POWER PLANT: Four Wright R-1820-97 “Cyclone” turbo-supercharged radial engines, rated at 1,200 hp each
PERFORMANCE: 300 mph at 30,000 ft
COMMENT: The Boeing B-17 Flying Fortress is a four-engine heavy bomber developed in the 1930s for the United States Army Air Corps (USAAC). 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 four-engine Consolidated B-24 Liberator and the multirole, twin-engine Junkers Ju 88,
The Boeing B-17 began operations in World War II with the Royal Air Force (RAF) in 1941, and in the Southwest Pacific with the U.S. Army. In July 1942, the first USAAF Boeing B-17Fs were sent to England to join the Eighth Air Force. Later that year, two groups moved to Algeria to join Twelfth Air Force for operations in North Africa. The B-17Fs were primarily involved in the daylight precision strategic bombing campaign against German targets ranging from U-boat pens, docks, warehouses, and airfields to industrial targets such as aircraft factories. In the campaign against German aircraft forces in preparation for the invasion of France, B-17 and B-24 raids were directed against German aircraft production while their presence drew the Luftwaffe fighters into battle with Allied fighters.
Soon, Boeing B-17Fs proved to be unsuitable for combat use over Europe. The defense expected from bombers operating in close formation alone did not prove effective and the bombers needed fighter escorts to operate successfully. Especially the head-on attacks of German fighters were dangerous, To improve defense a modification in form of a power-operated Bendix “chin” turret mounting two 0.5-in. machine guns was introduced in the last production model, the Boeing B-17G. With the two “cheek” guns and the “chin” turret the protection against incoming fighters was increased enormously. In order to improve the field of fire to the rear a so-called “Cheyenne” tail gun mounting was fitted bringing the total number of guns from seven (B-17F) to 13 (B-17G). Incorporating all changes made to its predecessor, in total 8,680 B-17Gs were built, the last (by Lockheed) on July1945.
During World War II, the B-17 equipped 32 overseas combat groups, inventory peaking in August 1944 at 4,574 USAAF aircraft worldwide (Ref.: 24).
The aircraft shown here belonged to the 486th Bombardment Group (H), 832BS (Bombardment Squadron) stationed at Sudbury, UK. All B-17Gs were in natural metal. Group markings: W in square. In late 1944 red and blue bands forming chevron were painted on wing with blue band towards tip. From January 1945 wing tips and complete tail section painted yellow and three parallel bands of yellow round rear fuselage. In place nose bands and aircraft letter on fuselage (forward national insignia) in squadron color: 832BS in yellow, 833BS in medium blue, 834BS in red, and 835BS in bright green (Ref.: 2).
POWER PLANT: Jacob R-915-3 radial engine, rated at 300 hp
PERFORMANCE: 110 mph
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).
POWER PLANT: Four Wright R-1820-97 Cyclone supercharged radial engines, rated at 1,200 hp each
PERFORMANCE: 287 mph
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).
POWER PLANT: Four Pratt & Whitney R-1830-43 Twin Wasp radial engines, rated at 1,200 hp each
PERFORMANCE: 303 mph at 25,000 ft
COMMENT: The Consolidated B-24 “Liberator was a heavy long-range bomber of the USAAF during WW II and large aircraft for its day. It had a wing span of 110 feet and a gross weight of more than 30 tons. Powered by four 1,200 hp radial engines, it had a maximum fuel capacity of 2,814 US gallons and the bomb load varied from 2,000 to 4,000 kp depending on the distance of the target to be attacked. The crew varied from eight to 10 men, five or six of whom acted as gunners, manning the 10 machine guns usually carried for defence.
The operating technique with these heavy bombers was, after take-off, to assemble large formations of from 20 to 40 aircraft while climbing to operational altitude of 20,000 to 25,000 feet. This was coordinated by means of “Assembly Ships” (or “Formation Ships”) specially fitted to aid assembly of individual group formations. They were equipped with signal lighting, provision for quantity discharge of pyrotechnics, and were painted with distinctive group-specific high-contrast patterns of stripes, checkers or polka dots to enable easy recognition by their flock of bombers. The aircraft used in most cases were veteran B-24Ds. All armament and armor was removed and arrangements for signal lighting varied from group to group, but generally consisted of white flashing lamps on both sides of the fuselage arranged to form the identification letter of the group. Such an assembly was despatched from a single airfield and joined with other formations to form a division column of perhaps 500 to 600 bombers.
The 446th Bombardment Group (H) with Component Squadrons 784th, 785th, 786th and 787th Bombardment Squadron (H) was activated on 1 Aug. 1943 at Alamogordo AAFd. NM. The training for combat commenced at Kearns Fd. Utah end Aug. 43, remaining there until Nov, 43, when the group moved back to Alamogordo AAFd, NM. In early Feb. 44 the group moved to Topeka AAFd, Kan and after a week’s stay began movement to the UK. Here the group was stationed at Attlebridge, Norfolk, for the last year of the war in Europe.
Combat aircraft were Consolidated B-24H, B-24J, B-24L and B-24M. In total the group flew 232 missions in the course of the year against strategic objectives like U-boat installations in Kiel, ball bearing works in Berlin, aircraft factories in Munich and oil refineries in Hamburg. Remarkably, the 785th Bomb Squadron flew 55 consecutive missions without loss. The aircraft shown here is the assembly ship of the 446th Bombardment Group. It’s a veteran Consolidated B-24D named “Striped Ass” (Ref: 2).
Notice: Identification markings of this aircraft are mostly hand-made. After airbrushing the surface with different aluminum-silver shading red stripes are applied according to the original. For this I used microthin precision slit tape, Bishop Graphics. Inc., Westlake Village, Ca. This is self-adhesive, in red color, extreme thin and easy to apply. Unfortunately transparent it needed to be painted stripe by stripe before being applied.
POWER PLANT: Four Allison J35A-3 turbojet engines, rated at 1.815 kp each
PERFORMANCE: 439 mph at 15,000 ft
COMMENT: In 1944, the US War department was aware of aviation advances in Germany and issued a requirement for a range of designs for medium bombers weighing from 36,287 kg to more than 90,718 kg. Designs from this competition, sometimes named the “Class of ’45”, included the Convair XB-46, the Martin XB-48, and the North American XB-45 “Tornado”.
In the fall of 1945, Convair found it was competing with itself with its XB-46 turbojet bomber when the USAAF became interested in an unorthodox forward-swept wing turbojet attack design, the Convair XA-44 that the company had also been working on. With the end of WW II severely curtailing budgets, the company considered canceling the XB-46 in favor of the other project as there was insufficient funding for both. Company officials argued that it made more sense to allow them to complete the XB-46 prototype as a stripped-down testbed omitting armament and other equipment and for the USAAF to allow them to proceed with two XA-44 airframes in lieu of the other two XB-46s on contract. In June 1946, the USAAF agreed to the substitution but that project was ultimately cancelled in December 1946 before the prototypes were completed. The XB-46 would be completed with only the equipment necessary to prove its airworthiness and handling characteristics.
The Convair XB-46 was a graceful design and had a long streamlined oval torpedo-shaped fuselage, long narrow straight shoulder-mounted wings with four Chevrolet-built Allison J35-C3 axial-flow eleven stage turbojets of 1.730 kp static thrust paired in an integral nacelle under each wing. The fuselage turned out to be a problem, as it distorted under flight loads. The pilots sat in tandem in a pressurized fighter-style cockpit under a single Plexiglas teardrop canopy with the bombardier-navigator-radio operator in a transparent Plexiglas nose section.
The straight wing had an aspect ratio of 11.6, and was equipped with Fowler flaps which extended over 90 percent of the span, in four sections. The flaps extended via electrical actuators, and had very small ailerons. Each wing had five spoilers made of perforated magnesium alloy. The engine air intakes were flat oval inlets, with a duct curving downward in a flat “S” to the engines, which were mounted behind the leading edge of the wing. The unusual flight control system utilized a system of pneumatic piping to transmit the pilots control inputs and actuate various systems, rather than the more typical hydraulic, manual or electrical control lines and systems of most aircraft of the era.
Production versions were to be equipped with a pair of .50 caliber Browning M2 machine guns in a tail turret designed by Emerson Electric Company and provision was made for an APG-27 remote control optics and sighting system, but no weaponry was fitted into the prototype.. Likewise, production aircraft were intended to be built with the General Electric J47 engines with 2.345 kp static thrust rather than the J35s used on the prototype
The XB-46’s first flight occurred 2 April 1947 after a month of taxi testing, and lasted ninety minutes. The pilot praised its handling qualities. Basic flight testing took place for five months, and by September 1947 it was concluded after 127 hours aloft on 64 flights by both the Convair Company and USAAF test pilots. Stability and control were excellent but there were engineering problems with engine de-icing, the cabin air system, and vertical oscillations caused by harmonic resonance between the wing and spoilers. There was also concern regarding the ability of the three man crew to exit the aircraft in case of an emergency, since the exit plan relied on the pneumatic system to hold the main door open against the airstream.
The B-46 program was cancelled in August 1947, even before flight testing had been completed, because it was already obsolete. The North American B-45 “Tornado” already had production orders, and even it would be eclipsed by the Boeing B-47 “Stratojet’s” superior performance (Ref.: 24).
POWER PLANT: Four Pratt & Whitney R-4360-31 “Wasp Major” radial engines, rated at 3,250 hp each
PERFORMANCE: 470 mph
COMMENT: The Republic XF-12 “Rainbow” was an American four-engine, all-metal reconnaissance aircraft designed by the Republic Aviation Company in the late 1940s. The aircraft was designed with maximum aerodynamic efficiency in mind. The XF-12 was referred to as an aircraft that was “flying on all fours” meaning: four engines, 400 mph cruise, 4,000 miles range, at 40,000 feet. It is still the fastest piston-engined airplane of this size, exceeding by some 50 mph the Boeing XB-39 of 1944. Although highly innovative, the postwar XF-12 “Rainbow” had to compete against more modern turbojet engine technology, and did not enter production.
In August 1943, U.S. President Franklin D. Roosevelt’s son, Colonel Elliot Roosevelt, commander of the F-5 (modified P-38) “recon” unit, recommended the acquisition of a dedicated high-performance photo reconnaissance aircraft, capable of providing pre-strike target acquisition and photo interpretation. Followed by additional overflights to provide post-strike analysis of their subsequent destruction, this would give commanders the ability to make pivotal strategic decisions and set up subsequent raids. The XF-12 “Rainbow” was Republic Aviation’s attempt to meet those goals. Its primary competition during this time was the Hughes XF-11. Both were introduced at the same time, and both were powered by the new Pratt & Whitney R-4360. The XF-12’s first flight was made on 4 February 1946. During the XF-12’s subsequent flight testing and development period, it demonstrated the capability of operating at 45,000 feet, at a speed of 470 mph, over a range of 4,500 mi, so it met and exceeded the design goals for which it had been designed. Neither the XF-11 nor the XF-12 was purchased in any quantity by the U.S. Army Air Forces (two each), as their need evaporated after hostilities ended in World War II.
When the XF-12 was modified with increased “all weather” equipment and outfitted with its new engines capable of providing short burst of extra power, it suddenly assumed tremendous importance in the eyes of both the U.S. Air Force and the State Department. As a potent intelligence weapon, the XF-12 had the ability to obtain photographs both in daylight and under conditions of restricted visibility at high altitudes over long ranges and with great speed. In theory, operating from northern bases (Alaska and Canada), this “flying photo laboratory” was capable of mapping broad stretches of territory in the Arctic regions performing reconnaissance with near-invulnerability.
Low drag was a primary consideration throughout the design of the XF-12. Many of its features were taken directly from Republic’s considerable experience with fighter plane design. In an extremely rare case of design direction, absolutely no compromise with aerodynamics was made in the shape of its fuselage, the sharp nose and cylindrical cigar shape of the XF-12 fulfilled a designer’s dream of a no compromise design with aerodynamic considerations.
To fulfill its reconnaissance role, the XF-12 contained three separate photographic compartments aft of the wing. One vertical, one split vertical, and one trimetrogon each using a six-inch Fairchild K-17 camera. For night reconnaissance missions, the XF-12 had a large hold in the belly which accommodated 18 high-intensity photo-flash bombs; these were ejected over the target area. All of the bays were equipped with electrically operated, inward retracting doors (again designed for maximum aerodynamic cleanliness). The camera lenses were electrically heated to eliminate distortion. All of this combined to allow full photo operations during high speed flights. The XF-12 also carried a variety of photographic equipment, including complete darkroom facilities to permit the development and printing of films in flight. This was augmented by adjustable storage racks, able to handle any size film containers and additional photo equipment. This allowed the Army Intelligence units to have immediate access to the intelligence the aircraft was able to collect, with no delay in processing.
The XF-12 “Rainbow” featured a wing of straight taper with squared tips and high aspect ratio for maximum efficiency. The engines featured a sliding cowl arrangement to facilitate cooling airflow instead of the normal cowl flaps, which caused too much drag. At the front of the cowls, the engines were also fitted with a two-stage “impeller fan” directly behind the propeller hub and prop spinner. This allowed the engines to be tightly cowled for aerodynamic efficiency, but still provide the cooling airflow the engines required. When the sliding cowl ring was closed (during flight), the air used for cooling the engine was ducted through the nacelle to the rear exhaust orifice for a net thrust gain, as opposed to the usual cooling drag penalty.
All of the air for the engine intakes, oil coolers and intercoolers was drawn through the front of each wing between the inboard and outboard engines. This allowed less drag than with individual intakes for each component. In addition, because the air was taken from a high-pressure area at the front of the wing, this provided a “ram air” benefit for increased power at high speeds, and more effective cooling of the oil and intercoolers. The intake portion of the wing comprised 25% of the total wingspan. They were extensively wind tunnel tested for intake efficiency and inlet contour efficiency. This cooling air, after being utilized, was ducted toward the rear of the nacelle, to provide additional net thrust. The entire engine nacelle was the length of a Republic P-47 “Thunderbolt”. Each engine featured twin General Electric turbochargers, situated at the aft end of the nacelle. All of the exhaust from the engines was ducted straight out of the back of the nacelles. This provided additional thrust. Research showed that roughly 250 equivalent horsepower was generated by each engine exhaust during high speed cruise at 40,000 ft.
The original design of the XF-12 called for contra-rotating propellers, similar to those used on the original XF-11. However, due to the added complexity and reliability issues, the propellers were never installed. They would have been twin three-bladed propellers (rotating in opposite directions). As it was, the aircraft used standard four-bladed Curtiss Electric propellers for all flights.
Had the XF-12 “Rainbow” been available in 1944, it almost inevitably would have been ordered in quantity, and along with its civilian counterpart, the whole postwar structure of aircraft markets might have been altered. As it was, the XF-12 disappeared into oblivion, despite its graceful lines and high performance. The “Rainbow” remains the ultimate expression of multi-engine, piston-powered aircraft design. Its high speed, near-perfect streamlined form, and neatly cowled engines make it a design classic, often unappreciated, and not very well known. The XF-12 was the fastest, four engine pure piston-powered aircraft of its day, and the only one ever to exceed 450 mph in level flight. (Ref.: 24).
POWER PLANT: Two Pratt & Whitney R-2800-27 “Double Wasp” radial engines, rated at 2,000 hp each
PERFORMANCE: 355 mph
COMMENT: The A-26 “Invader” was Douglas Aircraft’s successor to the A-20 (DB-7) “Havoc”, also known as Douglas “Boston”, one of the most successful and widely operated types flown by Allied air forces in World War II. The Douglas XA-26 prototype first flew on 10 July 1942. Flight tests revealed excellent performance and handling, but problems with engine cooling led to cowling changes and elimination of the propeller spinners on production aircraft. Repeated collapses during testing led to strengthening of the nose landing gear.
The Douglas A-26 was originally built in two different configurations. The Douglas A-26B had a gun nose, which originally could be equipped with a combination of armament including 12.7 mm machine guns, 20mm or 37mm auto cannon, or even a 75mm pack howitzer (which was never used operationally). Normally the gun nose version housed six (or later eight) .50 caliber machine guns, officially termed the “all-purpose nose”, later commonly known as the “six-gun nose” or “eight-gun nose”. The Douglas A-26C “Invader” had a glass” nose, officially termed the “Bombardier nose” and contained a Norden bombsight for medium altitude precision bombing.
After about 1,570 production aircraft, three guns were installed in each wing, coinciding with the introduction of the “eight-gun nose” for A-26Bs, giving some configurations as many as 14 12.7 mm machine guns in a fixed forward mount. A-26C nose section could be exchanged for an A-26B nose section, or vice versa, in a few man-hours, thus physically and officially changing the designation and operational role. The “flat-topped” canopy was changed in late 1944 after about 820 production aircraft, to a clamshell style with greatly improved visibility.
Alongside the pilot in an A-26B, a crew member typically served as navigator and gun loader for the pilot-operated nose guns. A tractor-style “jump seat” was located behind the “navigator’s seat”. In most missions, a third crew member in the rear gunner’s compartment operated the remotely controlled dorsal and ventral gun turrets, with access to and from the cockpit possible via the bomb bay but only when that was empty. The gunner operated both dorsal and ventral turrets via a novel and complex (and problematic) dual-ended periscope sight, which was a vertical column running through the center of the rear compartment, with traversing and elevating/depressing periscope sights on each end. The gunner sat on a seat facing rearward, and looked into a binocular periscope sight mounted on the column, controlling the guns with a pair of handles on either side of the column. When aiming above the centerline of the aircraft, the mirror in the center of the column would flip, showing the gunner what the upper periscope was seeing. When he pressed the handles downward, as the bead passed the centerline the mirror would automatically flip, transferring the sight “seamlessly” to the lower periscope. The guns would aim wherever the periscope was aimed, automatically transferring between upper and lower turrets as required, and computing for parallax and other factors. While novel and theoretically effective, a great deal of time and trouble was spent trying to get the system to work effectively, which delayed production, and it was difficult to keep maintained in the field even once production started.
The Douglas Company began delivering the production model A-26B to the USAAF on September 1943, with the new bomber first seeing action with the Fifth Air Force in the Southwest Pacific Theater on June 1944, when Japanese-held islands near Manokwari were attacked. The pilots in the 3rd Bomb Group’s 13th Squadron, “The Grim Reapers”, who received the first four A-26s for evaluation, found the view from the cockpit to be restricted by the engines and thus inadequate for low-level attack. General George Kenney, commander of the Far East Air Forces stated that, “We do not want the A-26 under any circumstances as a replacement for anything”.
Douglas needed better results from the “Invader’s” second combat test, so A-26s began arriving in Europe in late September 1944 for assignment to the Ninth Air Force. The initial deployment involved 18 aircraft and crews assigned to the 553rd Squadron of the 386th Bomb Group. This unit flew its first mission on September 1944. No aircraft were lost on the eight test missions, and the Ninth Air Force announced that it was happy to replace all of its Douglas A-20s and Martin B-26 “Marauders” with the Douglas A-26 “Invader” (Ref.: 24).
ACCOMMODATION: Crew of four plus troops or freight
POWER PLANT: Four Wright R-3350-35 “Duplex-Cyclone” radial engines, rated at 2,200 hp each
PERFORMANCE: 330 mph at 10,000 ft
COMMENT: Following the Attack on Pearl Harbor and the United States entering WWII, the assembly lines at the Lockheed Aircraft Corporation were taken over by the American government for the war effort. Along with the assembly lines, the Lockheed L-049 “Constellation” airliner was also requisitioned and designated C-69 and was to be used as a cargo and personnel transport by the United States Army Air Forces (USAAF).
Due to the direction the war was heading during summer 1942, the need for a large troop transport capable of crossing the Atlantic Ocean o Pacific Ocean (by flying from island to island) became more important. This would help avoid the risks the convoys in the Atlantic were facing due to U-Boat attacks.
The Douglas C-54 “Skymaster” planned for these roles was not completely capable. So on September 1942, the American War Department signed contract with Lockheed for nine L-049 aircraft under construction for TWA. Soon after 150 more C-69A and C-69B aircraft were ordered along with C-69C and C-69D VIP transport versions. In reality, only one C-69C was produced out of all these planned variants.
Around the same time the prototype XC-69 was completed and rolled out in December 1942. The aircraft was painted in olive green and grey camouflage colors and the civilian registration. However, problems developed with the aircraft’s powerplant, the Wright R-3350 “Duples Cyclone”. A consideration to replace the R-3350 engines with Pratt & Whitney R-2800 had been taken up.
On July 1943, the XC-69 was symbolically handed over to the USAAF and later that same day, the XC-69 returned to Lockheed for further testing. It is worth mentioning that the C-69 was able to attain a higher maximum speed than the Mitsubishi A6M “Zero” fighter.
Major problems, however, surfaced with the Wright R-3350 powerplant that powered the C-69 and finally the USAAF ceased production of the R-3350 until the troubles that plagued the engines were solved. This caused the development of the C-69 to slow down and furthermore, the C-69 was not declared a priority. Lockheed continued to focus on building combat aircraft while the Douglas C-54 “Skymaster”, the C-69’s competitor was already flying and officially ordered.
Unfortunately for Lockheed, the C-69 became less important to the war effort as time progressed, especially since the tide of the war had turned in favor of the Allies. Only a small number of C-69 aircraft would see service in the last year of the war. Even so, Lockheed was able to conduct tests at the expense of the government to solve problems with the aircraft’s design. Although the problems with the R-3350 were being solved, the B-29 had priority for the engines over the C-69. Even with all the effort put forth by Lockheed, the USAAF favored the C-54 “Skymaster” over the C-69. At the end of the war, only 22 Lockheed C-69s “Constellations” were produced, seven of which were never delivered (Ref.: 24).
POWER PLANT: Two General Electric J31-GE-5 turbojet engines, rated at 750 kp each
PERFORMANCE: 413 mph at 30,000 ft
COMMENT: The Bell P-59 “Airacomet” was a twin turbojet-engine fighter aircraft, the first produced in the United States, designed and built by Bell Aircraft Corporation during WW II. The United States Army Air Force was not impressed by its performance and cancelled the contract when fewer than half of the aircraft ordered had been produced. Although no P-59s entered combat, the fighter paved the way for another design generation of U.S. turbojet-powered aircraft, and was the first turbojet fighter to have its turbojet engine and air inlet nacelles integrated within the main fuselage.
Major General H. H. “Hap” Arnold became aware of the United Kingdom’s turbojet program when he attended a demonstration of the Gloster E.28/39 in April 1941. He requested, and was given, the plans for the aircraft’s powerplant, the Power Jets W.1, which he took back to the U.S. He also arranged for an example of the engine, the Whittle W.1X turbojet, to be flown to the U.S in October 1941 in the bomb bay of a USAAF Consolidated B-24 “Liberator” along with drawings for the more powerful W.2B/23 engine and a small team of Power Jets engineers. On 4 September, he offered the U.S. company General Electric a contract to produce an American version of the engine, which subsequently became the General Electric I-A. On the following day, he approached L. D. Bell, head of Bell Aircraft Corporation, to build a fighter to utilize it. Bell agreed and set to work on producing three prototypes. As a disinformation tactic, the USAAF gave the project the designation “P-59A”, to suggest it was a development of the unrelated Bell XP-59 fighter project which had been canceled. The design was finalized in January 1942, and construction began. In March, long before the prototypes were completed, an order for 13 “YP-59A” preproduction machines was added to the contract.
In September 1942, the first XP-59A was sent to Muroc Army Air Field in California by train for testing. While being handled on the ground, the aircraft was fitted with a dummy propeller to disguise its true nature. The aircraft first became airborne during high-speed taxiing tests on October although the first official flight one day later. A handful of the first “Airacomets” had open-air flight observer later cut into the nose; over the following months, tests on the three XP-59As revealed a multitude of problems including poor engine response and reliability – common shortcomings of all early turbojets – , insufficient lateral stability, i.e., in the roll axis, and performance that was far below expectations. Chuck Yaeger flew the aircraft and was dissatisfied with its speed, but was amazed at its smooth flying characteristics. Nevertheless, even before delivery of the YP-59As in June 1943, the USAAF ordered 80 production machines, designated P-59A “Airacomet”.
The 13 service test YP-59As had a more powerful engine than their predecessor, the General Electric J 31, but the improvement in performance was negligible, with top speed increased by only 5 mph and a reduction in the time they could be used before an overhaul was needed. One of these aircraft, the third YP-59A was supplied to the Royal Air Force, in exchange for the first production Gloster “Meteor”. British pilots found that the aircraft compared very unfavorably with the turbojets that they were already flying. Two YP-59A “Airacomets” were also delivered to the U.S. Navy where they were evaluated as the YF2L-1 but were quickly found completely unsuitable for carrier operations.
Faced with their own ongoing difficulties, Bell eventually completed 50 production “Airacomets”, 20 P-59As and 30 P-59Bs; deliveries of P-59As took place in the fall of 1944. Each was armed with one 37 mm M4 cannon and 44 rounds of ammunition and three 12.7 mm machine guns with 200 rounds per gun. The P-59Bs were assigned to the 412th Fighter Group to familiarize USAAF pilots with the handling and performance characteristics of jet aircraft. While the P-59 was not a great success, the type did give the USAAF experience with the operation of jet aircraft, in preparation for the more advanced types such as the Lockheed P-80 “Shooting Star” that would shortly become available. Nevertheless, early in 1944 Bell designers began the development of a turbojet powered fighter of similar configuration as the P-59 “Airacomet” but improved performance, the Bell XP-83. But the performance was somewhat disappointing, too, and the project was cancelled, only two prototypes were built (Ref.: 8, 24).
POWER PLANT: One Lycoming XH-2470-1 liquid-cooled engine, rated at 2,300 hp
PERFORMANCE: 381 mph at 28,500 ft
COMMENT: The Vultee Company had submitted a proposal in response to a US Army Air Corps request for an unusual configuration. The Vultee design won the competition, beating the Curtiss XP-55 “Ascender” and Northrop XP-56 “Black Bullet”. Vultee designated it Model 84, a descendant of their earlier Model 78. After completing preliminary engineering and wind tunnel tests, a contract for a prototype was awarded on January 1941. A second prototype was ordered on March 1942..
The XP-54 was designed with a pusher engine in the aft part of the fuselage. The tail was mounted rearward between two mid-wing booms, with the 12-ft propeller between them. The design included a “ducted wing section” developed by the NACA (National Advisory Committee of Aeronautics) that enabled installation of cooling radiators and intercoolers in the inverted gull wing. The Pratt & Whitney X-1800 engine was initially proposed as the power plant but after its development was discontinued, the liquid-cooled Lycoming XH 2470 was substituted.
In September 1941, the XP-54 mission was changed from low altitude to high altitude interception. Consequently, a turbo-supercharger and heavier armor had to be added, and the estimated empty weight increased from 5,200 to 8,200 kg.
The XP-54 was unique in numerous ways. The pressurized cockpit required a complex entry system: the pilot’s seat acted as an elevator for cockpit access from the ground. The pilot lowered the seat electrically, sat in it, and raised it into the cockpit. Bail-out procedure was complicated by the pressurization system and necessitated a downward ejection of the pilot and seat in order to clear the propeller arc. Also, the nose section could pivot through the vertical, three degrees up and six degrees down. In the nose, two 37 mm T-9 cannon were in rigid mounts while two .50 cal. machine guns were in movable mounts. Movement of the nose and machine guns was controlled by a special compensating gun sight. Thus, the cannon trajectory could be elevated without altering the flight attitude of the airplane. The large nose section gave rise to its whimsical nickname, the “Swoose Goose”, inspired by a song about Alexander who was half swan and half goose: “Alexander was a swoose.”
Flight tests of the first prototype, Serial Nr. 41-1210, began on 15 January 1943. Initial trials showed performance to be substantially below guarantees. At the same time, development of the XH-2470 engine was discontinued and, although it appeared possible to substitute the Allison V-3420 engine without substantial airframe changes, the projected delay and costs resulted in a decision not to consider production buys.
The prototypes continued to be used in an experimental program until problems with the Lycoming engines and lack of spare parts caused termination. The second prototype, 42-108994 (but mistakenly painted as 42-1211) equipped with an experimental General Electric supercharger, only made one flight before it was relegated to a “parts plane” in order to keep the first prototype in the air (Ref.: 24).
Scale 1:72 aircraft models of World War II
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