The Hurel-Dubois HD.31, HD.32, and HD.34 were a family of civil aircraft produced in France in the 1950s, based on Maurice Hurel's high aspect ratio

Aspect ratio (wing)

In aerodynamics, the aspect ratio of a wing is essentially the ratio of its length to its breadth . A high aspect ratio indicates long, narrow wings, whereas a low aspect ratio indicates short, stubby wings....

 wing designs.

History

Tests with the Hurel-Dubois HD.10

Hurel-Dubois HD.10

The Hurel-Dubois HD.10 was a French research aircraft first flown in 1948 to investigate Maurice Hurel's ideas about high-aspect ratio wings. It was a single-seat monoplane with retractable tricycle undercarriage, twin tails, and featuring an extremely long, slender wing with an aspect ratio of 30....

 research aircraft had validated Hurel's ideas about the practicality of such wings, and the French government agreed to sponsor the construction of two prototypes of a medium-range airliner

Airliner

An airliner is a large fixed-wing aircraft for transporting passengers and cargo. Such aircraft are operated by airlines. Although the definition of an airliner can vary from country to country, an airliner is typically defined as an aircraft intended for carrying multiple passengers in commercial...

 utilising this same principle. These aircraft, the HD.31 and HD.32 were conventional designs in all respects other than their unorthodox wings, and differed from one another only in their powerplants, although both were later converted to use the same engines. The twin-tails originally fitted were also later replaced by a large single tail fin, and with their new engines and tails, they were redesignated HD.321.01 and HD.321.02.

Air France

Air France

Air France , stylised as AIRFRANCE, is the French flag carrier headquartered in Tremblay-en-France, , and is one of the world's largest airlines. It is a subsidiary of the Air France-KLM Group and a founding member of the SkyTeam global airline alliance...

 originally placed an order for 24 aircraft to use as feederliners, but these were cancelled before they were constructed.

Production and Operation

A batch of eight aircraft was, however, ordered by the Institut Géographique National. The aircraft's wings made it ideal for long-duration, low-speed flight, ideal for aerial photography and survey work. These machines were designated HD.34 and were fitted with an extensively-glased nose and a retractable nosewheel. They flew with IGN between the late 1950s and mid 1970s. A single example remains airworthy, operated by the Association des Mécaniciens-Pilotes d'Aéronefs Anciens.

Variants

• HD.31 - prototype with Wright Cyclone
  Wright Cyclone
  Wright Cyclone was the name given to a family of air-cooled radial piston engines designed by Curtiss-Wright and used in numerous American aircraft in the 1930s and 1940s.-Background:...
  
   C7BA1 radial engine
  Radial engine
  The radial engine is a reciprocating type internal combustion engine configuration in which the cylinders point outward from a central crankshaft like the spokes on a wheel...
  
  s (1 built)
• HD.32 - prototype with Pratt & Whitney R-1830 radial engines (2 built)
  • HD.321 - prototype with Wright Cyclone 982 engines and single tail (2 converted from HD.32 by replacing twin boom with a single boom)
  • HD.324 - turboprop
    Turboprop
    A turboprop engine is a type of turbine engine which drives an aircraft propeller using a reduction gear.The gas turbine is designed specifically for this application, with almost all of its output being used to drive the propeller...
    
     version with Rolls-Royce Dart
    Rolls-Royce Dart
    |-See also:-Bibliography:* Gunston, Bill. World Encyclopedia of Aero Engines. Cambridge, England. Patrick Stephens Limited, 1989. ISBN 1-85260-163-9-External links:*...
    
     engines (not built)
• HD.33
  • HD.331 - projected militarised version for use as troop transport or air ambulance (not built)
• HD.34 - aerial survey version for IGN (8 built)

Specifications (HD.34)