Boeing 247

Design and development

Boeing introduced a host of aerodynamic and technical features into a new commercial airliner building on work with the earlier Monomail (Models 200, 221, 221A) mailplanes and B-9 bomber designs. The Boeing 247 was faster than the best U.S. fighter of its day, the open-cockpit biplane Boeing P-12. The low landing speed of 62 mph (100 km/h) avoided the need for flaps, and pilots learned that at speeds as low as 10 mph (16 km/h), the 247 could be taxied "tail high" for ease of ground handling.

The 247 could fly on one engine. With controllable-pitch propellers, the 247 could maintain 11,500 ft (3,500 m) at maximum gross weight on one engine. Aside from its size, much lower wing loading, and the wing spar obstructing the cabin, many of its features became the norm for airliners, including the Douglas DC-1, before World War II. Originally planned as a 14-passenger airliner powered by Pratt & Whitney R-1690 Hornet radial engines, the preliminary review of the design concept by United Air Lines' pilots had resulted in a redesign to a smaller, less capable configuration, powered by R-1340 Wasp engines.

One concern of the pilots was that in their view, few airfields could safely take an eight-ton aircraft. They also objected to the Hornet engines, which had a detonation problem when using the available low octane fuel, and suffered from excessive vibration. Pratt & Whitney's chief engineer, George Mead, knew the problem would be resolved eventually, but P&W's president, Frederick Rentschler acquiesced to the airline pilots' demand. The decision created a rift between Mead and Rentschler. Despite the disagreements, the 247 would be Boeing's showcase exhibit at the 1933 Chicago World's Fair.

The slope of the early 247's windshield was reversed from normal. This was a design solution, also used on other contemporary aircraft, to the problem of control panel instrument lights reflecting off the windshield, but the reversed windshield reflected ground lights instead, especially during landings, and it also increased drag. By the introduction of the 247D, the windshield was sloped normally, and the glare was resolved with a glarescreen extension over the panel.

Boeing incorporated design elements to enhance passenger comfort, such as the thermostat controlled, air conditioned, and noise-proofed cabin. The crew included a pilot and copilot, as well as a flight attendant (then known as a "steward"), who could tend to passenger needs. The main landing gear did not fully retract; the wheels extended slightly below the nacelles, typical of designs of the time, as a means of reducing structural damage in a wheels-up landing. The tailwheel was not retractable. While the Model 247 and 247A had speed-ring engine cowlings and fixed-pitch propellers, the Model 247D incorporated NACA cowlings and variable-pitch propellers.

Operational history

As the 247 emerged from its test and development phase, the company further showcased its capabilities by entering a long-distance air race in 1934, the MacRobertson Air Race from England to Australia. During the 1930s, aircraft designs were often proven in air races and other aerial contests. A modified 247D was entered, flown by Colonel Roscoe Turner and Clyde Pangborn. The 247, race number "57", was essentially a production model, but all airliner furnishings were removed to accommodate eight additional fuselage fuel tanks. The MacRobertson Air Race attracted aircraft entries from all over the globe, including both prototypes and established production types, with the grueling course considered an excellent proving ground, as well as an opportunity to gain worldwide attention. Turner and Pangborn came in second place in the transport section (and third overall), behind the Boeing 247's eventual rival, the new Douglas DC-2.

Being the winner of the 1934 U.S. Collier Trophy for excellence in aviation design, the first 247 production orders were earmarked for William Boeing's airline, Boeing Air Transport. The 247 was capable of crossing the United States from east to west eight hours faster than its predecessors, such as the Ford Trimotor and Curtiss Condor. Entering service on May 22, 1933, a Boeing Air Transport 247 set a cross-country record of 19+1⁄2 hours on its San Francisco to New York City inaugural flight.

Boeing sold the first 60 247s, an unprecedented $3.5 million order, to its affiliated airline, Boeing Air Transport (part of the United Aircraft and Transport Corporation, UATC), at a unit price of $65,000. TWA (Transcontinental & Western Air) also ordered the 247, but UATC declined the order, which resulted in TWA President Jack Frye setting out requirements for a new airliner and funding Don Douglas to design and build the Douglas DC-1 prototype. Douglas eventually developed the design into the DC-2 and DC-3.

The Boeing design had been the first to enter series production, but the 247 proved to have some serious deficiencies. Airlines considered its limited capacity a drawback, since it carried only 10 passengers, in five rows with a seat on each side of the aisle, as well as a stewardess.