SAAB J 21

Přehled verzí
SAAB J 21 - track version



     
Label the Design of the aeroplane - a description
, SAAB J 21A-1 the first series of fighter aircraft, cannon Hispano
SAAB J 21A-2 the second and third series, cannon Bofors
SAAB B 21A-3 the fourth and fifth series, battle version, a bomb armament
SAAB J-21RA the first series of jet fighters, engine Goblin II
SAAB J 21RB a second series of jet fighters, engine Goblin III
SAAB 21R battle adjustment of the two previous versions, the case with machine guns and unguided rockets




     
Manufacturer production Period Manufactured units
SAAB AB in Trollhättan and Linköping 04.1941 – 06.1944 development and construction of prototypes 3 pcs
1.12.1945 – 5.12.1946 54 aircraft J 21A-1
13.7.1946 – 27.6.1947 62 aircraft J 21A-2
11.6.1947 – 14.11.1947 62 aircraft J 21A-2
22.5.1947 – 8.5.1948 59 aircraft B 21A-3
12.5.1948 – 17.1.1949 60 aircraft B 21A-3
10.8.1948 1 aircraft B 21A-3
12.1945 - 1947 4 prototypes of the J 21R (converted J 21A-1)
2.8.1949 – 21.8.1950 30 aircraft J 21RA
1.7.1950 – 24.1.1951 30 aircraft J 21RB


sources:
Bo Widfeld, Aircraft in Profile No. 138, The Saab 21 A & R, Leatherhead, Surrey, UK: Profile Publications Ltd., 1966.
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History of aeroplane SAAB J 21

Flygvapnet before the war.
In the first half of 1939, at a time when it began to be obvious that if the Swedish air force Flygvapnet secure the neutrality of the country, must be quickly and effectively strengthened and modernized. Obsolescence is most manifested in the Swedish fighter force.

the Immediate solution to the situation.
The simplest solution was the purchase of aircraft abroad, and so the Swedish purchasing commission purchased in the United states 254 fighter planes, these were the types of the Seversky EP-1 (EP means Export Pursuit), which was a fighter P-35 relaxed for export, the Swedes put it into the loadout as J-9 (how - fighter). The second purchased type of was the Vultee 48C Vanguard, this type of eventually to the loadout Flygvapnetu didn't get, because the american administration in October 1939 imposed on the weapons for the european countries (excluding Britain) embargo. In total, Sweden received only 60 aircraft J-9. The swedes were forced to buy quickly and, in Italy, purchased a 72 biplane fighters Fiat CR-42 (J-11) and 60 jednoplošných fighters Reggiane Re-2000 (the J-20). All of these aircraft, however, definitely did not belong to the tip and in addition spare parts have to be imported. At the time the decision was taken that the other aircraft should not be own design.

Domestic factories.
Sweden had the production capacity in the factory SAAB AB, Svenska Aeroplan Aktiebolaget, this manufacturer of aviation equipment shortly before that (in 1939) merged with the factory ASJA, which was headquartered in Linköping, should SAAB AB its original factory and development department in the city of Trollhättan and the other in Linköping. In production capacity would, therefore, wasn't the problem, however, was the lack of experience of technicians and engineers with the development of the modern executive of a fighter aircraft. Both the factory then produced a single-engine bomber aircraft SAAB B 17 and later a twin engine SAAB B 18, developers Saab presented the project of a fighter aircraft SAAB 19, which resembled a japanese fighter jet Mitsubishi A5M Zero, this project was rejected. The solution, however provisional, was for the Swedish fighter air force fighter jet FFVS J 22 made in the total number of 198 aircraft, the production ran from mid-1942 until the end of the war.

Project J 21
The main designer of the company SAAB Frid Wänström, however, in the spring of 1941 began to work on a completely new project of a fighter aircraft J 21. The designer opted for a little used arrangement of the aircraft - low-wing center trupovou the gondola at the end of which was the engine with a pusher propeller and tail surfaces were carried by the two beams emanating from the wings. Such a solution in addition to a few of the disadvantages brought substantial benefits - good view from the cockpit during the takeoff and during the landing, it was still enhanced by the undercarriage nose wheel type and no less important advantage was the bow of the aeroplane, to which it was possible to install a larger armament, and her cadence was not limited to the synchronizer. The disadvantages of this arrangement then they are less the efficiency of the pusher propeller, the need to allow its crew to carry out a safe emergency exit from the aircraft, it is also necessary to count with higher static problems, if it would be the power unit radial engine (and with it the Frid Wänström counted) arise problems with its cooling. Aware of all the advantages and disadvantages presented Frid Wänström your project to assess, as I've already mentioned, as the power unit of the chosen designer of the american the engine Pratt & Whitney S3C4-G Twin Wasp, which was přeplňován engines. In the meantime, but the situation has changed, the Swedish ministry of aviation has negotiated the supply of a small amount of engine Daimler-Benz DB 601, more important was that she purchased the rights to the licensed production of these engines with the appendix that will be in the Swedish factory Svenska Flygmotor follow the license production of a modern and efficient engines, DB 605. This fundamentally changed the situation and Frid Wänström modified your project for the invert liquid-cooled engine DB 605B. Problems with the cooling for the liquid cooled engine can be better addressed. Already in April 1941, submitted Wänström the council of the military air force of your modified project, the council for the approval of the project asked safe rescue system for the pilot, finally, it was selected a simple ejection seat, which the pilot safely gets out of range of the pusher propeller. The project was approved and so the engineers, technicians, and workers began two years of hard work, when they had to solve many problems and most of the problems then solved a system of trial and error, trial and error.

the Construction of the prototypes
To address some of the structural units joined by the stockholm technique, its professors and students specifically participated in the design and calculations of high-speed laminar profile wings. Aircraft with not very usual arrangement had to be verified in a wind tunnel, for these purposes were built mock-ups in scale 1 : 4 and 1 : 10. Aerodynamic tests fell in the vast majority of very well and has confirmed the fears of directional instability or from vibration of the wings. The fears were not confirmed even in the actual aircraft, here to help the pusher propeller, which in its suction effect to eliminate the air that is wrapped around the pod and its transition into the wings, the rear of the GTC was due to blowing off more effective. The ejection seat was first tested on a single-engine bomber, the SAAB B 17 and the chassis was tested on, for this purpose adapted, a training aircraft Sk-14A.

The first prototype of the J 21A (Sn. 21001) took off on 30. July 1943, a start was thanks to the poor instructions very dramatic, the pilot Claes Smith before take-off, exactly according to the instructions, the fully extruded wing flaps, you instead have to reduce the take-off, act as aerodynamic brakes and take-off extended. The aircraft for runway end finally picked up, the whole flight was cool and met all expectations, the pilot performed all the required tests and was directed to the airport in Malmslättu, which had a longer runway. After the extrusion of the chassis followed by a smooth touchdown, but thanks to krkolomnému take-off were discarded brakes, the aircraft at the end of the track laid on one wing, undercarriage legs are broke, it happened also thanks to the deformations suffered during take-off. The repair lasted a few weeks, the prototype was subsequently tested on the base of the Satenäs, where, after an erroneous setting of the stabilization pad again the crash occurred, the aircraft was again damaged landing gear and after several months of repairs began the first prototype in early 1944 to fly again.

The second prototype flew in June 1944 and had a more efficient cooling system. The cooling liquid was cooled by two aluminum exchangers inside the midsection of the inlets of the cooling air were in the facing edges of the baffles were on the lower side of the wings. If the engine speed fell below a certain value (1 800 rpm) were automatically running fans, which provide forced cooling. Engine cooling was one of the few weaknesses of these machines, maybe to a certain extent participated in the pilots control valve kept rather closed, or is closing too soon, because these significantly increase the aerodynamic resistance, the worsened speed, climb and range.

The third prototype ( Sn. 21003) never flown, was designed to strength the static test deformation of character.

Start of production of the J 21A-1.
The Swedish air force was with the progress of the tests are satisfied and so already in the summer of 1943, ordered the first čtyřiapadesátikusovou series, with the preliminary one delivery date. Start of production is gradually extended up to July 1945, the causes were several, the delay to begin license production of the engines, the Germans deliberately impeded the delivery of complete documents for production, other problems were technological, welding aluminum radiators, the unreliability of the weapons, etc. the First serial machine (Sn. 21101) was a Swedish air force taken by the air wing of F-8. The pilots of the new machines accepted with reservations, vytýkali airplane that is on the steering at sharp turns required too great a force. Otherwise, however, , J 21A-1 proven, it was maneuverable and stable, the bow the chassis was reliable and facilitate the take-off and landing, the firepower was massive, unfortunately, the conclusions of the weapons were not very reliable. The last aircraft of the first series was delivered 5. December 1946.

J 21A-2
The second production series is from the first production block of different second-hand cannon, the first series had a cannon Hispano, the second series of bore cannon Bofors M-45 of the same caliber. Deliveries commenced before the end of the production aircraft of the first series 13. July, 1946 and terminated was 27. June 1947, the total was made 62 aircraft designated J 21A-2. The third series consisted of also 62 aircraft with the same designation and took place from 11. June 1947 to 14. November 1947. At that time it was already clear that these are aircraft such as fighter jets become obsolete, but they can successfully fulfill battle tasks.

Arises attack aircraft B 21A3.
22. may 1947 it started the production of the offensive version, which is marked B, 21A-3, this was about the fourth series and the order for 59 aircraft has been completed 8. may 1948, but already 12. may of the same year began production of the fifth, this time šedesátikusové series, the last aircraft of this series was completed on 17. January 1949. What was the difference between fighter and assault "jedenadvacítkami"? Already in itself the designation B 21A-3 (B = bomb) will tell us that these drones could carry bombs and missiles under the fuselage, it was possible to hang up a mountain lion weighing 250-500 kg or four 50 kg bombs or two missiles Bofors caliber 180 mm, or under the outer part of the wings it was possible to hang up a total of eight 145mm unguided rockets. The focus of the weapons used british gunsight K-14. Designation later changed to AND 21A-3 (A= attack), the aircraft could carry a flat auxiliary tank volume of 160 liters, these tanks were just přimknuty under the wing, next was the opportunity to hang at the end of the wing a large drop tanks with a volume of 400 l. To facilitate the take-off of this congested planes, it was possible under the tail joists to hang the auxiliary starter solid rocket fuel.

Project J 21B
At the time of its inception was J 21A performance on the eur and could be compared to contemporary fighter aircraft, two to three years after the war, however, has lagged and was out of date. The swedes of course would like to increase the performance of their fighter force, Flygvapnet demanded that initiated the development of a new version coming in early 1945. Required was mainly due to the higher speed, more armament, more perfect sight, which should be linked to a radar rangefinder. The project of the new version was designated J 21B were set out terms for the construction of the mock-ups, for the completion of the prototype and to begin serial production. The design team was led by Ragnar Härdmark, he tried to get what may be the most powerful engine, logically it would be easiest to use a more powerful engine Daimler-Benz DB 605E, but Germany was in the spring of 1945 other things to worry about, than to sell the licensing rights for the production of engines. The next choice fell on the use of the engine Rolls-Royce Merlin, then his license form from american companies Packard, here the Swedish engineers had stumbled upon a fairly fundamental problem - Merliny should be on the output shaft smaller speed than the engines of the Daimler-Benz, help can be either a four-blade propeller of larger diameter, that would fit between the beams of the tail, or would it be necessary to use a propeller five-petalled, she had again an unpleasant heeling moment. Finally found the most viable solution - the engine DB 605 was modified for gasoline with an octane rating of 100, increased filling pressure of the air and the engine achieves performance comparable with the american version of Merlinu, but at the cost of less life of the engine.
In the meantime, have been designed to another, mainly aerodynamic adjustments, sharply protruding the cabin should be replaced by kapkovitou cabin similar to the cabin of the american Mustang. The frontal cross-section of the fuselage gondola managed to shrink and in August 1945 was to the representatives of the ministry of aviation and Flygvapnetu presented a wooden mockup of the front part of the fuselage. Project J 21B was finally completed, the used were just modified engines DB 605B. It was obvious to everybody that the way for increasing performance is the use of jet engines.

Other projects
We must not imagine that the development of spun only around the J 21, after the end of the second world war in Europe originated in Sweden several completely different projects, in which it was calculated with the engines piston (Rolls-Royce Merlin and Griffon) and at the same time, projects in which it was calculated with the jet engines for the Swedish origin. The designers of these engines, however, still dealing with rather large issues. Describe here each of the projects would be outside the scope of the article about the J 21. An important moment was the 9. November 1945, when Flygvapnet ordered the factory SAAB AB to end and interrupted projects of fighter aircraft, which was calculated with reciprocating engines, or jet engines of domestic production.
What it cost for this regulation? British factory de Havilland offered Sweden a convenient delivery of their jet engines of the Goblin, these engines were compared to domestic drivers of reliable and well-tuned. The british have shipped to Sweden a few dozen complete engines and sold the rights to their licensed production. The Swedish air force through the air ministry announced specifications for the installation of the jet engine into the airframe of the J 21A.

Arises the jet J-21R
Work on this project took the chief designer Ragnar Härdmark, the initial proposals suggested that for the development of the jet engine, it will be necessary to change only 20 % of the parts. The signs were all there - the engine of the Goblin in the torso "came" and the other adjustments should not be too challenging. The preliminary project looked very profitably and so Flygvapnet, just on the basis of this proposal, ordered the construction of 120 jet fighters, designated J 21R. The first four prototypes are created by the four dragons of the J 21A-1 (Sn. 21116, 21119, 21121 and 21123) were built turbofan engines Goblin II. Only now have come the designers to the realization that their estimate for the replacement of 1/5 of the parts was very, very optimistic and in the course of remodeling it turns out that it is in fact necessary to change to the airframe 50% of the parts. In addition to the adjustments necessary for the installation of the new engine (we can include lateral input channels, with which the air has been sucked), it was necessary to reconstruct the tail surfaces. SOP had to be enlarged, because the bore of the GBC, which had to move to a higher position, so to get beyond the reach of the hot gases emanating from the outlet nozzle of the engine. Modifications has also undergone wing, slightly changed its profile, amended with the rising edge and slightly increased wing area. SAAB J 21 finally, finally got rid of the problems with the overheating of the engine, the situation is completely reversed and the jet engine had to be modified for the cold Swedish climate. Construction is constantly expanding, Swedish designers are still some flaws out by trial and error. The order was meanwhile reduced to half, because the Flygvapnet has included in his armament of british aircraft de Havilland Vampire Mk.I.

Serial production of the J 21R.
At the beginning of 1949 was finally launched serial production of the jet fighter SAABů J 21R. The first was made třicetikusová series, these aircraft the air force has taken in the period between the 2. August 1949 and 21. August of the following year. Swedish military pilots were from the new aircraft greatly disillusioned, to demonstrate the obsolescence of the design, the aircraft had limited range, and the pilots had to spend a considerable force in control of the plane, high-rise properties were rather poor (at a height of over 10 000 m had to pilot carefully maneuvered the aircraft at these altitudes passed into a tailspin). Pilots had to keep an eye on and the maximum speed that was greater than the aerodynamic capabilities of the airframe of the aircraft and so it happened that the aircraft became uncontrollable after reaching the critical speed and that was already after a short dive. The new jet fighter was just looking for a hard to your application - for patrol or escort flights fit for your small range, for overflow prosecution had a small climb and inappropriate high-rise properties. The big advantage, however, was the stability of the aeroplane and so was eventually found to be suitable for attacks on ground targets. The second třicetikusová series was the air force passed on from 1. July 1950 to 24. January 1951, the main difference was the installation of slightly more powerful engine a Goblin 3. Also, these machines were quickly classified as assault, their designation changed to AND 21RB, the role of the fighters took the british aircraft Vampire which Sweden purchased.

Offensive AND 21R
After a short time of each current SAABy into the role of attack aircraft, for this role were not armed with bombs under the wings was standard zavěšováno eight unguided rockets Bofors caliber 145 mm, 've tried other types, but those in practice almost did not occur. Interesting arms complement was oval-shaped housing suspended below the fuselage, in this case it was carried eight machine guns, caliber 7.9 mm and with a supply of ammunition. These machine guns should, thanks to his number and cadence, a devastating effect on the unprotected ground targets. The best of these attack aircraft accepted by the pilots of the battle wings F-7, was due to the fact that here replaced the older propeller driven AND 21A-3, so the transition to jet aircraft, do the pilots of this unit no problems. Aircraft AND 21R in the armor of this unit remained until the middle of 1954, the longest (until the end of 1956) were flying unit F-17, when they were replaced by SAABy J 32 Lansen.

sources:
Bo Widfeld, Aircraft in Profile No. 138, The Saab 21 A & R, Leatherhead, Surrey, UK: Profile Publications Ltd., 1966.
William Green and Gordon Swanborough, the Encyclopedia of fighter aircraft. Translation of Martin Mudra, Prague, Svojtka and Co., 2002, ISBN 80-7237-341-2
Hans G. Andersson, Saab Aircraft since 1937 (1st ed.), London, Putnam, 1989. ISBN 0-85177-831-3.
L+K 1, 2 and 3 / 1989, George Hornát, Monographs of the SAAB 21.
L+K no. 11 / 1977, Václav Němeček, Aircraft 39-45, SAAB J-21
www.x-plane.org
http://www.saabgroup.com/
www.flightglobal.com
http://www.airwar.ru/enc/fww2/j21.html
http://www.airwar.ru/enc/fighter/j21r.html
www.dogswar.ru
www.airplanesandrockets.com
www.smb.nu
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