Aviation of World War II
The Ki-44 "Seki" army fighter was not produced in such numbers as, for example, "Hayabusa", and was not very popular among Japanese pilots due to the complexity of control, but its role in the fight against American heavy bombers is quite significant. By the time the air offensive against Japan began in mid-1944, many of the imperial army's air defense fighter regiments were armed with this particular type of aircraft.
The need for a relatively heavy single-engine fighter capable of effectively intercepting enemy high-speed aircraft was realized by representatives of the Japanese Army Aviation Headquarters back in 1938, when the Nakajima company was given a technical assignment for the development of such a machine. The requirements of the assignment provided, first of all, a high speed of the interceptor - 600 km/h at an altitude of 5000 m. The time to climb this altitude was to be less than 5 minutes. Two 12.7 mm and two 7.7 mm machine guns were planned as weapons.
The design team headed by Toru Kayama took up the design of the new fighter. The problem at that time was the choice of the power plant, since all the available Japanese engines were relatively low-powered. In the end, the engineers settled on a 14-cylinder, two-row Na-41 radial engine with a rated power of 1,250 hp. The risk of such a decision was that this engine, used on the Ki-49 Donryu heavy bombers, had a rather large diameter and, accordingly, weight. Therefore, the designers had to work hard to install it on their high-speed all-metal fighter. As a result, a "frontal" aircraft of small dimensions appeared, the fuselage of which, already from the location of the engine mount, rapidly narrowed towards the tail section. This design made it possible to minimize the aerodynamic drag of the vehicle in flight and at the same time reduce its weight. For the same purposes, a relatively small wing, unusual for the Japanese, was chosen. Although its chord was increased, nevertheless, the specific load on the wing remained too high, and special "combat" shields were provided to improve the takeoff and landing characteristics and maneuverability of the fighter. Other technical innovations included a drop-shaped cockpit canopy, retractable landing gear and a three-blade variable-pitch propeller.
The estimated weight of the prototype aircraft, designated Ki-44, was planned within 2,200 kg, however, due to a number of reasons, it was exceeded by 15%, and this naturally affected the flight data of the aircraft. The prototype first took to the air in August 1940, and was piloted by the chief pilot of the Nakajima firm Hayashi. The fighter generally showed good controllability in flight, but it did not meet the requirements of the technical specifications. So, the actually achieved maximum speed of the aircraft was only 550 km/h, and it took 5 minutes to climb 5,000 m. 54 sec. To by this time, the company built two more prototypes, and the started production of seven Ki-44 prototypes was suspended until the final decision on the fate of the fighter was made. The military refused to accept the fighter in this form, and the designers had to roll up their sleeves again. All efforts were aimed at reducing the weight of the aircraft and improving its aerodynamic shape. Improvements were carried out on the second and third prototypes. The first step was to dismantle the Ki-44 armament, increase the rigidity of its engine mount and change the shape of the air intake of the supercharger. Lightened by 200 kg, the fighter developed a speed of 570 km/h. Another 20 km/h was obtained by reworking the "skirt" of the hood, 26 km/h was won by multiple reworking of the supercharger air intake design, and, finally, after sealing the firewall and sealing the ventilation holes behind the engine hood, the aircraft's speed increased to 626 km/h. The result obtained allowed us to hope that after the installation of the weapon, the speed of the Ki-44 would remain within 580 km/h. The military resigned themselves to this indicator and gave the go-ahead for the revision of the experimental series machines.
The pre-production Ki-44 differed from the prototypes with a new rudder contour, an antenna mast moved from the cockpit canopy to the front of the fuselage, and a somewhat simplified cockpit canopy itself. If earlier the canopy consisted of three parts and its middle section was moved back, now it was made of two parts and its entire rear section was moved back. In addition, the fighters were equipped with two suspensions under the wing center section, on which two additional tanks with a capacity of 130 liters could be placed. The armament of the aircraft of the experimental batch consisted of two fuselage 7.7-mm machine guns "Type 89" and two wing 12.7-mm machine guns "Type 1" (No-103). A telescopic sight was mounted in the canopy of the lantern.
The Ki-44 was still a dubious aircraft for the Air Force headquarters, but nevertheless, the Nakajima firm in January 1942 still received an order for the production of 40 production aircraft of this type, designated "single-seat army fighter type 2 model 1 "Or Ki-44-I. They were built in several modifications, slightly different from each other. The Ki-44-I was almost identical to the machines of the experimental series, and on the Ki-44-Ia the fuselage rifle-caliber machine guns were replaced by 12.7-mm Type 1 machine guns. Another innovation of the Ki-44-Ib variant was the oil cooler, which was carried out from under the engine hood to the outside, while the Ki-44-Ic had flaps covering the wheel niches in flight, transferred from the landing gear to the fuselage.
Military tests have shown insufficient efficiency of the aircraft. In addition, the American air raids showed that the Japanese had no sufficiently effective high-speed interceptor fighters.
Firm "Nakajima" was again offered to improve the flight data of the machine, mainly to increase its speed and rate of climb. Chief designer Koyamauzhe on the Ki-44-Ic variant tried to solve this problem by mounting two-blade coaxial propellers D.8 on one of the aircraft. However, there was little benefit from this, and in addition, the complex transmission mechanism made it very difficult to service the fighter in the field. The only simple way out was to install a more powerful Na-109 engine on the Ki-44, which was almost the same size as its predecessor, the Na-41, but was 90 kg heavier. On-109 developed power at takeoff 1520 hp, and at an altitude of 5 250 m -1 320 hp. In August 1942, the company received an order for the production of five experimental and three pre-production Ki-44-II fighters with a new engine. They were manufactured in the autumn of the same year, and then mass production of the aircraft began. In addition to the new engine, the Ki-44-II also had a reinforced chassis, protected fuel tanks, a 13-mm pilot's armored backrest and a 40-mm armored frontal glass of the cockpit canopy. To increase the flight range under the wing center section, the suspension of two dropped additional tanks was provided. Among other innovations, it was planned to equip the fighter with a red dot sight, however, due to the delay in deliveries, many Ki-44-II aircraft of early production flew with the same telescopic sight. The serial Ki-44-IIa ("model 2A") carried armament consisting of two fuselage type 89 machine guns of 7.7 mm caliber and two wing 12.7 mm machine guns "type 1". Comparatively few cars of this variant were built. The Ki-44-IIb, equipped with four 12.7-mm type 1 machine guns, became much more numerous. The Ki-44-IIc was also produced specifically to combat enemy bombers, featuring various very powerful weapons. Some fighters of this version had two fuselage type 1 machine guns and two 37-mm wing-mounted No-203 cannons (25 rounds per barrel). The No-301 cannons were quite light due to the use of caseless shells filled with a small charge of gunpowder, but at the same time they were of little use for aerial combat, since their effective firing range did not exceed 150 m.In practice, they were used mainly against ground targets. One Ki-44-IIc was experimentally armed with four 20mm No-5 cannons.
The radical modernization of the aircraft, undertaken back in the middle of 1943, did not give satisfactory results. The Ki-44-III had a powerful 2000-horsepower Na-145 engine, to compensate for the increased weight of which it was necessary to increase the wing and tail area of the aircraft. In total, six copies of this version of the fighter were built in two modifications: the Ki-44-IIIa was armed with four 20-mm No-5 cannons, and the Ki-44-IIIb had two fuselage 20-mm No-5 cannons and two 37-mm wing cannons. But-203. Another innovation of the next version of the "Seki" - individual exhaust pipes of the engine cylinders - was also used on the Ki-44-II fighters of the latest series.
Seki production ceased in January 1945, and a total of 1,225 aircraft of this type were built, including prototypes.