Identified! [Paragon adjustable and reversible aircraft propeller created by Spencer Heath and tested on October 11, 1922, Bolling Field, Washington, D.C.] (LOC)

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Where: Unknown

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When: 01 January 1922

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Harris & Ewing,, photographer.

[Paragon adjustable and reversible aircraft propeller created by Spencer Heath and tested on October 11, 1922, Bolling Field, Washington, D.C.]

[1922 October 11]

1 negative : glass ; 4 x 5 in. or smaller

Title and date information from Flickr Commons Project, 2015; and Aerial Age Weekly, Dec. 1922.
Gift; Harris & Ewing, Inc. 1955.

United States.

Format: Glass negatives.

Rights Info: No known restrictions on publication.

Repository: Library of Congress, Prints and Photographs Division, Washington, D.C. 20540 USA,

Part Of: Harris & Ewing Collection (Library of Congress)

General information about the Harris & Ewing Collection is available at

Higher resolution image is available (Persistent URL):

Call Number: LC-H234- A-4924


Owner: The Library of Congress
Source: Flickr Commons
Views: 12673
libraryofcongress dc:identifier=httphdllocgovlocpnphec42506 xmlns:dc=httppurlorgdcelements11 aviation aircraftpropeller airplanepropeller propeller adjustablepitchpropeller paragonadjustableandreversibleaircraftpropeller variablepitchpropeller spencerheath heath mysterysolved bollingfield bollingafb hispanosuiza hispanosuiza8

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    • 02/Oct/2015 20:38:51

    Perhaps a crude dynamometer for an aircraft engine?

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    • 03/Oct/2015 02:24:06

    I am not positive, but I believe this airplane engine was adapted for agricultural use. The wind generated was used to prevent frost from forming on crops. The same technique was also used to keep birds from eating certain crops at harvest time.

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    • 03/Oct/2015 14:32:37

    I like Christian's idea. Notice there are some wheel chocks to keep the back wheels from rolling.

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    • 05/Oct/2015 02:00:40

    The engine resembles an Hispano-Suiza 8 aero engine in a V-8 arrangement. (The engine would have been common in US stocks as it powered a number of US military aircraft and it was produced under-license by the Wright Company). What is unusual for the era (if the 1922 photo date is correct) is that the engine appears to be driving an adjustable or variable pitch propeller - which is a type that would have been a cutting-edge technology under development during the time. Given that information, I can say with an almost certainty that this is a photograph illustrating a demonstration of the Paragon Adjustable and Reversible Propeller, most probably at or near Bolling Field in Washington, D.C. The December 1922 Aerial Age Weekly (Vol. 15, Pages 585-589) details the apparatus and the adjustable pitch propeller demonstrated, note also the photos on page 588 of the linked article which appears to show the test stand photographed above. Also, after examining the finer resolution TIFF version of this photo at the LOC site linked above, it would appear that Spencer Heath (1876-1963), the man who developed the variable pitch propeller being demonstrated, is the bearded man in the white (or light colored) coat leaning over the controls in the photo. Here is another photo of Heath: Spencer Heath distinguished himself in a number of varied fields. See his Wikipedia entry: Spencer Heath From Aerial Age Weekly, (December 1922, Vol. 15, Pages 585-589): Paragon Adjustable and Reversible Propeller The Paragon adjustable and reversible aircraft propeller, the invention of Spencer Heath, the pioneer propeller maker, made its official debut on October 11 at Bolling Field in a demonstration to representatives of the offices of the Chief of Air Service, Chief of the Bureau of Aeronautics of the Navy, of the Air Mail, the Press and motion picture news associations. The automobile truck trailer, upon which the propeller and a 150 h.p. Wright-Hispano engine was mounted, was made to maneuver about Bolling Field at the will of the operator. What new stunts may now be evolved with the aid of a reversing propeller may be left to the imagination. One can easily imagine the two-seater of the future suddenly reversing into a stall and taking a shot from underneath at his surprised adversary overhead. The device is to the aircraft what change speed gears are to the automobile. . . . Demonstration Under Power To show the action under power the propeller has been installed on a 150 H.P. Hispano-Suiza engine mounted with gasoline tank, observers’ seats, etc., on a trailer truck weighing about two tons which is free to roll on the ground. In the demonstrations thus far made the device is put through its entire range of performance, which includes disconnecting the pitch limiting mechanism so that the blade angels are controlled throughout a compete revolution of 360 degrees, both forward and reverse. With the engine turning at 1500 r.p.m. the angular change from full speed ahead to full speed astern is accomplished in about 3-1/3 seconds.

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    • 05/Oct/2015 03:59:25

    Excellent work.. that's definitely the same thing pictured in the December, 1922 Aerial Age.

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    Jon (LOC P&P)

    • 07/Oct/2015 20:44:16

    Thanks for all the good information TVL1970. It's clearly the same vehicle as in the "Aerial Age Weekly" article. I'm not sure I would want to be on there when the engine was running.