In 1940, the Su-2 (BB-1) bomber, designed by Pavel Osipovich Sukhoi, was put into production. This aircraft was created as part of the Ivanov program, which implied the creation of a single-engine, mass multipurpose aircraft capable of performing the functions of a reconnaissance aircraft and a light bomber. The Su-2 differed from other Soviet aircraft of this class by its advanced manufacturing technology and good visibility from the cockpit.
Su-2
With all the advantages of the new aircraft, it was ineffective when used as an attack aircraft. For this, it was required to strengthen weapons and increase security. Preliminary calculations showed the impossibility of implementing this on the Su-2, without deteriorating flight data. Therefore, it was decided to build a new aircraft.
In September 1939, a draft design for an armored attack aircraft was presented, and in early March, the government included it in the pilot aircraft construction plan for 1940.
The design team of P. O. Sukhoi was instructed to: "Design and build a single-engine armored single-seat attack aircraft with the M-71 engine."
The main difficulties in creating the attack aircraft were associated with the lack of M-71 conditioned engines. This is an 18-cylinder twin-row radial engine with a rated / maximum output of 1700/2000 hp. It was developed by A. D. Shvetsov and was a further development of the American Wright "Cyclone" R-1820.
The first version of the Su-6 was equipped with six ShKAS machine guns (of which 2 were synchronous). The in-body payload was designed in the following versions:
a) bomb FAB-100;
b) 2 bombs FAB-50;
c) 18 bombs AO-10, AO-15 or A0-20;
d) 72 bombs of caliber from 1.0 to 2.5 kg.
In addition, on the external sling, attack aircraft could carry 2 FAB-100 bombs or 2 FAB-250 bombs. The armor for the aircraft was designed in the form of an "armored hole" that protected the cockpit from below. The armored back eliminated the pilot's defeat from behind, and the bent armor plate covered the gas tank. Pilot protection from the sides - up to the chest. Up front, there was no booking. The pilot's head from above and the oil cooler in the original version also had no protection.
On March 1, 1941, test pilot of plant # 289, AI Kokin, took off the first prototype of the Su-6 aircraft. By May 1941, about ten flights were performed under the test program, during which they found and eliminated a number of defects in the power plant and aircraft systems. Most of all complaints were caused by the engine.
In this regard, the tests of the aircraft dragged on, and the outbreak of the war and the subsequent evacuation exacerbated the situation.
The Su-6 was able to enter state tests only in January 1942. The armament and armor of the attack aircraft were increased.
The test pilots noted the ease of control, the best flight and aerobatic properties of the aircraft in comparison with the serial Il-2 attack aircraft.
In the act of state tests of the Air Force Research Institute, the following data were reflected:
- The maximum speed at the ground is 445 km / h.
- Maximum speed with afterburner - 496 km / h.
- Maximum speed at an altitude of 2500 m - 491 km / h.
- Range at 0, 9 maximum speed - 450 km.
Armament:
- 2 guns of 23 mm caliber
- 4 machine guns of caliber 7, 62 mm
- 10 beams PC-132 or RS-82
Normal bomb load 200 kg, with a bomb bay capacity of 400 kg.
There is a suspension under the wings of 2 bombs of 100 kg each or 2 VAP-200, In terms of piloting technique, the aircraft is simple and accessible to pilots of average skill, has good stability and allows flight with a thrown stick in all modes. However, it was noted that the visibility on taxiing is insufficient and therefore it is necessary to steer with a snake. In the air, the review was assessed as satisfactory.
Reservation of the cockpit and the canopy is carried out similarly to the Il-2 aircraft. The rear cover of the engine with units is reserved, the engine cylinders are not booked.
The act of state tests also reported:
… the Su-6 aircraft with the M-71 engine is higher than the Il-2 AM-38 attack aircraft in terms of maximum horizontal flight speed;
- after completing the task (dropping bombs and PC-132), the Su-6 M-71 has a maximum speed of 483 km / h at a ten-minute afterburner. This speed makes the Su-6 difficult to reach for enemy fighters with a slight speed advantage;
- to consider it expedient to build a small military series of Su-6 M-71 aircraft, as they are of interest for a relatively high maximum horizontal speed and have powerful small arms and cannon and jet armament."
Despite the successfully passed tests, the new attack aircraft was not launched into the series.
At that difficult time for the country, mastering the production of a new attack aircraft and an engine for it would inevitably affect the rate of production of attack aircraft that were urgently needed by the front.
However, the improvement of the aircraft continued. To improve flight characteristics, the Su-6 was equipped with a forced M-71F engine with a rated / maximum power of 1850/2200 hp.
But by this time, based on the experience of hostilities, a two-seater version was already required. The Su-6 armored two-seater 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. The Su-6 possessed excellent stability and control characteristics, was simple and pleasant to fly.
The aircraft was equipped with powerful wing mechanization (it had automatic slats and Schrenk flaps), which made it possible to steadily perform maneuvers at high angles of attack. This was very important for a low-altitude battlefield aircraft. To launch an attack in a confined space above the target, the pilot had to maneuver mainly in the 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 the engine power. So, the serial IL-2 with AM-38F with a wing load of 159 - 163 kg / m2 had a vertical speed at the ground of about 7.2 m / s, and the Su-6 with a load of 212, 85 kg / m2 - 9.3 m / s.
The Su-6's armor was significantly 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 taking into account the influence of the aircraft structure elements (fuselage skin, bomb bays, etc.) on the geometry of the impact of the projectile against the armor from the most likely directions of fire in real air combat. This approach made it possible to seriously reduce the weight of the armor with significantly better protection of the crew and vital structural elements of the aircraft than that of the Il-2, in which, with a total weight of 957 kg of armor, the air gunner had practically no protection, and the armor parts most vulnerable to enemy fire turned out to be of insufficient thickness … The survivability of the attack aircraft was also increased by pressurizing the gas tank with exhaust gases and duplicating elevator and rudder controls. And the air-cooled engine itself was much more tenacious in the event of combat damage.
The aircraft had certain reserves in terms of enhancing armor protection. Based on the experience of combat operations, it was possible to replace the upper frontal armor of the hood with duralumin sheets, since this part of the aircraft practically did not come under fire.
The two-seater Su-6 had very powerful armament, it included two 37-mm NS-37 cannons (90 rounds of ammunition), two ShKAS machine guns (1400 rounds), a defensive machine gun UBT (196 rounds in four boxes) in a BLUB blister installation, 200 kg bombs and six RS-132 or RS-82. Two FAB-100 bombs could additionally be suspended on the external sling.
Compared to the Il-2 variant, which was armed with 37-mm air cannons, the Su-6's firing accuracy was significantly higher. This was due to the fact that the Su-6's guns were located much closer to the center of the aircraft. "Pecks" when firing, as was the case on the IL-2, were practically not felt. There was also the possibility of firing from one gun. The plane turned around, but not so much. Such powerful weapons significantly increased the ability to combat armored targets.
At state tests, the two-seater Su-6 aircraft was highly appreciated, and in the conclusion, according to the Air Force report, the spacecraft raises the question of introducing the aircraft into the series.
Comparative data of the Su-6 and Il-2 aircraft are as follows:
The speed at the ground of the Su-6 is 107 km / h more than that of the Il-2.
The speed at an altitude of 4000 m is 146 km / h more than that of the IL-2
The practical ceiling is 2500 m more than that of the IL-2
The flight range is 353 km longer than that of the IL-2
Su-6, having excellent maneuverability and speed characteristics, could be successfully used to combat enemy bombers and transport aircraft. For fighters, he also turned out to be a very difficult target. This was confirmed in 1944 in trial air battles with the Yak-3 fighter.
By the time the two-seat Su-6 was created, the Air Force specialists already possessed 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 Department of the Operational Directorate of the Air Force Headquarters on the analysis of aviation losses (August 1943), it was noted that of all the flight performance characteristics, it was maneuverability that had a decisive effect on combat survivability when operating against ground targets. Specialists from the Air Force Research Institute put forward similar requirements. 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 increasing the effectiveness of armor protection while reducing the proportion of armor in flight weight.
The Air Force leadership believed that it was the Su-6 that was the aircraft that the Soviet aviation lacked. In his opinion, the NKAP had the possibilities for the production of the M-71F engine and the Su-6 aircraft.
The production of the M-71F engines and the Su-6 attack aircraft could be adjusted at the existing capacities by reducing the production volumes of the M-82F and M-82FN engines and the Il-2 attack aircraft, which could not greatly affect the general situation at the front. In the rear (in the internal districts, in the Far East, in schools, at storage bases, etc.), a significant reserve of military vehicles has accumulated - about 20% more than in the active army, and at the front there was an almost three-fold superiority in forces over Luftwaffe. The number of aircraft produced at that time significantly exceeded the number of trained pilots for them.
Taking into account the high characteristics of the Su-6, the Design Bureau designed a high-altitude fighter.
After dismantling the armor, part of the armament and the defensive installation, according to calculations, the new aircraft should have had excellent flight data.
Serial production of the M-71F would make it possible to resolve the issue not only of launching the Su-6 attack aircraft into series, but also of the production of the promising I-185 fighter. In this case, a situation would develop when both strike and fighter aircraft were simultaneously re-equipped with equipment that surpassed the enemy's in all defining parameters, which would have the most favorable effect on the general course of the war. Meanwhile, the NKAP strongly opposed the production of the Su-6 and the M-71F engine in the series, motivating its position with a great technical risk when deploying their mass production in wartime. However, it seems that this was not the only problem. Having relied on quantity rather than quality, the leadership of the People's Commissariat was panicky to make any more or less serious changes to the already streamlined system of production of combat aircraft. In addition, having agreed with the proposal of the military, he would have had to actually admit the erroneousness of the adopted technical policy of the NKAP, starting in 1940.
Due to the lack of suitable engines, variants of the Su-6 with M-82 and AM-42 engines were tested.
With an air-cooled engine M-82 with a capacity of 1700 hp. The Su-6 showed higher performance in tests than the Il-2, but not as significant as with the M-71-F.
Installation of the AM-42 liquid engine on the attack aircraft by P. O. Sukhoi considered it a “step backward,” which he has repeatedly stated. Nevertheless, such an aircraft was built and tested. Due to the unreliable operation of the propulsion system, the tests were delayed. By the time they ended, the Il-10 attack aircraft with a similar engine was launched into mass production, and the relevance of this topic was lost.
Su-6 with AM-42 engine
The main reason for the rejection of mass production was the lack of production of the M-71 engine, for which it was originally developed. The Su-6 had excellent data for its time, and no doubt, if adopted, it would quickly surpass the famous Il-2. This aircraft would have remained effective in the first post-war decade. Unfortunately, this did not happen.
Chief designer P. O. Sukhoi was awarded the 1st degree State Prize, which he donated to the Defense Fund. But the high award only "sweetened the pill."
