Revolution in the Air: Gallaudetâ€™s D-5, DM-5 and D-7 Models

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d-5 In the winter of 1917, the Gallaudet Engineering Company finally completed their much anticipated land monoplane that used their patented Gallaudet-Drive Mechanism, a revolutionary engine driving a remote, mid-fuselage mounted propeller. The newly produced aircraft, call signed D-5, were to be the Company’s first true landplane platform after years of experimenting with the famous D-2 biplane.

In early January 1918, the company was submerged in developing the D-4 project, a tactical fighter for which they would receive a construction contract the following month from the United States Navy. But despite the immense work being done on the 4 model, Gallaudet engineers still found time to explore new ideas such as the 5 type. This new design was to use the reliable Liberty engine, first tested years before on American Expeditionary Force’s Farmans. Gallaudet designers use the D-5 project as a test bed for new technology. Chief among them was a cantilever wing structure with a thick airfoil, which have the distinction of being the first such wing design fitted into an American-develop air platform.

On the morning of January 7th, the company officially submitted a proposal to W.F. Durand; chairman of the influential NACA, for transmittal to the Aircraft Board for the building of what Edson Gallaudet called a “200-mph fighting monoplane”. The 5′s general arrangement is dated January 6th, so this proximity to the proposal and the lack of another competing design at this period, makes it almost certain that the D-5 was the 200-mph plane. Attached to the letter Durand received on the 7th were several detailed blueprints and specification sheets, with one of them being the D-5.

The designed D-5 was a mid-winged monoplane powered by a Liberty engine mounted on the nose. It had a 39′ wing span. The fuselage was 30’4″ in length and possessed a height of 7′-9″. The vaunted Liberty drove a mid-frame two blade propeller. The pilot was seated in an open cockpit between the engine and the propeller. The reconnaissance officer or observer as was call at the times, sat behind the propeller. Two fuel tanks were fitted at the front and the rear of the pilot’s seat. Tail surfaces were identically to the D-4, except for the absent of stub fins. The tail skid was an extension of the small rudder post. A cantilevered, thick and tapered wing gave the plane a distinct look.

Another departure from the D-4 was the use of rectangular spars in the fuselage’s cross section. The ailerons had an inverse taper with a wide base at the tips. A tall, fixed landing gear was fastened between the two wing spars near the wing root, which is estimated to be at 12 percent, thicker than usual for the era. The relative small air frame made it a necessity for the Liberty engine’s upper and down sections to be expose to the air stream.

During the early part of the March 1918, Gallaudet surprised the nascent aviation industry with another monoplane design, DM-5. the ‘M’ designation suggest a modified version of another platform, although no official documentation has been found to prove it. At the heart of the new version lay basically an improved D-5. The airframe was extended to 3’6″ wide and by 4′ high in order to fully enclose the Liberty engine. Still, the motor was big enough, in comparison with the mid frame, that the bottom oil sump was not covered. The wing was now a constant chord with a thin airfoil and no longer cantilevered, with a streamlined bracing line on top and bottom to the front and rear spars.

The ‘M’ concept called for two rectangular outlines on the wing’s surfaces near the root, which served as airfoil radiators similar to the ones used on the D-4. The biggest departure from the D-5 model was the incorporation of a retractable landing gear. A single leg per wheel retracted forward into the nose section beside the engine. The front of the airframe was composed on tubular longerons connected with cast bronze fittings braced by thin wires. The engine bearers appeared to have been built-up, sheet metal channel type as used on the D-4. There were three wing spars. All widest at the brazing wires attachment points and tapered from there towards both the tips and fuselage. The spars were rectangular in section and constructed out of metal sheet. The top and bottom parts of the aircraft were channel-shaped of .0625″ of thickness and the webs were .025″. All held together by an eight to a quarter diameter rivets.

Another of Gallaudet’s lesser known designs is the D-7 Mail Carrier. The drawing, which probably was made accordingly to a mid-1918 request by the United States government, was the project less coveted by Edson Gallaudet at that time frame. Unfortunately, little is know about the concept beyond its indented purposes of transporting mail through the air. But the few sketches that had survived pain a picture of a truly remarkable aeroplane. The design looks like a slightly larger, fixed landing gear version of the ‘M’ version. There are no indications of pilot seating or cockpit arrangement. No engine area is visible on the incomplete blue print. Span was to be around fifty feet. Fuselage length was 30’3″ with a total wing area of 337.5 square feet. The wing had two spars which were only indicated by a single dotted line on the paper. The rest of the data is missing or inconclusive.

It’s a testament to his innovating vision that almost a century later, all three models, D-5, DM-5 and D-7, are once again gaining the interest of aviation aficionados the world over.

The Aeroplane as a Long Range Gun, Journal of the Royal Artillery, R.G. Cherry, June 1919
Alpha, Bravo, Delta: Guide to the U.S. Air Force, Walter J. Boyne, editor, Penguin Books 2003
The Encyclopedia of Military Aircraft, Robert Jackson, Parragon Publishing, 2002
The Early Aviation History, American Years, Edward Von der Porten, Crowell Company, 1969

An article by Raul Colon: rcolonfrias@yahoo.com