DFS 228 V1 (Huma Models)

TYPE: Rocket powered high-altitude reconnaissance aircraft

ACCOMMODATION: Pilot only in prone position in pressurized cockpit

POWER PLANT: One Walter HWK 109-509 bi-fuel liquid rocket engine, rated at 1,650 kp at 40,000 ft

PERFORMANCE: 435 mph at 75,459 ft

COMMENT:   Beginning in 1940, the DFS (Deutsches Forschungsinstitut für Segelflug, German Research Institute for Sailplanes) started an ambitious program to achieve supersonic flight. Since the only engines powerful enough and available at the time were rocket engines, it was realized that the solution was to have the assault on the sound barrier take place at a high altitude. It was decided to divide the program into three sections:
The first part was concerned with developing and testing of the pressurized cockpit section, the method of pilot escape in case of emergency and performance testing of rocket engines at high altitudes.
The second part was to discover the performance of various sweptback wing configurations. The DFS acquired the Heinkel P.1068 designs for a four-engined turbojet bomber with various wing sweep angles.
The third and last part was to actually build a supersonic aircraft with information learned in the above two steps, which was eventually to become the DFS 346.
The DFS decided to design a new aircraft (although much was learned in an earlier design, the DFS 54) to investigate the first part of their three-step program. Thus, in 1941, the RLM assigned the number 228 to the aircraft, and requested that the DFS 228 also be designed for high-altitude reconnaissance duties as well as research work.
The first prototype of the DFS 228 (coded D-IBFQ) was completed in 1943 by the DFS, although the control sections and landing skid were built by Schmetz Company. The fuselage of the DFS 228 V1 consisted of three circular sections: the nose section containing the cockpit; a center section which contained the landing skid, fuel tanks and a Zeiss infra-red camera; and the tail section with the Walter HWK 509A-1 or A-2 rocket engine. The wing was attached at the mid-fuselage point, and featured 4.5 degrees of dihedral. Wooden construction was used for the entire wing, with a single laminated wooden spar running from wingtip to wingtip, wooden ribs and a plywood covering.  Wide-span divided ailerons were fitted to the wing (the inner section acted as landing flaps), and lift spoilers were also fitted to the upper and lower wings. A conventional tail unit was used, also with all wooden construction. Landing was done on a retractable skid. Since the DFS 228 was to operate in extremely high altitudes, a completely pressurized cockpit was designed. Although it was thought at first that the pressure cabin could be of wooden construction, a metal compartment was built after the wooden one failed to hold sufficient pressure. The nose section was double-walled constructed with aluminum foil insulation. The V1 prototype had a conventional seated pilot’s position, but the V2 and later aircraft were to have a prone pilot position, due to the difficulty of of sealing such a large compartment with the pilot seated upright. All glazed areas were made of double layered Plexiglas and were provided with warm air circulation between layers to prevent frosting of the Plexiglas.
After pressure sealing problems became apparent on the V1 cockpit, it was decided to go with a prone pilot. An adjustable horizontal couch was provided for the pilot to lay on; all controls, oxygen supplies and cockpit equipment mounted directly to the steel tube structure which was then attached directly to the main fuselage bulkhead at the back of the cockpit. This also had the added advantage of keeping the pressurized area small. Thus it was easier to keep sealed. The new cockpit arrangement was incorporated in to the DFS 228 V2 and later aircraft.
A very interesting flight plan was arranged for the operational recognizance DFS 228. It was to be mounted above (or could be towed behind) a carrier aircraft (usually a Do 217K), where it was then carried to approximately 32.808 feet. Upon release, the DFS 228 would then ignite its rocket engine until an altitude of about 75.460-82.021 feet was reached. By this time, the DFS 228 would be over its photographic target area and after its reconnaissance mission was fulfilled, the aircraft would then make a long glide back to base.
In the case of an emergency at high altitudes, the complete pressurized nose section (with all life support equipment attached) could be jettisoned by firing four explosive bolts, or it could take place automatically when the cockpit pressure dropped below a minimum level. An automatic parachute would then deploy to stabilize and slow the descent. When a safe altitude was reached, the pilot was ejected by compressed air, and would then descend to the ground using his personal parachute. This escape procedure was successfully tested by the Soviets after the war, with a captured DFS 346, which had a similar escape system.
DFS 228 V1 flight trials were made at Hörsching, southwest of Linz, by the DFS and also by Erprobungsstelle Rechlin in late 1944. Over 40 test flights were made, and although powered flight was to take place in February 1945, none were actually made using rocket power, and none exceeded 32.808 feet. It was in these tests that the upright pilot’s position was found to be unsuitable for proper cockpit pressurization. The decision was made to go with the prone position cockpit, and was included into the DFS 228 V2, which was built and also flight tested.
The main faults found with the 228 were that it suffered from poor aileron effectiveness at high altitudes and that the elevators were very sensitive. Other than the early pressurization problems, the general handling was satisfactory and the problems would not hamper the intended role of the aircraft. A potential problem could have arisen with the use of the Walter HWK 509A1 or A-2 rocket engines, due to the fact that the flight profile meant for the rocket engine to be intermittently operated, and the possibility existed of valves and pumps freezing up at the extreme altitudes and low temperatures in which the flight was to take place. Of course, newer rocket engines were continually being developed, and perhaps some sort of heating system or the possibility of using M-Stoff and A-Stoff (methanol and oxygen) for fuels, which could have operated at much lower temperatures, could have been developed.
Although powered flight had not been attempted at the time of Germany’s collapse, the construction of a pre-production batch of 10 DFS 228A-0 aircraft had begun at Griesheim, near Darmstadt.
The DFS 228 V2 was destroyed at Hörsching in May 1945, only the forward section had parts worth salvaging. The DFS 228 V1 survived the war, and was surrendered at Ainring in the US Zone of Occupation. On June 18, 1945, it was taken by road to the US Air Technical Intelligence Unit at Stuttgart. It was later sent to the RAE Farnborough in June 1946, and although allegedly was sent to the scrap pile in 1947, another report has the DFS 229 V1 being sent to Slingsby Sailplanes Ltd. at Kirkbymoorside in Yorkshire. Strangely enough, Slingsby offered a design for their T44, a stratospheric research sailplane which incorporated several DFS 228 features, including the detachable pressurized cockpit section (Ref.: 17).

North American AJ-1 “Savage”, Naval Air Test Center, Patuxent River, (Anigrand Models, Resin)

TYPE: Carrier-borne medium bomber

ACCOMMODATION: Crew of three

POWERPLANT: Two Pratt & Whitney R-2800-44W Double Wasp radial engines, rated at 2,400 hp each plus one Allison J33-A-10 turbojet engine, rated at 2,040 kp thrust


COMMENT: The North American AJ-1 “Savage” was designed shortly after WW II to carry atomic bombs and this meant that the bomber was the heaviest aircraft thus far designed to operate from an aircraft carrier.
At the end of World War II, the U.S. Navy began a design competition on August 1945 for a carrier-based bomber which could carry a 4,536 kg bomb that was won by North American Aviation. Later that year, the Navy decided that it needed to be able to deliver atomic bombs and that the AJ Savage design would be adapted to accommodate the latest Mark 4 nuclear bomb the next step in development from the more sophisticated imploding Plutonium sphere design Mark 3 “Fat Man” used on Nagasaki. A contract for three XAJ-1 prototypes and a static test airframe was awarded on June 1946. The first prototype made its maiden flight two years later on July 1948. That same year the US Navy began an interim capability program employing the Lockheed P-2 “Neptune” carrying a crash program reproduction of the smaller simpler all uranium ‘gun’ design Mark 2 “Little Boy” nuclear bomb as its first carrier launched nuclear bomber aircraft until the “Savage” was in service. The “Neptune” launched using Jet Assisted Take-Off (JATO) rockets but could not land on existing carriers; if launched they had to either ditch at sea after its mission or land at a friendly airbase.
The AJ-1 was a three-seat, high-wing monoplane with tricycle landing gear. To facilitate carrier operations, the outer wing panels and the tailfin could be manually folded. The two piston engines were mounted in nacelles under each wing with a large turbocharger fitted inside each engine nacelle, and an Allison J33-A-10 turbojet that was fitted in the rear fuselage. Only intended to be used for takeoff and maximum speed near the target, the jet was fed by an air inlet on top of the fuselage that was normally kept closed to reduce drag. To simplify the fuel system, both types of engines used the same grade of avgas. Self-sealing fuel tanks were housed in the fuselage and each wing. The aircraft usually carried 300-US-gallon tip tanks and it could house three fuel tanks in the bomb bay with a total capacity of 1,640 US gallons. Other than its 5,400 kg bombload, the bomber was unarmed.
Two of the three prototypes crashed during testing, but their loss did not materially affect the development of the aircraft as the first batch of “Savages” had been ordered on October 1947. The most significant difference between the XAJ-1 and the production aircraft was the revision of the cockpit to accommodate a third crewman in a separate compartment. The first flight by a production aircraft occurred in May 1949 and Fleet Composite Squadron FIVE (VC-5) became the first squadron to receive a “Savage” in September. The squadron participated in testing and evaluating the aircraft together with the Naval Air Test Center (NATC) in order to expedite the “Savage’s” introduction into the fleet. The first carrier takeoff and landing made by the bomber took place from the USS “Coral Sea” on April and August 1950, respectively.
When first deployed, the AJ-1 was too large and heavy to be used by any American aircraft carrier except for the “Midway” class. The modernized “Essex” class carriers with reinforced decks and the very large “Forrestal” class could also handle the “Savage”. The aircraft was not popular aboard ship as it was too big and cumbersome that it complicated any other flight operations the ship was required to conduct. One problem was that the wings had to be folded one at a time by a crewman on top of the fuselage with a portable hydraulic pump, a time-consuming process, so that the bomber could be moved out of the way to allow other aircraft to land or take off. One pilot reported that the AJ-1 was “a dream to fly and handled like a fighter”, when everything was working properly. The aircraft, however, was not very reliable, possibly because it was rushed into production before all the problems could be ironed out. The bomber was replaced by the Douglas A3D “Skywarrior” beginning in 1957. In total140 aircraft were built plus three prototypes (Ref.: 24).

Focke-Wulf Fw 186 (Planet Models, Resin)

TYPE: Autogiro, reconnaissance, observation

ACCOMMODATION: Pilot and observer

POWER PLANT: One Argus As 10c air-cooled inline piston engine, rated at 240 hp


COMMENT: German helicopter development began with Focke-Wulf’s acquisition of the rights to manufacture Cierva autogyros during the 1920’s. Over 30 Cierva C.19 and C.30 autogyros were built during the late 1920’s and early 1930’s, and from this experience, Heinrich Focke, the engineering half of the Focke-Wulf company, decided to develop an original autogyro design to compete in the Luftwaffe’s contest to provide a utility-liaison aircraft. The Focke-Wulf entry, designated Fw 186, was essentially a Focke-Wulf Fw 56 “Stösser” (Goshawk) parasol wing advanced trainer, with wings removed, tail unit and landing gear redesigned, and configured for two seats in tandem. The engine remained unchanged, with a clutch arrangement installed to start the blades rotating for takeoff. An autogyro, similar in principle to today’s gyrocopters, uses the main power plant for forward thrust, while the rotors freewheel in flight. The aircraft could take off and land in very short distances, but it could not hover or take off and land vertically.
The first flight of the Focke-Wulf  Fw 186 was on July 1939 and although very successful, it was beaten out by the Fieseler Fi 156 “Storch” (Stork) for the Luftwaffe contract, and disappeared from the scene afterward. Only two examples were built (Ref.: Planet Models).

Kayaba Ka-1 (Frank-Airmodel, Resin)

TYPE: Autogyro, reconnaissance, observation


POWER PLANT: One Argus As 10c air-cooled engine (Ka-1) or Jacobs L-4MA-7 air-cooled radial engine (Ka-2), both rated at 240 hp


COMMENT: By order of the Imperial Japanese Army (IJA) the Kayaba Industry developed an autogyro designated Kayaba Ka-1 for reconnaissance, artillery-spotting, and anti-submarine uses. The design based on an American Kellet KD-1A, which had been imported to Japan in 1939, but which was damaged beyond repair shortly after arrival. Kayaba Industry was tasked by the IJA to develop a similar machine, essentially a repaired Kellet KD-1A but powered by a German Argus As 10c engine and shared similar aspects to the German Focke-Wulf Fw 61, which was first flown in 1936, but only about 20 were produced.
The first Kayaba Ka-1 took off from Tamagawa Airfield in May 26, 1941. In the following Army trials, performance was deemed excellent. Originally, it was planned to send the Ka-1 to spot for the artillery units based in mainland China, but the change of the course of war in that theater rendered those plans meaningless. Instead, a few Ka-1 were sent to the Philippines to perform the duties of liaison aircraft as replacements for the Kokusai Ki-76. Soon, an improved version with a Jacobs L-4MA-7 radial engine was on the production line as Kayaba Ka-2. After some time the IJA finally decided on the best use of these unique aircraft, and the majority of Ka-1 and Ka-2 were pressed into service as anti-submarine patrol aircraft. Pilot training for this duty started in July 1943 with the first batch of 10 pilots graduating in February 1944; followed by another batch of 40 pilots in September 1944.
Originally, the plan was to deploy the Ka-1/Ka-2 from 2D-class cargo ships to spot enemy submarines, but these ships turned out to be too cramped for operations; therefore the Ka-1/Ka-2 unit was assigned to the Army-operated escort carrier Akitsu Maru from August 1944 until her sinking in November 1944. From 17 January 1945 ASW patrols were resumed from an airstrip on Iki Isaland with a maintenance base located at Gannosu Airfield in Fukuoka prefecture. ASW patrols also started from May 1945 from Izuhara airfield on Tsushima Island. These missions helped to protect one of the last operational Japanese sea lanes between the ports of Fukuoka and Pusan. Eventually US carrier-based aircraft began to appear even in the Tsushima Strait, so in June 1945 the Ka-1/Ka-2 units were relocated to Nanao base on the Noto Peninsula, in the Sea of Japan, operating from there until the end of the war. The Ka-1/Ka-2 did not directly sink any submarines during the war however, they were well regarded for issuing submarine warnings
A total of 98 Ka-1 and Ka-2 airframes were produced by the end of war, of them 12 were destroyed before being delivered to the IJA and about 30 never had an engine installed, about 50 were delivered to the IJA, but only 30 were actually deployed. Some sources have stated that 240 were built, but this cannot be verified (Ref.: 24).

Kellett YO-60 (LF model, Resin)

TYPE: Autogyro, reconnaissance, observation


POWER PLANT: Jacob R-915-3 radial engine, rated at 300 hp


COMMENT: The Kellett YO-60 was a military derivative of the civil Kellet KD-1 autogyro built by the Kellett Autogiro Company by order of the United States Army in the late 1930. It had the distinction of being the first practical rotary-wing aircraft used by the United States Army and inaugurated the first scheduled air-mail service using a rotary-wing aircraft.
Using the experience gained in building Cierva autogyros under license the Kellett Autogiro Company developed the KD-1 which was similar to the contemporary Cierva C.30. It had two open cockpits, a fixed tailwheel landing gear and was powered by a 225 hp Jacobs L-4 radial engine. After testing of the prototype a commercial variant designated the Kellett KD-1A was put into production. The KD-1A had a three-bladed rotor with folding blades and a number of minor detail improvements. A KD-1B which was a KD-1A with an enclosed cockpit for the pilot was operated by Eastern Airlines and inaugurated the first scheduled rotary-wing air-mail service on July 1939.
In 1935 the United States Army bought a KD-1 for evaluation and designated it Kellett YG-1, a second aircraft followed which had additional radio equipment and was designated the Kellett YG-1A. These two aircraft were followed by a batch of seven designated Kellett YG-1B.
In 1942 seven more aircraft were bought by the US Army Air Force for use in the observation role as the Kellet XO-60. During initial test phase several improvements were incorporated compared to the KD-1. A new style clutch had discs and used a planetary reduction gear system at the engine with a larger drive shaft running directly from the power takeoff on the engine to the rotor head and the pilot was put in the front seat and added a transparent plastic cover over both cockpits and a large transparent plastic panel in the belly beneath the pilot’s feet. The observer’s seat could swivel so he could ride backwards and work at a small table behind the rear seat. When the observer was not in place, ballast had to be carried in the rear cockpit. Furthermore, the power plant was changed to a Jacobs R-915-3, seven cylinder, air-cooled, radial engine providing 330hp through a Hamilton-Standard constant speed propeller and the engine mount was removable at the firewall. In this way a quick change power plant package could be stocked. The fuselage structure was similar to the earlier KD-1/YG-1. The fairing was different with flatter sides giving the observer better downward vision out the side windows. The enclosure over the two cockpits hinged open and slid to the right to permit entrance and exit from the cockpits on the left.
The model was soon changed from Kellett XO-60 to YO-60 and seven were built. Only six were delivered, one was damaged in a run-up accident and was not repaired.
One YG-1B was modified with a constant-speed rotor and was re-designated the Kellett YG-1C, it was later re-engined with the more powerful R-915 and re-designated again as the Kellett XR-2. The XR-2 was destroyed by rotor ground resonance problems and the evaluation was continued with another modified YG-1B designated the Kellett XR-3. In total app. 24 Kellett autogyros were built for the US Army Air Force.
One Kellet KD-1A been imported to Japan in 1939 and was prototype for the Kayaba Ka-1 and Ka-2 autogyro (Ref. 24).

Focke-Wulf Fw 191 V1 (Airmodel, Vacu-formed)

TYPE: Medium bomber

ACCOMMODATION: Crew of seven

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).

Yokosuka K5Y2 (“Willow”)

TYPE: Intermediate trainer


POWER PLANT: One Hitachi “Amakaze” radial engine, rated at 300 hp


COMMENT: The Yokosuka K5Y2 was a two-seat unequal-span biplane trainer (Allied reporting name “Willow”) that served in the Imperial Japanese Navy during World War II. Due to its bright orange paint scheme (applied to all Japanese military trainers for visibility), it earned the nickname “Red dragonfly”, after a type of insect common throughout Japan.
The aircraft was based on the Yokosuka Navy Type 91 Intermediate Trainer, but stability problems led to a redesign by Kawanishi in 1933. It entered service in 1934 as Navy Type 93 Intermediate Trainer K5Y1 with fixed tail-skid landing gear, and remained in use throughout the war. Floatplane types K5Y2 and K5Y3 were also produced. After the initial 60 examples by Kawanishi, production was continued by Watanabe (556 aircraft built), Mitsubishi (60), Hitachi (1,393), First Naval Air Technical Arsenal (75), Nakajima (24), Nippon (2,733), and Fuji (896), for a total of 5,770. These aircraft were the mainstay of Imperial Japanese Navy Air Service’s flight training’s, and as intermediate trainers, they were capable of performing demanding aerobatic maneuvers. Two further land-based versions, the K5Y4 with a 480 hp “Amakaze” 21A engine and the K5Y5 with a 515 hp “Amakaze” 15, were projected but never built.
A K5Y of the Kamikaze Special Attack Corps 3rd Ryuko Squadron was credited with sinking the destroyer USS Callaghan on July 29, 1945, the last US warship lost to kamikaze attack during the war (Ref.: 24).

Boeing B-17F “Flying Fortress, 303 BG “Hell’ Angels”, 8th USAAF (Hasegawa)

TYPE: Heavy bomber


: Four Wright R-1820-97 Cyclone supercharged radial engines, rated at 1,200 hp each


COMMENT: The Boeing B-17 “Flying Fortress” was a four-engine heavy bomber developed in the 1930s for the United States Army Air Corps (USAAC). Competing against Douglas and Martin for a contract to build 200 bombers, the Boeing entry (prototype Model 299, XB-17) outperformed both competitors and exceeded the air corps’ performance specifications. Although Boeing lost the contract (to the Douglas B-18 “Bolo”) because the prototype crashed, the air corps ordered 13 more B-17s for further evaluation. From its introduction in 1938, the B-17 “Flying Fortress” evolved through numerous design advances becoming the third-most produced bomber of all time, behind the American four-engined Consolidated B-24 “Liberator” and the German multirole, twin-engined Junkers Ju 88.
On 8 August 1934, the USAAC tendered a proposal for a multiengine bomber to replace the Martin B-10. The Air Corps was looking for a bomber capable of reinforcing the air forces in Hawaii, Panama, and Alaska. Requirements were for it to carry a “useful bombload” at an altitude of 10,000 ft, a range of 2,000 mi and a top speed of at least 250 mph was desired.
The prototype XB-17, with the Boeing factory designation of Model 299, was built at Boeing’s own expense. It combined features of the company’s experimental XB-15 bomber and Model 247 transport. The first flight of the Model 299 was on  July 1935 and on 20 August 1935, the prototype flew from Seattle to Wright Field in nine hours and three minutes with an average cruising speed of 252 miles per hour, much faster than the competition.
The USAAC had been impressed by the prototype’s performance, and on January 1936, through a legal loophole, the air corps ordered 13 YB-17s (designated Y1B-17 after November 1936 to denote its special F-1 funding) for service testing.
The YB-17 incorporated a number of significant changes from the Model 299, including more powerful Wright R-1820-39 Cyclone engines. Although the prototype was company-owned and never received a military serial (the B-17 designation itself did not appear officially until January 1936, nearly three months after the prototype crashed), the term “XB-17” was retroactively applied to the airframe and has entered the lexicon to describe the first “Flying Fortress”.
Opposition to the air corps’ ambitions for the acquisition of more B-17s faded, and in late 1937, 10 more aircraft designated B-17B were ordered to equip two bombardment groups, one on each U.S. coast. Improved with larger flaps and rudder and a well-framed, 10-panel plexiglas nose, the B-17Bs were delivered in five small batches between July 1939 and March 1940. In July 1940, an order for 512 B-17s was issued, but at the time of the attack on Pearl Harbor, fewer than 200 were in service with the army.
The aircraft went through several alterations in each of its design stages and variants. Of the 13 YB-17s ordered for service testing, 12 were used by the 2nd Bomb Group of Langley Field, Virginia, to develop heavy bombing techniques, and the 13th was used for flight testing at the Material Division at Wright Field, Ohio. Experiments on this aircraft led to the use of a quartet of General Electric turbo-superchargers which would become standard on the B-17 line
As the production line developed, Boeing engineers continued to improve upon the basic design. To enhance performance at slower speeds, the B-17B was altered to include larger rudders and flaps. The B-17C changed from three bulged, oval-shaped machine gun blisters to two flush, oval-shaped machine gun window openings, and on the lower fuselage, a single “bathtub” machine gun gondola housing, which resembled the similarly configured and located ventral defensive emplacement on the German Heinkel He 111P-series medium bomber.
While models A through D of the B-17 were designed defensively, the large-tailed B-17E was the first model primarily focused on offensive warfare. The B-17E was an extensive revision of the Model 299 design: The fuselage was extended by 10 ft; a much larger rear fuselage, vertical tailfin, rudder, and horizontal stabilizer were added to the design; a gunner’s position was added in the new tail; the nose (especially the bombardier’s well-framed, 10-panel nose glazing) remained relatively the same as the earlier B through D versions had, but with the addition of a Sperry electrically powered manned dorsal gun turret just behind the cockpit, and the similarly powered Sperry-built manned ventral ball turret just aft of the bomb bay. The B-17’s turbocharged Wright R-1820 Cyclone 9 engines were upgraded to increasingly more powerful versions of the same power plants multiple times throughout its production, and similarly, the number of machine gun emplacement locations was increased to enhance the aircraft’s combat effectiveness.
In April 1942, the B-17F was introduced onto the production lines, and outwardly this variant differed from the B-17E only in having an extended Plexiglas nose which was frameless except for the optically flat bomb-aiming panel, paddle-blade airscrews for maximum operating performance, extra fuel cells, improvements of the bomb stowage, brake system, communications equipment and oxygen system. As the cross weight was increased, the undercarriage was strengthened.
Owing to the constant modifications being applied to aircraft on the production lines and the immense scale of production orders, a system of “Block Designations” was instituted.  Thus, the first Boeing-built B-17F Fortress became B-17F-1-BO, and all aircraft in this production block were identical insofar as equipment and installations were concerned. Blocks B-17F-5-BO, -10-BO, etc., followed, the intervening number being left to indicate subsequent changes made at modification centres. Production of the B-17F continued for 15 months, during which 2,300 were built by Boeing, 600 by Douglas (suffix DL) and 500 by Locked Vega (suffix VE). The final production blocks of the B-17F from Douglas’ plants did, however, adopt the Bendix “chin turret” with two machine guns, giving them a much-improved forward defense capability.
The B-17F variants were the primary versions flying for the Eighth Air Force to face the Germans in 1943. The maximum bomb load of the first B-17F was 4.350 kg, but on typical missions to Germany, Eighth Air Force Fortresses carried 1.800- 2.270 kg over operating ranges averaging 1,400 miles. Beyond these distances, the bomb load fell rapidly, so that the effective combat radius of B-17F was about a maximum of 800 miles. Later modifications already referred to increase the fuel capacity as well as bomb load and by that the USAAF was enabled to build up an immense striking force in the European Theatre of Operations (Ref.: 4, 24).

Arado Ar 234B-2 “Blitz” (“Lightning”), (9/KG 76), (Dragon)

TYPE: Fast medium bomber


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).

Messerschmitt Me 262 HG III/ Concept 3 (Unicraft Models, Resin)

TYPE: High-speed test aircraft. Project


POWER PLANT: Two Heinkel-Hirth HeS 011 turbojet engines, rated at 1,300 kp thrust each

PERFORMANCE: High subsonic speed, estimated

COMMENT: In early 1941 several high speed versions of the basic Messerschmitt Me 262 were designed on the drawing board. The first of these “Hochgeschwindigkeitsjäger” (HG), (High-speed fighter) was the Messerschmitt Me 262 V9, unofficially called HG I. This aircraft featured modified wing leading edges of the inner wing section, swept angles of stabilizers, and a “Rennkabine” (Racing canopy), shallow, low-drag cockpit canopy and windscreen with low profile.
Other two projects were created following this way: The Me 262 HG II called for an outboard wing of increased chord and an improved air intake and engine installation, and finally  the Me 262 HG III, which was the final stage of development. It required more radical modifications, as a new 45 degree swept wing with engines housed in the wing roots. Three variants of the Me 262 HG III are known correspond to the original layout.
Entwurf 1” (Concept 1) had a the original tail plane of the Me 262, “Entwurf 2” (Concept 2) had a butterfly-type tail plane, and “Entwurf 3” (Concept 3) together with various subtypes was considerably altered in the fuselage area, where the cockpit was relocated at the rear and formed a part of the empennage group. The swept back stabilizers were located behind the cockpit. This Messerschmitt Me 262 HG III/ Concept 3 attained a very high state of fighter technology, which in the post-war period was the only realized abroad after a passage of several years.