Author: WO2 Alan Taylor – Technical Historian
The Vimy “Silver Queen II” seen after landing at Bulawayo
The Rolls-Royce Eagle was the first aircraft engine to be developed by Rolls-Royce Limited. At the outbreak of World War I in August 1914, the Royal Aircraft Factory asked Rolls-Royce to develop a new 200hp air-cooled engine and despite initial reluctance they agreed, on condition that it be cooled by water rather than air, as this was the company's area of expertise.
Development of the new 20lt engine was led by Henry Royce from his home in Kent and was based initially on the 7.4lt 40/50 Rolls-Royce Silver Ghost.
It was introduced in 1915 and powered many British single and twin-engine military aircraft. Altogether nine variants of the Eagle were built, 3 302 examples of the Eagle VIII of 300hp being built at Derby between 1917 and 1922.
Photo left: De Havilland DH4s at Zwartkop Air Station in the late 1920s
Apart from the Vickers Vimy “Silver Queen” with which van Ryneveld and Brand began their flight from England to Cape Town, the Eagle also powered the de Havilland DH4s which formed part of the Imperial Gift.
This engine, serial number 6746 was one of the two engines which were installed on the “Silver Queen” and “Silver Queen II”. It was salvaged and sent to the Aircraft Depot and held in storage, having run a total of 110 hours since new.
The original logbook had been lost and a new logbook was opened during August 1925 when the engine underwent a complete overhaul.
The overhaul was completed in 1926 and the engine was issued to the Central Flying School at Zwartkop Air Station in October 1928.
Photo right: Close up of the front section of a SAAF De Havilland DH4
showing the large front-mounted radiator and 4-bladed propeller made up simply by mounting two 2-bladed propellers together.
Photo right:It was installed in DH4 no. 210 on the 13th, only for the aircraft to crash at Z.A.S. on 6 November 1928. Both aircraft and engine were returned to the Aircraft Depot on 15 November, the DH4 being struck off charge the following year and the engine undergoing a servicing, having flown some 9 hours 20 minutes in the DH4.
The engine was installed in DH4 no. 209 on 15 December 1928 and issued to the Central Flying School at Z.A.S. on the 19th. The aircraft force-landed at Z.A.S. and was eventually struck off charge while the engine, having flown a total of 213 hours and 25 minutes, was removed on 13 October 1929 and issued to the Air Depot. It was placed in storage, from where it was presented to the National Museum in Bloemfontein on 25 November 1936.
It was later transferred to the SAAF Museum on long-term loan and was placed on display at the SAAF Museum branch in Port Elizabeth.
In early 2020 the National Museum enquired as to whether the SAAF Museum would wish for it to be one of its assets. The SAAF Museum expressed its appreciation for this historic engine to be become theirs permanently and in September the National Museum’s Board of Directors approved its transfer.
The engine is currently undergoing refurbishment by members of the Port Elizabeth branch of the Friends of the SAAF Museum.
Above: Advertisements for the Rolls-Royce Eagle and Vickers Vimy which appeared in British aviation magazines of the time, with the companies proudly announcing their products’ long distance flight achievements
It is one of three known examples in South Africa; one is on display at the Ditsong National Museum of Military History in Johannesburg while the other is displayed at the SAAF Museum at AFB Swartkop.
The historic RR Eagle seen at the SAAF Museum branch in Port Elizabeth currently undergoing refurbishment by volunteer members of the local Friends of the SAAF Museum
- Type: 12-cylinder liquid-cooled 60° Vee aircraft piston engine
- Bore: 4.5 in (115 mm)
- Stroke: 6.5 in (165 mm)
- Displacement: 1,239 in³ (20.32 L)
- Length: 72.6 in (1,844 mm)
- Width: 42.6 in (1,082 mm)
- Height: 46.4 in (1,178 mm)
- Dry weight: 900 lb (408 kg)
- Valve train: Overhead camshafts
- Fuel system: Twin Claudel-Hobson carburettors
- Cooling system: Liquid-cooled
- Power output: 360 hp (268 kW) at 1,800 rpm
- Specific power: 0.32 hp/in³ (13.4 kW/L)
- Compression ratio: 5.22:1
- Fuel consumption: 24 gallons per hour (90 Litres per hour)
- Power-to-weight ratio: 0.40 hp/lb (0.66 kW/kg)