Boeing’s Metal Monoplanes of the 1930s

In 1930, Boeing created the Monomail, which was made entirely of metal and had no struts.

The B-9 bomber was the earliest plane based on the Monomail design.

The Boeing P-26A was the first all-metal monoplane fighter produced in quantity for the U.S. Army Air Corps. It was called the "Peashooter" by its pilots. Its first flight took place on March 20, 1932.

A group of P-26 Peashooters in formation.

The Model 247, developed in 1933, was an all-metal, twin-engine airplane and the first modern passenger airliner.

This article courtesy of Centennial of Flight

By the end of the 1920s, biplanes were becoming obsolete and manufacturers turned to building all-metal monoplanes. Boeing Aircraft led this technological revolution with welded steel tubing for fuselage structure. This soon became standard in the industry until it was replaced by monocoque sheet metal structures in the mid-1930s.

Boeing’s first all-metal monoplane was the Monomail, designed to carry cargo and mail, and the single unsuccessful XP-9 monoplane fighter. The Monomail had a sleek, aerodynamic low-wing design, cantilever construction, retractable landing gear, a streamlined fuselage, and an engine covered by a cowling. The Monomail Model 200 was a mail plane, and the Model 221 was a six-passenger transport. Only one of each plane was built. Their first flights were in May 1930. Both were later modified for transcontinental passenger service as Model 221As.

The major drawback of the Monomail was that its design was too advanced for the engines and propellers that were available. The airplane required a low-pitch propeller for takeoff and climb and a high-pitch propeller to cruise. By the time the variable-pitch propeller and more powerful engines were available, newer, multiengine planes were replacing it.

The Monomail inspired the B-9 bomber, which first flew in April 1931. The B-9 was the U.S. Air Corps’ first all-metal monoplane bomber. It could reach top speeds of 186 miles per hour (299 kilometers per hour), faster than fighters in service at the time, and a cruise speed of 165 miles per hour (266 kilometers per hour) with a five-person crew and carrying a 2,400-pound (1,089-kilogram) bomb load. The two-engine plane had semi-retractable landing gear and metal construction. Even though the Air Corps production contract went to Glenn Martin’s B-10 bomber and the B-9 never progressed beyond the prototype stage, the plane influenced the development of the Boeing 247.

The twin-engine Boeing 247 made the three-engine airplane obsolete and gave an enormous boost to the U.S. airline industry. United Air Lines, a member of the holding company United Airlines and Technology Corporation (UATC), purchased 60 of the planes and soon outdistanced all of its competitors. The remaining 15 went to other customers including Col. Roscoe Turner and Clyde Pangbourne, two air race competitors, and Germany’s Lufthansa airline.

Company conflict accompanied its development. Boeing’s chief engineer R.J. Minshall had called for a plane no larger than the planes in current production, claiming that pilots liked smaller planes and a larger plane would create problems such as the need for larger hangars. Fred Rentschler of Pratt & Whitney Engine Company, a member of the UATC, as well as Igor Sikorsky, who had been building large planes for years and also a member of UATC, favored a larger plane and claimed that it would offer more comfort to their passengers on long flights. Those in favor of the smaller plane won, and performance prevailed over comfort. Extra headroom was added, though, to try to make it easier for passengers to get around the wing spar that protruded across the cabin aisle.

Disagreements also ensued over whether to have a co-pilot, which would increase passenger safety and comfort but would also add to the weight. The co-pilot was added. The propeller was also a source of controversy. Frank Caldwell’s two-position variable-pitch propeller had already been perfected in 1932. But Boeing argued that the device weighed too much, and decided to use a fixed-pitch propeller. Nevertheless, with some foresight, the plane was designed so that there would be sufficient propeller clearance if a variable-pitch propeller was added later. This turned out to be a smart decision, since the 247D switched to the newer propeller.

United ordered its 60 planes at $52,700 each. Production problems delayed delivery and Boeing was forced to increase its workforce to 2,200, working in three shifts, to complete the planes. The inexperienced work force created additional problems, and the cost per plane to Boeing rose from the original $45,000 to $77,000 for the first 10 planes. Final costs per plane for the 60 that United had ordered came to $68,000. Boeing figured it would just break even.

The first 247 didn’t fly until February 8, 1933, a year later than planned. It went into service with United on March 30, and most of the first 25 planes were delivered during April and May.

The modern twin-engine 247 demonstrated new aerodynamic qualities. It was a low-wing, all-metal monoplane with retractable landing gear and powered by two 550-horsepower (410-kilowatt) Pratt & Whitney Wasp radial engines. Lightweight alloys reduced its weight. It had enough power to climb on one engine with a full load, and it was also the first airliner to use wing flaps. Its final version, the 247D, had variable-pitch propellers and improved performance at higher altitudes to compete with the Douglas DC-2. It had room for 10 passengers, two pilots, and a stewardess (as flight attendants were then called), plus mail and baggage.

When the plane’s rollout finally occurred, some 15,000 visitors came to watch. It was an outstanding plane—capable of cruising at 150 miles per hour (241 kilometers per hour) and flying 485 miles (781 kilometers) before needing to refuel. The passenger cabin had soundproofing, a lavatory (although no mirror or running water), individual air vents and reading lights, and heating and cooling that were thermostatically controlled. Its navigation instruments included an autopilot and two-way radio.

On display at the 1933 Chicago World’s Fair, it was estimated that 61 million people viewed it. The success of the plane provided a response to the aerial feat of Italy’s air minister, General Italo Balbo, who had just led a fleet of 24 Savoia-Marchetti flying boats across the Atlantic Ocean from Rome to Amsterdam, Iceland, and Canada, before landing on Lake Michigan near the fair at Chicago and then returning to Rome ten days later. On June 12, 1933, the 247 made its first transcontinental commercial flight, flying from Newark Municipal Airport to San Francisco in only 21 hours. On its return flight, it set a record for flying coast-to-coast, reaching Newark in just 19 hours 45 minutes, cutting travel time eastbound by seven hours.

The all-metal monoplane structure was also adopted by the military with the P-26 “Peashooter,” a favorite of Army pilots, which had developed from the unsuccessful 1930 XP-9 monoplane, The Peashooter was the first monoplane fighter produced in quantity for the U.S. Army Air Corps and the first that was all metal. (The first all-metal monoplane fighter was the 1932 Model 248—only three were built.) The prototype P-26 first flew in March 1932, went into production in January 1933, and entered service in 1934. It could fly 27 miles per hour (43 kilometers per hour) faster than its biplane counterparts. The wings on this plane were braced with wire rather than with the rigid struts used on other airplanes, so the airplane was lighter and had less drag. The P-26 was also the last Army Air Corps pursuit aircraft accepted with an open cockpit, a fixed undercarriage, and an externally braced wing. Significantly faster in level flight than previous fighters, the P-26A’s relatively high landing speed led to the introduction of landing flaps to reduce the speed.

The U.S. Army ordered 136 Peashooters, and 12 versions were designed for export. For almost five years, they were front-line equipment in the United States, the Panama Canal Zone, and in Hawaii. Nevertheless, the Peashooter seemed outmoded next to the Martin B-10 bomber that was introduced in 1934 with its enclosed cockpit, retractable landing gear, and 212-mile-per-hour (341-kilometer-per-hour) top speed. And compared to the 1936 Seversky P-35 and Curtiss P-36 fighters, the Peashooter seemed even more ancient. It had become obsolete within three years and was the last fighter that Boeing produced in quantity.

-Judy Rumerman

Sources:

Angelucci, Enzo and Matricardi, Paolo. World Aircraft, 1918-1935. Chicago: Rand McNally & Co., 1976.

Bilstein, Roger E. The American Aerospace Industry. New York: Twayne Publishers, 1996.

Van der Linden, F. Robert. The Boeing 247: The First Modern Airliner. Seattle, Wash.: and London: The University of Washington Press, 1991.

On-Line References:

“Boeing P-26A.” U.S. Air Force Museum. http://www.wpafb.af.mil/museum/early_years/ey13d.htm

“Boeing Model 247.” http://www.aviation-history.com/boeing/247.html

Guttman, Robert, “Boeing’s Trailblazing P-26 Peashooter.” http://www.thehistorynet.com/AviationHistory/articles/0796_text.htm
(Site has become extremely difficult to navigate.)

“Metal Monoplanes.” Boeing History – The Beginnings. http://www.boeing.com/history/boeing/monoplanes.html .

Other References:

Rodgers, Eugene. Flying High – The Story of Boeing and the Rise of the Jetliner Industry. New York: The Atlantic Monthly Press, 1996.

Serling, Robert J. Legend and Legacy – The Story of Boeing and Its People. New York: St. Martin’s Press, 1992.