Yak-4/BB-22bis

Short- range Bomber
First flight: 1940
Yakovlev

The Yakovlev Yak-4 (BB-22 bis) was a Soviet bomber aircraft, a development of the Yak-2. The Yak-4 used more powerful Klimov M-105 V-12 engines than its predecessors.

"Airplane No. 23" with M-105 engines, similar in everything else to "aircraft No. 22", was being worked out at the stage of preliminary design of the first-born combat aircraft of the Yakovlev Design Bureau. It was assumed that a car with a more powerful power plant would be able to reach a speed of about 625 km / h. Later estimates became more realistic, but interest in this option remained. In March 1940, factory # 1 completed the conversion of the serial aircraft into the BB-22bis version. Outwardly, this machine (No. 1002) differed little from the usual BB-22 bombers (with a lowered gargrot) produced by the factory No. 1. Only elongated exhaust pipes, metal linings on the wing that protected the plywood sheathing from burning, and the lack of a standard green-blue paint her in the photographs. It was on this machine that the installation of an additional 8-inch oil cooler on the inner surface of engine nacelles, variable pitch propellers VISH-22E and twin wheels on the main landing gear was first tested. It should be noted that at that time the M-105 engines were still very "raw" and were delivered to the leading engineer F.V. Pimenov and the leading pilot P.N. Moiseenko has a lot of troubles.

In May 1940, factory tests of the BB-22bis were completed. In the course of their implementation, it was possible to obtain a maximum flight speed at the ground of 460 km / h, and at the second border of altitude (4800 m) - 574 km / h The time to climb 5000 m was reduced to 5.45 minutes. Despite a significant number of identified defects, the tests added optimism to the creators of the BB-22 and the Air Force leadership. Suffice it to point out that the speed of the car at the design altitude turned out to be 20-25 km / h higher than that of the serial German Bf 109E fighter tested at the Air Force Research Institute in June 1940. As a result of the visit by the commission of General Astakhov to plant No. 81, it was concluded that the BB-22 has only completely removable manufacturing defects and the absence of serious design flaws (it will take less than six months for the Air Force command to radically change its views).

Plant # 81 began production of serial BB-22bis reconnaissance bombers in October 1940. These machines differed markedly from aircraft # 1002. First of all, each of the engine nacelles, instead of two cylindrical oil coolers, was equipped with one segment (horseshoe) nacelle located in beard ", as it was first done on the" backup "BB-22bis. At the exit of the radiator tunnel, a flap was mounted, which made it possible to regulate the oil temperature in flight (the BB-22 oil coolers did not have such a device). Another notable feature was the serial mobile installation of the TSS-1 navigator with a ShKAS machine gun, of the same type as that installed on the Pe-2. The stock of cartridges for it is 800 pieces, the nasal firing point remains the same. There were a lot of other, smaller changes. For example, the serial BB-22bis on an external sling could carry up to four bombs on the D2-MA-250 locks (with a total weight of no more than 500 kg).

No less important was the fact that instead of the "two-step" screws VISH-2K, the new modification was equipped with variable pitch screws VISH-22E, which ensured more rational fuel consumption. In order to increase the flight range, the serial BB-22bis received suspended 100-liter tanks. The total capacity of the six built-in tanks was 960 liters. The flight range at a speed that corresponded to 90% of the maximum, reached 1100 km (for the BB-22 at the most advantageous speed - no more than 900 km). During the tests of the serial BB-22bis No. 70603, the maximum speed of 533 km / h was recorded. But the specific load on the wing has stepped over 200 kg / m & # 178 ;.

However, in the second half of December 1940, the situation changed dramatically. It was at this time that the Pe-2 twin-engine dive bomber made its first flight at the plant number 39 (then it was also called PB-100). In accordance with the order of the NKAP, Yakovlev machines also received new names: BB-22 with M-103 engines became known as Yak-2, and BB-22bis with M-105 engines - Yak-4. At the end of 1940, several "yaks" of autumn construction were handed over to state tests at the end of 1940. It was then that A.S. Yakovlev, real troubles began! Comparison of the flight technical and operational data of "pawns" and "yaks" -bombers was clearly not in favor of the latter. In terms of speed and range, bomb load and power of defensive weapons - in almost all important parameters - the lead production Pe-2 surpassed the Yak-4, not to mention the Yak-2.

In the conclusion on the state tests of two Yak-2 and two Yak-4, the head of the Air Force Research Institute, Major General A.I. Filin highlighted the point that the aircraft "in a tested form are not reliable and combat-ready" ... The requirements for military acceptance were sharply tightened. On February 17, 1941, Lieutenant General Astakhov, Deputy Chief of the Air Force P.V. Rychagov, in a letter to the People's Commissar of the aviation industry A.I. Shakhurin called the situation with the serial production of the Yak-4 intolerable and asked for his personal intervention. As of January 31, plant No. 81 had built fifty "fours", but only three of them were flown. Most of the aircraft standing under the snow had defects in the propeller-engine group, which did not allow the aircraft to be lifted into the sky.

By a government decree of February 11, 1941, the serial production of the Yak-4 at plant number 81 was stopped. By the time of the official cessation of production, plant No. 81 managed to build 28 Yak-2 and 57 Yak-4. The latter underwent lengthy refinement and ended up in units only in the spring of 1941. In addition, at the joint instructions of the People's Commissar and the chief of the Air Force Main Directorate, 33 more Yak-4s were released after receiving an order canceling the order. Thus, the total output of twin-engine "yaks" at the two plants was 109 Yak-2 (all built in 1940) and 90 Yak-4 (27 - in 1940 and 63 - in 1941). Plus two production vehicles that suffered accidents before being sent to combat units. Consequently, 201 aircraft were built by both factories.

As of June 22, 1941, 36 Yak-4s were still at the plant's airfield. Immediately after the start of the war, an order was received to transfer them to combat units. The first to arrive at the plant was a representative of the 314th RAP military technician of the 2nd rank Serov, who accepted all the vehicles, but later they were equally divided between the 314th and 316th RAP and in the second decade of July was sent to replenish regiments at the front.

On June 28, at the direction of the People's Commissariat of the Aviation Industry, plant number 81 began evacuation to Omsk, where, merging with other enterprises, it received a new number - 166.

Petlyakov's Pe-2 became a real alternative to the BB-22, or rather the Yak-2 and Yak-4. It was noticeably larger than the Yakovlev car (normal takeoff weight 7700 kg, wing area 40.8 m²). With identical engines, the head serial Pe-2 produced in January 1941 slightly surpassed the serial Yak-4 in maximum speed (540 km/h versus 533 km/h). The normal bomb load of a "pawn" was considered to be 600 kg, and in most cases, when performing bombing from a horizontal flight, the vehicle carried 700 - 800 kg of bombs. The third crew member covered the Pe-2 from bottom-rear attacks, he also conducted radio traffic, freeing the navigator to solve other tasks. The Pe-2 was all-metal and, as a result, more durable and tenacious than the Yakovlev machine. So, in the face of the "pawn", the Soviet Air Force received a quite worthy replacement for the Yak-4.

Aviation of World War II

Yak-4/BB-22bis

Bibliography