5 Engine: Rolls-Royce Merlin
Aero engines rarely gather to themselves a glamorous image, but the Rolls-Royce Merlin was an exception to the rule. Admittedly, it was its association with the ultra-glamorous Supermarine Spitfire in 1940 that helped it stake out this reputation, but even today, its distinctive note at airshows can make elderly ex-pilots grow misty-eyed.
The Merlin appeared after it became apparent in the early 1930s that the earlier Kestrel was approaching the limit of its development.
The Merlin, initially designated PV12 for Private Venture, as it was funded from the company’s internal resources, grew immensely in importance in the middle of the decade when its promise of low frontal area, compactness and high power output saw it chosen as the powerplant for both the Spitfire and Hawker Hurricane. The 1,030hp (770kW) Merlin II appeared in 1938.
A 12-cylinder, 60-degree ‘upright Vee’ liquid-cooled powerplant, the Merlin proved to have great development potential. The 1,175 hp (876 kW) Merlin XII appeared on the production lines as the Spitfire Mark II was introduced in June 1940; eventually the Merlin 130 would reach 2,030hp.
The engine’s qualities were acknowledged by its choice as powerplant for other iconic aircraft such as the Avro Lancaster and de Havilland Mosquito. Built under licence in the US by Packard it gained another lease of life when it replaced the Allison V-1710 in the North American Mustang.
The Merlin transformed both the performance and the role of the Mustang. From a low-level army co-operation fighter, it became the long-range, high-altitude escort fighter par excellence, accompanying US bomber formations deep into enemy-occupied Europe and holding its own against both Me109s and FW190s.
In all, more than 168,000 Merlins were built.
6 Military Aircraft: Supermarine Spitfire
Seldom can an aircraft have become so synonymous with a moment in time, a military campaign and a nation.
Although the Spitfire served with RAF units from 1938-57, it was its performance in the summer and autumn of 1940 in the skies over the UK that both created and sealed its reputation. While more squadrons during the Battle of Britain were equipped with the Hawker Hurricane – sturdier and no less loved by its pilots – it was the Spitfire’s elegant, thoroughbred lines that captured the public’s imagination.
Ironically, the first aircraft to bear the name had been distinctly short of elegance. Supermarine’s chief designer, RJ Mitchell and his team had created a gull-winged, open-cockpit monoplane with a heavily spatted undercarriage to meet Air Ministry Specification F7/30 of 1931. First flown in 1934, it quickly proved a disappointment and was not selected for service.
Mitchell’s team then looked to their company’s ultra-streamlined Schneider Trophy-winning seaplanes for inspiration. Their design for the Supermarine Type 300 featured retractable undercarriage, an enclosed cockpit and the newly-developed Rolls-Royce Merlin powerplant. The Air Ministry wrote a new Specification around this design and ordered 310 in July 1936.
Mitchell’s design, with its slim, elliptical wing and compound curves, was technically more complex than the Hurricane and much trickier to production engineer, but was highly efficient.
The design was also capable of huge development, as demonstrated by the number of Marks that reached service and by the installation of a new engine, the Griffon. (Late versions of the latter engine in the Seafire naval variant developed more than double the horsepower of the original 1030hp Merlin.)
Indeed, the Spitfire was the only Allied fighter to remain in production throughout the Second Word War, with more than 22,000 being built.
Some variants were more successful than others. As a carrier-borne fighter its reputation was mixed, its lack of visibility over the nose when approaching a pitching deck and relatively narrow-track undercarriage resulting in many accidents. But as one of the most beautiful aircraft ever to fly, its reputation remains undimmed today.
16 Military Aircraft: North American P-51 Mustang
Born out of an urgent British requirement for new fighter aircraft in 1940, the P-51 became one of the all-time great fighters.
Approached by the British Air Purchasing Commission to build Curtiss P-40s for the UK, North American’s president, James Kendelberger instead proposed a new design. The commission agreed, so long as a prototype was available in 120 days; the first XP-51 was available in 117.
With its laminar-flow wing and Allison V-1710-39 engine, the early P-51s were highly-rated for low- and medium-level roles such as ground attack and tactical reconnaissance.
When the airframe was matched with a Packard-built Merlin, however, a different beast emerged. This was equally adept at high-level work and became a formidable air-to-air performer.
Indeed, with almost 5,000 enemy aircraft destroyed the Mustang became the deadliest Allied fighter in the European theatre of operations.
34 Military Aircraft: Messerschmitt Me262
Powerful design: too little, too late
35 Military Aircraft: de Havilland Mosquito
Perfection in plywood
Through the decades