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The Boeing Model 40 Aircraft

by John M. White |

During World War I the airplane became an integral part of the military and was used in many roles ranging from spotting enemy lines through reconnaissance to aerial combat between aircraft over the skies of Europe. Upon conclusion of the war the marketplace was flooded with  surplus wartime airplanes from all of the military air arms of combatants.

Within a couple of months after the end of World War I in January 1919 Germany authorized its first airline which began passenger air service between Berlin and Weimar.  In the United States, however, commercial aviation took on a different role with the military flying mail for the U.S. Postal Service.  In May of 1918 the U.S. Army was flying mail from New York to Washington, DC and less than 2 1/2 years later the mail carrying route stretched more than 3,000 miles from coast to coast.

During its first year of operations the Post Office realized a profit of $ 19,000, the only time that airmail service generated a profit.  Mainly the Post Office used surplus JN-4H and DH-4 aircraft, with a few newer post war aircraft added as they became available.  The post office continued to try and find the optimal aircraft to operate over its mail routes.

In 1926 the post office began turing their routes over to industry contractors but had already asked for bids for a replacement aircraft to standardize the mail route fleet.  Eleven aircraft companies submitted their bids for this aircraft, and The Boeing Aircraft Company in 1925 entered their new Model 40 prototype into the competition.  The winning design had the potential for production of 50 or more aircraft, making the contract a lucrative endeavor.

Soon the competition had narrowed down to three aircraft, the Boeing Model 40, the Douglas M-1 and the Curtiss Carrier Pigeon.  The evaluation of the aircraft was based mainly on pilot's comments and pilot reports from post office pilots flying the prototypes on mail routes.  Eventually the Douglas M-1 was chosen after the front runner, the Curtiss Carrier Pigeon, was involved in a fatal accident.

Of the original 40 post office pilots 32 died in fatal accidents while flying the mail.  During the evaluation phase the Boeing Model 40 experience a number of mechanical problems, and missed flying the designated mail route ten times during the evaluation period, giving the aircraft a reputation for not being reliable.

However, with the development of the Pratt & Whitney 420 hp Wasp engine the problems of the Liberty engine were put behind them, and the Boeing Company won the bid to fly the Chicao-San Franscico route and received an order for 25 Boeing Model 40A's with spares.  While performance numbers between the Liberty engine powered Model 40 and the Pratt & Whitney powered Model 40A seem quite similar, the Model 40A could carry 200 pounds more useful load giving it a substantial advantage in carrying the mail.

Boeing Air Transport began air mail service as scheduled on July 1, 1927 from San Francisco's Crissy Field.  The Model 40A allowed Boeing Air Transport to astound its critics and make a profit during the first year of operations, flying a million and a half miles over the route.  After two years of operation the airline had flown over 5,500,000 miles carrying 1300 tons of mail and some 6,000 passengers with only three fatalities.

While some air mail contract operators did not think that the passenger business would ever be profitable, William Boeing and his friend Fred Rentschler of Pratt & Whitney thought otherwise.  They believed it was possible to increase revenue with passengers being carried in addition to the air mail contracts providing additional revenues for the fledgling airline.

To handle the increase in air transporation routes a new management company called "United Aircraft and Transportation Corporation" (soon to become United Airlines) was formed to handle the growth of the "Boeing System".  The Boeing Model 40B-4 was a four passenger version of the venerable Model 40.

Currently there are only two original Model 40s in existance, one in Chicago and the other in Detroit.  However, there are three other Model 40s, two replicas and one a reproduction.  The replica is a Model 40B-2 which is part of the Museum of Flight's Air Mail exhibit in the Museum's Great Gallery.  In addition Permberton & Sons Aviation has restored a flying reproduction of the original Model 40C. Boeing_40C-1

The Boeing Model 40 was a historically significant aircraft not only from the point of view of engineering but also that it was the right aircraft at the right time and place in aviation history.  You can learn more about this interesting aircraft at Pemberton & Sons.

Until next time keep your wings straight and level Hersch!


"High Flight"

Oh, I have slipped the surly bonds of earth,
And danced the skies on laughter-silvered wings;
Sunward I've climbed, and joined the tumbling mirth
Of sun-split clouds...and done a hundred things
You have not dreamed of...wheeled and soared and swung
High in the sunlit silence. Hov'ring there,
I've chased the shouting wind along, and flung
My eager craft through footless halls of air.
Up, up, the long, delirious burning blue
I've topped the windswept heights with easy grace
Where never lark, nor even eagle flew.
And while with silent, lifting mind I've trod
The high untrespassed sanctity of space...
...put out my hand, and touched the face of God.

by John Gillespie Magee, Jr.

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