World Library  
Flag as Inappropriate
Email this Article

Boeing 40

Model 40
Role Mail plane
Manufacturer Boeing
First flight July 20, 1925
Introduction July 1, 1927
Primary users Boeing Air Transport
Varney Air Lines
Pacific Air Transport
Number built ca. 80

The Boeing Model 40 was a United States mail plane of the 1920s. It was a single-engined biplane that was widely used for airmail services in the United States in the 1920s and 30s, especially by airlines that later became part of United Airlines. It became the first aircraft built by the Boeing company to carry passengers.

Development and design

In 1925, the US Post Office issued a requirement for a mailplane to replace the ex-military DH-4s then in use. The new aircraft was required to use the same water-cooled Liberty V12 engine as used by the DH-4, of which large stocks of war-built engines were available.[1] The resultant aircraft, the Boeing Model 40, was a conventional tractor biplane, with the required Liberty engine housed in a streamlined cowling with an underslung radiator. The aircraft's fuselage had a steel tube structure, with aluminum and laminated wooden covering. Up to 1,000 lb (450 kg) of mail was carried in two compartments in the forward fuselage, while the single pilot sat in an open cockpit in the rear fuselage. The wings and tail were of wooden construction, and the Model 40 had a fixed conventional landing gear.[1][2]

The Model 40 made its first flight on July 7, 1925. Although the prototype was purchased by the US Post Office, the production order went to the Douglas M-2.[1][3]

The Contract Air Mail Act of 1925 set out the gradual privatization of the Post Office's Air Mail routes. In late 1926, bids were requested for the main transcontinental trunk mail route, which was to be split into eastern and western sections, with Boeing bidding for the western section. Boeing revived the design for the tender, with the Model 40A replacing the Liberty engine with a 425 hp (317 kW) air-cooled Pratt & Whitney Wasp radial engine, which was 200 lb (91 kg) lighter than the Liberty, ignoring the weight of the Liberty's radiator and cooling water. The fuselage was redesigned to make more extensive use of welded steel tubing, and an enclosed cabin was fitted between the mail compartments, allowing two passengers to be carried as well as 1,200 lb (540 kg) of mail. Boeing's bid of $3 per lb was much less than any of the competing bids, and Boeing was awarded the San Francisco to Chicago contract in January 1927, building 24 Model 40As for the route (with a further aircraft being used as a testbed by Pratt & Whitney).[4][3][5]

The next model to reach production was the Model 40C, with an enlarged cabin allowing four passengers to be carried. Meanwhile Boeing Air Transport's Model 40As were modified by replacing their Wasp engines with 525 hp (391 kW) Pratt & Whitney Hornet radial engines to become the Model 40B-2.[6] The Model 40B-4 was a new-build aircraft combining the four passenger cabin of the Model 40C with the Hornet engine of the B-2.[7] Production continued until February 1932.[8]

Operational history

Boeing's airline, Boeing Air Transport, commenced operations on the San Francisco–Chicago route on July 1, 1927.[9]


Model 40
Original 1925 design with Liberty engine.
Model 40A
Revised 1927 design for BATC. the aircraft was powered by a Pratt & Whitney Wasp radial engine, plus seating for two passengers in an enclosed cabin; 25 built. Received Dept of Air Commerce Approved Type Certificate #2.[10]
Model 40B
Model 40As re-engined with a 525 hp (391 kW) Pratt & Whitney Hornet radial piston engine. 19 Model 40A were converted. Redesignated Model 40B-2.
Model 40B-4
Revised Model 40B with seating for four passengers and other improvements. Equipped with openable windows, plus seating for four passengers; 38 built.
Model 40B-4A
One Model 40B used as engine testbed by Pratt & Whitney.
Model 40H-4
Four Model 40B-4s built by Boeing Canada. Two aircraft were exported to New Zealand.
Model 40C
Similar to Model 40B-4 but with Pratt & Whitney Wasp engine of Model 40A. (10 built, all later converted to Model 40B-4 standard).[11][12]
Model 40X
Unique special-order machine similar to Model 40C with only two-passenger cabin and extra open cockpit forward of pilot's cockpit.
Model 40Y
Unique special-order machine similar to Model 40X, but with Pratt & Whitney Hornet engine.


 United States


As of February 17, 2008, Boeing 40C c/n 1043 became the only airworthy example in the world. It also holds the title of the oldest flying Boeing in the world. In 1928, the aircraft was substantially damaged in a crash near Canyonville, OR. After being recovered, it was completely rebuilt over an eight-year period and an estimated 18,000 man hours by Pemberton and Sons Aviation[14] in Spokane, Washington. On May 8, 2010, this airplane had an aerial rendezvous with Boeing's newest passenger aircraft, the Boeing 787 Dreamliner.[15] This aircraft spends its winters living at the Western Antique Aeroplane & Automobile Museum in Hood River, Oregon.

The Henry Ford Museum in Dearborn, Michigan, contains a 1927 Boeing 40B-2, number 285.

The Museum of Science and Industry in Chicago, Illinois has a 1928 Boeing Model 40-B on display in its Transportation Gallery. (N288)

The Museum of Flight in Seattle, Washington has a complete full-scale replica and two partially finished replica fuselages (showing what the original Boeing factory would have looked like circa 1928-29) on display.

Specifications (Model 40A)

Data from Boeing Aircraft since 1916[16]

General characteristics
  • Crew: 1
  • Capacity: 2 passengers and 1,200 lb (540 kg) mail
  • Length: 33 ft 214 in (10.12 m)
  • Wingspan: 44 ft 214 in (13.47 m)
  • Height: 12 ft 318 in (3.74 m)
  • Wing area: 547 sq ft (50.82 m²)
  • Empty weight: 3,531 lb (1605 kg)
  • Max. takeoff weight: 6000 lb (2727 kg)
  • Powerplant: 1 × Pratt & Whitney Wasp, 420 hp (313 kW)


Accidents and incidents

  • February 26, 1928: A Boeing Air Transport Model 40B (c/n 891, registration NC280) crashed near Marquette, Nebraska after the aircraft struck trees when flying low to avoid air turbulence; the passenger was killed, but the pilot survived.[17]
  • April 17, 1928: A Boeing Air Transport Model 40B (c/n 893, registration NC282) crashed at Federal, Wyoming, killing one of two on board.
  • November 18, 1930: A Pacific Air Transport Model 40B-4 (c/n 1036, registration NC5340) crashed into a mountainside at 4500 feet in a snowstorm, killing all 3 on board.
  • January 22, 1931: A Varney Air Lines Model 40B-4 (c/n 1148, registration NC741K) crashed into Bluff Mountain in dense fog, killing the pilot.
  • May 5, 1931: A Pacific Air Transport Model 40B-4 (c/n 1044, registration NC5390) crashed into Las Tunas Canyon while attempting to land at Burbank Airport in low visibility, killing both crew.
  • September 16, 1931: A Pacific Air Transport Model 40B-4 (c/n 1428, registration NC10347) crashed into San Francisco Bay after takeoff for reasons unknown, killing all 4 on board.
  • November 23, 1931: A Boeing Air Transport Model 40, registration NC7465, crashed 8 miles west of Salt Lake Airport, killing the pilot; it was believed that the plane overturned while attempting to land at night.
  • November 26, 1931: A Varney Air Lines Model 40B-4 (c/n 1419, registration NC10338) crashed near Pasco, Washington in low visibility while attempting to land, killing the pilot.
  • February 2, 1932: A Boeing Air Transport Model 40, registration NC7470, crashed on landing at Rio Vista, California; the plane struck an irrigation ditch and caught fire, killing one of two on board.
  • May 3, 1932: A Varney Air Lines Model 40B-4 (c/n 1155, registration NC830M) crashed at Portland, Oregon, killing both crew.
  • May 16, 1932: A Pacific Air Transport Model 40, registration NC5589, crashed and burned in fog while attempting to land at Burbank Airport, killing all 3 (both pilots, radioman) on board.
  • December 14, 1932: A Boeing Air Transport Model 40B-4 (c/n 1168, registration NC842M) crashed at Rocky Ridge, Colorado, killing the pilot.

See also


Further reading

External links

  • Boeing History – Boeing Model 40A Commercial Transport Retrieved June 17, 2006.
  • One-of-a-Kind Restored Boeing 40 Flying To AirVenture (2008, Oshkosh, Wi. Photos included)
  • Prelude to AirVenture appearance, 7 minute video, accessed 8 August 2008
  • Pemberton-Tobin-Scott transcontinental air mail re-enactment
  • Pemberton and Sons Aviation Website
This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.

Copyright © World Library Foundation. All rights reserved. eBooks from Project Gutenberg are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.