This week in 1942: Rolls-Royce Merlin 61 engine

This fascinating example of how World War II upped the pace of technology development looks at Rolls-Royce’s Merlin 61 engine, which made its debut on the Mark IX Spitfire.

Designed in response to the Focke-Wulf 190, the Luftwaffe’s most effective fighter, the huge performance improvements brought about by the Merlin 61 supercharged engine enabled the RAF’s most iconic aircraft to claw back its aerial superiority.

Commenting on the technical one-upmanship that characterised the battle between German and Allied engineers, The Engineer wrote that ‘the war demands that the performance of all types of aircraft, and particularly that of fighter aircraft, shall continually improve. Ranking above the need for more and more aircraft of all types is the overriding necessity that ours shall have technical superiority over those of the enemy.’

Describing the engine, the report claimed that ‘by using a double-stage supercharger with a water-cooled passage between the first and second stages of the supercharger, and a cooler between the supercharger outlet and the induction pipe to the rear cylinder, it is found possible with the new engine to develop double the power output. When operating at a height of 40,000ft, the charge of air and fuel is now raised by the supercharger to six times the pressure of the surrounding atmosphere.’

This redesign, concluded the article, had the desired effect. ‘The results obtained from the improved Spitfire have, we learn, more than fulfilled the hopes and expectations of all who have helped in the work. The advent of the new German Focke-Wulf 190 with its 1,600hp air-cooled supercharged engine caused some uninformed persons to believe that the Germans had stolen a march on us in the high-performance fighter class of aircraft. But as enemy fighter losses continually show, the improved Spitfire with its new Merlin 61 engine was there to surpass it.’

Jon Excell