It was (possibly) on this day in aviation history that the second version of the Boeing Model 80 made its first flight, the model 80A. (although some sources give the date of the first flight as July 18th 1929) lets forget about the date and look at the history of this Boeing!)
The very first flight of a Model 80 took place on the 27th of July 1928, 16 months after Boeing Air Transport was founded by William Boeing. Boeing Air Transport (which would later on in the 20th century become United Airlines) was founded to operate the mail service between San Francisco and Chicago, initially operating the route with single-engined Boeing 40A biplanes, The Model 40 aircraft could carry 4 passengers besides the mail, which was an additional source of revenue, on top of the mail contract revenue. Due to demand Boeing decided to develop a larger aircraft with a bigger passenger capacity. This would be the Model 80, a tri-motor bi-plane. The biplane would give the aircraft good performance from some of the hot and high airports on the mail route.
The fuselage was steel and aluminium tube construction which was covered in fabric. It had accommodation for 12 passengers in a nicely upholstered cabin. The wings were also fabric-covered and were structurally composed of duralumin and steel. The upper wing had detachable wingtips for easier storage in hangers, Four Model 80's powered by P&W Wasp Radial would be build before a bigger and more powerful plane was required, the model 80 interior this was the Model 80A.
The Model 80A had several improvements compared to the Model 80:
Stronger engines, P&W Hornet Engines
Longer fuselage, with capacity for 18
Improved aerodynamics
Boeing Air Transport Boeing 80-A (N)C226M (c/n 1084)
The Model 80 and Model 80A remained in service till 1934, when they were replaced with the Boeing 247.
Some other variants of the Model 80 were also developed, a small overview of the different model 80's;
Model 80, four built The original version, powered by P&W Wasp engines
Model 80A, ten built Improved versions, powered by P&W Hornet engines
Model 80A-1, all 10 Model 80A's modified to this standard Revised empennage and finlets added to the tailplane
Model 80B-1, one built The only model 80A built with an open flight deck, later modified to Model 80A-1
Model 226, one built Converted Model 80A for Standard Oil executives, it had a modified tail, which later would be used on the Model 80's to modify them to Model 80A-1 standard
Some specifications for the Boeing Model 80A:
Crew: Three
Capacity: 18 passengers and 898 lb (408 kg) cargo
Length: 56 ft 6 in (17.22 m)
Wingspan: 80 ft 0 in (24.39 m)
Height: 15 ft 3 in (4.65 m)
Wing area: 1,220 sq ft (113.4 m2)
Empty weight: 10,582 lb (4,810 kg)
Max takeoff weight: 17,500 lb (7,940 kg)
Powerplant: 3 × Pratt & Whitney R-1690 Hornet air-cooled radials, 525 hp (392 kW) each
Performance
Maximum speed: 138 mph (222 km/h, 120 kn)
Cruise speed: 125 mph (201 km/h, 109 kn)
Stall speed: 55 mph (89 km/h, 48 kn)
Range: 460 mi (741 km, 400 nmi)
Service ceiling: 14,000 ft (4,270 m)
Rate of climb: 900 ft/min (4.6 m/s)
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