Avia Rk.17

Rk.17
Rk.17 in Letecké muzeum Kbely, Prague
Type	9-cylinder air-cooled radial
National origin	Czechoslovakia
Manufacturer	Avia (Avia akciova spolecnost pro prumysl letecky), Prague

One of Avia's own designs and built in Czechoslovakia, the 1930s Avia Rk.17 was a 9-cylinder radial engine, developed from the 7-cylinder Avia Rk.12, with a rated output of 270 kW (360 hp).

Design and development

As well as producing aircraft and building Hispano-Suiza and Lorraine aero-engines under licence, Avia also designed and built their own radial engines. The Rk.17 was a 9-cylinder supercharged model, rated at 360 hp. It was a nine-cylinder version of their Rk.12.^[1]

It was a conventional air-cooled radial: nitrided steel barrels with integral fins were screwed into heat treated Y alloy heads. The pistons were also of heat treated Y alloy. The crankcase was cast from heat treated silumin alloy, with some minor parts using magnesium alloy. The single throw two piece crankshaft was linked to the pistons with an I-section Y alloy master rod, with a single piece big end, which carried the other eight piston rods.^[1]

Applications

• Avia Ba.122
• Letov Š-50

Specifications

Data from Jane's All the World's Aircraft 1938^[1]

General characteristics

• Type: 9-cylinder air-cooled radial
• Bore: 130 mm (5.12 in)
• Stroke: 140 mm (5.51 in)
• Displacement: 16.72 L (1,020 cu in)
• Length: 1,065 mm (41.93 in)
• Diameter: 1,184 mm (46.61 in)
• Dry weight: 260 kg (573 lb) with ancillaries, without propeller hub

Components

• Valvetrain: one inlet and one exhaust valve per cylinder, operated by push-rods via rocker gear. Eight cam push-rod disc drive.
• Supercharger: impeller drive ratio 10.7:1
• Fuel system: single barrel Stromberg NAR80G carburettor
• Ignition system: Scintilla magnetos, automatic advance
• Fuel type: petrol, 85 Octane
• Oil system: dry sump, with one pressure and one scavenging pump
• Cooling system: air-cooled
• Reduction gear: direct drive

Performance

• Power output: rated maintained up to 2,750 m (9,000 ft), at 2,200 rpm 270 kW (360 hp)
• Power output: maximum continuous at 2,200 rpm 300 kW (400 hp)
• Power output: take-off at 2,020 rpm 330 kW (440 hp)
• Compression ratio: 6.4:1
• Specific fuel consumption: 255 g/(kW.h) (0.562 lb/(hp.h))
• Oil consumption: 8.7 g/(kW.h) (0.23 oz/(hp.h))

References

Wikimedia Commons has media related to Avia Rk.17.