Gallaudet D-2

The Gallaudet D-2 was a prototype American biplane observation aircraft built by the Gallaudet Aircraft Company during World War I. Based on the earlier Gallaudet D-1, the D-2 had more powerful engines and had other improvements. Two aircraft were completed from a four-aircraft contract, but further development ceased after they both crashed.

D-2
Role Reconnaissance aircraft
Manufacturer Gallaudet Aircraft Company
Designer Edson Gallaudet
First flight October 1917
Number built 3
Developed from Gallaudet D-1

Background and description

The D-2 was designed to partially meet an requirement for a two-seat, twin-float, twin-engined biplane for coastal-defense duties issued by the Aviation Section, U.S. Signal Corps in October 1916. Edson Gallaudet, chief designer for the Gallaudet Aircraft Company had submitted a design exactly meeting these requirements, but it had been rejected.[1] The Aviation Section had been following the reports on the Gallaudet D-1 that had been ordered by the United States Navy, intrigued by its revolutionary "Gallaudet Drive" in which the propeller revolved around a hub buried in the middle of the fuselage. And when the D-1 passed its acceptance trials, the Aviation Section placed an order for four aircraft utilizing Gallaudet's propulsion configuration on 27 January 1917.[2]

The D-2 was a two-bay, staggered-wing biplane with the fuselage suspended between the wings by cabane struts. Unlike the D-1, the aircraft had three cockpits, two in the nose and one aft of the engine for two observers and the pilot who was in the middle cockpit. The structure of the fuselage was built from steel tubing. Forward of the engine compartment, its sides were covered by mahogany plywood with the top and bottom covered by fabric. The engine bay was had aluminum sheets all around and the rear fuselage was covered in fabric. The outer structure of the fabric-skinned empennage and its control surfaces was also steel tubing, but the ribs and stringers were wooden.

The two-spar wings were swept backwards 8.5° outside the straight center sections. Outboard of the center sections, the upper wings consisted of three panels and the lower wings of two panels. The wing spars were steel tubing and each panel had three wooden stringers. Unlike the D-1, only the upper wing was fitted with ailerons. The D-2 had fixed conventional landing gear that included a tailwheel at the extreme end of the fuselage. The telescopic legs for the main wheels were attached to the bottom of the forward wing spar and to the fuselage with V-struts and bracing wires.

The first prototype was fitted with a pair of water-cooled, straight-six Hall-Scott A-5a engines, side-by-side in the center fuselage. Each engine developed about 165 horsepower (123 kW) and they were clutched together to drive the four-bladed wooden propeller immediately in front of the aft observer. The second prototype had a water-cooled V-12 Liberty engine with the same total horsepower. The D-2s had a pair of 84-US-gallon (320 L; 70 imp gal) fuel tanks located below and behind the engines. Each tank was provided with two air-driven pumps that fed a 4-US-gallon (15 L; 3.3 imp gal) "service tank" in the center section of the upper wing that gravity-fed the engines. The engines were provided with a 23.5-litre (5.2 imp gal; 6.2 US gal) lubricating oil tank behind the fuel tanks.[3][4]

Specifications (D-2 with Liberty engine and wheeled undercarriage)

Data from The Gallaudet Story: Part 14B: The Model D-2 for the Army[5]

General characteristics

  • Crew: 3
  • Upper wingspan: 69 ft (21 m)
  • Lower wingspan: 53 ft (16 m)
  • Height: 15 ft 1 in (4.60 m)
  • Wing area: 1,060 sq ft (98 m2)
  • Empty weight: 4,775 lb (2,166 kg)
  • Fuel capacity: 168 US gal (640 L; 140 imp gal)
  • Powerplant: 1 × Liberty L-12 water-cooled V12 engine, 330 hp (250 kW)
  • Propellers: 4-bladed fixed-pitch propeller

Performance

  • Maximum speed: 100 mph (160 km/h, 87 kn)

References
  1. Gordon, The Gallaudet Story, Part 9, pp. 40–41
  2. Gordon, The Gallaudet Story, Part 14A, pp. 26–27
  3. Gordon, The Gallaudet Story, Part 14A, p. 27
  4. Gordon, The Gallaudet Story, Part 14B, p. 30
  5. Gordon, The Gallaudet Story, Part 14B, pp. 29–30

Bibliography
  • Gordon, Robert (February 2005). "The Gallaudet Story: Part 9: 1916 Designs (Non-Gallaudet Drive Types)". WWI Aero: The Journal of the Early Aeroplane (187): 39–50. ISSN 0736-198X.
  • Gordon, Robert (August 2006). "The Gallaudet Story: Part 14A: The Model D-2 for the Army". WWI Aero: The Journal of the Early Aeroplane (193): 26–40. ISSN 0736-198X.
  • Gordon, Robert (November 2006). "The Gallaudet Story: Part 14B: The Model D-2 for the Army". WWI Aero: The Journal of the Early Aeroplane (194): 23–31. ISSN 0736-198X.
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