Bf 109 into service and into action - A, B, C and D variants

Bf 109B-1

By the beginning of 1937, the Bf 109 production lines were well established, official testing and evaluation was building experience with the fighter and the first examples were entering squadron service. All of this was providing feedback regarding the design to Messerschmitt, and the aircraft began to evolve.

There is a great deal of confusion over the first four versions of the Bf 109 to enter service with the Luftwaffe, largely due to the aircraft being in a state of flux. Modifications and improvements were added to the production line as they occurred, causing a number of differing models to appear concurrently or out of sequence. It quickly became apparent that in the Bf 109 the Luftwaffe had a world beating fighter, but shortcomings with power and armament were highlighted by the test and evaluation E-Stelle units and by the pilots who first took the Bf 109 into combat over Spain. These evaluation comments and the operational feedback caused Messerschmitt to reexamine several facets of his fighter, and in solving the problems the company rapidly created a range of prototypes and sub variants of the four basic models. For simplicity I will take the individual versions in alphabetical rather than chronological order, as with some of these aircraft the picture is obscure enough without complicating matters unnecessarily.

The Bf 109A

The A model, or Anton as it was known from the German phonetic alphabet of the time, started with the Bf 109 V4 prototype which first flew in August 1936. This was never really a set version of the Bf 109, rather a combination of aircraft with differing engines and experimental armament combinations which can be regarded as an extension of the V series of prototypes. The Bf 109 V4 and at least half the A model aircraft had a 640hp Jumo 210D engine which was driving a two bladed simple fixed pitch propeller. The armament initially consisted of just the upper cowling mounted pair of MG 177.9mm machine guns, but this was being found to be too little firepower by the pilots already operating the Bf 109B version in the Luftwaffe's Condor Legion fighting in the Spanish Civil War. Since other fighters of the day, such as the British Spitfire and Hurricane, were already armed with eight.303in machine guns, increasing the firepower of the Bf 109 became a priority. Firstly, a third MG 17 was fitted firing through the hollow propeller shaft which became designated the Bf 109A-0. During the limited production run, the more powerful 670hp Jumo 210D engine became available, so this was fitted on the production lines, but not all of the new aircraft received the additional machine gun. Experiments with the armament continued, with the engine mounted machine gun being replaced with a single MG C30 20mm cannon on several of the prototypes and at least four of the production Bf 109Bs, which according to some sources were later redesignated as the Bf 109A-1, despite the majority of them being based on a later model. Problems were encountered with both the engine mounted machine gun and the cannon, not least in terms of vibration when either were fired. This could be so severe as to damage the engine, or at least to make aiming a question of luck.
Providing adequate cooling to the weapons was also problematic, as a consequence ammunition feed and breech jams were frequent. The overall layout of the Bf 109A was not fixed, the aircraft were relatively individual in having differing oil cooler shapes and locations as the ideal cooling solution was sought. The change in engine during production caused the nose cowling shape to be modified several times along with the oil cooler modifications, and additional cooling vents and slats were added or deleted to suit the armament of the individual aircraft. It is known that 16 of these early development aircraft were sent to Spain, where the solution to the oil cooling and armament problems were most pressing.

Read the full article in Aviation Classics # 18 (2013, Messerschmitt BF 109)