Bendix Trophy Race.
Vincent Bendix congratulates Jackie Cochran on winning the 1938 Bendix Trophy Race.

— Jackie Cochran: An Autobiography, by Jacqueline Cochran and Maryann Bucknum Brinley, Bantam books, New York 1987, Pages 160–165.

Jackie Cochran was the third pilot to leave Burbank, but the first to arrive at Cleveland. Her elapsed time for the flight from California to Ohio was 8 hours, 10 minutes, 31.4 seconds, for an average speed of 249.774 miles per hour (401.895 kilometers per hour).

After being congratulated on her win by Vincent Bendix and other race officials, Cochran had her Seversky monoplane refueled. She then got back in to its cockpit and took off for Bendix, New Jersey. She landed there 10 hours, 7 minutes, 1 second after leaving Burbank at 3:00 a.m. This was a new West-to East Transcontinental Speed Record.

Sversky AP-7 NX1384, seen from below. In this configuration, the landing gear folds rearward.
Sversky AP-7 NX1384, seen from below. In this configuration, the landing gear retracts rearward.

© 2016, Bryan R. Swopes

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29 August 1938

Major Alexander P. de Seversky in his Seversky AP-7, NX1384, at Floyd Bennett Field, 1938. (San Diego Air and Space Museum Archives)

29 August 1938: At 7:37 a.m., Alexander Nikolaevich Prokofiev-Seversky departed Floyd Bennett Field, Brooklyn, New York, flying a Seversky AP-7 Pursuit, NX1384, an all-metal monocoque monoplane of his own design and manufacture, enroute to the Lockheed Air Terminal, Burbank, California, a distance of 2,457 miles (3,954 kilometers). He completed the flight in 10 hours, 2 minutes, 55.7 seconds, setting a new speed record for an East-to-West Transcontinental Flight. Major Seversky refueled during a 30-minute stop at Kansas City.

Larry Therkelson of the National Aeronautic Association was the official timer for the record attempt.

Sversky AP-7 NX1384, seen from below. In this configuration, the landing gear folds rearward.
Seversky AP-7 NX1384, seen from below. In this configuration, the landing gear retracts rearward.

The Los Angeles Times reported:

SEVERSKY SETS RECORD

Flies across Country in Few Minutes More than Ten Hours

     Maj. Alexander P. (Sascha) de Seversky, who flew fighting planes for the Czar of Russia and now builds pursuit ships for the American Army, yesterday notched another hour off the already incredibly narrow time-space separating the Atlantic and Pacific coasts.

In a “civilianized” fighter made at his Long Island factory, de Seversky thrashed along the 2600-mile airway from Floyd Bennett Field, N.Y., to Union Air Terminal, Burbank, in ten hours, three minutes, seven seconds, better than 260 miles per hour.

START AND FINISH

He had gobbled a husky breakfast of oatmeal, orange juice and toast in Manhattan as dawn arose over the skyscrapers (at 3:37 a.m. P.S.T.)

Under a blazing Southland sun that shot the mercury to 100 deg. at Burbank, he toyed with a chicken sandwich fifteen minutes after he set his pursuiter’s trim wheels down at exactly 1:40:07 p.m.

De Seversky was greeted—warmly—by Jacqueline Cochran, America’s No. 1 woman speed flyer for whom he was ferrying the all-metal monoplane to Los Angeles. She will retrace his course in the small hours of Saturday, seeking the lion’s share of the $30,000 Bendix Trophy purse.

It was, he said, “Practically nothing.”

TIME WASTED

     In a new age of aeronautics, when pilots break records just in the day’s work during routine assignments, de Seversky stands with the best of ’em.

His time and speed would have been materially bettered if he’d been “trying,” he admitted. At Kansas City, plopping down into TWA’s hangars for refueling, he wasted a precious twenty-nine minutes while mechanics tinkered with his tricky gasoline system.

      “Once I was traveling more than 300 miles an hour,” De Seversky admitted.

MERELY A WARM-UP

     How much faster he could have flown, the esrtwhile White Russian declined to say—”Wait until ‘Jacky’ starts for Cleveland in the Bendix race,” he interposed.

      “I used oxygen part of the way, especially when I climbed to 16,000 over the Kansas prairies during a hailstorm,” he said. “This whole flight was nothing but a warm-up. I could have flown nonstop. Instead, I tried different wing loadings and paused at Kansas City. Sometimes I throttled down to less than 240 miles an hour.”

     Two hundred and forty!

     Between bites of chicken sandwich, De Seversky pointed out that his 1200-horsepower plane can soar 3000 miles without refilling its wing-to-wing tanks that carry 540 gallons of high octane fuel. That, he observed, carries huge military significance.

     “We are learning in the Army,” this builder of the nation’s fastest pursuit ships declared, “that bombardment craft are vulnerable to attack from the air unless properly convoyed.

Turn to Page 5, Column 2

Record Upset by Seversky

Continued from First Page

So—the ‘flying fortress’ that cruises 5000 miles must be accompanied by pursuit ships that can go equally as far nonstop. To Europe from America, for example.

THREE UNDER WAY

     “In the United States at least three such planes are underway today. I am building one. Others may be twin-engined—such as the ship being readied at the Lockheed plant—and capable of terrific speeds.”

     By Christmas of this year, de Seversky promised, a standard military fighter, soon to be released to Air Corps testers, will crack the long-sought-after 400-miles-an-hour mark.

BENDIX MARK SEEN

     De Seversky was cool as he braked his craft to a halt under the gaze of Larry Therkelson, official National Aeronautic Association timer. He removed his earphones, slipped out of his jumper and asked, “When’s lunch?” To statements that he had knocked Roscoe Turner’s five-year-old record of 11h. 30m. silly, he only shrugged.

OTHERS IN RACE

     Others in the Bendix race will be Frank Fuller and Miss Cochran in Seversky planes, Robert Perlick, Glendale, in a Beechcraft; Robert Hinschey and Charles LaJotte, Glendale, in a Sparton; Ross Hadley, Burbank, in a Beechcraft; George Armistead, Los Angeles, in a Q.E.D. Special; Bernarr Macfadden, New York publisher, and Ralph Francis, former TWA pilot, in a Northrop Gamma; Paul Mantz, Burbank, in a Lockheed Orion; Frank Cordova, New York, in a Bellanca; Lee Gehlbach, New York, in a Wedell-Williams, and Max Constant, Burbank, in a Beechcraft.

Los Angeles Times, Vol. LVII, Tuesday Morning, 30 August 1938, Page 1, Column 5, and Page 5, Column 2

Jackie Cochran with the Seversky AP-7A, NX1384. Her racing number, 13, has not yet been painted on the fuselage. (San Diego Air and Space Museum Archive)
Jackie Cochran with the Seversky AP-7A, NX1384, at Burbank, California. The landing gear has been modified. Her racing number, 13, has not yet been painted on the fuselage. (San Diego Air and Space Museum Archive)

NX1384 was built especially for Jackie Cochran. The AP-7 racer was an improved version of Seversky’s P-35A fighter, which was the U.S. Army Air Corps’ first all-metal single-engine airplane with an enclosed cockpit and retractable landing gear.

Cochran’s AP-7 was powered by an air-cooled, supercharged, 1,829.39-cubic-inch-displacement (29.978 liter) Pratt & Whitney Twin Wasp S1B3-G (R-1830-11) two-row 14-cylinder radial engine with a compression ration of 6.7:1. It was rated at 850 horsepower at 2,450 r.p.m. at 5,000 feet (1,524 meters), and 1,000 horsepower at 2,600 r.p.m. for take off. The engine turned a three-bladed Hamilton-Standard controllable-pitch propeller through a 3:2 gear reduction. The R-1830-11 was 4 feet, 8.66 inches (1.439 meters) long with a diameter of 4 feet, 0.00 inches (1.219 meters), and weighed 1,320 pounds (599 kilograms).

Jackie Cochran paints her race number, 13, of the fuselage of her Seversky AP-7. (Unattributed)
Jackie Cochran paints her race number, 13, of the fuselage of her Seversky AP-7. (Unattributed)

Two days later, 1 September 1938, Jackie Cochran flew this same airplane to win the Bendix Trophy Race from Burbank to Cleveland, Ohio, a distance of 2,042 miles (3,286 kilometers). Her winning time was 8 hours, 10 minutes, 31.4 seconds, for an average speed of 249.774 miles per hour (401.895 kilometers per hour). After a 40 minute refueling stop, and being congratulated for her Bendix win, she flew on to Bendix, New Jersey, setting a West-to-East Transcontinental Speed Record with a total elapsed time of 10 hours, 7 minutes, 1 second.

The Seversky AP-7 and its military version, the P-35, would be developed over the next few years to become the Republic P-47 Thunderbolt.

Seversky AP-7 NX1384, c/n 145. (San Diego Air and Space Museum Archives)
Seversky AP-7 NX1384, c/n 145, with Jackie Cochran’s race number, 13, at Cleveland, Ohio. (San Diego Air and Space Museum Archives)

 

© 2017, Bryan R. Swopes

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