The Fokker D.XXI is a single-engine, single-seat fighter, a cantilever low-wing aircraft of mixed design with a fixed landing gear and an enclosed cockpit. Developed under the direction of Jiri Szatzki at the Fokker plant, first flight on March 27, 1936. Operated in the Air Forces of the Netherlands, Finland and Denmark.

Construction . The basis of the fuselage was a truss welded from chrome-molybdenum steel pipes, closed in the front part with removable panels made of light alloy "Electon", and in the back - sheathed with canvas. In the front, the fuselage had a circular cross-section, in the rear - elliptical. The pilot's cockpit was located in the middle of the car, heated with hot air and completely covered with a transparent triplex and plexiglass lantern. To land the pilot, the middle section of the canopy was opened along the longitudinal axis. and the left part was hinged down. In an emergency, it could be dropped completely. Behind the pilot's seat, the supporting truss of the fuselage was developed upward, forming an anti-hood frame.

A trapezoidal wing with rounded tips had two box spars made of spruce (Oregon from a dream) and plywood ribs (some of them are of a caisson type). The lining of the sock was made of "Electone" and then - of plywood impregnated with bakelite resin. The wing carried landing flaps and ailerons (steel frame, covered with canvas), attached to the rear spar. Flettners were on the ailerons.

The plumage had a metal set and was completely covered with canvas. The stabilizer from below was supported by struts and from above it was connected to the keel with braces. On the elevators, trim tabs were installed, and on the rudder, there was a Flettner.

The chassis of the main ("colonial") variant D XXI, according to the terms of reference, was non-retractable. The wheels were covered with drop-shaped fairings with a small step for the mechanic. Cantilever struts, also hood-mounted, had oil-pneumatic shock absorbers. An option was also developed with a retractable landing gear (with a hydraulic drive) - the struts were folded to the axis of the aircraft with the wheels laying in the wing niches. The tail wheel was not retracted in all cases. It had a mechanical connection with the rudder and was damped by a package of rubber plates. A drop-shaped fairing was provided for the wheel, but it was mounted on only one of the prototypes.

Almost any engine with a capacity of 600 to 1100 hp could be installed on the D XXI. from. According to the assignment, the British air-cooled engine Bristol "Mercury" VI-S (645 hp) was supposed, but the designers worked on the installation of other modifications of the "Mercury", the star-shaped engines Bristol "Perseus" X, Wright R-1820 "Cyclone" , Pratt Whitney "Twin Wasp Junior", Hispano Suiza 14Ha, and in-line V-shaped Rolls-Royce "Kestrel" IV and Hispano Suiza 12 Ycrs. These motors had to rotate various two- and three-blade variable pitch propellers. The shift in the center of gravity with different engines was compensated for by changing the capacity of the front (in front of the cab) and rear (behind the cab) gas tanks. An additional tank could be placed in the left wing half. The project provided for the protection of all gas tanks.

We have prepared no less options for armament. "Colonial" D.XXI was supposed to carry one 7.92-mm FN-Browning machine gun in the fuselage (500 rounds of ammunition) and two of the same in the wing (300 rounds per barrel). In addition, there were at least six more schemes for placing two or four machine guns of 7.92 and 12.7 mm caliber on the fighter, or their combination with 20-mm Madsen cannons. "Oerlikon", "Hispano", including the assembly with the installation of a motor gun (on the Hispano Suiza 12Ycre motor). An even greater choice was provided for instruments, electrical and radio equipment.

A total of 139 aircraft were produced.

Weapons . Two 7.69-mm M.36 machine guns in the front of the fuselage with 500 rounds of ammunition per barrel and two M.36 machine guns with 300 rounds of ammunition per barrel.

Photo	Description
	Drawing Fokker D.XXI Danish Air Force
	Fokker D.XXI prototype 4

Aircraft Modifications

• D.XXI-1 . With 645 hp PD Bristol Mercury VI-S. Single-seat low-wing fighter, prototype; two were assembled for the Danish Air Force.
• D.XXI-2 . 1937, with 760 hp PD Bristol Mercury VIII. Option for the Dutch and Finnish Air Forces.
• D.XXI (1938) . With the Soviet M-25 engine. Spanish version.
• D.XXI (1939-40) . With 760 hp PD Bristol Mercury VIII. Danish licensed model, 10 built. Carrying 20mm Madsen underwing cannons.
• D.XXI-3 . With 760 hp PD Bristol Mercury VIII. Option with armament in drop-shaped fairings, 38 units were built in 1939. for Finland.
• D.XXI-E1 . With 760 hp PD Bristol Mercury VIII. An experimental version with a pronounced narrowing of the wing towards the end.
• D.XXI-4 . 1941 year. with 1050-hp PD Pratt & Whitney R-1535 Twin Wasp Junior. Delivered 50 pieces, ammunition from the fuselage moved to the wing.
• D.XXI-5 . 1944, with 920 hp Bristol Pegasus X. The last batch of five Finnish cars.

Bibliography

• Fokker D.XXI / World of Aviation. Vladimir Kotelnikov. /
• "Flying Dutchmen" / Wings of the Motherland. Sergey Ivannikov. /