Messerschmitt Bf-109 Part I: Development History Bob Hart January 14, 2007

This article is part of a continuing series by Bob Hart on the Best Fighter Aircraft of WWII. Feedback and discussion is welcome.

Milch vs Messerschmitt

If Erhard Milch had his way, the Messerschmitt Bf-109 would have never been produced as Nazi Germany's first single engine fighter. That accolade would have instead gone to the Heinkel He-112. If that decision had occurred, the air war would have taken a different course. But it must be remembered the still limiting factor of German aircraft production, the slow and troubled development of aero engines would have also plagued the Heinkel fighter.

The animosity between Milch and Messerschmitt was well known, stemming from two disastourous crashes of Messerschmitt produced M-20b mail planes which cost Lufthansa dearly. However the bad blood between the two men would greatly alter the development and introduction of service of other Messerschmitt designs rather than the Bf-109.

Production Begins

Design of the Messerschmitt fighter began in early 1934 when Messerschmitt was joined by Chief engineer Walter Rethel - a man with considerable experience in high speed aircraft design with the Arado company. Progress was rapid despite the complexity of the design and the introduction of new technology, the most controversial at the time being the automatic Handley Page leading-edge slots and fully enclosed cockpit.

The Messerschmitt Bf-109 was an all metal, low wing, cantilever monoplane with flush riveted stressed skinning. The fuselage was an oval section, light metal alloy monocoque construction. The basic design concept of the new fighter was simple - to employ the largest, most powerful engine in the lightest airframe possible. Strangely, this design concept would both make the Bf-109 a formidable opponent and enforce limitations that would disadvantage the aircraft late in its career. But it must be stressed that Willy Messerschmitt was designing an aircraft that was to be in frontline service until 1941 at the latest, not as it turned out-1945.

The fact the Messerschmitt Bf-109 was produced in greater number than any other fighter, some 33,000 being produced from 1935 to 1945, is a testament to the soundness of the original design. In the hands of an experienced pilot the Messerschmitt fighter was still competitive with the latest Allied fighters in the last months of the war, defying many ill founded conclusions about the aircraft. Finally it the Messerschmitt Bf-109 shot down more enemy aircraft, than any other fighter.

The three highest scoring aces in the Luftwaffe, Eric Hartmann, Gerd Barkhorn and Gunther Rall, favoured the Messerschmitt over any other fighter and between them claimed nearly one thousand enemy aircraft in the type.

The Bf-109a appeared in August 1935 and after strengthening of the undercarriage began taxiing trials and first flew in the following month. A hint of the future problems with German aero engines became evident with the non availability of the Junkers Jumo 210 engines, and the prototype flew with power provided by a Rolls Royce V 12 cylinder upright vee engine. Though underpowered, it was obvious the new fighter possessed enormous potential, which was further confirmed with the January flying trials of the Jumo powered V2 prototype.

It soon became apparent that the Bf-109 was superior to the Luftwaffe's principal fighter, the bi-plane Heinkel He-51 and test pilots after initial misgivings spoke glowingly of the performance of the new fighter. Although the He-112 had its share of supporters, official interest was beginning to lean towards the Bf-109. This support grew dramatically with the first flight of the Supermarine Spitfire in April 1936 and the granting of a production contract in June placed further pressure on the Fighter Acceptance Commission to make a decision.

The Heinkel contender was still in an early stage of its development and an impressive flying display by the Messerschmitt at evaluation trials at Travenmunde impressed the Commission's representatives and a contract for production was handed down in August after another awe inspiring display by a Bf-109 over the Olympic stadium in Berlin.

Soon after the Bf-109's impressive capabilities were demonstrated at Rechlin where the new fighter easily outclassed four He-51 fighters in mock combat in front of Goering and other high ranking officials. The future of the Messerschmitt fighter was secured and in November pre-production, Bf-109 fighters were sent to Spain for service evaluation trials.

As the production flow of the new Messerschmitt fighter increased samples were sent to serve in the Condor Legion where under the guidance of Werner Molders suitable tactics were developed.

The early versions of the Bf-109 were never intended to be 'major production' models due to the continuing development of the type. The Bf-109B-1 first appeared in February 1937, was powered by the Jumo 210Da engine and was armed with three MG 17 machine guns.

This was followed by the Bf-109C-1 variant in the spring 1938. This more powerful version was equipped with the Jumo 210Ga power plant and was armed with four MG 17 machine guns, two weapons in the nose and two in the wings. A prototype at the time was fitted with the harder hitting MG FF 20mm cannon in the wings, but due to development problems this weapon would not be introduced until the production of the Bf-109E.

Production Difficulties

There were production difficulties largely due to the length of time it took sub contracted companies to enter full production. Another factor which led to the tardy production levels of all German aircraft at this time was many factories only worked one shift per day. As of 1st August 1938 Luftwaffe fighter strength was 643 machines with less than half Bf-109 fighters. Due to more factories coming on line this figure was lifted to 583 machines by the end of September.

In late spring the first Daimler powered Bf-109D-1 came off the production line. The DB-600Aa was not a reliable engine and when the Bf-109E-1 entered service in February 1939 it was powered by the more reliable DB-601.

1,056 Bf-109 fighters of all types were in service at the time of the Polish invasion, but only two hundred of the Messerschmitts were used in the attack, the remainder formed a shield in the west in the event of attack from Britain or France. Losses of the Bf-109 were not heavy in Poland, but there were causes for concern, principally the light firepower of the MG 17s, poor rearward visibility, short range, and some losses incurred in take off and landing accidents. This last problem has often been stated as a major weakness of the design and I will deal with this later.

The improved Bf-109E-3 entered service in late 1939. The cannon armed E-4 version was available in the spring of 1940 and this version formed the bulk of the fighter force that would later participate in the Battle of Britain. With this version Luftwaffe pilots often recalled how the heavy cannon armament would often 'shatter' enemy fighters. By May 10, 1,016 Messerschmitts were available for the attack in the West. While the Bf-109 did sweep the skies clear of opposition, the short range was becoming an inhibiting factor. The drop tank equipped Bf-109E-7 saw service in the late stages of the Battle of Britain; though it must be said problems of leakage prevented their widespread use.

With Germany largely on the defence in the west after the conclusion of the daylight bombing offensive, the first Bf-109F's appeared in March 1941 before the new Spitfire MkV established superiority over the older Messerschmitts. The F model was the first major cleanup of the basic design and many German pilots claimed it to be the best model of the 109. The removal of the tail struts caused some early problems in high G manoeuvres. Also, some vibration was experienced at a certain rev range, a high-frequency oscillation set up in the tailplane spar was overlapped by the engine, causing sympathetic vibrations resulting in structural failure. The installation of external reinforcing plates soon solved the problem. The one criticism of the F variant was its lighter armament, which was partially brought about by the tortured development of the MG 151 cannon. The lower velocity MG FF 20mm cannon firing through the spinner was introduced and with the two nose mounted MG 17 machine guns the armament was seen as adequate as long as the cannon did not jam.

More Improvements Meant more Difficulties

To compensate for the lack of fire power, field conversion sets were introduced to mount two 20mm cannon beneath the wings. By this time the Messerschmitt was being offered in a Jabo version. As the war spread and the demands on the Luftwaffe grew it was to be the single engine fighter that would plug the gaps and a bewildering array of variants would appear.

The Messerschmitt had reached such a stage of development that for every improvement there was a penalty. An example was the demand for greater firepower, which meant more guns, more weight, bigger engine, more weight, and loss of agility. It became a vicious cycle and was made worse for the Messerschmitt since its planned replacement the Fw-190 had failed to deliver good high altitude performance.

The introduction of the DB601E-1 powered Bf 109F-4 with the high velocity MG 151 is seen by many pilots as the definitive version of the fighter. However the demands for a faster, more heavily armed fighter would result in what some would think as a retrograde step - the Bf-109G. The G versions were the most prolific and well known version of the 109 and they were destined to fight till the end of the war. Development of this high speed, high altitude fighter began in the middle of 1941. The centrepiece of the new version was the more powerful DB 605 engine and cockpit pressurization, the latter improvement a direct result of the changing nature of the air war.

The obvious penalty of the larger DB 605A engine was the change in appearance of the upper cowling and the enlarged oil cooler. The first variants, Bf 109G-1 powered by DB 605A-1 engines and fitted with nitrous oxide (GM 1) injection appeared early in the Spring of 1942, along with the non pressurized version the Bf 109G-2. In May 1942 the RAF first encountered the G-3 and G-4 versions which were equipped with the FuG 16z R/T.

The new G versions were an unpleasant surprise to the RAF, with their decided speed advantage over the Spitfire V. The next major version and the most numerous was the G-6, which began coming off the production lines in autumn of 1942. This was the first variant to accept the multitude of Field Conversion Sets and could be equipped with several variants of DB 605A engines and from early 1944 the DB 605D engine. Methanol water (M50) fuel injection was now available allowing ten minutes of boost pressure. Of course this application of water methanol injection played havoc with spark plug life.

Another significant improvement with the G-6 was the introduction of the MK 108 30mm cannon firing through the airscrew hub. A single hit from one of these shells was usually enough to bring down a fighter and three or four hits could knock out a four engine bomber. Fortunately for the Allied air forces, deliveries of this weapon were slow and the MG 151 20mm cannon was retained.

By late summer 1942, the G variant made up two thirds of the frontline Bf 109 strength. During 1943, under the firm hand of Erhard Milch and German fighter production rose dramatically with July seeing Luftwaffe acceptance of no less than 725 G model 109 fighters. Total production of Bf-109G fighters was over 6,300 aircraft in 1943. In 1944 this would rise to nearly 14,000 aircraft.

In spring 1944, the G-10 version entered service. Several versions of the DB 605 engine with different grades of fuels and types of injection were now the standard engine. The DB 605 DC powered G-10 was the fastest of all the g variants and speeds of 426 mph were attained at 25,000 feet. Standard armament was either the 30mm or 20mm cannon with a pair of nose mounted MG 131 13mm machine guns.

What proved to be a drawback for the G-10 were the number of Field Conversion Sets, all of which had detrimental effects on performance. Also, many alterations introduced on the production lines, most notably the so called Galland hood, and tail plane modifications. All this greatly complicated the flow of spare parts to the frontline units, disrupted the transport system and further led to the low serviceability returns of the frontline units.

The Final Versions

These were but a few of the problems which forced the Fighter Staff to introduce changes which would culminate in the Bf 109K. Before this version entered service the final G variant - the G-14. The major modifications to this model were to the control surfaces in an effort to lighten the controls. The 109 always felt heavy or stiff at the higher end of the speed range and the continuing weight spiral associated with new models only exacerbated the problem. The DB 605AM or DB 605AS engines were now standard.

The final major production model was the Bf 10K-2 and K-4, non-pressurized and pressurized fighters. Now standard was either a 30mm MK 108 or MK 103 cannon and two MG 151 15mm machine guns. The Galland hood was standard as was a new enlarged, wooden tail assembly and semi retractable tail wheel. Other versions developed were the K-6 and the K-14, the latter capable of 452 mph at 37,700 feet a truly amazing performance, but of little consequence in the last weeks of the war.

The story of the Bf 109 did not end with the war, as several nations still flew variants well into the 1950's. However this is a story better left for another time. Part II of this article will deal with operations and the pilots' assessment of the Messerschmitt and also discussion of the myth and legend surrounding this remarkable fighter.

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