Me 109T, the Carrier-based fighter
Prior to the war, the Kriegsmarine played with the concept of an aircraft carrier, named the Graf Zeppelin
. Starting from scratch, the Germans looked on the British and Japanese practiced and soon through about a dedicated air group. After many changes over the years they eventually settled on the Messerschmitt Bf 109T, which was to operate with the Ju 87C, as a dive bombers. The latter has shown indeed its great effectiveness against ships from the Mediterranean to the black sea. The 'T' meant Träger (carrier). It is not sure a T-0 was ever built, however it was registered that Bf 109 B, Bf 109 C, and Bf 109 E were later converted for testing special equipment like a tail-hook, and catapult fittings. But the most recognizable trademark was the much increased wingspan to 11.08 m (36.35 ft). The ailerons were also increased, the slats, and flap travel for smoother landings, and better support when taking off in rough seas. However oddly no folding provision was made, since the ship was designed around these planes, with tailored lifts.
Flight and catapult tests were performed in a second phase with 70 planned T-1 planes propelled by the with DB601N (made by Fieseler, Kassel) but cancellation meant when only 7 were ever built (later upgraded to T-2 standard) while the remaining 63 were modified as T-2s. They were armed with two nose 7.92 mm (.312 in) MG 17s and wings 20 mm MG FF/M cannons, lacked carrier equipment but it was found they compared well to the E-4/N. Their short take-off/landing capabilities made them joined the Norway-based I/JG.77, dealing better with its powerful cross-windy short strip. The unit was move back in Germany in the end of 1941 (E-3s were shipped as replacements), because the Carrier program regained momentum.
When interest rose up again for the Graf Zeppelin, intended Bf 109T were outdated. So Messerschmitt upgraded the Me 155A as a response, but as the unfortunate carrier was again suspended, these fighters became high-altitude interceptors and given for completion to to Blohm & Voss (They ended as the BV 155). The purpose-less Bf 109Ts ended in training units by 1943. In April 1943 however the Jagdstaffel Helgoland operating from Düne used some of these. They were later moved to Lista (south Norway) as 11./JG 11 in November 1943, and served until the summer of 1944, and were back in Germany for training.
Me 109H, the high-altitude fighter
The Bf 109H was intended to be a high-altitude fighter, based on the bf 109F. Its wingspan was increased with constant-chord inner wing panels being added, raising it to 11.92 m (39.11 ft). The stabilizer was widened and received a supporting strut. Top speed was 750 km/h (470 mph) at 10,100 m (33,140 ft) due to the engine with high-octane gasoline and booster. Only a handful of these Bf 109 H-1s were built, leading interceptions over Britain and France.The H-2 and H-5 developments were planned and abandoned. Indeed wing flutter problems were soon discovered and never solved on the H-0 Pre-production serie. Those were later converted as F-4/Z, powered by a DB 601E engine fitted with the GM-1 boost. The H-1 main production version used the G-5 airframe and was given the DB 605A /GM-1 boost. A single Bf 109H-1, was converted to a photo-recon aircraft used by the long-range reconnaissance group Fernaufklärungsgruppe 123, in May 1944. It flew 15 km (49,200 ft) over the French coast soon after the Normandy landings.
Me 109X, the radial BMW 109
Zürich, 1937, Udet found interested into the idea of an export version of the Bf 109, mated with a simpler and more available engine to spare DB 601s. The Pratt & Whitney "Twin Wasp" SC-G of 1200 hp as first tried on a modified cell. A contract from the RLM on 13 June 1938 on the 21st prototype led to a possible first flight, but later Hermann Wurster flew it at Augsburg on 17 August 1939. By September 1940 the DVL (Deutsche Versuchsanstalt für Luftfahrt) tried it at Brauschweig-Völkenrode. Later the BMW 801 radial engine became available. A Bf 109F was therefore converted with this engine, becoming the Bf 109X A-0, prototype for the serie Bf 109X, which had a wider cross-section, new canopy, and Bf 109 E wing tips. This A-0 was flown by Flugkapitän Fritz Wendel, 2 September 1940, test went on right to early 1942 but never went further. The concept was abandoned.
Me 109Z "Zwilling" the twin 109
The twin-Me 109 was an experimental attempt to built a long-range fighter with the expedient of joining two Type F airframes by means of a new wing centre section, new tailplane of constant chord. The pre-production model right fuselage cockpit was closed while the pilot took place in the left fuselage. The main undercarriage hinges were relocated further inboard. The fuselage were strengthened as the wing forward structure. Four variants were proposed, the first two were apparently built, a five 30 mm (1.18 in) cannon interceptor capable of carrying a 1,000 kg (2,200 lb) bomb load, a fighter-bomber with two MK 108 cannons and bombs, both with the DB605 engine. The two others never left paper, and had Jumo 213 engines. The only Bf 109Z ever built, never flown. It was half-destroyed in its hangar in 1943 after an Allied raid and the program was closed the next year.
Me 109TL, the jet 109
Perhaps the most interesting of all, the Bf 109TL propelled the serie to the jet age. It resulted of a 22 January 1943 RLM conference when three prototypes of the Me 262 had been completed. This 109TL was conceived as a backup if the Me 262 production was delayed too long. It has been argued also as a cheaper, second mass-production jet fighter. In fact components of the two planes were to be used, with a Bf 109H/BV 155B high-altitude fighter fuselage, receiving a new armed nose and a new tail. Also, the straight wings were borrowed from the dropped Me 409 project, combined with the Me 309 tricycle carriage. Junkers Jumo 004B-1 turbojet (900 kgf thrust) or BMW 003A (800 kgf) from the 262 were also to be fitted in the wings roots. The cockpit came from the Bf 109E/G. Performance was potentiall even better than the Me 262. Indeed the TL had a narrower fuselage, so less drag. The Bf 109TL was researched actively until March 1943, when it was found that many other modifications and new components were needed, and it was abandoned, while the Me 262 project had all priority.
Messerschmitt Me-109 T, the naval fighter
Messerschmitt Me-109 H, the high altitude fighter
Messerschmitt Me-109 X, BMW 801 prototype
Messerschmitt Me-109 Z "Zwilling"
Messerschmitt Me-109 TL