Due to the Messerschmitt Bf 109's versatility and time in service with the German and foreign air forces, numerous variants were produced in Germany to serve for over eight years with the Luftwaffe.

The new radiator position also had the effect of counterbalancing the extra weight and length of the DB 601, which drove a heavier three-bladed Vereinigte Deutsche Metallwerke (VDM)-made propeller.

[12][13] The E-3 was replaced by the E-4 (with many airframes being upgraded to E-4 standards starting at the beginning of the Battle of Britain), which was different in some small details, most notably by using the modified 20 mm MG-FF/M wing cannon and having improved head armour for the pilot.

[23] The E-7 rectified this problem as it was the first Bf 109 subtype to be able to carry a drop tank, usually the standardized Luftwaffe 300 L (80 US gal) capacity unit mounted on a centre-line rack under the fuselage, which increased its range to 1,325 km (820 mi).

The wings were not modified to be folding since the ship Graf Zeppelin was designed around the intended aircraft, so the lifts could accommodate the Bf 109T with its 11 m (36 ft) wingspan.

The fourth prototype, V24 VK+AB, W.Nr 5604, flew with the clipped wings but featured a modified, "elbow"-shaped supercharger air-intake, which was eventually adopted for production, and a deeper oil cooler bath beneath the cowling.

A two-piece, all-metal armour plate head shield was added, as on the E-4, to the hinged portion of the canopy, although some lacked the curved top section.

Modifications included a reinforced wing structure, an internal bullet-proof windscreen, the use of heavier, welded framing for the cockpit transparencies, and additional light-alloy armour for the fuel tank.

[60][61] Like most German aircraft produced in World War II, the Bf 109 G-series was designed to adapt to different operational tasks with greater versatility; larger modifications to fulfil a specific mission task, such as long-range reconnaissance or long-range fighter-bomber, were with "Rüststand" and given a "/R" suffix, smaller modifications on the production line or during overhaul, such as equipment changes, were made with kits of pre-packaged parts known as Umrüst-Bausätze, usually contracted to Umbau and given a "/U" suffix.

[62] Up to 1944, the G-series was powered by the 1,475 PS Daimler-Benz DB 605 driving a three-blade VDM 9-12087A variable-pitch propeller with a diameter of 3 m (9.8 ft) with even broader blades than used on the F-series.

The Bf 109G continued to be improved: new clear-view cockpits, greater firepower in the form of the 30 mm (1.18 in) MK 108 cannon were introduced in late 1943; and a new, enlarged supercharger in the high-altitude DB 605AS engine, a larger vertical stabilizer (G-5 onwards), and MW 50 power boost in 1944.

Erich Hartmann, the world's top scoring fighter ace, claiming 352 victories, flew only the Bf 109G, of which he said: It was very manoeuvrable, and it was easy to handle.

[63]From the Bf 109 G-5 on an enlarged wooden tail unit (identifiable by a taller vertical stabilizer and rudder with a morticed balance tab, rather than the angled shape) was often fitted.

The former were capable of carrying two 300 L (80 US gal) drop tanks, one under each wing; and the latter received pressurized cockpits for pilot comfort and GM-1 nitrous oxide "boost" for high altitudes.

In addition, the angled armour plate for the pilot's head was replaced by a vertical piece which sealed-off the rear of the side-hinged cockpit canopy.

There were two Rüstzustand[citation needed] planned for G-2s: The rack and internal fuel lines for carrying a 300 L (80 US gal) under-fuselage drop-tank were widely used on G-2s, as were the underwing 20 mm MG 151/20 cannon gondolas.

[78] The G-6 was very often seen during 1943 fitted with assembly sets, used to carry bombs or a drop tank, for use as a night fighter, or to increase firepower by adding rockets or extra gondola-style, underwing gun pod mount ordnance.

Because of their aerodynamically more efficient form in a side-view of DB 605AS and D -powered Bf 109 Gs and Ks, the agglomerations were barely discernible compared with the conspicuous fairings they replaced.

Despite what the designation would suggest, it appeared in service after the G-14 in November 1944, largely replacing previous G-series aircraft on the production lines of Erla, WNF and Messerschmitt Regensburg factories.

Apart from the standardised streamlined engine cowlings, G-10s with the DB605 D-2 were equipped as standard with the MW-50 booster system (DB 605DM, later 605DB) and had a larger Fo 987 oil cooler housed in a deeper fairing.

The G-8 often had only the Motorkanone engine cannon or the cowling machine guns installed, and there were several subversions for short- or long-range reconnaissance missions with a wide variety of cameras and radios available for use.

Aircraft could be modified in the factory with Umrüst-bausatz (Umbau) conversion kits or by adding extra equipment, called Rüstzustand,[citation needed] to convert standard airframes for special roles, a reconnaissance or bad-weather fighter, for example.

The wingspan was increased through the addition of new, constant-chord inner wing panels to 11.92 m (39.11 ft), and the widened stabilizer again received a supporting strut leading from the fuselage, like the B through E models.

[99] Additional Rüstsätze (equipment kits) such as a 300 L (80 US gal) drop tank (R III), bombs up to the size of 500 kg (1,100 lb) (R I), underwing 20 mm Mauser MG 151/20 cannon gondola pods (R IV) or 21 cm (8.3 in) Wfr.Gr.

He preferred the G-10 as a dogfighter, as the K-4's bulky armament sharply reduced its manoeuvrability.There were problems with the 30 mm (1.2 in) MK 108 Motorkanone, which often jammed while the aircraft was manoeuvring in battle, leaving the pilot to fight on with the two MG 131 heavy machine guns.

[citation needed] With such a high rate of production, despite continuous heavy fighting, by the end of January 1945, 314 K-4s – about every fourth 109 – were listed on hand with the first line Luftwaffe units.

Two airframes are listed as delivered to II./JG52 under Major Wilhelm Batz in late spring of 1945, these being armed with only one 30 mm (1.18 in) cannon, but the type's existence cannot be positively confirmed.

This experimental aircraft was essentially two Bf 109F airframes joined by means of a new wing centre section and new tailplane, both of constant chord, in a manner paralleled by the F-82 Twin Mustang.

These were modified Bf 109G-14s, the latter with the inferior Junkers Jumo 211F engine, which resulted in an aircraft with remarkably poor handling characteristics and a tendency to crash during landings.

Many of these aircraft have been used for theatrical purposes, posing (rather obviously, given their very distinctive undernose air intakes, mandated by the R-R Merlin engines they used) as "Emils" and "Gustavs" in Battle of Britain and The Tuskegee Airmen, respectively.