The Su-6 single-seat aircraft was designed in 1940 and built according to government orders, released in the spring of 1941 and handed over for testing just before the war. Evacuation and other circumstances made it impossible to test the aircraft in a timely manner. This was done only in 1942. But by this time, a two-seat version was already required. The Su-6 double armored attack aircraft with the M-71F engine was designed and built in 1942 and from June 20 to August 30, 1943 brilliantly passed state tests (A.V. Sinelnikov was the lead engineer, A.I. Kabanov was the lead pilot , P.M. Stefanovsky took part in the overflight of the aircraft). Despite the rather large wing load - 212.85 kg / m², this machine, thanks to an exceptionally successful combination of shapes, dimensions and careful layout, showed excellent flight data. In terms of maximum speeds, rate of climb, maneuverability, ceiling, range, armament and armor, the two-seat "dry" significantly exceeded the two-seat Il-2, which was in service with the Air Force. The Su-6 had excellent stability and controllability, was simple and pleasant to pilot.

The aircraft was equipped with powerful wing mechanization (had automatic slats and Schrenk flaps), which allowed for stable maneuvers at high angles of attack. The latter was very important for a battlefield aircraft designed to operate at low altitude. For the pilot to attack in a limited space above the target, it was necessary to maneuver mainly in a vertical plane. It was possible to significantly improve the data of the Su-6 in comparison with the Il-2 without deteriorating maneuverability in the vertical plane by reducing the load on engine power. So, serial Il-2 with AM-38F with a wing load of 159 - 163 kg / m² had a vertical speed near the ground of about 7.2 m / s, and the Su-6 at a load of 212.85 kg / m²- 9.3 m / s.

The armor of the Su-6 was much better than that of the Il-2. Thanks to a more rational distribution of sheet thicknesses, the total weight of the armor was only 683 kg — 18.3% of the weight of the empty aircraft. The thickness of the armor in the gunner's cockpit and in the area of ​​the propeller group was chosen explicitly taking into account the influence of aircraft structural elements (fuselage skin, bomb bays, etc.) on the geometry of projectile impact with armor from the most probable directions of fire in a real dogfight. This approach made it possible to seriously reduce the weight of the armor with significantly better protection for the crew and vital structural elements of the aircraft than for the Il-2, in which, with a total armor weight of 957 kg, the air gunner had practically no protection, and the armored parts most vulnerable to enemy fire turned out to be of insufficient thickness. The armor of the Su-6 also had drawbacks, but it provided more effective protection against 12.7 mm caliber bullets and anti-aircraft shell fragments. The survivability of the attack aircraft was also increased by pressurizing the gas tank with exhaust gases and duplicating the control of the elevators and rudders.

The armament of the aircraft included two 37-mm 11P-37 cannons (90 rounds of ammunition), two ShKAS machine guns (1400 rounds), a UBT defensive machine gun (196 rounds in four stores) in a BLUB blister mount, 200 kg of bombs (overloaded) and six RS-132 or RS-82. Two FAB-100 bombs could additionally be suspended on an external sling.

By this time, Air Force specialists already had a large amount of statistical data to analyze the causes of losses of aircraft for various purposes, including attack aircraft. In the conclusions of the report of the 2nd Division of the Operational Directorate of the Air Force Headquarters on the analysis of aviation losses (August 1943), it was noted that of all flight performance characteristics, it is maneuverability that has a decisive influence on combat survivability when operating on ground targets. Similar requirements were put forward by specialists from the Air Force Research Institute. They paid special attention to the horizontal and vertical maneuverability of a promising attack aircraft, equipping it with an air-cooled engine, as well as to increasing the effectiveness of armor protection while reducing the share of armor in flight weight.

Judging by the documents, the leadership of the Air Force believed that it was the Su-6 that was the machine that was lacking in Soviet aviation. In his opinion, the NKAP had the opportunity to put the M-71F engine and the Su-6 aircraft into series.

At the same time, a decrease in the production of M-82F and M-82FN engines and aircraft equipped with them, as well as Il-2 attack aircraft, could not greatly affect the general situation at the front. In the rear (in the interior districts, in the Far East, in schools, at storage bases, etc.), a significant reserve of combat vehicles has accumulated - about 20% more than in the army, and at the front, an almost threefold superiority in forces over Luftwaffe.

With the start of mass production of the M-71F, it would be possible to solve the issue not only of launching the Su-6 attack aircraft, but also of the production of the promising I-185 fighter. In this case, a situation would arise in which both attack and fighter aircraft would simultaneously be re-equipped with equipment that surpassed the enemy’s in all determining parameters, which would most favorably affect the overall course of the war. Meanwhile, the NKAP strongly resisted the production of the Su-6 and the M-71F engine, motivating its position with a great technical risk when deploying their mass production in wartime conditions. However, it seems that this was not the only issue. Relying on quantity rather than quality, the leadership of the People's Commissariat was terrified of making any more or less serious changes to the already well-established system for the production of combat aircraft. In addition, by agreeing with the proposal of the military, he would actually have to admit the fallacy of the adopted technical policy of the NKAP, starting from 1940.

Su-6 (S2A) - two-seater with M-71F engine of 2200 hp. (up). The flight qualities of the experimental aircraft were outstanding (as in the single-seat version). The speed (single and double) near the ground is 510 and 480 km / h, at an altitude of 527 and 514 km / h, which is 100 km / h higher than the speed of the Il-2 attack aircraft. Maneuverability was excellent. It was tested in 1944 in test air battles at an altitude of 6000 m with the Yak-3 fighter.

Here you can pay attention to the fact that the wing area of ​​the Su-6 was one and a half times less than that of the Il-2 (26 m² and 38.5 m²), the mass is much less, and the power is - A bit more. Aerodynamically, it was more perfect, the chassis was completely retracted. This is the reason for its much better performance.

As a Su-6 attack aircraft (especially a two-seater with an M-71F-type C2A engine), it had excellent stability and control characteristics, was simple and pleasant to pilot, but it appeared too late, and the engine was not serial. Therefore, the Su-6 was not put into production.

Armament in a double version: two OKB-16 37 mm cannons or 11-P-37 long-barreled anti-tank guns (90 rounds), two ShKAS machine guns (1400 rounds) and one UBT machine gun (196 rounds) for the shooter. In addition, 200 kg of bombs could be suspended under the wing.

Photo	Description
	Drawing Su-6 modifications
	Drawing Su-6 powered by M-71F
	The Su-6 powered by M-71F during official trials in the Research institute of Air Force.
	The Su-6 (S2A) powered by water-cooled AM-42.

Unlike the Su-6 M-71F, the wing panels of the Su-6 AM-42 were made of metal with an area increased to 28.6 m².

In addition, the compensation of the elevators and ailerons was increased, a 400x150 mm tail wheel was installed instead of 300x125 mm, a PBP-16 sight (instead of BB-1) and a four-bladed propeller AV-9L-172 with a diameter of 3.4 m were installed.

Due to the need to armor the AM-42 engine from all sides, the weight of the armor increased by 252 kg (the thickness of the armored hood is 4 mm).

The weight of the empty aircraft was 4370 kg, the weight of the payload was 1375 kg.

The gunnery armament of the attack aircraft remained the same: two NS-37 wing cannons (the same 11P-37 in the series) with an ammunition load of 90 rounds, two ShKAS wing machine guns (1400 rounds) and one UBT machine gun in a blister (196 rounds). Bomb load increased to 400 kg (overload).

In the process of working out the state flight test program, a number of serious design and manufacturing defects of the AM-42 copy installed on the aircraft were revealed (ignition of the mixture in the suction pipes, oil consumption increased by 4-5 times), generated by the high-speed design of the engine in wartime conditions.

In this regard, it was not possible to completely remove the flight characteristics of the Su-6 AM-42 with NS-37 guns.

The maximum speed of the attack aircraft at an altitude of 1000 m was 508 km / h, at an altitude of 2000 m - 519 km / h. The plane climbed to a height of 1000 m in two minutes, and to 3000 m in six minutes.

During the tests, the NS-37 large-caliber guns were replaced with standard guns of the Red Army attack aircraft - VYa-23 (240 shells). The maximum weight of the bomb load has increased to 600 kg. The weight of the empty aircraft became - 4366 kg.

On April 28, 1944, the Su-6 AM 42 with VYa-23 guns entered state tests, which were already suspended on May 15 due to completely abnormal engine operation.

By this time, the state tests of the Il-8 AM-42 heavy attack aircraft had ended and the issue of launching it into a series was being decided.

In this regard, on May 19, 1944, P. 0. Sukhoi sent a letter to A. I. Shakhurin, in which he asked to take into account the preliminary results of tests of the Su-6 AM-42 aircraft.

He noted that the pilots of the GK NII VVS KA gave a positive opinion on the stability and controllability of the Su-6 aircraft, as well as on the ease of landing.

Sukhoi compared the flight data of the Il-8 AM-42 and Su-6 AM 42 aircraft based on test results.

"The Su-6 aircraft, yielding somewhat in range, has, with equal armament, a significantly higher speed than the Il-8 aircraft," Pavel Osipovich wrote in a letter.

The Su-6 was tested with two OKB-16 37 mm cannons, two ShKAS machine guns and 400 kg of bombs.

When replacing the guns on the VYa-23, the bomb load was 600 kg, as well as on the Il-8.

The maximum flight speed of the Il-8 at the ground was 428 km / h, while according to the Civil Code of the Air Force Research Institute, the maximum flight speed of the Su-6 with an unsatisfactory engine was 482 km / h, and according to factory tests with a more satisfactorily working engine -490 km/h

The speed at an estimated altitude of 2500 m for the Il-8 is 472 km/h, and for the Su-6 at an estimated altitude of 2800 m it is 523 km/h. The flight range at an altitude of 1000 m at a flight speed of 308 km / h for the Il-8 was 990 km, and for the Su-6 at a flight speed of 340 km / h - 850 km.

It should be noted that the flight speed of the Su-6 was higher when determining the range. In addition, the engine had an unfavorable adjustment in terms of fuel consumption, an over-enriched fuel mixture. Therefore, with a normal engine, the results in flight range could be almost the same.

It is important to note that with the same combat load, the takeoff weight of the Su-6 was 1000 kg less than that of the Il-8, that is, the weight return of the Su-6 aircraft was significantly higher.

At the same time, the IL-8 had a significant advantage when used as an armored bomber.

The maximum bomb load reached 1000 kg with two FAB-500 bombs suspended under the wings. In addition, the Il-8 aircraft was equipped with a bomber sight.

In May 1944, the Il-10 AM-42 attack aircraft successfully completed state tests, which showed high flight performance.

Comparison of the flight and combat properties of the Sukhov attack aircraft with the Il-10 was not in favor of the first. The Su-6 AM-42 was inferior to the Ilyushin machine in most of the defining characteristics. As a result, it was concluded that it was not advisable to launch the Su-6 AM-42 into mass production.

However, after the installation of a new copy of the AM-42 engine on the Su-6, the state tests of the attack aircraft were resumed and continued until July 44th.

In total, in the period from April 28 to July 2, 1944, 24 flights were performed on the Su-6 AM-42 with VYa-23 guns with a total flying time of 10 hours 25 minutes.

With a flight weight of 6200 kg (600 kg of bombs, ammunition for cannons and machine guns), the speed of the attack aircraft near the ground was 492 km / h, and at an altitude of I860 m - 521 km / h. The ascent time to a height of 1000 m was two minutes, to a height of 5000 m - 11 minutes. The maximum flight range is 790 km.

Photo	Description
	Drawing Su-6 with AM-42 engine

Bibliography

• "The history of designs of planes in USSR 1938-1950" /Vadim Shavrov/
• "Attack aircrafts of Red Army" /Vladimir Perov Oleg Rastrenin/
• "Attack aircrafts Su-2. " /Dmitriy Khazanov, Nikolay Gordyukov/