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This object is not on display at the National Air and Space Museum. It is either on loan or in storage.

Collection Item Summary:

Dowty R391 Advanced Propeller System

Dowty introduced the R391 for the Lockheed Martin C-130J Hercules transport in 1996. Its six thin, swept-back blades are made of composite materials, mainly carbon and glass fibers with polyurethane foam filling. It generates increased takeoff and climb performance and is quieter and half the weight of other propellers. The origin of the hydraulic constant-speed mechanism dates back to the Hele-Shaw-Beacham propeller of 1924, one of the first successful variable-pitch designs.

Four R391s on Rolls-Royce AE2100D3 turboprop engines power the Hercules, which serves the armed forces of the United States, United Kingdom, Italy, Australia, Kuwait, and Denmark. The Alenia Aeronautica C-27J Spartan transport and ShinMaywa US-1A Kai amphibian also use R391s. This is the first R391; it bears serial number 0001.

Gift of Smiths Aerospace LLC dba Dowty Propellers-Americas

Type:Hydraulic constant-speed, counterweight, reversible, full-feathering

Blades:6 composite blades and aluminum hub

Diameter:4.1 m (13 ft 6 in)

Weight:314.8 kg (694 lb)

Engine:Rolls-Royce AE2100D3, rated at 3,458 kW (4,637 shp)

Manufacturer:Dowty Propellers, Gloucester, England, 1996


Collection Item Long Description:

Data Source

National Air and Space Museum


Do not reproduce without permission from the Smithsonian Institution, National Air and Space Museum


Credit Line

Gift of Smiths Aerospace LLC dba Dowty Propellers-Americas


Carbon spar, hard-foam core with glass-fiber reinforced resin envelope, steel hub

Country of Origin




Physical Description

  • Type: Hydraulic constant-speed, counterweight, reversible, full-feathering
  • Number of Blades: Six composite blades and steel hub
  • Diameter: 13.5 ft (4.115 m)
  • Weight: 800 lbs (362.9 kg)
  • Engine Application: Rolls-Royce AE2100D3 rated at 4,637 shp (3,458 kW)
  • Manufacturer: Dowty Aerospace, Gloucester, England, 1999


PROPULSION-Propellers & Impellers

Inventory Number


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