The PWS-21 was a Polish passenger aircraft for 4 passengers, built in PWS factory in 1930, that remained a prototype.
60-521: The aircraft was developed for a contest for a successor of Junkers F-13 in LOT Polish Airlines . The first design of 1929, named PWS-21 , developed by Stanisław Cywiński and Jarosław Naleszkiewicz, was a braced high-wing plane, but it was not realized because LOT demanded bigger passenger cab. The next design, named PWS-21bis , was a cantilever high-wing plane, similar to Fokker F.VIIa /1m design. The only prototype (markings SP-AEC) first flew in
120-510: A 127 kW (170 hp) Mercedes D.IIIa inline upright water-cooled engine. The first production machines had a wing of greater span and area and was furnished with the more powerful 140 kW (185 hp) BMW IIIa upright inline water-cooled motor. Many variants were built using Mercedes, BMW, Junkers, and Armstrong Siddeley Puma liquid-cooled inline engines , and Gnome-Rhône Jupiter and Pratt & Whitney Hornet air-cooled radial engines . The variants were mostly distinguished by
180-466: A consequence of this arrangement, the profile of the wing had to be considerable thicker to accommodate these supporting members; while orthodox attitudes of the era favoured thin profiles, the aerodynamic qualities of the F 13 was quite favourable, largely as a result of diligent experimentation. Another advantage was that, while the polar curve for thin profile wings typically had a relatively restricted range of application, such as for high-speed flight or
240-435: A domed profile that further increased the maximum compression – the ü was for "über", meaning "overcompressed". Additionally, a new altitude-compensating carburetor was added, which improved performance at higher altitudes. To support operations at these altitudes, water from the radiator was used to heat the air intake and prevent icing in the carburetor. The aü model, which included upgraded D.III and D.IIIa engine blocks,
300-403: A few minutes. A cantilever girder comprised the core of the wing's framework. The external metal covering, which was corrugated for increased strength, helped to withstand the stress of torsion while the overall structure was fairly resistant to dynamic overloading. In another departure from conventional practices of the time, the fuselage was placed on the wing; this permitted the framework of
360-430: A few. A feature that made the F 13 popular internationally was the ease with which its landing gear could be converted to floats . During the formative years of commercial aviation, bodies of water such as rivers, lakes, seas and oceans were more abundant than landing strips and civil airports in many parts of the world, so seaplanes were commonplace and even, in some places, more useful than regular aircraft. Aside from
420-415: A fuselage, under the wing, there was a cabin for 4 passengers, with a door on the left. The cabin had a toilet. The fifth passenger could be taken instead of the mechanic. 9 cylinder radial engine Skoda Wright Whirlwind J-5 (240 hp take-off power, 220 hp nominal power) in the fuselage front, fitted with a Townend ring . Two-blade metal propeller of a fixed pitch. Conventional landing gear , with
480-420: A rapid rate of climb, of a higher climb, the polar curve of thicker profile wings could perform more adequately across both circumstances. In terms of its material composition, the F 13 had intentionally discarded traditional materials, such as wood and fabric , in favour of an all-metal approach that had been pioneered by Junkers. This switch eliminated concerns over the variable quality of available wood, and
540-402: A rather prominent overhead cam operating the single intake and exhaust valves, powered by a shaft running up from the crankshaft at the rear of the engine. Ignition was provided by two sets of spark plugs , one located on either side of the cylinders, each powered by a separate magneto for redundancy. The ignition cables were protected in tubes running down either side of the cylinders. Fuel
600-412: A rear skid; struts with shock absorbers joined the main gear with wings. Fuel tanks 250 L in central wing section. Data from Polish aircraft 1893-1939 General characteristics Performance Related development Aircraft of comparable role, configuration, and era Junkers F-13 The Junkers F 13 is the world's first all-metal transport aircraft, designed and produced by
660-586: A reconstruction of the F 13 was launched in 2009; the first flight was in September 2016. The reconstruction is equipped with radio and a transponder, and uses a 1930s Pratt & Whitney R-985 Wasp Junior engine, but is otherwise as close as possible to the original. Additional reconstructions are to be sold for $ 2.5 million each. Junkers Flugzeugwerke (SD303) has resurrected the Junkers F 13 as an all-new airplane to honor Hugo Junkers’ achievements. The company completed
SECTION 10
#1733085920246720-526: A replica of the type was put back in production in the 2010s, taking flight once again nearly a century after the type first flew. What would become the F 13 originated in the work of Professor Hugo Junkers and his Research Institute in Dessau , Germany throughout the 1910s. These efforts were responsible for producing multiple new ideas pertaining not only to aerodynamics but also the employment and working of lightweight metal construction in aviation. The F 13
780-417: A short timeframe. The frontal radiator was specially designed by Junkers to possess a high level of efficiency as well as being relatively lightweight; the pilot was able to regulate the engine temperature via the adjustable shutters. Those aircraft intended for use in a tropical country were typically provided with an additional radiator. Considerable attention was paid to the development of propellers, which
840-419: A threaded cylinder of steel into an aluminium crankcase did not exist at that time. Jackets for cooling water covered the top 2/3 of the cylinder, feeding a radiator via connections at the back of the engine. The only obvious design change from the earlier D.II was to use separate cooling jackets for each cylinder, whereas the D.II used one jacket each for a trio of adjacent pairs of cylinders. The D.III featured
900-511: A two letter code, the first letter signifying the airframe and the second the engine. Junkers L5-engined variants all had the second letter -e, so type -fe was the long fuselage -f airframe with a L5 engine. The F13 was the basis for developing the Junkers W 33 and Junkers W 34 . The Junkers F 13 was an all-metal transport aircraft; its construction and several of its design features, such as its cantilever wing, were particularly noteworthy for
960-535: The BMW III , was available only in very limited numbers. Compared to the Allied engines it faced, the D.III was generally outdated. The D.III was based on the same pattern as the earlier Mercedes D.II , suitably scaled up for higher power settings. Like most inlines of the era, it used a large aluminium crankcase as the main structural component, with separate cylinders made from steel bolted onto it. The technology for screwing
1020-583: The German aircraft manufacturer Junkers . Produced shortly after the end of the First World War , it was a cantilever -wing monoplane with enclosed accommodation for four passengers and a two seat open cockpit. Like all Junkers duralumin-structured designs, from the 1918 J 7 to the 1932 Ju 46 , (some 35 models), it has an aluminium alloy ( duralumin ) structure entirely covered with Junkers' characteristic corrugated and stressed duralumin skin. Internally,
1080-626: The Liberty L-12 Allied V-12 aviation engine. Confusingly, the "ü" was not an official part of the name. This leads to a number of problems in various references, which often confuse the IIIa with the IIIaü, listing the former as a 130 kW (180 hp) engine. There are two D.IV engines — from the IdFlieg aircraft powerplant class designations based on power output — one the straight-eight based on
1140-685: The Red Army . There were some other military users. The Colombian Air Force used the F 13 (and the related W.33, W.34 and K.43) as bombers in the Colombia–Peru War in 1932–23. The Republic of China flew F 13s converted into scout bombers until the January 28 Incident in 1932, when they were destroyed by the Japanese along with the Shanghai Aircraft Factory. The Turkish Flying Forces flew
1200-416: The elevator and ailerons were actuated by the pilot via a column with a wheel while the rudder was operated using pedals. Various sliding doors were present for inspection and serviceability purposes for the various control cables, levers, and tubes. Provision was made for the installation of dual flight controls, a feature that was thought to be of particular importance during long-range flights. All of
1260-465: The 140 mm bore D.III pistons; and the later, six-cylinder Mercedes D.IVa with 160 mm bore cylinders, which was essentially unrelated. The D.III line of engines would find themselves eclipsed in performance by the BMW IIIa of 138 kW (185 hp) and then 150 kW (200 hp)(British rated it at 170 kW (230 hp)) in 1918, however, the small number of BMW's produced ensured that
SECTION 20
#17330859202461320-499: The 75 kW (100 hp) to 89 kW (120 hp) range such as the earlier Mercedes D.II . By 1916 new designs had grown in size and performance and the D.III became popular on new designs. By 1917 the D.III was being widely used in fighters, most notably on the famous Albatros D.I . Production of this version was essentially wound down by May 1917, with only a handful continuing to be delivered until October. British HP ratings being slightly different (with 746 watts = 1 hp) to
1380-516: The D.IV proved prone to breaking. The original D.III was introduced in 1914. While it saw widespread use in early examples of the C-series of two-seat general-purpose biplanes, the D.III was too large for contemporary fighter designs and did not see use in that role. At the time, fighters were generally powered by lighter rotary engines of power output levels from 60 kW (80 hp) to about 82 kW (110 hp), or by water-cooled inline engines in
1440-503: The F 13s produced before production ended in 1932 were built at Junkers German base at Dessau . During the difficult 1921–23 period production was transferred to Junkers plants at Danzig and Reval . In 1922–23, Hugo Junkers signed a contract with the Soviet Union to produce the aircraft in a Soviet factory at Fili near Moscow, which became known as "Plant no. 22". Some of these aircraft served Soviet airlines while others were used by
1500-530: The German PS or Pferdestärke standard of roughly 735 watts per PS horsepower, it is probable that this engine would have had a slightly higher rating under British HP numbers. Fuel consumption was 11.75 gallons per hour. Its compression ratio was 4.5:1. Development of the basic design led to the slightly modified 130 kW (170 hp) D.IIIa , which took over on the production lines in June 1917. The main change
1560-676: The Mercedes D.III series would be the primary German fighter engine up to the last month or two of the war and it would still be seen in very large numbers even at the end. At the end of the war the D.IIIaü would still be the numerically predominant German fighter engine. As a result, the Fokker D.VII's (those not equipped with BMW IIIa's) and the Pfalz D.XII's would be engine-limited in performance (as opposed to "airframe-limited") and yet would still be formidable adversaries to their Allied counterparts. The D.IIIaü
1620-607: The USA and, in the following years with SCADTA (Colombia) and the United States Post Office Department . John Larsen Aircraft in the USA purchased a production licence, their machines being designated JL-6. In 1922 there were sales in England, France Italy and Japan. The F13 was a very popular civilian aircraft, carrying it is estimated 40% of the world's air traffic in the early 1920s. In Bolivia, LAB's first airplane
1680-463: The ability to replace a single blade (instead of the whole propeller), a lack of sensitivity to climate influences, and the potential to shape the propeller hub to vary the propeller pitch for either speed or climb. Behind the single engine was a semi-enclosed cockpit for the crew, roofed but without side glazing. There was an enclosed and heated cabin completed with both with windows and doors. Passenger seats were fitted with seat belts , unusual for
1740-437: The aircraft in 2016 and it is at EBACE commemorating the type's maiden flight 100 years ago. The model is available for purchase, and three others like it are currently under construction. Work was in progress on the second and third aircraft during 2019, with airframe number two's maiden flight planned for early that summer. The replica F 13 made its maiden flight on 15 September 2016, the culmination of many of years of work on
1800-529: The av, accounting for most of the gains in power. It is unclear if any av's saw service use. The increased use of Benzol in German aviation fuel may have helped this final upgrade of power, its higher octane rating being better suited for the higher compression ratio. All of the D.III series were generally very similar to other models, with the exception of the piston profile, carburetor details and valvetrain details. It appears that upgrades were available for many of
1860-430: The engines upgraded or replaced as quickly as possible. This engine has been referred to in postwar British analysis as generating 130 kW (180 hp) A more "radical" upgrade was the 130–150 kW (180–200 hp) D.IIIaü , introduced in late 1917, the D.IIIaü was a standardized refinement of the D.III and D.IIIa design and the ü designation was never official. This engine changed the pistons again, this time to
PWS-21 - Misplaced Pages Continue
1920-509: The engines, certainly for the III to IIIa, and IIIa to IIIaü. It would seem unlikely that early III's would ever make it to the IIIaü standard, as they would almost certainly have been worn out in service before then. The valvetrain changes concerned the layout of the rocker arms that operated the valves. Early models had square rocker boxes positioned directly over the cylinders with the rocker arms exiting through vertical slots, one cut into each of
1980-430: The era. Unlike traditional wings of the era, which had to use external struts and guywires out of necessity, the wing of the F 13 lacked any stay-wires; their elimination meant that a major source of drag was entirely avoided. Instead of exposing the supporting elements to the external air currents, all of the bracing was located within the wing itself, thus providing a neater solution from an aerodynamic perspective. As
2040-407: The fuselage from sustaining serious damage. Furthermore, special connections were present for the installation of floats , which could be rapidly substituted for the wheels, to convert the F 13 into a floatplane . These floats, which were made of duralumin, were each internally divided into six tight compartments. The aircraft could be similarly equipped for taking off or landing upon snow or ice via
2100-413: The installation of all supporting framework internally, the use of metal enabled a substantial number of new construction features to be adopted. Although the specific gravity of duralumin is greater than that of wood, the weight of the Junkers F 13 was beneath that of all other airplanes, wood or metal, of the same class, as a result of thorough aerodynamic studies conducted by the company. Furthermore, it
2160-461: The life of a metal aircraft was believed to be far greater than that of a wooden one. The supporting surface, which was the basis of the structure, comprises three parts, in order to facilitate transportation. The outer portions of the wings were secured to the framework of the central wing section, whose spars consisted of nine duralumin tubes, in a manner that assured symmetry of the wings. These wings could be mounted and demounted by two men within
2220-476: The now fully exposed rocker arms with the exposed shaft ends, as shown at right. The newer arrangement was stated as being interchangeable as a set with the complete camshaft, rocker boxes, rocker arms and valve springs, with the D.III's earlier "side-slot" cam drive system design - the later system seems to have influenced both Packard 's and Hall-Scott 's engine designers to adopt a nearly identical "slotless" rocker-box overhead cam valvetrain design feature for
2280-461: The obvious addition of floats, little modification was needed for this conversion; however, the different configuration could cause issues with directional control, and so some models had their rudder extended to compensate for this. From their introduction in 1919 F 13s were in service for more than thirty years; the last commercial F 13 was retired in Brazil in 1951. A German-Swiss project to build
2340-399: The opposing sides of the boxes, as shown at left. The earlier "side-slot" rocker arm design had also been used for the Mercedes D.I and D.II engines' valvetrains. In later versions of the D.III engines, the boxes were relocated rearward on the tubular camshaft housing, and the now easily sealable cylindrical rocker arm shafts protruded forwards through the front surfaces of the boxes, operating
2400-656: The part of supporters of the project. . The replica was created from original blueprints and also a laser scan of the type at the Museum of Air and Space at Le Bourget, Paris. The replica has 2600 parts and tens of thousands of rivets and is powered by a Wasp radial engine. [REDACTED] Mexico There are five surviving F 13 airframes, all in museums. Data from Hugo Junkers Pionier der Luftfahrt - Seine Flugzeuge , Junkers: an aircraft album No.3 General characteristics Performance Mercedes D.III Mercedes D.VI The Mercedes D.III , or F1466 as it
2460-399: The procurement difficulties in obtaining high quality wood that would be well-suited for aeronautical purposes. It also dispensed with various other concerns, as it was perceived as more difficult to maintain the calibrated dimensions of wood due to warping , the same factor also hindered interchangeability; metal posed less of a fire hazard as well. Unlike Junker's early metal aircraft, which
PWS-21 - Misplaced Pages Continue
2520-399: The removal of the wheels and substituting them for duralumin runners while a shoe would be attached to the tail skid. The aerodynamic efficiency of the F 13 meant that less engine power than had been anticipated could be used; various engines from a variety of suppliers could be installed. Easy access to all points of the engine was possible while various components could be exchanged within
2580-562: The spring, probably April 1930 in Biała Podlaska . Its counterpart was Lublin R-XI . The plane appeared not successful. It was too heavy, what resulted in poor speed, ceiling and range, and long take off. In 1931 it was evaluated in LOT airlines, but after a test flight it was returned to the factory. However, at that time there was its development, PWS-24 built, sharing the same lightweight wing, which
2640-481: The tail surfaces had fairly large areas that benefitted not only the aircraft's manoeuvrability but also its steadiness in flight. Another departure from convention was the means of adjusting the stabilizer to compensate for weight variations; a trimming tank positioned near the rear of the fuselage could offset nose-heaviness or tail-heaviness by means of a pump controlled by the pilot that would withdraw or add sufficient fuel to achieve equilibrium. The undercarriage
2700-406: The time. The F 13 has a fixed conventional split landing gear with a rear skid, though some variants were fitted with floats or on skis. The cabin was relatively sizable and elegantly furnished for the era; in addition to the four passengers it accommodated, room for another passenger or crew member was present alongside the pilot. Any manufacturer of civil aircraft immediately after World War I
2760-611: The wing was built up on nine circular cross-section duralumin spars with transverse bracing. All control surfaces were horn balanced . A total of 322 aircraft were manufactured, a considerably large number for a commercial airliner of the era, and were operated all over the world. It accounted for over a third of air traffic in the early 1920s. It remained in production for thirteen years and in commercial service for more than thirty. There were many versions including floatplanes for water landing, skis, mailplane, and different engines. Several survive in various states of repair in museums, and
2820-401: The wing's central section to form the base of both the fuselage and the cabin. Accordingly, the aircraft had a relatively strong superstructure while also reducing its weight. One advantage of the position of the wing was that it afforded the best possible protection to the cabin and its occupants, in the event of a rough or emergency landing. The flight controls were fairly conventional, both
2880-824: Was a Junkers F 13; first flight took off from Cochabamba on September 23, 1925. Junkers set up its own airline – Junkers Luftverkehr AG in 1921 to encourage the acquisition of the F 13 by German airlines and was flying 60 of them by 1923. They also established a branch of this airline in Iran. Other marketing techniques were used, providing F 13s on cheap leases and free loans, with such effect that some 16 operators across Europe were flying them. When Junkers Luftverkehr merged into Luft Hansa in 1926, 9.5 million miles had been flown by them. Luft Hansa itself bought 55 aircraft and in 1928 were using them on 43 domestic routes. Even in 1937, their F 13s were flying over 50 flights per week on four routes. They were finally withdrawn in 1938. Most of
2940-460: Was a very advanced aircraft when built, an aerodynamically clean all-metal low-wing cantilever monoplane. It was the world's first all-metal passenger aircraft and Junkers' first commercial aircraft. The designation letter F stood for Flugzeug (aircraft); it was the first Junkers aeroplane to use this system. Earlier Junkers notation labelled it J 13. Russian-built aircraft used the designation Ju 13. The F 13 first flew on 25 June 1919, powered by
3000-557: Was also felt that the metal approach would increase structural safety and serviceability. In comparison to its wooden contemporaries, the F 13's all-metal approach was slower to fatigue ; it was also less expensive to protect against humidity and most other atmospheric conditions. Termites were unable to damage metal aircraft. It was partially for this reason that use of the F 13 in various tropical countries, particularly those in South America , quickly became commonplace. In general,
3060-405: Was composed of steel and thus quite heavy, the F 13 was made of duralumin , a light-weight alloy that would find widespread use in aeronautical circles. This metal has greater uniform strength to the aircraft, which made it easier to design; greater ease of calculation increased the economics of this choice as well. Somewhat offsetting the difficulties of developing a new arrangement to permit
SECTION 50
#17330859202463120-587: Was faced with competition from the very large numbers of surplus warplanes that might be cheaply converted – for example, the DH.9C . German manufacturers had further problems with the restrictions imposed by the Inter-Allied Aeronautical Commission of Control, which banned the production of warplanes and of any aircraft in the period of 1921-22. Junkers picked up orders abroad in 1919 in Austria, Poland and
3180-454: Was fed into the cylinders via pipes on the left side of the engine, supplied from a twin-barrel carburetor located just above the crankcase. Both the fuel and oil reservoirs were pressurized by an air compressor run off the crank. Daimler also used the pistons of the D.III to produce the reduction geared, eight-cylinder 160 kW (220 hp) Mercedes D.IV during this period, but it did not see widespread use. The lengthened crankshaft of
3240-481: Was known internally, was a six-cylinder SOHC valvetrain liquid-cooled inline aircraft engine built by Daimler and used on a wide variety of German aircraft during World War I . The initial versions were introduced in 1914 at 120 kW (160 hp), but a series of changes improved this to 130 kW (170 hp) in 1917, and 130 kW (180 hp) by mid-1918. These later models were used on almost all late-war German fighters, and its only real competition,
3300-416: Was largely composed of steel tubing; a total of four streamlined supports functioned as spring struts. A V-shaped strut arrangement assured sufficient rigidity while the distance between the wheels was thought to be sufficient to prevent the aircraft turning over even during an oblique landing. The tail skid was both jointed and shock-absorbing ; it could be readily replaced and was sizable enough to protect
3360-429: Was ordered by LOT. High-wing cantilever monoplane of mixed construction, with closed cab and single engine. A fuselage made of a steel frame, covered with canvas . Straight one-piece wooden wing, with elliptical endings, plywood covered, two-spar. Crew of two (pilot and mechanic), in a cabin before the wing, with twin controls. The cabin had a vertical front windshield and doors on both sides. Next and slightly below in
3420-488: Was shaped by extensive research into aspects such as the pitch, blade section and diameter. The initial propellers used were composed of laminated wood that was protected by metal along their leading edges and achieved a mechanical efficiency at least equal to that of wooden ones. Junkers also worked on metal propellers of its own make, the hollow sections of which diminishes in line with the laws of bodies of uniform resistance. Advantages presented by metal propellers include
3480-414: Was the 150 kW (200 hp) (149–162 kW (200–217 hp)) D.IIIav (or avü), introduced mid-October 1918. The av used slightly longer pistons made of aluminium (possibly a first for a production engine), increasing the compression yet again, while at the same time allowing them to move faster due to the reduced weight. The maximum allowable RPM increased from 1,400 in the earlier models to 1,600 in
3540-593: Was the most prolific German fighter engine of 1918 and designed into most fighter designs from late 1917 on. This included most of the entries in the First Fighter Competition at Adlershof in January 1918, notably the famed Fokker D.VII . In British post war evaluation the D.IIIaü demonstrated 150 kW (200 hp) according to the British standards. A final version attempting to keep the D.III block competitive
3600-562: Was to change the piston profile to have a flat head instead of the former concave one, thereby slightly increasing maximum compression to 4.64:1. Other changes were mainly in design details, notably a redesigned crankcase and new carburetor. Many of the accessories were also redesigned or moved around on the engine. This model was produced only briefly, for use on the Albatros D.III but there are indications that possibly some early Albatros (Alb.) made Fokker D.VII's were also equipped but probably had
#245754