Focke-Wulf Ta 154 “Moskito”

Focke-Wulf Ta 154 “Moskito”

By September 1939 Germany had one of the most powerful air forces in Europe following the rapid build-up that had begun in earnest in the mid 1930s. However, the Luftwaffe’s High Command did not anticipate the global war that was about to break out and therefore fine-tuned the air arm to be an efficient force in local confrontations with weaker enemies such as Czechoslovakia or Poland and to present itself as a deterrent to European superpowers.

This strategic vision had to be abandoned when France and Great Britain declared war on Germany on September 3, 1939. Despite the initial success of the blitzkrieg in Poland, Denmark and Norway, followed by victorious campaigns in Belgium, Holland and France, the Germans failed to bring Britain to her knees and to secure a much needed peace treaty.

Origins of the design

In the summer of 1940 the RAF launched a strategic bombing campaign against targets deep inside Germany. The area bombing tactics that was intended to terrorize the civilian population of the Reich forced the Luftwaffe’s High Command to look for appropriate countermeasures. The first step was an immediate decision to build a night fighter force (Nachtjagd) and to beef up the air defenses around the German cities. Initially the British raids caused only limited damage. The RAF bombers appeared in formations that rarely exceeded 200 – 300 aircraft, many of which never made it to the target area. Those that did often dropped their bombs on targets of opportunity.
Matters began to change rather quickly in late 1941. The lethality of British raids increased dramatically thanks to the improvements to navigational equipment and the introduction of twin-engine DH 98 Mosquito aircraft in the pathfinder role to mark targets for the RAF “heavies”. In the spring of 1942 the Bomber Command launched a night-time bombing offensive against Germany, which culminated with operation “Millennium” on the night of May 30 – 31, 1942 when 1 042 RAF bombers dropped bombs on the city of Cologne. The attack was the first of the so called “Thousand Bomber” raids.
Overwhelmed by the massive attack the German air defenses managed to knock down a mere 3.8 percent of the British force. There was more of the same two nights later when 800 RAF bombers struck the city of Essen. Only 37 British machines were lost in that operation.

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The Luftwaffe brass responded immediately with orders to increase the use of the Junkers Ju 88 aircraft in the night fighting role. At the same time Heinkel and Focke-Wulf received the urgent requirement for a new purpose-built night fighter aircraft. Generalfeldmarschall Erhard Milch, Generalluftzeugmeister der Luftwaffe1 was immensely impressed with the British DH 98 Mosquito and demanded that a German equivalent (with much improved performance) be immediately developed. The British Mosquito, made almost entirely of wood, was designed as a twin-engine multi-role aircraft that could be employed as a fast bomber or a reconnaissance platform. The Mosquito’s maiden flight demonstrated that the aircraft had a superb performance and remarkable agility, despite its fairly big size, which made the design ideal not just in the bomber or reconnaissance roles, but as a day or night fighter as well.
When they first appeared in front-line service in May 1942, the Mosquitoes came as a total surprise to German air defense units. Not only did they operate at altitudes between 8 000 and 9 000 m, they were also extremely fast. The twin Rolls-Royce Merlin 21 engines developing 1 460 HP each allowed the “Wooden Wonder” to cruise comfortably at 424 km/h and gave it a top speed of 604 km/h. Equipped with external fuel tanks a Mosquito could take a 2 000 kg bomb load all the way to Berlin. Later variants, powered by improved engines, could fly even faster and operate at higher altitudes. The fastest Mosquito version, the P. R. Mk. VIII had a top speed of 697 km/h, while the highest flying night fighting variant, the NF Mk. XV, had a service ceiling of 13 097 m.
During a staff meeting on August 18, 1942 Generalluftzeugmeister GFM Erhard Milch demanded that the platform should be developed to utilize the available stocks of Junkers Jumo 211 F engines. Several weeks later, on September 11, 1942 a decision was made to make a greater use of “Homogenholz” plywood in the design of airframes. Thus the idea was born to build a German version of the Mosquito – a fast bomber of mainly wooden construction powered by a pair of Junkers Jumo 211 engines.
Focke-Wulf design bureau was the first to respond to the RLM requirement. They presented the “Entwurf 1” (Project 1) - a preliminary design of an unarmed fast bomber of mixed construction powered by two Jumo 211 Fs.
Kurt Tank2 had been the chief designer at Focke-Wulf since 1934 and had already made his mark with such world-class designs as the four-engine Focke-Wulf Fw 200 Condor bomber, or the Focke-Wulf Fw 190 fighter. It was therefore no wonder that he would be personally responsible for the new project. The chief engineer Ludwig Mittelhuber became the leader of the design development team, while Ernst Nipp would oversee the actual design work. Gotthold Mathias’s team was responsible for the new aircraft’s aerodynamics and Herbert Wolf would oversee flight performance calculations.


 

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The airframe’s structure was to be 50 percent wood, 39 percent steel and 11 percent other materials. Over one half of all wooden elements of the design would be manufactured using beech plywood (0.8 mm to 6 mm thick), and solid or pressed beech wood. The “Entwurf 1” had the following characteristics when it was first submitted to the RLM on September 22, 1942:
Application: fast conventional bomber.
Airframe design: a twin-engine, high-wing monoplane with a monococque fuselage made of plywood with retractable landing gear.
Powerplant: two Junkers Jumo 211 F engines developing 1 340 HP each.
All-up weight: 7 200 kg, range of 2 000 kg with a 500 kg bomb load.
Design strength: N = 4 at 7 200 kg.
Crew: 1
Defensive armament: none.
Bomb load: 1 SC 250 bomb, or 1 SC 500 bomb, or 1 SD 1000 bomb.
Armor protection: pilot’s seat and headrest (65 kg).
Fuel and oil: self-sealing tanks with total capacity of 1 920 l placed in the fuselage. Two armored oil tanks in engine nacelles holding 80 l each.
Radios: FuG 16 Z, FuG 25.
In late September 1942 Milch requested that the project should be modified to include defensive armament. On October 7, 1942 the “Entwurf 1” was re-submitted to the RLM with the following changes:
All-up weight: 7 500 kg, range of 2 000 kg with a 500 kg bomb load.
Design strength: N = 4 at 7 500 kg.
Defensive armament: two fixed aft-firing MG 151 guns with 200 rounds of ammunition per gun.
Gun sight: BZ A 20
Armor protection: none
Fuel and oil: three self-sealing fuel tanks in the fuselage with total capacity of 1 400 l. Two armored engine oil tanks in engine nacelles holding 80 l each.
GM 1 installation: an option to include two GM 1 tanks holding 160 l each allowing the continuous operation of the system for 30 minutes with a range of 1 500 km.
Bomb load:
– one SD 1000 bomb (overweight configuration)
– 2 SD 500 bombs (overweight configuration)
– 1 SC 500 bomb
– 2 SC 250 bombs
– 1 F 5 canister with 223 SD 2 HE munitions, or 191 B1 E 2 incendiary munitions, or 69 BB 3 incendiaries, or 138 NB 2 smoke canisters, or 42 SC 10 fragmentation bombs
– 1 F 2,5 canister with 118 SD 2 HE munitions, or 113 B1 E 2 incendiary munitions, or 32 BB 3 incendiaries, or 70 NB 2 smoke canisters, or 23 SC 10 fragmentation bombs
– 8 AB 36 canisters
– 8 AB 42 canisters
All types of ordnance could be carried internally.
Tank’s team also worked on the night fighter version of the aircraft designated “Entwurf 2”, which was submitted to the RLM on September 22, 1942. The night fighter variant had the following design characteristics:
Application: night fighter.
Airframe design: a twin-engine, high-wing monoplane with a monococque fuselage made of plywood with retractable landing gear.
Powerplant: two Junkers Jumo 211 F engines developing 1 340 HP each.
All-up weight: 7 450 kg
Design strength: N = 4 at 7 450 kg.
Crew: 2 (pilot and observer/radio operator)
Armament: Two fixed forward-firing MK 103 cannons, Two fixed forward-firing MG 151 cannons.
Armor protection: 100 kg
Fuel and oil: self-sealing tanks with total capacity of 1 850 l placed in the fuselage. Two armored engine oil tanks in engine nacelles holding 80 l each.
Radios: FuG 17, Peil G VI, FuBl 2 F, FuNG 101, FuG 25a, FuG 28a, FuG 212.

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In the meantime German air defenses had a very difficult time trying to intercept the RAF Mosquitoes. The incoming British aircraft had to be picked up by radar before their position could be relayed to the closest night fighter unit. By the time the alert aircraft were scrambled and climbed to the Mosquito’s operating ceiling any hope for a successful intercept had been all but gone. Knocking down a Mosquito thus became a simple matter of luck. It was painfully clear that the only way to counter the threat was to develop an aircraft that could outperform its British counterpart.
However, the difficulties with access to raw materials and the limited capacity of German aircraft production industry placed significant limitations on the new design. Below are the technical requirements for an all-weather night fighter as formulated by the TechnischesAmt des Reichsluftfahrtministeriums:
– aircraft must be powered by engines that are currently in serial production,
– offensive armament will consist of four forward-firing 30 mm or 30 and 20 mm cannons,
– flight endurance will be no less than 2.75 hours,
– airframe design will make only limited use of steel and light metals,
– flight test program must commence no later than 12 months after the orders have been placed.
Kurt Tank’s “Entwurf 2” seemed to fit the RLM’s specification quite closely. To pay tribute to the chief designer the proposed aircraft would also receive the “Ta” designation in place of the customary “Fw” prefix used in other Focke-Wulf designs.

The RLM’s standard practice was to assign a numerical designation to each new design. Fixed wing aircraft were assigned number 8 followed after a dash by a three-digit group. The original RLM designation for “Entwurf 2” was 8-211. The aircraft engines were all assigned number 9, so Junkers powerplant intended for the new aircraft was designated 9-211. The similarity of the designations of the aircraft and its powerplants could lead to mistakes in documentation or in the procurement of spare parts. Tank received designations 152, 153 and 154 for his aircraft. Numbers 152 and 153 had already been reserved for the development versions of his Fw 190 series fighters, so the original Focke-Wulf designation of the “Entwurf 2” – Ta 211 – was changed to Ta 154.
“Entwurf 3” was another Ta 154 proposal submitted by Tank’s team to the RLM on October 14, 1942. Unlike the previous design concepts, “Entwurf 3” featured tricycle landing gear arrangement. In this configuration forward visibility from the cockpit was much improved during take-offs and landings, a much desired feature for a night fighter. The characteristics of the “Entwurf 3” were as follows:
Airframe design: a twin-engine, high-wing monoplane with a monococque fuselage made of plywood with retractable, tricycle landing gear.
Powerplant: two Junkers Jumo 211 F engines developing 1 340 HP each.
All-up weight: 8 250 kg
Design strength: N = 5.5 at 8 250 kg.
Crew: 2 (pilot and observer/radio operator)
Armament: Two fixed forward-firing MK 108z cannons with 110 rounds of ammunition, two fixed fuselage-mounted MG 151 weapons with 250 rounds of ammunition, one MK 108 cannon with 150 rounds mounted in the fuselage at a 45° angle.
Gun sight: reflector type.
Armor protection: 150 kg of armor plating around the forward cockpit area.
Fuel and oil: two self-sealing tanks with total capacity of 1 600 l placed in the fuselage. Two armored engine oil tanks in engine nacelles holding 70 l each.
Radios: FuG 17e, Peil G VI, FuBl 2 F, FuNG 101, FuG 25a, FuG 28a, FuG 212.

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Tank’s proposal for the use of plywood and solid wood in the construction of the airframe sat well with the decision-makers at the RLM. Experts at the Technisches Amt understood very well that the front-line night fighter types in service with the Luftwaffe (Bf 110s and Ju 88s) had been approaching the limits of their development potential and would have to be replaced with a new generation fighter. Tank’s design seemed to fit the bill not only because it would be manufactured using non-strategic materials, but also because its projected performance figures looked impressive.
As early as mid October 1942 Milch issued orders to discontinue the development of the fast bomber version and to focus on the design of the all-weather night fighter aircraft powered by Junkers Jumo 211 engines. The Focke-Wulf plant was supposed to receive orders for the production of the initial batch of 50 aircraft of the new type.
The Luftwaffe’s commander, Reichsmarschall Hermann Göring, gave the project a green light on October 20, 1942 and three days later the official document containing design characteristics of the Ta 211 night fighter was filed with the RLM.
Following Milch’s orders of October 30, 1942 the task to manufacture and test the new fighter went to Focke-Wulf’s plant at Langenhagen near Hannover. On November 13, 1942 Technisches Amt officially changed the project’s designation to Ta 154 and placed an order for the construction of ten prototype machines (Ta 154 V1 to Ta 154 V10). On January 18, 1943 the key personnel were summoned to Berlin to review the progress of the Ta 154 project. One of the issues discussed in the meeting was the difficulties in sourcing specialists with experience in application of wood in aircraft manufacturing. The obvious choice would have been skilled workers employed in the production of World War I aircraft, but even those were hard to find since in most cases they had been drafted into active service. Another problem was the Ta 154’s proposed powerplants. It became obvious that in the long run the Jumo 211 engines would need to be replaced with more powerful units. To make matters worse, it appeared that the use of flame dampers and the installation of FuG 212 aerials would reduce the aircraft’s top speed by some 35 to 45 km/h. The Jumo 213 engine, the most promising alternative to the 211, was still undergoing tests and by the looks of things was not going to go into full-scale production any time soon. Milch, who viewed the Ta 154 project as a stop-gap measure before the introduction of the He 219 night fighter, did not exactly help when he demanded that Tank’s machine should be armed with four MK 103 cannons, which would necessitate a complete re-design of the aircraft’s fuselage.

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The troubles did not end there. In June 1943 Focke-Wulf management received the requirements of chiefs of different Luftwaffe commands. It was the wish of the General der Jagdflieger (inspector general of the fighter command) that all Ta 154s should be equipped with the GM-1 installation. The General der Kampfflieger (inspector general of the bomber command) wanted bomb bays to make the Ta 154 a close match for the British Mosquito, while the General der Aufklärungsflieger (inspector general of reconnaissance command) thought the Ta 154 would make an ideal reconnaissance platform.
The threat to German aircraft industry posed by Allied (mainly American) bombings resulted in orders to disperse the production of the Ta 154 and to make a wider use of a network of subcontractors. As a result three production areas were established: Fertigungskreis Schlesien (Silesian production area) tasked with the production of the Ta 154 A-2 (single-seat day fighter), B-1 (two-seat night fighting version) and C-1 (another two-seat night fighter variant); Fertigungskreis Thüringen (Thuringia production area) would see the production of the A-1 machines (two-seat day fighter version), A-2, B-1, B-2 (single-seat day fighter) and the C-4 (two seat day fighter-bomber); the A-1, A-2, B-1, B-2 and C-4 models would be assembled in Fertigungskreis Warthegau (Warthe District production area).
Some of the preliminary work included stress testing of the aircraft’s fuselage, since it was especially vulnerable to high loads because of the weight of internally mounted armament and radio gear. To this end a mock-up of the Ta 154 fuselage underwent a series of underwater tests at Graf Zeppelin test site at lake Alatsee near Füssen. The tests that began in December 1942 included the towing of the instrumented fuselage section behind a speedboat to establish the actual strength of the design.

 

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