Messerschmitt Bf 109

Le Bf 109 du musée de Speyer

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Initially, the Bf 109 was regarded with suspicion by the E-Stelle test pilots because of its steep ground angle,
resulting in poor forward view on the ground; the sideways-hinged cockpit canopy, which could not be opened in flight;
and the automatic wing [Vous devez être inscrit et connecté pour voir ce lien] which, it was thought, would inadvertently open during aerobatics, possibly leading to crashes.

They were also concerned about the high wing loading.

Bf 109 G

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The Heinkel He 112, based on a scaled-down Blitz was the favourite of the Luftwaffe leaders.

Compared with the Bf 109, it was also cheaper.

Positive aspects of the He 112 included the wide track and robustness of the undercarriage, considerably better visibility from the cockpit, and a lower wing loading that led to easier landings.

However, the He 112 was also structurally complicated, being some 18% heavier than the Bf 109, and it soon became clear that the thick wing, which spanned 12.6 m (41 ft 4 in) with an area of 23.2 m² (249.7 ft²) on the first prototype (V1), was a disadvantage for a light fighter, decreasing the aircraft's rate of roll and manoeuvrability.

Because of its smaller, lighter [Vous devez être inscrit et connecté pour voir ce lien], the Bf 109 was 30 km/h (20 mph) faster than the He 112 in level flight, and superior in climbing and diving. As a result, the He 112 V4 which was used for the trials had new wings, spanning
11.5 m (37 ft 8.75 in) with an area of 21.6 m² (232.5 ft²).

In addition, the V4 had a single-piece, clear-view, sliding cockpit canopy and a more powerful Jumo 210Da engine with a modified exhaust system.

However, the improvements had not been fully tested and the He 112 V4 could not be demonstrated in accordance with the rules laid down by the Acceptance Commission, giving a distinct advantage to the Bf 109.

The Commission ruled in favour of the Bf 109 because of the Messerschmitt test pilot's demonstration of the 109's capabilities during a series of spins, dives, flick rolls and tight turns, throughout which the pilot was in complete control of the aircraft.

BF 109 E

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In March, the RLM received news that the British [Vous devez être inscrit et connecté pour voir ce lien] had been ordered into production; with this information, a quick result to the contest was needed in order to get the winning design into production.

On 12 March, they released a document that outlined the results of the contest, Bf 109 Priority Procurement, as a
result of which the RLM instructed Heinkel to radically re-design the He 112, while ordering the Bf 109 into production.

The Messerschmitt 109 made its public debut during the [Vous devez être inscrit et connecté pour voir ce lien], when the V1 prototype was flown.

Bf 109 G

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Design features


As with the earlier Bf 108, the new design was based on Messerschmitt's "lightweight construction", which was essentially aimed at reducing the total number of parts in the aircraft as much as possible.

Examples of this could be found in the use of two large, complicated brackets which were fitted to the main engine
firewall; these brackets incorporated the lower engine mounts and landing gear pivot points.

A large forging attached to the firewall carried the main-spar pick up points, and carried most of the wing loads.

Contemporary design practice was usually to have these main load-bearing structures mounted on different parts of the airframe, with the loads being distributed through the main structure via a series of strong-points.

By centralising the loads on the main bulkhead, the main structure of the Bf 109 was able to be made relatively light and uncomplicated.

Bf 109 E

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An advantage of this design was that because the outboard-retracting main landing gear, retracting through roughly an 85º angle, was attached to the [Vous devez être inscrit et connecté pour voir ce lien],
it was possible to completely remove the wings of the aircraft for servicing without the need for additional equipment to support the fuselage.

It also meant that the wing structure was able to be simplified through not having to carry the weight of the aircraft and not having to bear the loads imposed during takeoff or landing.

However, this had one major drawback — this landing gear arrangement had a narrow [Vous devez être inscrit et connecté pour voir ce lien] making the aircraft
unstable while on the ground.

To increase stability the legs had to be splayed out, creating another problem in that the loads imposed during takeoff and landings were transferred at an angle up through the legs.

The small rudder of the Bf 109 was relatively ineffective at controlling the strong swing created by the powerful slipstream of the propeller, and this sideways drift created disproportionate loads on the wheel opposite to the swing.

If the forces imposed were large enough, the pivot points often broke and the landing gear leg would be forced sideways into its bay.

Because of the large ground angle caused by the long legs, visibility for the pilot, especially straight ahead, was very poor, a problem exacerbated by the sideways-opening canopy.

This meant that the pilots often had to "snake" the aircraft during taxiing manoeuvres, which again imposed stresses on the splayed undercarriage legs.

Ground accidents were, however, more of a problem with rookie pilots, especially during the later stages of the war.

Bf 109 G

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Even experienced pilots, especially those who were tired, were caught out.

Most Finnish pilots reported that the swing was easy to control, but some of the less-experienced pilots lost fighters on startup.

At least 10% of all Bf 109s were lost in takeoff and landing accidents, 1,500 of which occurred between 1939 and 1941.

The provision of a fixed "tall" tailwheel on some of the late G-10s and 14s and the K-series helped alleviate the problem to a large extent.

Une série de planche, docs zipés, sur le site russe airwar.ru

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