Boeing 247 247D

The 247D began as a one-off built as a racing aircraft for the 1934 MacRobertson Air Race from England to Australia. Hamilton Standard variable-pitch propellers gave it a gain of 11 km/h, and the resulting configuration was incorporated into the production series under the same designation.

The 247D also fixed two visible flaws of the original model: the windshield recovered its normal rake — glare was cured with a glarescreen extension over the panel — and the speed-ring cowlings gave way to NACA cowlings.

The racing 247D, race number 57, was flown by Colonel Roscoe Turner and Clyde Pangborn. It was essentially a production aircraft with all airliner furnishings stripped out to make room for eight additional fuselage fuel tanks. Turner and Pangborn came second in the transport section and third overall, behind exactly the rival that would displace the 247: the new Douglas DC-2.

That aircraft still exists. It first flew on 5 September 1934, was leased from United Airlines for the race and returned afterwards, serving in scheduled airline work until 1937. It then went to the Union Electric Company of St. Louis as an executive transport, and in 1939 the Air Safety Board bought it and used it for fourteen years before donating it to the National Air and Space Museum in Washington. It is displayed in two liveries at once: the left side carries NR257Y in Turner's 1934 MacRobertson colours and the right side United Airlines markings as NC13369.

The 247 stayed in airline service until the Second World War. The Royal Canadian Air Force's 121 Squadron operated seven 247Ds as medium transports early in the war; one was passed to the RAF for radar testing under the new serial DZ203, and with it the world's first fully automatic blind landing was made on 16 January 1945.

In China, warlord Zhang Xueliang ordered two 247Ds for his air force and used one of them, named Bai-Ying — White Eagle — during the 1936 Xi'an incident. A 247D bought by the RAF became a testbed for instrument approach equipment, with a non-standard nose, new powerplants and fixed landing gear. Some 247s were still flying in the late 1960s as cargo transports and business aircraft.