Messerschmitt Bf 109

The Messerschmitt Bf 109 was a World War II fighter aircraft designed in the early 1930s, one of the first truly modern fighters of the era. It was the standard fighter of the Luftwaffe from just before the start of the war, and spend the first half of the war locked in combat with its "natural foe", the Supermarine Spitfire. By the second half of the war the Spitfire was outperforming it, and newer designs from both the British and US outclassed it considerably. Nevertheless a truly all-round replacement never entered production, and in the end the Bf 109 became one of the most produced aircraft of all time, with 33,000 examples being built.

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Background

During 1933 the Technisches Amt (or T-Amt, the technical department of the RLM) concluded a series of research projects into the future of air combat. The result of the studies were four broad outlines for future aircraft:

• Rüstungsflugzeug I for a multi-place medium bomber
• Rüstungsflugzeug II for a tactical bomber
• Rüstungsflugzeug III for a two-place heavy fighter
• Rüstungsflugzeug IV for a single-place fighter

The Rüstungsflugzeug IV was intended to be an all-metal monoplane single seat fighter aircraft, or interceptor actually, replacing the Arado Ar 64 and Heinkel He 60 biplanes then in service. While it was intended the R-IV aircraft would best all others then flying, the requirements were nevertheless not terribly hard to meet.

The plane needed to have a top speed of 400km/h at 6000m (250mph at 19,500ft) which it could maintain for 20 minutes, while staying in the air for a total of 90 minutes. It was to be powered by the new Junkers Jumo 210 engine of about 700hp. It also needed to be armed with at least three 7.9mm machine guns with 1000 rounds each, or one 20mm cannon with 200 rounds. One other interesting specification was that the plane needed to keep wing loading below 100kg/m², which is a way of defining the plane's ability to turn and climb. The priorities for the plane were level speed, climb speed, and then maneuverability (in that order).

In fact the R-IV specifications were not really thought up inside the T-Amt at all. In early 1933 both Heinkel and Arado had sent in privately-funded designs for a monoplane fighter, and the T-Amt simply collected the best features from both and sent them back out again, adding Focke-Wulf to the tender. In May 1934 the R-IV request was sent out and made official. Each were asked to deliver three prototypes to be delivered for head-to-head testing in late 1934.

Messerschmitt was originally not invited to the competition. Most of this was due to personal animosity between Messerschmitt and Erhard Milch, director of the RLM, after an earlier airliner design of his proved a disaster in Lufthansa use, and he had also designed another airliner for the Romanians. Nevertheless he was on very good terms with many high ranking Luftwaffe officers based on the success of the Messerschmitt Bf 108 Taifun sports plane. After a delay of several months, Bayerische Flugzeugwerk (Bavarian Aircraft Manufacturers, or BFW) was finally invited to take part in early 1935, although Milch let it be known that they would never win the contract.

Development history

Messerschmitt had already designed much of the Bf 109 by this point however. Like the Bf 108, the new design was based on Messerschmitt's "lightweight construction", which essentially aimed to reduce the total number of strong parts in the aircraft as much as possible. One of the more notable examples of this was the mounting of all structural points to a strong firewall at the front of the cockpit, including the wing spars, engine mounts and landing gear. Typically these would be mounted to different points on the aircraft, with a framework distributing the load among them.

Another part of this construction technique was the use of a single box-spar in the wing, mounted near the leading edge. Most planes of the era used two spars, near the front and rear, but the box was much stiffer torsionally, and eliminated the need for the rear spar.

Another major difference was the much higher wing loading than the other designs. While the R-IV contract called for a wing loading of v100kg/m², Messerschmitt felt that this was unreasonable; with the engines available to them, the fighter would end up slower than the bombers it was tasked with catching.

A wing generates two forms of drag, parasitic drag due to its form, and induced drag which is a side effect of generating lift. The former dominates at high speeds, when the airflow hitting the wing causes drag that rises with the square of the aircraft's speed. The latter dominates at lower speeds, where the lack of airflow requires the wing to be angled into the airflow at a higher angle of attack. Since the fighter was being designed primarily for high speed flight, a smaller wing would be optimized for high speed use.

The downside of such a tradeoff is that low speed flight would suffer, the smaller wing would require more airflow to generate enough lift to stay flying. In order to address this, the Bf 109 included advanced high-lift devices on the wings, including automatically opening slats on the leading edge, and fairly large split flaps on the trailing edge. When opened, these devices effectively increase the size of the wing, making it better at low speeds and high angles of attack. The only downside to such systems is their complexity.

Another drawback of the high wing-loading is that the plane would require more energy to manuver. Given the limited amount of power available, this effectively meant that the Bf 109 would not be able to turn as tightly as other designs with larger wings. The high lift devices would offset this to some degree, but they also increased drag and so slowed the plane further. Given that manuverability was last on the RLM's wish-list, Messerschmitt was certain the benefits outweighted the drawbacks.

Prototypes

The first prototype (Versuchs 1 or V1) was completed by May 1935, but the German engines were not yet ready. In order to get the designs into the air, the RLM acquired four Rolls-Royce Kestrel VI engines by trading Rolls-Royce a Heinkel He 70 Blitz to test their engines on. Messerschmitt received two of these engines, and started work on adapting V1 to mount it. This work was completed in August, and V1 took its completed its early flight tests in September 1935. It was then sent to the Luftwaffe Test Center at Rechlin to take part in the contest.

It was here that another side-effect of the lightweight construction started to become obvious. With the landing gear attached to the corners of the firewall, they had very little distance between the tires when opened, known as "track". This resulted in tricky ground handling, and the plane tended to "snake" around during takeoff and landing. In order to address this the gear were angled out as much as possible to increase the track, but this made them considerably weaker. In the end this design feature would prove to be the Achilles heel of the design, and a huge number of Bf 109s were written off when the gear collapsed on landing.

By the late summer the Jumo engines were starting to become available, and V2 was completed with the Jumo 210A of 610hp in October 1935. V3 followed, being the first to actually mount guns, but another 210 was not available and it ended up delaying the flight of V3 until May 1936. Like V1, V2 and V3 were sent to Rechlin after acceptance tests at the factory.

The flight data of these three planes were very nearly identical. The maximum airspeed was about 470km/h at 4000m altitude, and the service ceiling was about 8300m.

After Luftwaffe acceptance trials were completed at Rechlin, the planes were moved to Travemünde for the head-to-head portion of the contest. The Heinkel design arrived first, in early February 1936, and the rest of the V1's had all arrived by the beginning of March.

Because most of the fighter pilots of the Luftwaffe were used to good-natured biplanes with open cockpits, light g-forces and easy handling, they were very critical about the Bf 109 at first. However it was soon a front-runner in the contest, as the Arado and Focke-Wulf entries proved to be hopelessly outdated. Perhaps this isn't suprising, considering that those entries had actually been designed two years earlier, and given the rate of change in aircraft design at the time, they really had little chance against the much more modern 109.

The only serious competition to the 109 was the Heinkel entry. Based on a scaled down Blitz, the He 112 proved to be similar but different. Positive aspects of the He 112 included the wide track and robustness of the landing gear, considerably better visibility from the cockpit, and a lower wing loading that led to easier landings and better manuverability. But the Bf 109 was 30km/h faster than the He 112 in level flight, and also was superior in climbing and diving. But still the He 112 was the favorite of the Luftwaffe leaders.

Orders for a further ten examples of both types were placed, and they started trickling in over the next few months. However by this point the Jumo-powered examples of both designs had arrived for testing, and the 109's better streamlining and lower drag meant that it was considerably faster given the lower-power engine.

Even before the pre-production models arrived the contest was basically over. In March the RLM received news that the Spitfire had been ordered into production, and a form of mass panic broke out. On March 12 they released a document that basically contained the outcome of the contest, Bf 109 Priority Procurement. Nothing occured over the summer to change their minds, and the RLM instructed Heinkel to re-design the He 112 radically, while ordering the Bf 109 into production.

Bf 109A

The planned Bf 109A series was canceled, before production begun, because of the weak armament. Instead of this, the Me109 V-4 was constructed, carrying a third MG 17, mounted behind the engine, firing through the propeller axis. In the following three prototype planes, the new Jumo 210 B engine was installed. They also were armed with three machine guns and were quite identical with the Bf 109 B-0 pre-production series.

The first Bf 109 model that went in serial production, the B-1, got the more powerful Jumo 210 D engine. When the new Jumo 210 E engine was developed with 670 hp, it was fitted to the cell of the Bf 109 B. The resulting plane was called the B-2. These Bf 109 B-2 were the first Bf 109 to go into combat. 24 of them were assigned to "Legion Kondor" in Spain and demonstrated that the armament was still inadequate, so the Bf 109 V-8 was constructed to test the fitting of two more machine guns in the wings. In the following V-9 both wing guns were replaced by 20 mm MG FF cannon. Both planes therefore had no gun in the propeller axis.

So Bf 109 C-0, the pre-production series, carried four MG 17, the C-1 series was identical to this C-0. The C-2 again got one machine gun in the nose, carrying now five MG 17. The next model, the V-10 prototype, was identical to the V-8, except for the engine. It had a Jumo 210 Ga engine at first, that later was replaced by a Daimler-Benz DM 600 Aa, the V-8 was fitted with a Jumo 210 Da instead. So the V-10 was the link to the Bf 109 D. It followed the goal of increasing the performance of more than just the armament, by installing the Daimler-Benz engine. Therefore three more prototypes, the V-11, V-12 and V-13, were built and tested. The knowledge gained with these prototypes was used in the Bf 109 D-0 pre-production series. These were modified planes of the C-3 series, that were built, but never used by the Luftwaffe. It was armed like the Bf 109 V-9, which means two MG 17 above the engine and one 20mm MG FF canon in each wing. Quite identical to the Bf 109 D-0 was the D-1 series, which was produced in low numbers, because the new Daimler-Benz DB 601 engine was ready for duty, promising still more power.

The Bf 109 E "Emil"

To test this new engine, with its 1100 hp, two more prototypes, the V-14 and V-15, were built, that differed in their armament. While the V-14 was armed with the two MG 17 above the engine and one 20mm MG FF canon in each wing, the V-15 got the two MG 17 and one canon firing through the propeller axis. The Bf 109 E-0 was identical to the V-14 except for the armament, as the E-0 had two additional MG 17 in the wings instead of the MG FF in the propeller shaft. In the production version E-1, the two wing guns were replaced by MG FF again. To improve the performance of the Bf 109 E, the last two real prototype planes were constructed, the V-16 and V-17. They got some structural improvements and stronger armament. These prototypes were the basis of the Bf 109 E-3 version. They were armed with the two MG 17, one MG FF cannon in each wing and one MG FF/M, firing through the propeller axis. The E-3 also received heavier armor than the E-1.

The E-3 was replaced by the E-4, which was different in some small details and would be the base for all further Bf 109 E developments.

Background, Bf 109T

Prior to the war the German Navy had become fascinated with the idea of the aircraft carrier. Borrowing ideas from the British and Japanese (mainly the Akagi), they started the construction of the Graf Zeppelin in 1936. The armament for the carrier was settled on Messerschmitt Bf 109T fighters and Junkers Ju 87C dive bombers.

The 109T was essentially the E-3 with basic carrier equipment, as well as longer folding wings that were to make takeoff and landings easier.

The ten Bf 109T-0 were originally Bf 109E-3, which were modified by adding a tail-hook, catapult fittings and structural strengthening. Also the landing gear track was a little wider. Still, the very concept of landing a 109 on a carrier is somewhat laughable considering that the plane was difficult enough to land on solid ground.

Following the flight tests, especially the catapult tests, a series of 60 Bf 109T-1 was produced at the Fieseler facilities in Kassel. Because the carrier never went into service, these planes were assigned to the JG 5 "Eismeergeschwader", deployed in Norway. Since the modifications for the use with a carrier were unnecessary now, they were removed to save weight. After removal the planes were called Bf 109 T-2. The armament of the Bf 109T consisted of two MG 17 above the engine and one MG FF cannon in each wing.

Interest in the Graf Zeppelin grew when the value of the carrier became obvious, and in 1942 the ship was back in the yards for completion. By this time the Bf 109T was hopelessly outdated and a new fighter would be needed. Messerschmitt responded with the updated Me 155A series, but work on the ship was again cancelled and the Me 155 was later re-purposed as a high-altitude interceptor.

"Fritz" - Bf 109 F, aerodynamic in perfection

After February 1940 an improved engine, the Daimler-Benz DB 601 E, was developed for use with the Bf 109.

The constructors at the Messerschmitt facilities took a Bf 109 E-1 and installed this new engine. The cell and especially the cowling were modified and in the end more aerodynamic. Its relation to the E-1 was obvious, because the trapeziform wings were taken from the E-1, but changed in the production planes. This plane was the prototype for the Bf 109 F series. The first Bf 109 F planes were not well tested, and so some planes crashed or nearly crashed, due to vibrations which caused either the wing surface to curve or break, or caused the stabilizer to break away. In one such accident, the commander of JG 2 "Richthofen", Wilhelm Balthasar lost his life when he was attacked by a Spitfire during a test flight. Making an evasive maneuver, his wings broke away and Balthasar was killed when his plane hit the ground. When the wreck was investigated, not a single bullet hole was found.

Externally the Bf 109 F differed from the E-series, resulting from many aerodynamic improvements. The stabilizer struts were removed, the cowling was shaped to be more streamlined, the big underwing radiators were much smaller, the opening for the supercharger was improved, the flaps were completely changed, the wingspan was increased, and the wing tips now were formed elliptically, which supposedly caused some confusions with the Spitfire. The redesigned wing made the internal mounting of guns impractical, so armament was revised. The armament of the Bf 109 F consisted of the two MG 17 above the engine plus a cannon firing through the propeller hub. The early F versions were equipped with the MG FF/M cannon, the F-2 got the MG 151, and from F-4 on the MG 151/20 was used.

Most produced version: The Bf 109 "Gustav"

When the Daimler-Benz DB 605 engine was available, a new Bf 109 series, the G-series, was developed. The early versions of the Bf 109 G looked quite similar to the Bf 109 F-4, and at first carried the same armament. The G series saw the appearance of the notorious bulges in the cowling (the addition of 13mm MG 131 guns) and on the wings (due to larger main gear wheels), leading to the Bf 109 G's nickname "The Bulge" (German: "Die Beule"). Other changes included an enlarged supercharger for the DB 605 and the enlarged vertical stabilizer (G5 onwards).

The G-6 model, the most produced Bf 109 version, had very heavy armament. The G6/R6/U4 variant was armed with two MG 131 above the engine, a MK 108 cannon shooting through the propeller axis and one MG 151/20 in each wing. The G-6 was very often fitted with assembly sets, used to carry bombs or a drop tank, for use as nightfighter, or to increase fire power by adding rockets or extra guns.

All following Bf 109 G versions were modified older Bf 109 Gs. So the G-10 was not an uniform type, but consisted of all kinds of Bf 109 Gs being transformed partially to Bf 109 G-10 specifications. The most recognizable change was the use of the "Erla-Haube" canopy. This canopy improved the pilots view, which was often criticized before. The Bf 109 G-10, also called "Super-Bulge" (German: "Super-Beule"), was the fastest Bf 109 during World War II. The G-10 saw a refinement of the bulges covering the breeches of the cowl mounted MG 131, these taking on a more elongated and streamlined form. A similar varying product was the Bf 109 G-12. This was a two-seat trainer version of the Bf 109 and was rarely armed.

Last developments: Bf 109 H and K

Somewhere between the drawing board and full production was the Bf 109 H. This was a special high-altitude fighter, developed from the Bf 109 F series. The wingspan was increased to 11.92 m, the stabilizer again received a strut leading to the fuselage, and it was also widened. In fact was only a low number of Bf 109 H-0 and H-1 were produced, because of problems with vibration.

More of the planes of the Bf 109 K series saw duty. This series was the evolution of the Bf 109 G-10, being very similar, at least the K-0, K-2 and K-4 models. In the K-6, K-8 and K-14, the armament saw some changes. The K-6 carried two MG 131 above its engine and one MK 103 in each wing and behind its propeller hub. The K-8 was armed with a MK 103, firing through the propeller axis and one MK 108 in each wing. The engine gun was changed in the K-14 and replaced by a MK 108. Only the K-4 saw action in numbers, approximately 700 being delivered to squadrons before the end of hostilities.

Developments after the war

After the end of the war, some Me 109s were produced in the CSSR (Czechoslovakia) as the Avia S-99 and Avia S-199, modified Me 109G-14s, the latter with a Junkers Jumo 211F engine. In Spain, a modified Me 109G-2, called the Hispano Ha 1112 was built with various engines fitted.

Also the original Bf 109, produced before 1945, remained in service a long time after the war. The former German allies, Romania and Hungary, used their Bf 109s until 1955. The Finnish air force did not retire their Bf 109 Gs until the mid 1950s. In Israel, the Czech Avias were used in combat against Egyptian Spitfires until 1949. The Spanish Hispanos, however, flew longer. Some were still in service in the middle of the 1970s. Later, they appeared in films, playing the role of the Bf 109. Some Hispano fuselages were sold to museums, which rebuilt them as Bf 109s.