POWER PLANT: One Daimler-Benz DB 606A-2, twenty-four-cylinder liquid-cooled coupled engine, rated at 2,350 hp
PERFORMANCE: 367 mph at 14,755 ft
COMMENT: The Heinkel He 119 was an experimental single-propeller monoplane with two coupled engines, developed in Germany. A private venture by Heinkel to test radical ideas by the Günter brothers, the He 119 was originally intended to act as an unarmed reconnaissance bomber capable of eluding all fighters due to its high performance.
Design was begun in the late summer of 1936. A notable feature of the aircraft was the streamlined fuselage, most likely as an evolutionary descendant of the 1932-vintage Heinkel H 70 record-setting single-engined mailplane design, but without the He 70’s protruding canopy-enclosed crew accommodation existing anywhere along the exterior. Instead, the He 119’s forward fuselage featured an extensively glazed cockpit forming the nose itself, heavily framed with many diagonally braced windows immediately behind the propeller spinner’s rear edge. Two of the three-man crew sat on either side of the driveshaft, which ran aft to a “power system”, a coupled pair of Daimler-Benz DB 601 engines mounted above the wing center-section within the fuselage, mounted together within a common mount (the starboard component engine having a “mirror-image” centrifugal supercharger) with a common gear reduction unit fitted to the front ends of each component engine, forming a drive unit known as the Daimler-Benz DB 606, the first German aircraft to use the “high-power” power plant system meant to provide German aircraft with an aviation power plant design of over 2,000 PS output capability.
The DB 606 engine was installed just behind the aft cockpit wall, near the center of gravity, with an enclosed extension shaft passing through the centerline of the extensively glazed cockpit to drive a large four-blade variable-pitch airscrew in the nose. An evaporative cooling system was used on the first aircraft (V1), with the remaining prototypes receiving a semi-retractable radiator directly below the engine to augment cooling during take-off and climb.
Only eight prototypes were completed and the aircraft did not see production, mainly because of the shortages of DB 601 “component” engines to construct the 1,500 kg “power systems” they formed. The first two prototypes were built as land planes, with retractable landing gear. The third prototype (V3) was constructed as a seaplane with twin floats. This was tested at the “Erprobungsstelle Travemünde” military seaplane test facility on the Baltic coast, and was scrapped in 1942 at Heinkel’s factory airfield in the coastal Rostock-Schmarl community, then known as Marienehe.
On November 1937, the fourth prototype (V4) made a world class-record flight in which it recorded an airspeed of 314 mph, with a payload of 1,000 kg, over a distance of 1,000 km. The four remaining prototypes were completed during the spring and early summer of 1938, the V5 and V6 being A-series production prototypes for the reconnaissance model, and the V7 and V8 being B-series production prototypes for the bomber model.
These four aircraft were three-seaters with a defensive armament of one 7.92 mm MG 15 machine gun in a dorsal position, V7 and V8 having provision for a normal bombload of three 250 kg bombs or maximum bombload of 1,000 kg. V7 and V8 were sold to Japan in May 1940, and extensively studied; the insights thus gained were used in the design of the Yokosuka R2Y1 “Keiun” The remaining prototypes served as engine test-beds, flying with various prototype versions of the DB 606 and DB 610 (twinned Daimler-Benz DB 605) and the experimental DB 613 (twinned Daimler-Benz DB 603).
In 1944, a high-speed bomber development, designed as a private venture by Heinkel to test radical ideas by the Günter brothers, was the Heinkel He 519. It was designed to use the 24-cylinder Daimler-Benz DB 613, but the aircraft remained a concept and was abandoned at the end of the war. (Ref.: 24).
POWER PLANT: Two Daimler-Benz DB 610A-1/B-1 liquid-cooled engines, rated at 2,950 hp each
PERFORMANCE: 407 mph at 22,300 ft
COMMENT: Prior to the receipt of RLM instructions to prepare for production of the Daimler-Benz DB 606-powered Junkers Ju 288, the Junkers construction bureau had introduced some major changes in the basic design of the bomber which had resulted in the Ju 288C intended specifically for the Daimler-Benz engines. One of the most noticeable external changes was the provision of a redesigned and elongated nose which increased overall length substantially. Defensive armament was supplemented by a ventral barbette aft of the bomb-bay, instrumentation was greatly improved and the structure was strengthened.
The first C-series prototype, the Ju 288 V101 with DB 606A/B engines, was completed in August 1942, this being followed within a few weeks by the similar Ju 288 V102.
The Ju 288C programme continued with high priority, production standards were finalized, and modifications dictated by flight test programme, together with production features, were embodied by the next prototype, the Ju 288C V103. Fitted with the more powerful DB 610 engines and introducing provision for underwing weapons racks, the Ju 288C V103 had the full complement of four remotely-controlled gun barbettes, and was flown for the first time in spring of 1943.
The Junkers Ju 288C V103 was intended as the first production prototype for the Ju 288C-1, and was rapidly followed by the Ju 288 V104 and V105 which were flown in May 1943, and the V106 which flew in June, these all being powered by DB 610A/B engines and differing only in minor items of equipment. At this time, it was proposed to manufacture the bomber in three versions which differed primarily in the defensive armament fitted. The Ju 288C-1 was to have a chin, dorsal and ventral barbettes each mounting twin MG 131 machine guns, and a tail barbette mounting a MG 151 cannon; the Ju 288C-2 was to have had twin MG 151 cannon in each chin, dorsal and ventral barbettes, and either two MG 131s in tail barbette or four MG 131 in a manned tail turret, and the Ju 288C-3 was to have been a night bomber with defensive armament restricted to twin MG 131s in a ventral barbette.
Suddenly, in June 1943, Junkers was informed by the Technische Amt that the entire “Bomber B” programme had been abandoned owing to increasing shortages of strategic materials and the effect that the launching of a major production program for a new bomber would have on existing production programmes at a critical phase in the conflict. However, despite the cancellation of the programme, Junkers completed two additional machines, the Ju 288 V107 and V 108, which were flown in July 1943, other airframes on the assembly line being scrapped. Some flight testing of the Ju 288 was continued until the summer of 1944, by which time a least 17 of the 22 prototypes had crashed while engaged in flight development. With the termination of the test programme, several of the surviving Ju 288B- and C-series prototypes were transferred to the Luftwaffe, and fitted with ventral gun pods similar to that fitted to the Junkers Ju 88P-4 and mounting a single 50 mm BK 5 (KwK 39) cannon, these saw limited operational use during the closing stages of the conflict (Ref.:7).
POWER PLANT: Two BMW 801MA radial engines, rated at 1,677 hp each
PERFORMANCE: 388 mph
COMMENT: The Junkers Ju 288, originally known within the Junkers Company as the EF 074, was a German bomber project designed during WW II, which only ever flew in prototype form. The first of an eventual 22 development aircraft flew on 29 November 1940.
The Ju 288 was the winner of the “Bomber B” contest, although the contest was started by Junker’s submission of the EF 074 and their selection was never really in doubt. “Bomber B” intended to replace the Junkers Ju 88 with a design that was larger, offer cabin pressurization for high altitude work, have longer range, a much greater war load, be even faster, and have improved defensive firepower. The design would replace all the bombers then in German Luftwaffe service.
Delivering all of these requirements in a single airframe demanded much more powerful engines, and all of the “Bomber B” concepts relied on the Junkers Jumo 222 engine to deliver this power. Ultimately, the Jumo 222 was a failure in spite of massive effort and several redesigns over a period of several years. No suitable replacement was ever forthcoming, dooming the Ju 288 program, and leaving the Luftwaffe with older bomber designs during the second half of World War II.
Junkers had been outlining a variety of improved models of the Ju 88 since 1937, powered by the planned Jumo 222 multibank engine, or Jumo 223 inline multibank diesel of greatly increased power of at 2,000 horsepower. The EF 074 was essentially a scaled-up Ju 88, sharing its general layout and most of its fuselage and wings with extensions in various places. The nose was redesigned with a more streamlined “stepless” cockpit, having no separate windscreen panels for the pilot and co-pilot. This layout allowed cabin pressurization to be more easily implemented. This design approach had been growing in favour, subsequently appearing in various German types, notably the Heinkel He 111P and H’s.
No serious work was undertaken on these versions, but after Heinrich Hertel left Heinkel and joined Junkers in 1939, the EF 074 design was submitted to the RLM in May 1939. Accordingly, the RLM sent out the specifications for the “Bomber B” design competition in July, the Ju 88 retroactively becoming the second aircraft to be designated “Bomber A”, as the June 1936 specification for the Heinkel He 177 also had that name. The “Bomber B” program aimed at replacing all of the medium bombers in the Luftwaffe inventory with a new design based on the EF.74 or something with equal performance. “Bomber B” was intended to have even better speed than the Ju 88, high-altitude cruising with a pressurized cockpit, heavier defensive armament, range allowing it to cover any point in the British Isles, and a 4,000 kg war load, double that of the earlier generation bombers. A number of companies returned proposals, but these were to some extent a formality, the EF.74 had already been selected as the winner, and of the rest of the designs submitted, only the Focke-Wulf Fw 191 and Dornier Do 317 progressed even as far as prototypes, and the Henschel Hs 130 coming under consideration as a late entrant.
Work began on building prototypes in early 1940, and the first example was completed by mid 1940. Power was supposed to be supplied by two Junkers Jumo 222 six-bank, four cylinders per bank, over 2.000 hp output class powerplants, but problems with the Jumo 222’s development — as with almost every new concept for over 2.000 hp output reciprocating aircrafts engienes then underway in the Third Reich — meant the first prototypes flew with BMW 801 radial engines, instead. The first flight-quality Jumo 222s did not arrive until October 1941, and even at this point it was clear they were nowhere near ready for full-scale production. When it became apparent the Jumo 222 was not likely to become a viable powerplant, in May 1942, Junkers proposed replacing them, for their projected Ju 288C version, with the much heavier Daimler Benz DB 606‘s instead; the same 1.5 tonne, twin-crankcase „weldet-together engines“ that Reichsmarschall Hermann Göring complained about some three months later, regarding the Heinkel He 177’s own endless powerplant troubles
Late in January 194, after protracted ground trials, the first prototype, the Ju 288 V1, was flown for the first time. It was powered by two BMW 801 MA engines, each rated at 1,600 hp. The defensive armament arrangement reverted to that of the original EF 074 proposal, dummy barbettes being mounted in forward dorsal and aft ventral positions.
During the early spring 1941, the first prototype was joined by the Ju 288 V2 which differed from its predecessor only in having spoiler-type dive brakes in place of slatted-type surfaces which were also featured by the Ju 288 V3, this third prototype commencing flight trials during the early summer, by which time work had begun on a further series of prototypes, the first of these being the Ju 288 V4.
The Ju 288’s intricate main landing gear system’s design proved to be troublesome. Such a complex main gear design, with only the single pivoting retraction point for its oleo struts taking the primary stress of touchdown, was likely only one of the many potential sources of trouble causing the Ju 288’s main gear units to repeatedly collapse on touchdown.
Although the Junkers Ju 288 never even reached production status, let alone official operational service, the aircraft did see limited combat duty. In 1944, following the cancellation of the Ju 288 programme, the surviving A and C series prototypes were hurriedly fitted with defensive armament and equipment and deployed as reconnaissance bombers on the Western Front. Very few missions were flown, owing to the scarcity of aviation fuel and spare parts, and the unresolved problems with the aircraft’s power plant and undercarriage. It is believed] that the few Ju 288’s were attached to the same unit operating the small number of Junkers Ju 388 reconnaissance planes that saw service (Ref.: 7. 24).
POWER PLANT: Two BMW 801A radial engines, rated at 1,539 hp each
PERFORMANCE: 385 mph at 20,800 ft
COMMENT: The Focke-Wulf Fw 191 was a prototype German bomber of WW II, as the Focke-Wulf firm’s entry for the Bomber B advanced medium bomber design competition. Two versions were intended to be produced, a twin-engine version using the Junkers Jumo 222 engine and a four-engine variant which was to have used the smaller Daimler-Benz DB 605 engine. The project was eventually abandoned due to technical difficulties with the engines
In July 1939, the RLM issued a specification for a high-performance medium bomber (the “Bomber B” program). It was to have a maximum speed of 370 mph and be able to carry a bomb load of 4,000 kg to any part of Britain from bases in France or Norway. Furthermore, the new bomber was to have a pressurized crew compartment, of the then-generalized “stepless cockpit” design (with no separate windscreen for the pilot) pioneered by the Heinkel He 111P shortly before the war and used on most German bombers during the war, remotely controlled armament, and was to utilize two of the new 2,466 hp class of engines then being developed (Jumo 222 or DB 604), with the Jumo 222 being specified for the great majority of such twin-engined designs, that Arado, Dornier, Focke-Wulf and Junkers had created airframe designs to use. The Arado Ar E340 was eliminated. The Dornier Do 317 was put on a low-priority development contract; and the Junkers Ju 288 and Focke-Wulf Fw 191 were chosen for full development.
Overall, the Fw 191 was a clean, all-metal aircraft that featured a shoulder-mounted wing. Two 24-cylinder Junkers Jumo 222 engines (which showed more promise than the DB 604 engines) were mounted in nacelles on the wings. An interesting feature was the inclusion of the Multhopp-Klappe, an ingenious form of combined landing flap and dive brake fitted in four sections to the wing trailing edges, which was developed by engineer H. Multhopp. The entire fuel supply was carried in five tanks located above the internal bomb bay, and in two tanks in the wing between the engine nacelles and fuselage.
The tail section was of a twin fins and rudders design, with the tailplane having a small amount of dihedral. The main landing gear legs retracted to the rear and rotated 90° to lie flat in each engine nacelle with the mainwheels resting atop the lower ends of the gear struts when fully retracted, much like the main gear on the production versions of the Junkers Ju 88 already did. Also, the tailwheel retracted forwards into the fuselage. A crew of four sat in the pressurized cockpit, and a large Plexiglas dome was provided for the navigator; the radio operator could also use this dome to aim the remotely controlled rear guns.
The Fw 191 followed established Luftwaffe practice in concentrating the crew in the nose compartment, also including the nearly ubiquitous “Bola”, inverted-casemate undernose gondola for defensive weapons mounts first used on the Junkers Ju 88A before the war, and in the use of a “stepless cockpit”, having no separate windscreen for the pilot, as the later -P and -H versions of the Heinkel He 111 already did. This was pressurised for high-altitude operations. The proposed operational armament consisted of one 20 mm MG 151 cannon in a chin turret, twin 20 mm MG 151 in a remotely controlled dorsal turret, twin 20 mm MG 151 in a remotely controlled ventral turret, a tail turret with one or two machine guns and remotely controlled weapons in the rear of the engine nacelles. However, different combinations were mounted in the prototype aircraft. Sighting stations were provided above the crew compartment, as well as at the ends of the aforementioned “Bola” beneath the nose.
The aircraft had an internal bomb bay. In addition, bombs or torpedoes could be carried on external racks between the fuselage and the engine nacelles. The design was to have had a maximum speed of 370 mph, a bomb load of 4,000 kg, and a range allowing it to bomb any target in Britain from bases in France and Norway.
It is said that the intention to use electric power for almost all of the aircraft’s auxiliary systems (also a fact for the successful Focke-Wulf Fw 190 fighter), requiring the installation of a large number of electric motors and wiring led to the nickname for the Fw 191 of “Das fliegende Kraftwerk” (the flying power station). This also had the detrimental effect of adding even more weight to the overburdened airframe, plus there was also the danger of a single enemy bullet putting every system out of action if the generator was hit. On its maiden flight early in 1942, the Focke-Wulf Fw 191 V1 showed immediate problems arising from the lower rated engines not providing enough power, as was anticipated. Additional problems occurred with the Multhopp-Klappe, which presented severe flutter problems when extended, and pointed to the need for a redesign. At this point, only dummy gun installations were fitted and no bomb load was carried. After completing ten test flights, the Fw 191 V1 was joined by the similar V2, but only a total of ten hours of test flight time was logged. The 2,466 hp Junkers Jumo 222 engines which would have powered the Fw 191 proved troublesome. In total only three prototype aircraft, V1, V2 and V6, were built. The project was crippled by engine problems and an extensive use of electrical motor-driven systems. Problems arose almost immediately when the Junkers Jumo 222 engines were not ready in time for the first flight tests, so a pair of 1,539 hp BMW 801A radial engines was fitted. This made the Fw 191 V1 seriously underpowered. Another problem arose with the RLM’s insistence that all systems that would normally be hydraulic or mechanically activated should be operated by electric motors.
At this point, the RLM allowed the redesign and removal of the electric motors (to be replaced by the standard hydraulics), so the Fw 191 V3, V4 and V5 were abandoned. The Fw 191 V6 was then modified to the new design, and also a pair of specially prepared Junkers Jumo 222 engines were fitted that developed 2,170 hp for takeoff. The first flight of the new Fw 191 took place in December 1942. Although the V6 flew better, the Junkers Jumo 222 was still not producing their design power, and the whole Jumo 222 development prospect was looking bad due to the shortage of special metals for it. The Fw 191 V6 was to have been the production prototype for the Fw 191A series.
Due to the German aviation engine industry having ongoing problems in producing power plant designs capable of output levels matching or exceeding the 2,100 hp figure throughout the entirety of the war years, that had any demonstrable level of combat-ready reliability, the Jumo 222 engines were having a lot of teething problems, and the Daimler Benz DB 604 had already been abandoned, a new proposal was put forth for the Fw 191B series.
The Fw 191 V7 through V12 machines were abandoned in favor of using the Fw 191 V13 to install a pair of Daimler Benz DB 606 or 610 “power system” engines, which were basically coupled pairs of either DB 601 or 605 12-cylinder engines. Their lower power-to-weight ratio, however, from their 1.500 kg weight apiece for each “power system”, meant that the armament and payload would have to be reduced. It had already been decided to delete the engine nacelle gun turrets, and to make the rest manually operated. Five more prototypes were planned with the new engine arrangement, V14 through V18, but none were ever built, possibly from the August 1942 condemnation by Reichsmarschall H. Göring of the coupled “power system” DB 606 and 610 power plants as “welded-together engines, in regards to their being the primary cause of the unending series of power plant problems in their primary use, as the engines on Heinkel’s He 177A “Greif”, Germany’s only production heavy bomber of World War II.
One final attempt was made to save the Focke-Wulf Fw 191 program, this time the Fw 191C was proposed as a four engined aircraft, using either the 1,322 hp Junkers Jumo 211F, the 1,332 hp Daimler-Benz DB 601E, the 1,455 hp Daimler-Benz DB 605A or similar rated DB 628 engines. Also, the cabin would be unpressurized and the guns manually operated, with a rear step in the bottom of the deepened fuselage — in the manner of the near-ubiquitous “Bola” gondola used by the majority of German bombers for ventral defense under the nose — being provided for the gunner.
However, at this time, the whole “Bomber B” program had been canceled, due mainly to no engines of the 2,500 hp class being available, which was one of the primary requirements in the “Bomber B” program. Although the Fw 191 will be remembered as a failure, the air frame and overall design eventually proved themselves to be sound; only the underpowered engines and insistence on electric motors to operate all the systems eventually doomed the aircraft. All in all, there were only three Focke-Wulf Fw 191s ever built (V1, V2 and V6), and no examples of the Fw 191B or C ever advanced past the design stage. The RLM kept in reserve for Focke-Wulf the future number: Fw 391 for follow-up designs, but nothing ever developed. The project was eventually scrapped (Ref.: 24).
POWER PLANT: Two Junkers Jumo 004B-1 turbojet engines, rated at 900 kp each
PERFORMANCE: 461 mph at 20,000 ft
COMMENT: In late 1940, the Reichsluftfahrtministerium (RLM, Reich Air Ministry), offered a tender for a jet-powered high-speed reconnaissance aircraft with a range of 1,340 mi. Arado was the only company to respond, offering their E.370 project, a high-wing conventional-looking design with a Junkers Jumo 004 tubojet engine under each wing.
Arado estimated a maximum speed of 480 mph at 20,000 ft, an operating altitude of 36,000 ft and a range of 1,240 mi. The range was short of the RLM request, but they liked the design and ordered two prototypes as the Arado Ar 234. These were largely complete before the end of 1941, but the Jumo 004 engines were not ready, and would not be ready until February 1943. When they did arrive they were considered unreliable by Junkers for in-flight use and were cleared for static and taxi tests only. Flight-qualified engines were finally delivered, and the first prototype, the Ar 234 V1 made its first flight on July 1943 at Rheine Airfield.
By September 1943, four prototypes were flying and four more prototypes under construction. The sixth and eighth aircraft of the series were powered with four BMW 003 turbojet engines instead of two Jumo 004s, the sixth having four engines housed in individual nacelles and the eighth flown with two pairs of BMW 003s installed within “twinned” nacelles underneath either wing. These were the first four-engine jet aircraft to fly.
The projected weight for the aircraft was approximately 8 tonnes. To reduce the weight of the aircraft and maximize the internal fuel the eight prototype aircraft were fitted with the original arrangement of trolley-and-skid landing gear, intended for the planned operational, but never-produced Arado Ar 234A version.
Arado did not use the typical retractable landing gear. Instead, the aircraft was to take off from a jettisonable three-wheeled, tricycle gear-style trolley and land on three retractable skids, one under the central section of the fuselage, and one under each engine nacelle.
The RLM had already seen the promise of the design and in July 1943 had asked Arado to supply two prototypes of a “Schnellbomber” (“Fast bomber”) version as the Arado Ar 234B. Since the original skid-equipped Ar 234A’s fuselage design was very slender and filled with fuel tanks, there was no room for an internal bomb bay and the bombload had to be carried on external racks.
Since the cockpit was directly in front of the fuselage, the pilot had no direct view to the rear, so the guns were aimed through a periscope, derived from the type used on German World War II tanks, mounted on the cockpit roof. The Ar 234B version was modified to have fully retractable tricycle landing gear, with the mid-fuselage very slightly widened to accommodate the forward-retracting main gear units, the nose gear retracting rearwards. The first twin-Jumo 004 powered prototype Ar 234B (V 7) flew on 10 March 1944 for the first time and made history on 2 August 1944 as the first jet aircraft ever to fly a reconnaissance mission.
Production B-series aircraft were slightly wider at mid-fuselage to house the main landing gear, with a central fuel tank present (the middle one of a trio of fuel tanks) in the mid-fuselage location forward tank, central and an aft. Under tests with maximum bombload consisting of three SC 500 bomb, the Ar 234 V9 aircraft could reach 418 mph at 16,000 ft. This was still better than any bomber the Luftwaffe had at the time, and made it the only bomber with any hope of surviving the massive Allied air forces. The normal bombload consisted of two 500 kg bombs suspended from the engines or one large 1,000 kg bomb semi-recessed in the underside of the fuselage with maximum bombload being 1,500 kg. In case the full bomb load was to be deployed on an Ar 234B for an operational sortie, fuel had to be reduced and two Walter HWK 109-500A-1 “Starthilfe” (Take-off assistance) liquid fuel jettisonable JATO rocket pods delivering 500kp thrust each were fixed under each wing.
Production lines were already being set up, and 20 Arado Ar 234B-0 pre-production aircraft were delivered by the end of June 1943. Later production was slow, as the Arado plants were given the simultaneous tasks of producing aircraft from other bombed-out factories hit during the USAAF’s “Big Week”, and the ongoing license-building and nascent phasing-out of Heinkel’s heavy He 177A bomber, even as the Arado firm was intended to be the sole subcontractor for the Heinkel He 177B (He 277) series strategic bomber, meant to start construction at Arado as early as October 1944. Meanwhile, several of the Ar 234 prototypes – including a few of the surviving six twin-engine Jumo 004-powered “trolley-and-skids” Ar 234A-series prototypes – were sent forward in the reconnaissance role. In most cases, it appears they were never even detected, cruising at about 460 mph at over 29,900 ft, with the seventh prototype achieving the first-ever wartime reconnaissance mission over the United Kingdom by a Luftwaffe-used jet aircraft.
The few 234Bs entered service in autumn and impressed their pilots. They were fairly fast and completely aerobatic. The long takeoff runs led to several accidents; a search for a solution led to improved training as well as the use of two jettisonable RATO units. The Jumo 004 engines were always the real problem; they suffered constant flameouts and required overhaul or replacement after about 10 hours of operation.
The most notable use of the Arado Ar 234 in the bomber role was the attempt to destroy the Ludendorff Bridge at Remagen. The aircraft continued to fight in a scattered fashion until Germany surrendered on 8 May 1945. Some were shot down in air combat, destroyed by flak, or “bounced” by Allied fighters during takeoff or on the landing approach, as was already happening to Messerschmitt Me 262 jet fighters. Mostly the remaining aircraft sat on the airfields awaiting fuel that never arrived.
Overall from mid-1944 until the end of the war a total of 210 aircraft were built. In February 1945, production was switched to the Arado Ar 234C variant. It was hoped that by November 1945 production would reach 500 per month. Only a few of this four engine aircraft were built before Germany finally collapsed (Ref.: 24).
POWER PLANT: Two Junkers Jumo 222 or Daimler-Benz DB 604 (both liquid-cooled) or BMW 802 (radial) piston engines PERFORMANCE: 360 mph
COMMENT: In 1939, the “Technisches Amt des Reichluftfahrtministeriums” (RLM); (Technical Office of the Reich Air Ministry) issued specification for a “Bomber B” requirement.
The Reich Air Ministry ordered the aircraft to replace the Junkers Ju 88 and Dornier Do 217 bombers by 1943. At first four manufacturers submitted plans to the Air Ministry: Arado project E.340, Dornier Do 317, Focke-Wulf Fw 191, and Junkers Ju 288. Later, Henschel was asked to submit its Henschel Hs 130 design due to the expertise of this company with its experiments with pressurized cockpits. Meanwhile, Project “Bomber B” contest winner was the Arado design, officially named Ar 340.
While the designs of all other contenders were of more conventional layout the Arado Ar 340 was designed with a central fuselage containing all four crew members. The cockpit and rear compartment were glazed and pressurized. The projected Junkers Jumo 222 engines were positioned in a unique twin-boom arrangement connected only through the wing assembly, a configuration which offered the crew better visibility. The landing gear was mounted to the load-bearing wing center-section. The tail of the aircraft was a unique design, where the tail plane did not connect the two booms but was cantilevered outwards instead, each similar to the asymmetric Blohm & Voss Bv 141B booms and tail arrangement. Also similarly, this would have provided the rear gunner with a clear range of fire directly behind. The fuselage extended forwards beyond the engines, with the gunners situated behind the cockpit, ahead of the bomb bay and wing spars. The MG 151 cannon in the tail of the central fuselage would have been controlled with remote aiming through periscopes. There were also two remote-controlled “Fernbedienbare Drehlafette FDL 131” 13mm (remotely-controlled gun turrets) to be placed above and below the fuselage.
The Ar 340 was one of the steadily growing numbers of later-war military airframe designs designed to use the troublesome Junkers Jumo 222 engine. Otherwise an innovative design, these powerful engines were selected because they would have allowed the Arado Ar 340 to carry the required payload of 5,900 kg within a relatively compact airframe, despite their still-strictly developmental nature. As the development of the Junkers Jumo 222 engines were cancelled, plans were discussed to power the Arado Ar 340 with Daimler-Benz DB 605 liquid-cooled engines or BMW 802 radial engines. Meanwhile the RLM favoured the Junkers Ju 288 and the Arado project was not pursued.
Ultimately, the entire “Bomber B project” was cancelled, primarily as a result of the failure to develop the required engines (Ref.: 24).
POWER PLANT: Two Daimler-Benz DB 603A liquid-cooled piston engines, rated at 1,750 hp each
PERFORMANCE: 348 mph at 19,685 ft
COMMENT: When the “Führungsstab der Luftwaffe” (Operations Staff of the Luftwaffe) drafted its so-called “Bomber B” requirement which was translated into a specification for issue to selected airframe manufactures in July 1939 by the “Technischen Amt des Reichluftfahrtministeriums” (RLM), (Technical Office of the RLM), its intention was nor merely the provision of successors for the Junkers Ju 88 and Heinkel He 111; its aim was also to carry the state of the art in medium bomber design a significant step forward.
The specification was noteworthy in the performance advances that it stipulated, and equally so in design innovations that it called for. The “Bomber B” had to possess a range of 2,237 miles do endow it with a radius of action sufficient to encompass the entire British Isles from bases that it was assumed would be available in France and Norway, a maximum speed of 373 mph at 19,685-22,965 ft., which compared favourably with the speeds of the best contemporary fighters, and a bomb load of 4,410 lb. It had to carry three or four crew members, possess a loaded weight of the order of 44,090 lb., and be of twin-engined configuration, utilizing the extremely advanced 24-cylinder liquid-cooled Daimler-Benz DB 604 or Junkers Jumo 222 engines then at an early stage in development, but the really radical demands of the specification were its insistence on pressurized accommodation for the crew, and the use of remotely-controlled barbettes to house defensive armament.
Initially, the specification was issued to four manufacturers: Arado, Dornier, Focke-Wulf and Junkers, although the scope of the contest was later to be broadened to include Henschel (Henschel Hs 130) when it was realized by the RLM that this company has more pressure cabin experience than any other contestants, with the possible exception of Junkers. The final proposals of the original four competing companies were submitted to the “Technisches Amt” in July 1940, and evaluation eliminated the Arado contender, the Ar 340, prototypes being ordered of each of the other contender, Dornier Do 317, Focke-Wulf Fw 191 and Junkers Ju 288.
Dornier’s proposal was based broadly on the design of the Dornier Do 217, the four crew members being housed ahead of the wing in a pressure cabin which, taking the form of a detachable compartment pressurized by tapping the superchargers of the Daimler-Benz DB 604 engines, was extensively glazed by a series of curved panels.
Two versions of the Do 317 were proposed: the simplified Do 317A, powered by two DB 603A engines (instead of the troublesome Daimler-Benz DB 604) and featuring conventional defensive armament, and the more advanced Do 317B with the heavy 1.5 tonnes apiece, counter-rotating DB 610A/B “power system” engines, remotely aimed “Fernbedienbare Drehlafette” (FDL)-style gun turrets (remotely-controlled turrets), heavier bombload, and an extended wing.
Six prototypes of the Dornier Do 317A were ordered, and the first of these, the Do 317 V1, commenced its flight test program on September 1943. The Do 317 V1 was very similar in appearance to the later Dornier Do 217K and -M subtypes, with a visually reframed slight variation of its multiple glazed-panel “stepless cockpit”, fully glazed nose design that accommodated a pressurized cabin provision, and triangular tailfins. Trials with the Do 317 V1 revealed no real performance advance over the Do 217. However, it was clear even at this point that the call for designs was to some extent a formality, as the Junkers Ju 288 design had already been selected for production. So it was decided to complete the remaining five prototypes without cabin pressurization equipment and fit them out with FuG 230 “Kehl-Straßburg” radio guidance transmitting gear to employ them as Henschel Hs 293 missile launchers. In this form, the prototypes were redesignated Dornier Do 217R. At this time, the Do 317B project was abandoned due to changing wartime conditions (Ref.: 7, 24).
POWER PLANT: Three Heinkel-Hirth HeS 011 turbojet engines, rated at 1,200 kp each
PERFORMANCE: 627 mph
COMMENT: During the summer of 1944, the Messerschmitt Me P.1102/105 project was on the drawing board at the same time as the Me P.1101 projects were designed, e. g. Me P.1101/92, Me P.1101/99 and Me P.1101/101. Several of these projects were of variable-geometry wing designs, a configuration which was a novelty in aircraft designing at that time.
The Messerschmitt Me P.1102/105 was developed as a fast bomber and heavy fighter.The variable-sweep wings were mounted in the center of the fuselage and could be swept between 15 and 50 degrees. For take-off and landing the wings were to be set at 20 degrees and for high speed flight the wings were to be set at the maximum of 50 degrees. The tail unit was of a normal configuration, with the tail planes swept back at 60 degrees.
Three jet engines powered the Me P.1102/105, two were located beneath the fuselage nose and one was located in the tail with an air intake on the top of the rear fuselage to feed this turbojet. Either three BMW 003 or Heinkel-Hirth He S 011 jet engines were to be employed. A single pilot sat in a cockpit located in the forward fuselage and three fuel tanks of 1200 liter capacity each were located behind the cockpit. The lower fuselage held an internal bomb bay and the tricycle landing gear.
The collapse of Germany ended work on this design. All Messerschmitt documentation relating to this projects series was seized by the US and was used in the development of several post-war aircraft. The Messerschmitt Me P.1102/105 project’s unusual three-engine power plant arrangement, in particular, was employed on the Martin XB-51 high-speed attack-interceptor which first flew in mid-1949 (Ref.: 17).
POWER PLANT: Four Heinkel/Hirth HeS 011 turbojet engines, rated at 1,300 kp each
PERFORMANCE: 565 mph
COMMENT: The Heinkel He 343 was a four-engine jet bomber project by Heinkel Aircraft Company in the last years of WW II. In 1944 a total of 20 of these aircraft were ordered. For shortening the development time and for re-use of existing parts, its general design was envisioned along the lines of an enlarged Arado Ar 234 “Blitz” (“Lightning”). For a choice of engines, the Junkers Jumo 004 and the Heinkel HeS 011 were planned. The DFS (Deutsche Forschungsinstitut für Segelflug), (German Research Institute for Gliding Flight) was involved in the project and created the project known as P.1068. By the end of 1944, work was nearly finished by the Heinkel engineers, with parts for the He 343 prototype aircraft either under construction or in a finished state, when the order was cancelled due to the “Jägernotprogramm (Emergency Fighter Program). Four versions were planned: the He 343A-1 bomber, the He 343A-2 reconnaissance aircraft, and the He 343A-3 and He 343B-1 “Zerstörer” (“Destroyer”) heavy fighters.
The Heinkel He 343A-1 was to be the bomber version. Depending on the engines used, the bomb load ranged between 2000 kg to 3000 kg, with 2000 kg to be carried internally, and 1000 kg to be carried externally. Trials were to be held with the Fritz X radio controlled bomb, which would have also added a third crew member. Defensive armament consisted of two fixed rear firing MG 151 20 mm cannon with 200 rounds each, which were mounted in the rear fuselage. None aircraft was completed. However, after WW II the Soviet Union utilized the design as the basis for the development of the Ilyushin Il-22, changing some of the parameters such as size and crew numbers. One prototype was built and flown. The results of the tests were used in development of the Ilyushin Il-28 (Ref: 24).
POWER PLANT: Two Heinkel-Hirth HeS 011 turbojet engines, rated at 1,300 kp each
PERFORMANCE: 659 mph at 45,900 ft
COMMENT: In 1944, Focke-Wulf Aircraft Company projected three designs of a bomber using two Heinkel-Hirth He S 011 turbojets. These bombers were known under the unofficial designation “1000x1000x1000 Bomber-Projekt A”, Projekt B and Projekt C. The designation “1000x1000x1000” meant that the aircraft could carry a 1000 kg (2205 lbs) bomb load over a distance of 1000 km (621 miles) and at a speed of 1000 km/h (621 mph).
The second design under the Focke-Wulf internal designation Fw P.031 0239/10 “3×1000 Bomber, Projekt B” was of a flying wing layout. There was a small fuselage which held the cockpit and forward landing gear. The wing was swept back at 35 degrees and the fuel load in flexible tanks was carried ahead of the main wing spar. The engines and main landing gear were located behind the main wing spar. Two Heinkel-Hirth He S 011 jet engines each developing 1300 kg of thrust were fed by air intakes located in the wing leading edge near the wing roots. The wing tips were bent downwards to act as vertical stabilizers and contained small rudders. The ailerons also served as elevators and in addition small deflectors were mounted within the jet exhaust, one of the first uses of thrust vectoring. The main landing gear retracted inwards and the nose gear swung up and forward. A single pilot sat in the extensively glazed cockpit located in the extreme nose, and no armament was planned at this stage in the development. A 1000 kg bomb load could be carried in the internal bomb bay located in the center wing. Since these designs would have taken several years to complete, the end of the war ended all development (Ref.: 17).
Scale 1:72 aircraft models of World War II
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