Rolls-Royce Kestrel

The Kestrel or type F was a 700 hp (520 kW) V-12 aircraft engine from Rolls-Royce, their first cast-block engine [Lumsden 2003, p.190.] and the pattern for most of their future piston-engine designs. Used during the interwar period it remains somewhat obscure, although it provided excellent service on a number of British fighters of the era.

Design and development

The Kestrel came about as a result of the excellent Curtiss D-12, one of the first truly successful cast-block engines. Earlier designs had used individually machined steel cylinders that were screwed onto a crankcase, whereas the cast-block design used a single block of aluminium that was machined to form cylinders. The result was both simpler to build as well as lighter and much stronger, requiring only an investment in new machining equipment.

The D-12 was one of the most powerful engines of its era, and continued to swap records with other high-power engines of its era. No British company could offer anything like it, and when Fairey selected it for their Fairey Felix design the Air Ministry had enough and ordered Napier & Son and Rolls-Royce to start work on cast-block engines of their own.

Arthur Rowledge, one of Napier's chief engineers and the designer of the famous Napier Lion, was becoming fed up with management and left for Rolls. [Lumsden 2003, p.164.] In this one move any Napier design effort ended while Rolls' got a boost. Applying every known advance since the D-12 was introduced, Rowledge designed the new engine to use supercharging at all altitudes, allowing it to outperform "naturally aspirated" engines by as much as they were willing to increase the boost pressure.

One key advance in the Kestrel was the use of a pressurised cooling system. Water boils at 100 °C at standard atmospheric pressure, but this temperature decreases with altitude. Since the amount of heat carried out of the engine is a function of coolant temperature and volume, if the coolant has to be kept below boiling an increasing amount of fluid has to be used, along with an increasingly large radiator to cool it. The solution was to pressurise the entire cooling system, thereby not only preventing the drop in cooling performance with altitude, but in fact increasing the boiling point even on the ground. The Kestrel was built to maintain enough pressure to keep the boiling point at about 150 °C.

The engine was first produced in 1927 at 450 hp (340 kW), which soon improved in the IB model to 525 hp (390 kW). This model saw widespread use in the famed Hawker Hart family that dominated British air power during the early 1930s. However it was not long before line improvements increased power dramatically; the V model provided 695 hp (520 kW) at 3,000 rpm with no basic change to the design, while the XVI used in the Miles Master delivered 745 hp (560 kW). Messerschmitt also tested its first Messerschmitt Bf 109 prototypes with Kestrel engines in 1935.

Increased availability of higher octane aviation fuels in the late 1930s allowed the engine to be boosted to higher power levels without suffering from detonation, and the Kestrel eventually topped out at 1,050 hp (780 kW) in the XXX model of 1940.

Further developments of the Kestrel were the Goshawk and the Peregrine (and therefore the Vulture). In practice, development of the Peregrine / Vulture was troubled and they were both cancelled with few built.

Applications

*Fokker D.XVII
*Blackburn Sydney
*Handley Page Heyford
*Hawker Audax
*Hawker Demon
*Hawker Fury
*Hawker Hardy
*Hawker Hart
*Hawker Hind
*Hawker Nimrod
*Hawker Osprey
*Heinkel He 112 Prototype
*Junkers Ju87 Prototype
*Miles Master MK I
*Renard R.31
*Short Singapore

pecifications (Kestrel VS)

pistonspecs

type=Supercharged liquid-cooled 60-degree V12 engine
bore=5 in (127 mm)
stroke=5.51 in (140 mm)
displacement=1,297 in³ (21.25 L)
length=74.61 in (1,895 mm)
length=
width=24.41 in (620 mm)
height=35.63 in (905 mm)
weight=957 lb (434 kg)
valvetrain=Two inlet and two exhaust poppet valves per cylinder
supercharger=Gear-driven centrifugal type supercharger
turbocharger=
fuelsystem=Rolls-Royce carburetor
fueltype=87 octane rating gasoline
oilsystem=
coolingsystem=Liquid-cooled, pressurised to 300°F (150°C)
power=
* 685 hp (511 kW) at 2,240 rpm for takeoff
* 631 hp (471 kW) at 2,900 rpm at 14,400 ft (4,400 m)
compression=6.0:1
specpower=0.53 hp/in³ (24.05 kW/l)
fuelcon=
specfuelcon=
oilcon=0.18-0.35 oz/(hp•h) (7-13 g/(kW•h))
power/weight=0.72 hp/lb (1.18 kW/kg)
reduction_gear=Spur, 0.553:1

ee also

*List of aircraft engines

References

Notes

Bibliography

* Lumsden, Alec. "British Piston Engines and their Aircraft". Marlborough, Wiltshire: Airlife Publishing, 2003. ISBN 1-85310-294-6.
* Rubbra, A.A."Rolls-Royce Piston Aero Engines - A Designer Remembers". Rolls-Royce Heritage Trust. Historical Series no 16. ISBN 1-872922-00-7]

External Links

* [http://www.rafmuseum.org.uk/cosford/collections/engines/engine_info.cfm?engine_id=38 Royal Air Force Museum - RR Kestrel]
* [http://www.oldengine.org/members/diesel/Duxford/ukaero3.htm Data sheet and comparison]