Messerschmitt Bf 109

The Messerschmitt Bf 109 is a German fighter-plane that served as the backbone of the Luftwaffe.

Characteristics
As with the earlier Bf 108, the new design was based on Messerschmitt's "lightweight construction" principle, which aimed to minimise the number of separate parts in the aircraft. Examples of this could be found in the use of two large, complex brackets which were fitted to the firewall. These brackets incorporated the lower engine mounts and landing gear pivot point into one unit. A large forging attached to the firewall housed 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 structure via a series of strong-points. By concentrating the loads in the firewall, the structure of the Bf 109 could be made relatively light and uncomplicated.

An advantage of this design was that the main landing gear, which retracted through an 85-degree angle, was attached to the fuselage, making it possible to completely remove the wings for servicing without additional equipment to support the fuselage. It also allowed simplification of the wing structure, since it did not have to bear the loads imposed during takeoff or landing. The one major drawback of this landing gear arrangement was its narrow wheel track, making the aircraft unstable while on the ground. To increase stability, the legs were splayed outward somewhat, creating another problem in that the loads imposed during takeoff and landing were transferred up through the legs at an angle.

The small rudder of the Bf 109 was relatively ineffective at controlling the strong swing created by the powerful slipstream of the propeller during the early portion of the takeoff roll, and this sideways drift created disproportionate loads on the wheel opposite to the swing. If the forces imposed were large enough, the pivot point broke and the landing gear leg would collapse outward into its bay. Experienced pilots reported that the swing was easy to control, but some of the less-experienced pilots lost fighters on takeoff.

Because of the large ground angle caused by the long legs, forward visibility while on the ground was very poor, a problem exacerbated by the sideways-opening canopy. This meant that pilots had to taxi in a sinuous fashion which also imposed stresses on the splayed undercarriage legs. Ground accidents were a problem with inexperienced pilots, especially during the later stages of the war when pilots received less training before being sent to operational units. At least 10% of all Bf 109s were lost in takeoff and landing accidents, 1,500 of which occurred between 1939 and 1941. The installation 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.

From the inception of the design, priority was given to easy access to the powerplant, fuselage weapons and other systems while the aircraft was operating from forward airfields. To this end, the entire engine cowling was made up of large, easily removable panels which were secured by large toggle latches. A large panel under the wing centre section could be removed to gain access to the L-shaped main fuel tank, which was sited partly under the cockpit floor and partly behind the rear cockpit bulkhead. Other, smaller panels gave easy access to the cooling system and electrical equipment. The engine was held in two large, forged, Elektron magnesium alloy Y-shaped legs, one per side straddling the engine block, which were cantilevered from the firewall. Each of the legs was secured by two quick-release screw fittings on the firewall. All of the main pipe connections were colour-coded and grouped in one place, where possible, and electrical equipment plugged into junction boxes mounted on the firewall. The entire powerplant could be removed or replaced as a unit in a matter of minutes, a potential step to the eventual adoption of the unitized-powerplant Kraftei engine mounting concept used by many German combat aircraft designs, later in the war years.

Another example of the Bf 109's advanced design was the use of a single, I-beam main spar in the wing, positioned more aft than usual (to give enough room for the retracted wheel), thus forming a stiff D-shaped torsion box. Most aircraft of the era used two spars, near the front and rear edges of the wings, but the D-box was much stiffer torsionally, and eliminated the need for the rear spar. The wing profile was the NACA 2R1 14.2 at the root and NACA 2R1 11.35 at the tip, with a thickness to chord ratio of 14.2% at the root and 11.35% at the tip.

Another major difference from competing designs was the higher wing-loading. While the R-IV contract called for a wing-loading of less than 100 kg/m2, Messerschmitt felt this was unreasonable. With a low wing-loading and the engines available, a fighter would end up being slower than the bombers it was tasked with catching.[citation needed]

A fighter was designed primarily for high-speed flight. A smaller wing area was optimal for achieving high speed, but low-speed flight would suffer, as the smaller wing would require more airflow to generate enough lift to maintain flight. To compensate for this, the Bf 109 included advanced high-lift devices on the wings, including automatically opening leading edge slats, and fairly large camber-changing flaps on the trailing edge. The slats increased the lift of the wing considerably when deployed, greatly improving the horizontal maneuverability of the aircraft, as several Luftwaffe veterans, such as Erwin Leykauf, attest. Messerschmitt also included ailerons that "drooped" when the flaps were lowered (F series and later the lower radiator flap operated as part of the flap system), thereby increasing the effective flap area. When deployed, these devices effectively increased the wings' coefficient of lift.

Armament and gondola cannons
Reflecting Messerschmitt's belief in low-weight, low-drag, simple monoplanes, the armament was placed in the fuselage. This kept the wings very thin and light. Two synchronized machine guns were mounted in the cowling, firing over the top of the engine and through the propeller arc. An alternative arrangement was also designed, consisting of a single autocannon firing through a blast tube between the cylinder banks of the engine, known as a Motorkanone mount in German. This was also the choice of armament layout on some contemporary monoplane fighters, such as the French Dewoitine D.520, or the American Bell P-39 Airacobra, and dated back to World War I's small run of SPAD S.XII moteur-canon, 37 mm cannon-armed fighters in France.

When it was discovered in 1937 that the RAF was planning eight-gun batteries for its new Hawker Hurricane and Supermarine Spitfire fighters, it was decided that the Bf 109 should be more heavily armed. The problem was that the only place available to mount additional guns was in the wings. Only one spot was available in each wing, between the wheel well and slats, with room for only one gun, either a 7.92 mm MG 17 machine gun, or a 20 mm MG FF or MG FF/M cannon.

The first version of the 109 to have wing guns was the C-1, which had one MG 17 in each wing. To avoid redesigning the wing to accommodate large ammunition boxes and access hatches, an unusual ammunition feed was devised whereby a continuous belt holding 500 rounds was fed along chutes out to the wing tip, around a roller, and then back along the wing, forward and beneath the gun breech, to the wing root, where it coursed around another roller and back to the weapon.

The gun barrel was placed in a long, large-diameter tube located between the spar and the leading edge. The tube channeled cooling air around the barrel and breech, exhausting from a slot at the rear of the wing. The installation was so cramped that parts of the MG 17's breech mechanism extended into an opening created in the flap structure.

The much longer and heavier MG FF had to be mounted farther along the wing in an outer bay. A large hole was cut through the spar allowing the cannon to be fitted with the ammunition feed forward of the spar, while the breech block projected rearward through the spar. A 60-round ammunition drum was placed in a space closer to the wing root causing a bulge in the underside. A small hatch was incorporated in the bulge to allow access for changing the drum. The entire weapon could be removed for servicing by removing a leading edge panel.

From the 109F-series onwards, guns were no longer carried inside the wings. Instead, the Bf 109F had a 20 mm gun firing through the propeller shaft. The change was disliked by leading fighter pilots such as Adolf Galland and Walter Oesau, but others such as Werner Mölders considered the single nose-mounted gun to compensate well for the loss of the two wing guns. Galland had his Bf 109F-2 field-modified with a 20 mm MG FF/M autocannon, the "/M" suffix indicating the capability of firing thin-walled 20mm mine shells, installed internally in each wing.

In place of internal wing armament, additional firepower was provided through a pair of 20 mm MG 151/20 cannons installed in conformal gun pods under the wings. The conformal gun pods, exclusive of ammunition, weighed 135 kg (298 lb); and 135 to 145 rounds were provided per gun. The total weight, including ammunition, was 215 kg. Installation of the under-wing gun pods was a simple task that could be quickly performed by the unit's armourers, and the gun pods imposed a reduction of speed of only 8 km/h (5 mph). By comparison, the installed weight of a similar armament of two 20 mm MG 151/20 cannon inside the wings of the Fw 190A-4/U8 was 130 kg (287 lb), without ammunition.

Although the additional armament increased the fighter's potency as a bomber destroyer, it had an adverse effect on the handling qualities, reducing its performance in fighter-versus-fighter combat and accentuating the tendency of the fighter to swing pendulum-fashion in flight.

Some of the projected 109K-series models, such as the K-6, were designed to carry 30 mm (1.18 in) MK 108 cannons in the wings.

History
They have a minor role and only appear in the battle of Britain segment. Capt. Rafe McCawley battled this plane with a Supermarine Spitfire during his time serving with the Brits, defeating several, though one eventually took him down.