Spitfire Progress – The Engine

28/09/201816:0028/01/2019 14:29

Progress continues on the restoration of Spitfire RW388 by the Medway Aircraft Preservation Society Limited (MAPSL). Much of the focus early on has been on the aircraft’s Merlin engine – arguably almost as much of a Second World War icon as the Spitfire itself.

Progress Report

RW388’s Merlin 266, photography courtesy of MAPSL

The Merlin 266 has been fully cleaned and painted, and various components have been refitted where possible. Some items had been removed by the RAF prior to the donation of the aircraft to the city, so there are some missing parts.

Engine with cowling test-fitted. Image courtesy of MAPSL.

These images really demonstrate the transformation that is taking place piece by piece. Consider the exhaust stubs – compare the cleaned and painted stubs above to the picture below.

Exhaust stubs as they were delivered to MAPSL in February 2018. Image courtesy of MAPSL.

Another item progressing well is the engine bearer frame, which does does exactly as the name suggests. The frame has been stripped and cleaned of stains and old, worn paint before being primed and repainted. Critically, it has been tested to make sure it is still up to the task of supporting the 3/4 tonne Merlin engine (it is!).

Engine bearer frame after cleaning stripping. Image courtesy of MAPSL.

Merlin 266

RW388 is fitted with a Merlin 266. Rolls-Royce produced a number of variants of the Merlin engine during the war, just like there were a number of different Spitfire variants.

In August 1941, The Luftwaffe’s (German air force) Focke-Wulf Fw190 began to fly operationally over France. It soon established superiority over Allied aircraft, including the Mk.V Spitfire.

The race was on to improve the performance of the Spitfire. Rolls-Royce developed the Merlin 60 series which promised to provide a solution by introducing a two-stage. two-speed supercharger. This gave the Spitfire more flexibility of performance at different altitudes. The drawback was that the Spitfire air frame needed to be redesigned in order to accommodate the new engine, creating the Mk. IX Spitfire in the process. The new engines and Spitfire designs improved performance and allowed pilots to compete more effectively against the Fw 190.

Merlin 61 wheel casing on display in the Spitfire Gallery at The Potteries Museum. These gears drove the supercharger.

Supercharger diagram from a Merlin manual, note the increase in pressure post-supercharger.

So what about the Merlin 266? Well, one of the engines in the series was the Merlin 66, tweaked for lower altitude flying. This was particularly relevant as the Allies gained air superiority towards the end of the Second World War. Pilots were now more likely to engage to air to ground attack than dogfights in the sky.

In order to meet demand, other companies were given licences to build Merlin engines. In the United States, Packard were issued with licences for several variants of the Merlin, including the Merlin 66. The prefix ‘2’ was added to avoid confusion with original Rolls-Royce Merlin 66 engines as they required slightly different tooling.

The Spitfire design was altered further to accommodate the new Packard-built Merlin 266. These were Mk.XVI Spitfires, of which RW388 is one example.

Written by Joe Perry (Curator, Local History)