Boeing 80A
American 3-engine biplane passenger aircraft

Overview ²

• Boeing Model 80A
• Role: Airliner
• Manufacturer: Boeing
• First flight: July 18, 1929
• Introduction: September 20, 1929 with Boeing Air Transport
• Retired: 1934
• Primary user: Boeing Air Transport
• Number built: 16
• Unit cost: $75,000 (Model 80A)

The Boeing 80 was an American airliner of the 1920s. A three-engined biplane, the Model 80 was built by the Boeing Airplane Company for Boeing’s own airline, Boeing Air Transport, successfully carrying both airmail and passengers on scheduled services.

Development and Design ²

Boeing Air Transport was formed on February 17, 1927 by William Boeing to operate the Contract Air Mail (CAM) service between San Francisco and Chicago (CAM.18), taking over the route on July 1, 1927. The route was initially operated by Single-engine Boeing 40A biplanes, which could carry four passengers, which provided a useful supplement to the subsidized revenue from carrying airmail.

In order to take better advantage of passenger traffic, Boeing decided that it needed a larger aircraft that was more suitable for passenger carrying, and in early 1928 designed a trimotor aircraft capable of carrying 12 passengers, the Model 80. Unlike the Fokker F.VII and Ford Trimotors operated by other airlines, the Model 80 was a biplane, chosen to give good takeoff and landing performance when operating from difficult airfields on its routes, many of which were at relatively high altitude. The fuselage was of fabric covered steel and aluminium tube construction, and carried its 12 passengers in three-abreast seating in a well-appointed cabin. The flight crew of two sat in an enclosed flight deck forward of the passenger cabin. The wings were of fabric covered steel and duralumin construction, with detachable wingtips to aid storage in hangars.

The first Model 80, powered by three Pratt & Whitney Wasp radial engines, flew on July 27, 1928. It was followed by three more Model 80s before production switched to the improved Model 80A, which was longer, allowing 18 passengers to be carried, and was powered by more powerful Pratt & Whitney Hornet engines, first flying on July 18, 1929 and receiving its airworthiness certificate on August 20, 1929.

Operational History ²

The Model 80 carried out its first scheduled mail and passenger service for Boeing Air Transport on September 20, 1928, and soon proved successful. The improved Model 80A entered service in September 1929. In May 1930, Boeing Air Transport introduced female flight attendants, hiring eight including chief stewardess Ellen Church; all were unmarried registered nurses. Flights carrying stewardesses began on May 15. The Model 80 and 80A remained in service with Boeing Air Transport (later renamed United Airlines) until replaced by the Boeing 247 Twin-engine monoplane in 1934.

Variants ²

• Boeing Model 80 - original production version with Pratt & Whitney Wasp engines (four built).
• Boeing Model 80A - improved aerodynamics and Pratt & Whitney Hornet engines (10 built).
• Boeing Model 80A-1 - version with revised empennage with an added finlet on each tailplane; all 10 Model 80As converted to this standard.
• Boeing Model 80B-1 - single Model 80A built with open flight deck. Later modified to Model 80A-1 standard.
• Boeing Model 226 - one-off Model 80A converted to executive transport for Standard Oil. Modified tail surfaces later adopted on all Model 80As (see Model 80A-1).

Operators ²

United States

• Boeing Air Transport
• Monterey Peninsula Airways
• Morrison-Knudsen Company
• Robert Campbell Reeve
• Standard Oil, California
• United Airlines

Surviving Aircraft ²

A single Model 80A-1, modified as a freighter for use in Alaska, was salvaged from a dump at Anchorage Airport in 1960, and following restoration is now on display at the Museum of Flight in Seattle.

Boeing Model 80A Specifications ²

Type

• Three-engined, twelve/eighteen-passenger, mail and express biplane.

Wings

• Biplane of unequal span and chord, of single-bay type, outside wing-engines.
• Normal Boeing type, wooden construction.
• Ailerons fitted to top planes only.

Fuselage

• Welded steel-tube structure, with no internal bracing.

Tail Unit

• Normal monoplane type.
• Welded steel-tube frames, covered with fabric.
• Balanced rudder and elevators.
• Adjustable tail-plane.

Undercarriage

• Divided type.
• Consists of two Vees, provided with Boeing combined oleo and spring suspension, mounted under each wing-engine, between which is slung one large-diameter wheel on a short axle.
• A radius-rod runs from each wheel axle to the bottom longerons of the fuselage.
• Steerable wheel-type tail-skid.

Power Plant

• Three 525 hp Pratt & Whitney Hornet air-cooled radial engines, one mounted on the nose and the other two carried midway between the planes, one on either side of the fuselage.
• Fuel carried in two tanks of 340 U.S. gallons (283 Imp. galls. = 1,285 L) carried in the top plane.
• Oil tanks mounted between each engine.
• All engine-mountings quickly detachable.
• All engines equipped with electric inertia starters and may be started from pilot’s cockpit.
• All engines fitted with cowling, permitting adequate temperature control.
• Standard Steel adjustable pitch metal airscrews.

Accommodation

• The pilot’s cockpit is in the nose and provides seats for two side-by-side.
• Single controls fitted.
• Side and front windows of unsplinterable glass, with sliding panel of celluloid in roof.
• The passenger cabin has seats arranged in four or six rows of three each, depending on the number of passengers for which the machine is designed.
• A separate compartment forward may either contain one row of seats or may be used as a mail compartment of 100 ft³ capacity when only twelve passengers are carried.
• Aft of the cabin is a large cloak room, as well as a lavatory with hot and cold running water.
• Forced ventilation and heating, and entire cabin is insulated and rendered as sound-proof as possible.
• Openable windows throughout length of cabin.
• Dome and shared wall-lights for night-flying.

Dimensions

• Span (top): 80 ft (24.37 m)
• Span (bottom): 64 ft 10 in (19.76 m)
• Length: 55 ft 0 in (15.76 m)
• Height: 15 ft 2 in (4.62 m)
• Wing area: 1,250 ft² (116.1 m²)

Weights and Loadings

• Weight empty (18 passengers): 10,417 lb (4,729 kg)
• Weight empty (12 passengers): 10,357 pounds (4,702 kg)
• Payload (18 passengers): 4,057 lb (1,842 kg)
• Payload (12 passengers): 4,117 lb (1,869 kg)
• Fuel and oil: 2,310 lb (1,048 kg)
• Weight loaded: 17,500 lb (7,945 kg)
• Wing loading: 14 lb/ft² (68.4 kg/m²)
• Power loading: 11.6 lb/hp (5.3 kg/hp)

Performance (with full load)

• Maximum speed: 138 mph (220 km/hr)
• Landing speed: 55 mph (88.5 km/hr)
• Initial rate of climb: 850 ft/min (260 m/min)
• Service ceiling: 14,000 ft (4,270 m)

References

1. Shupek, John. 3-view drawing, The Skytamer Archive, copyright © 2017 Skytamer Images. All Rights Reserved
2. Wikipedia, the free encyclopedia. Boeing Model 80
3. Grey, C. G. and Leonard Bridgman. The Boeing Type 80-A Biplane. Jane’s all the World’s Aircraft 1931. London: Sampson Low, Marston & company, Ltd., 1931, p. 254c. Print.