Jacobs R-915
# 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)
