Large numbers of aircraft were captured by opposing forces during the Second World War and in some cases these aircraft were airworthy allowing for the captor to assess its performance and develop countermeasures. One such aircraft was Supermarine Spitfire Vb EN830/NX-X which crashed in German-occupied Jersey having been hit by flak over France on November 18th 1942. It’s pilot, Pilot Officer (Sous Lt.) Bernard Scheidhauer of the Free French Air Force, crash landed the aircraft relatively intact in a turnip field and both he and his aircraft were transported back to Germany where he would later be shot for his part in a mass break out of allied PoWs.
With the aircraft repaired the Germans went about assessing it and it’s Merlin 45 engine comparing it to previous captured Spitfire marks and of course to their own Bf109 and Fw190 fighter aircraft. The aircraft was painted in Luftwaffe test markings in order to avoid any frontline Luftwaffe pilot mistaking it for an RAF machine and attacking it. Once these tests were completed talk turned to assessing how the aircraft would handle with a German engine installed. A similar experiment had been attempted on an earlier Spitfire with a DB 601 engine from a Messerschmitt Bf109 but it required too many modifications to be practical. The newer Spitfire Vb however had a much larger engine bay for its more powerful Merlin 45 and this afforded the Germans much more space to develop mounting brackets for the DB 605A-1 engine which would drive a Bf109 propeller. The project was given the go-ahead in early 1944.
The aim of the experiment was to establish whether the engine would dramatically improve the aircraft’s performance to the point far beyond that of the Luftwaffe’s fighter. The Germans knew they had an excellent engine in the DB 600 series and it was almost always slightly ahead of the Rolls-Royce Merlin series fitted to the Spitfire in terms of capability and technology. The results did indeed prove startling. The similar engined Messerschmitt Bf109G still proved faster at low altitude thanks to its smaller dimensions whereas the larger Spitfire/DB 605 incurred more drag. However this advantage was lost over 11,000 ft where the speeds evened out and the Spitfire handled better. The DB 605A engine gave the Spitfire a ceiling of 41,666 ft, a staggering improvement of some 5,000ft over the original Merlin 45 engine and was around 3,200 ft. more than the Bf.109G. This showed the soundness of the Spitfire’s design but as iconic as it has become in aviation circles the Merlin proved it was not the wonder-powerplant the British would have liked.
However, by the time this Franken-Spitfire had been properly tested the original material was already out of date with the Spitfire V having been replaced by the superlative Spitfire IX. This had the Rolls-Royce Merlin 66 engine which actually produced an aircraft with similar performance to the German experiment. The experiment itself came to an end abruptly on the 14th August 1944 when the aircraft was destroyed in a US air raid.