Junkers L5

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The Junkers L 5 was a six-cylinder, water-cooled, inline engine for aircraft built in Germany during the 1920s. First run in 1925, it was a much enlarged development of the Junkers L2, in turn a licensed development of the BMW IV.

Design and development

The Junkers L5 was a development of Junkers' first water-cooled engine, the L2, but at four times the swept volume was a much more powerful engine. It was a water-cooled upright inline 6-cylinder unit, four-stroke and petrol-fuelled, with a capacity of nearly 23 litres. It adopted some of the L2 features, having twin exhaust and inlet valves in each cylinder driven by an overhead camshaft, twin spark plugs and twin magnetos. The splash component of the L2's lubrication was abandoned in favour of a completely forced recirculating system. The twin carburettors of the L2 were replaced with a single float chamber, dual-venturi model. Like the L2, the L5 was a direct drive engine.^[2]

The compression ratio of the standard version was 5.5:1, but variants had other ratios to cope with fuels with octane ratings between 76 and 95. The G series introduced carburettor heating together with an hydraulically damped mounting system. There were also choices of starting system, from inertial or compressed air systems to the traditional hand swinging.^[2]

Operational history

The L5 proved to be reliable and became the engine of choice for most Junkers aircraft in the mid-1920s as well as powering aircraft from other German manufacturers.^[2] Many of these powered the Junkers F.13 and its derivatives like the W 33, which dominated world air transport in the mid-1920s.^[3]

The best demonstration of the reliability of the L5 was given by the unit which powered the single-engined W 33 Bremen in the first fixed wing east to west crossing of the Atlantic in April 1928. For this flight the compression ratio was raised to 7:1 to provide sufficient power for the heavily fuelled aircraft at take off. In July 1925 a W 33 powered by a L5 stayed aloft for 65 h 25 min, with a fuel consumption of 35.6 kg/h.^[2]

Variants

L5 many variants including a variety of on compression ratios, power output levels and starting systems.
L55 an upright V-12 built from two L5s on a common crankshaft.
L8 a significant 1929 development with the same swept volume but cruising at 2,100 rpm and delivering 354 hp; take off power was 413 hp. The output was geared down at ratios between 2.47:1 and 1.44:1 to enhance propeller efficiency. Only a few were produced, powering early configurations of the Junkers G 38 as outer engines, with two L55s inboard.^[2]
L88 an upright V-12 built from two L8s on a common crankshaft.

Applications (L5)

Specifications (Jumo L 5)

Preserved Junkers L 5 engine on display at the Junkers Museum

Data from ^[2]

General characteristics

Type: 6-cylinder liquid-cooled inline
Bore: 160 mm (6.30 in)
Stroke: 190 mm (7.48 in)
Displacement: 22.92 l (1,398.66 cu in)
Length: 1,750 mm (5.74 ft)
Width: 650 mm (2.13 ft)
Height: 1,265 mm (49.80 in)
Dry weight: 334 kg (736.34 lb) dry

Components

Valvetrain: large twin exhaust and twin inlet valves driven by a single overhead camshaft shaft and gear driven from the crankshaft
Supercharger: none
Fuel system: single float, dual venturi carburettor; twin plugs per cylinder, twin magnetos
Fuel type: 95 octane (dependent on compression ratio)
Oil system: forced^[2]
Cooling system: liquid

Performance

Power output: Take-off - 260 kW (348.7 hp) at 1,450 rpm

Cruise - 208.8 kW (280 hp)

Compression ratio: 7:1
Fuel consumption: 61.6 kg/h (136 lb/hr)
Power-to-weight ratio: 1.22 kg/kW (2.01 lb/hp) @ cruise rpm

References

↑ Gunston, Bill (1989). World Encyclopaedia of Aero Engines (2 ed.). Wellingborough: Patrick Stephens Ltd. p. 85. ISBN 1-85260-163-9.
↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 Kay, Antony (2004). Junkers Aircraft & engines 1913-1945. London: Putnam Aeronautical Books. pp. 264–5. ISBN 0-85177-985-9.
↑ Kay (2004) Ibid, p. 62

External links

Wikimedia Commons has media related to Junkers L5.

v t e Junkers Jumo aircraft engines

Piston engines	Junkers L1 Junkers L2 Junkers L5 Junkers L55 Junkers L7 Junkers L8 Junkers L88 Jumo 203 Jumo 204 Jumo 205 Jumo 206 Jumo 207 Jumo 208 Jumo 210 Jumo 211 Jumo 213 Jumo 218 Jumo 222 Jumo 223 Jumo 224

Turbojet	Jumo 004 Jumo 012 Jumo 022

See also HeS 30 (Junkers design built by Heinkel)

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