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F.F.V.S. J22 Fighter Aircraft
From a technical perspective
Service in the Swedish Airforce 1943-1952
From a technical perspective Service in the Swedish Airforce 1943-1952 |
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Fighter comparison, 1000-1150hp Fighter comparison, mid to late 1943 |
Trade studiesAircraft types When designing a new aircraft, you look at existing aircraft and compare numbers. It is called benchmarking. I am sure that Bo Lundberg was aware of the development of the FW 190, as in general the J22 was very similar in layout. The initial layout of the FW 190 had similar features to the J22, such as the radial engine and the landing gear design.
The FW 190 was eventually equipped with a landing gear attached to the main spar of the wing, but it is still interesting that the FW company considered the lower drag installation of the gear in the fuselage. The FW 190 was projected to have a cone-shaped intake for cooling the engine, but was later dropped since they were not able to cool the engine sufficiently, even though they had a supplemental cooling fan. The production design still maintained the cooling fan, but the cowl intake was more conventional.
The picture above shows the development stages of the FW190. The top pictures shows the original configuration with wing mounted landing gear, the middle picture shows the modified cowling and the bottom picture shows the production design with the canopy/cockpit moved further aft in order to reposition the Center of Gravity and eliminate the exposure to heat in the cockpit caused by the engine. I do believe that Bo Lundberg also looked at the Mitsubishi Zero, as it was one of the aircraft that the Swedish Airforce wanted to buy. However, that deal fell through since the Japanese could not guarantee the delivery. The J22 was in many ways very similar to the Zero. Perhaps not so much in appearance, as the data itself. Wing loading, power loading and engine power was very similar. The Zero was also a low level fighter with its best speed at around 15,000ft. Wing planform Looking at the wing planform, one can easily see the resemblance of an early BF 109. The main difference would be that the BF 109 used automatic slats for low speed and high angle of attack, as the J22 used a higher camber leading edge airfoil, on the outer portion of the wing, to maintain stability and reduce the risk of tip stall at higher angles of attack. It is interesting to note that the wing area of the BF 109 was almost identical to the J22. The wing area of the J22 was 172.5sqft and the wing area of the BF 109 was 173qft
Vertical tail design
Certain similarities in between the BF 109 vertical tail and the J22 vertical tail can be seen. They both share the same basic planform and the dynamic/static horn balance.
Engine Cowling design In order to minimize cooling drag, an efficient cowling and cooling air outlet was necessary. NACA had developed a series of cowl shapes for Radial engines and for the J22 the cowl design was most certainly based upon these findings. The pictures below show a few of the inlet shapes and pressure distribution. The shape used on the J22 most closely resembles a combination of the upper right hand picture and the middle left picture. A fairly normal design for the time. The drag was kept to a minimum and later when they added the spinner to the J22, the drag decreased and the speed increased 5 km/h (3.1 mph).
Cooling drag A radial engine has more frontal area and the amount of air flow needed to cool the engine is more than for a liquid cooled engine. In order to minimize cooling drag, cowl flaps would be necessary. The FW190 used a fixed, but very efficient cooling outlet in combination with exhaust ejectors. The J22 used cowl flaps, in a normal fashion. The spinner of the J22 extended almost all the way back the the cylinders. By doing this, the air flow remains attached, flow separation is avoided, drag is minimized and cooling is improved.
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