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Subject: Boeing 247
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https://en.wikipedia.org/wiki/Boeing_247
The Boeing Model 247 was an early United States airliner, considered the first
such aircraft to fully incorporate advances such as all-metal (anodized
aluminium) semimonocoque construction, a fully cantilevered wing and retractable
landing gear. Other advanced features included control surface trim tabs, an
autopilot and de-icing boots for the wings and tailplane.
"Ordered off the drawing board", the 247 first flew on February 8, 1933 and
entered service later that year. Subsequently, development in airliner design
saw engines and airframes becoming larger and four-engined designs emerged, but
no significant changes to this basic formula appeared until cabin pressurization
and high altitude cruise were introduced in 1940, with the first pressurized
airliner, the Boeing 307 Stratoliner.
Boeing had eclipsed other aviation manufacturers by introducing a host of
aerodynamic and technical features into a commercial airliner. This advanced
design, which was a progression from earlier Monomail (Models 200, 221, 221A)
and B-9 bomber designs, combined speed and safety. The Boeing 247 was faster
than the U.S. premier fighter aircraft of its day, the Boeing P-12, which was an
open-cockpit biplane. Yet its flight envelope included a rather docile 62 mph
(100 km/h) landing speed, which precluded the need for flaps, and pilots learned
that at speeds as low as 10 mph (15 km/h), the 247 could be taxied "tail high"
for ease of ground handling.
The 247 was the first twin-engined passenger transport able to fly on one
engine. With controllable pitch propellers (standard equipment on the 247D), the
247 could maintain 11,500 feet (3,500 m) at maximum gross takeoff weight. Its
combination of features set the standard for the Douglas DC-1 and other
airliners 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 design configuration, powered by R-1340 wasp engines.
One concern of the pilots was that no airfield then in existence, in their view,
could safely take an eight-ton aircraft. They also objected to the use of Hornet
engines, because most pilots were accustomed to the less-powerful Wasps and
would find Hornets overpowering. Pratt & Whitney's chief engineer, George Mead,
knew that this thinking was misguided and that within a few years it would seem
antiquated. P&W's president, Frederick Rentschler, faced with a tough decision,
decided to acquiesce to the airline pilots' unanimous demand. The decision
created a rift between Mead and Rentschler. Despite the bitter disagreements on
design and engines, the 247 was still a remarkable achievement and was Boeing's
showcase exhibit at the 1933 Chicago World's Fair.
The cockpit windshield of the first 247s was angled forward, instead of the
conventional aft sweep. This was the design solution (similar to that adopted by
other contemporary aircraft that used a forward-raked windscreen) to the problem
of lighted control panel instruments reflecting off the windshield at night, but
it turned out that the forward-sloping windshield would reflect ground lights
instead, especially during landings and it also increased drag slightly. By the
introduction of the 247D, the windshield was sloped aft in the usual way, and
the night-glare problem was resolved by installing an extension (the
glarescreen) over the control panel.
Boeing considered safety features highly, building in structural strength as
well as incorporating design elements that enhanced customer comfort and
well-being, such as the thermostatically-controlled, air conditioned and
soundproof cabin. The crew included a pilot and copilot as well as a flight
attendant who could tend to passenger needs. The main landing gear did not fully
retract; a portion of the wheels extended 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.
Role
Passenger airliner
Manufacturer
Boeing
First flight
February 8, 1933
Introduction
May 22, 1933
Status
Retired
Primary user
Boeing Air Transport
Number built
75
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 prototypes as well as established production types, with the gruelling
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 pace of ?19 1/2 hours on its San
Francisco to New York inaugural flight. For the first time airline passengers
could fly across the country without changing planes or stopping overnight.
Seventy-five 247s were built; by contrast, Douglas collected 800 civil orders
for DC-3s before the Pearl Harbor attack, and produced over 10,000 DC-3s,
including wartime production of C-47s; while the rival Lockheed Electra "family"
was eventually to reach over 3,000 in its various civilian and military
variants. Boeing Air Transport bought 60 examples, United Aircraft Corp. ten,
Lufthansa ordered three but only two were delivered, and one went to a private
owner in China. While the industry primarily standardized on Boeing's
competitors, many of United's aircraft were later purchased by Western Air
Express at "bargain basement prices".
The 247 remained in airline service until World War II, when several were
converted into C-73 transports and trainers. No. 121 Squadron, Royal Canadian
Air Force (RCAF) operated seven Model 247Ds as medium transports during the
early part of the war. Some 247s were still flying in the late 1960s, converted
either into cargo transports or personal business aircraft.
Specifications (Boeing 247D)
General characteristics
Crew: three
Capacity: ten passengers
Length: 51 ft 5 in (15.7 m)
Wingspan: 74 ft 1 in (22.6 m)
Height: 12 ft 5 in (3.8 m)
Empty weight: 8,921 lb (4,055 kg)
Max. takeoff weight: 13,650 lb (6,190 kg)
Performance
Maximum speed: 200 mph (320 km/h)
Cruise speed: 188 mph (304 km/h)
Range: 745 miles (1,200 km)
Service ceiling: 25,400 ft (7,620 m)
Rate of climb: 1,148 ft/min (350 m/min)
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