title: Jacobs R-915
text: # Jacobs R-915
  
  The Jacobs R-915 or Jacobs L-6 is a seven-cylinder, air-cooled, radial engine for aircraft manufactured in the United States, production started in 1936.
  
  ## Design and development
  
  The R-915 was effectively an enlargement of the R-755 with strengthened stressed parts. With a bore and stroke of 5.5 in × 5.5 in (140 mm × 140 mm), for a displacement of 915 cu in (15 L). Take-off power was around 330 hp (250 kW). The engine features steel cylinders with aluminum-alloy cylinder heads.
  
  ## Variants
  
  ### R-915A1
  
      Baseline variant; an enlarged R-755
  
  ### R-915A3
  
      Similar to the A1 but with Scintilla magnetoes
  
  ### R-915A4
  
      With a power take-off for autogyros
  
  ## Applications
  
  * Avro Anson Mk II and Mk III
  * Beechcraft Model 18D
  * Beechcraft F-17D Staggerwing
  * Fleet 50
  * Howard DGA-15J
  * Kellett KD-1
  * Waco AQC, AGC, ARE, AVN
  
  ## Engines on display
  
  * A preserved Jacobs R-915 is on display at the Nanton Lancaster Society.
  * A Jacobs L-6 is on display at the Canadian Museum of Flight
  
  ## Specifications (R-915A1)
  
  Data from Jane's
  
  ### General characteristics
  
  * Type: 7-cylinder air-cooled radial piston engine
  * Bore: 5.5 in (140 mm)
  * Stroke: 5.5 in (140 mm)
  * Displacement: 915 cu in (15 L)
  * Length: 40 in (1,030 mm)
  * Diameter: 45.5 in (1,160 mm)
  * Dry weight: 555 lb (252 kg)
  
  ### Components
  
  * Valvetrain: 2 valves per cylinder (pushrod-actuated); sodium cooled exhaust valves
  * Fuel system: Single Stromberg NA-R7A carburetor
  * Fuel type: 80 octane
  * Oil system: One pressure pump, two scavenge pumps
  * Cooling system: Air-cooled
  * Reduction gear: Direct drive, right hand tractor
  
  ### Performance
  
  * Power output: 330 hp (246 kW) at 2,200 RPM at sea level
  * Specific power: 0.36 hp/cu-in (16.4 kW/L)
  * Compression ratio: 6:1
  * Power-to-weight ratio: 0.6 hp/lb (1 kW/kg)
  