Twelve Spitfires reported over Berck-sur-Mer! We could still have a go at these lads…
Gathering speed while descending from an altitude of 8000 meters down to 5000, we intend to cut off the English. We are already over the middle of the Channel when a squadron of Spitfires looms ahead. Their tight, rigid formation gives them away for miles. We’re moving up-sun to stay hidden in its blinding rays and position ourselves for a bounce. We’re trailing the enemy formation like a shadow. Over Dungeness, when the English make a wide turn to starboard, the machine on the right flank falls slightly behind the others. Our Geschwaderkommodore1 closes in to point-blank range and from a distance of no more than 50 meters, opens up. The stricken Spitfire falls over on its port wing and plummets towards the ground streaming a long white trail.
Our commander immediately breaks away and pulls up in a steep, right turn, so that the others can also engage. I go straight for the next Spitfire but when I line him up in my sights, the English pilot gets wise and breaks away to starboard. I lay off a lot of deflection and press the trigger. I can see my rounds rake across his fuselage and cockpit. The Spitfire hurtles down and I follow him in his dive. Then I cast a quick glance over my shoulder – just in time! A swarm of Spitfires trails after me in hot pursuit. With all my strength I push the stick into the right corner of the cockpit and ram the throttle lever forward. After several anguished moments I outdistance my pursuers and head for home.
The commander arrives over our airfield shortly afterwards and waggles the wings of his Messerschmitt. Everybody is excited - the ground crews rush to shake his hand. Pity I didn’t see what happened to the Spitfire I had fired at. Perhaps he didn’t make it back, just like the one knocked down by our CO. Either way, I pumped a lot of lead into mine2.
Designing the ‘Friedrich’
In the autumn of 1938 the design team of the Bayerische Flugzeugwerke in Augsburg began work on a development version of the Messerschmitt Bf 109 E, which at that time was entering service as the primary fighter of the German Luftwaffe. Prof. Willy Messerschmitt, the company’s founder, and Robert Lusser, chief of project planning, sought to develop an improved version of the aircraft which could outperform earlier variants by means of an aerodynamically refined airframe and a more powerful engine.
The new fighter, designated Bf 109 F, was to be powered by the Daimler-Benz DB 601 E engine, a development version of its successful predecessor, the DB 601 A, used on the Bf 109 E. The new DB 601 E was an inline engine with direct fuel injection to the cylinders. Displacement was 3390 cm³ and maximum output at 17,750 ft (4,800 m) was 1,350 horsepower. This was a remarkable 23% increase in power3. The new engine was longer by 17.2 inches (452 mm), which necessitated a major redesign of the engine bearers and cowling. The ‘Friedrich’ (German phonetic name for the letter ‘F’) also incorporated a propeller spinner similar to that designed for the Me 209. The final result was an aerodynamically clean, superbly streamlined machine, which offered ground crews easy access to its powerplant. Furthermore, the chin oil cooler scoop was redesigned and the distinctive tailplane bracing struts of the Bf 109 E, removed. Introduction of the un-braced horizontal stabilizers required further modifications to the rear section of the fuselage.
An important factor in Messerschmitt’s quest for aerodynamic perfection were the revised wing-mounted coolant radiators, wider but flatter for less drag. The two-piece flaps, located at the rear of the radiators to regulate airflow, could be raised by 17° and dropped by 23°. The lower piece also acted as a regular wing flap. Concurrently, new wings with semi-elliptical wingtips, reshaped ailerons, leading edge slats and flaps, were designed. In order to save weight and increase the new fighter’s manoeuvrability, wing armament was discarded.
When it became clear that series production of the DB 601 E engine was far behind schedule, the Messerschmitt team had to resort temporarily to the readily available DB 601 A engine of 1100 hp instead. On 26th January 1939, the new airframe went through a series of flight tests. On that day Messerschmitt Bf 109 V22 (W.Nr. 1800, registered as D-IRPQ) took to the air for the first time, with test pilot Dipl. Ing. Heinrich Beauvais at the controls. The machine featured a new supercharger air intake scoop intended for the F-series and was powered by the older DB 601 A engine. The second prototype to be flown was the Bf 109 V23 (W.Nr. 1801, D-ISHN), fitted with one of the still-experimental DB 601 E units. Finally, the Bf 109 V24 (W.Nr. 1929) and V25 (W.Nr. 1930, D-IVKC) incorporated all the distinctive external features of the Bf 109 F, which included the modified fuselage and new wings with rounded wingtips4.
Flight test results were promising and the RLM placed an order for a pre-production batch of 15 Bf 109 F-0s. They were to be delivered to the Luftwaffe in the period between November 1939 and April 1940. However, due to Hitler’s decision to curtail development work on all combat aircraft designs, completion of the first batch of ‘Friedrichs’ was delayed until June 1940 – February 19415. Four more Bf 109 F-0s were assembled between March and June 19416. Most of them subsequently served as test-beds. At least five of these aircraft were converted standard Bf 109 E-3 airframes (W.Nr. 5601 through 5605). Messerschmitt Bf 109 F-0, W.Nr. 5601, was earmarked for “further constructional development” (Weiterentwicklung des Baumusters); it was powered by a DB 601 A engine and featured wings identical to that of the Bf 109 E variant. Bf 109 F-0, W.Nr. 5602, was used to test the new radiator systems intended for the F-series. It was lost during trials at Rechlin (the Luftwaffe’s main testing ground for new aircraft designs).
The first prototype of the definitive series-production Bf 109 F-1 was the Bf 109 F-0, W.Nr. 5603 (coded CE+BP) powered by a DB 601 N engine. This powerplant was an upgraded DB 601 A, rated at 1,175 hp. It ran on 96-octane C3 fuel (the octane number of the Luftwaffe’s standard B4 fuel was 87). Upon completing the tests the aircraft was returned to the Messerschmitt plant, where it was later used to develop the Me 309, being subsequently fitted with a new landing gear and nose wheel. Another Bf 109 F-0, W.Nr. 5604 (coded VK+AB), was used for testing the wing slats and radiator flaps. Messerschmitt Bf 109 F-0, W.Nr. 5605 (VK+AC), fitted with the standard wings of an E variant, served as a test-bed for the engine cooling system; it was also experimentally fitted with several different types of supercharger air intake.
The major difference between the ‘Friedrich’ and its predecessor was the onboard armament. The twin wing-mounted 20 mm MG FF/M cannons of the E variant were replaced by a single 15 mm Mauser MG 151 cannon installed between the engine cylinder banks and firing through the hollow propeller shaft. The new cannon, despite its smaller calibre, gave more firepower. This was due to the considerable increase in the rate of fire – from 530 rds/min to as many as 700! Furthermore, the increased muzzle velocity (1020 m/sec, compared to the previous 718 m/sec) gave the new weapon greater accuracy. Nevertheless, the process of preparing the MG 151 cannon for mass production was handicapped by numerous delays, as was the case with the DB 601 E engine. This left the Messerschmitt team with no option but to initiate production with the DB 601 N engine and the MG FF/M cannon.
Messerschmitt Bf 109 F-1
The Bf 109 F-1 was the first series-production ‘Friedrich’. In accordance with the aircraft production program issued on 1st April 1939, production was to begin as early as June 1940 with machines being manufactured by the Messerschmitt plant at Regensburg, the Arado plant at Warnemünde and the WNF plant at Wiener-Neustadt. It was estimated that 1072 aircraft of the type would have been constructed by March 1942.
The Messerschmitt Bf 109 F-1 was powered by a Daimler-Benz DB 601 N engine. It was a 12-cylinder, inverted-vee, inline engine with a displacement of 3390 cm³. It developed a maximum output of 1,175 hp. Maximum rpm at take-off/emergency power was 2600 at a boost pressure of 1.35 ata. “Climb and Combat Power”7 at 5400 meters was 1060 hp at 2400 rpm and 1.3 ata. Continuous power rating was 950 hp at 2300 rpm and 1.2 ata. The DB 601 N was similar to the earlier DB 601 A; its higher power was attained through the use of higher-octane C3 fuel and higher compression ratios. Its production continued until October 1939. The engine drove a VDM 9-11207A three-bladed metal propeller of constant speed type, with a diameter of 9 ft 10 in (3000 mm). The aircraft was equipped with a lever for manual adjustment of the propeller pitch in case the constant speed governor failed.
The oil tank of 56.5 litre capacity (it was normally filled with 50 litres of ‘Intava 100’, ‘Rotring’ or ‘Aero Shell mittel’ oils) was moved on top of the engine reduction gear’s housing. The oil had to be changed every 8-10 hours of engine running time. The oil cooler was built into the lower cowling. Airflow through it was automatically regulated by means of a thermostat and a hydraulically operated cooling flap. The engine was cooled by a mixture of water and ethylene glycol (in 1:1 proportion), together with 1.5% of Schutzöl 39 anti-corrosion additive. The coolant mixture was stored in two header tanks with a total capacity of 35 litres, located on either side of the engine. The underwing radiators were installed behind the main spar and fitted with flaps to regulate the airflow. The split flaps located behind the radiators were operated via hydraulic actuators and thermostatically controlled.