Ilyushin Il-12 Coach
Passenger and cargo planes with the letters IL painted on their hulls can often be seen roaming the skies over Russia and the international airspace. IL stands for the world-famous Ilyushin aircraft designers named after the outstanding Russian plane maker Sergei Ilyushin. Ilyushin is one of the leading aeronautical establishments in the Soviet Union and the Russian Federation. The main concern is the production of military transport, tanker and AWACS planes, wide body passenger jets and business jets.
The family of civil IL planes started with IL-12, launched in mass production in 1946, and later followed by IL-14, IL-18, IL-62... The development of twin-transport aircraft Ilyushin Il-12 began in 1943. Wartime commitments delayed the building of prototypes, and the first flight took place only in early 1946. The Il-12 is all-metal, featuring two star-shaped engines AL-82FNV, the plane had a crew of four people, and the cabin, accommodating 27 passengers. Later the number of seats increased to 32. The military version added a cargo hatch with the double-doors on the far left side of the fuselage, as well as machine guns, fired through the windows of what had been the passenger compartment.
It was founded in 1933 with the name of OKB Ilyushin (OKB=Special Construction Bureau) at Menjinski plant. It was then moved to Moscow. The first important work of the organization was was the DB-3 long range bomber which were produced in 1935 with a production quantity of 1538 planes. It was followed by another bomber Il-4 and in 1940 by the ground attack plane Il-2. Il-2 is one of the most successfull planes of the time. During the war time 6,800 DB-3 and IL-4 were built and 42,000 IL-2 armored ground support aircraft.
The defeat of the Nazi forces on the Kursk in the summer of 1943 marked a radical change not only in the Great Patriotic War, but also in World War II. This circumstance and the victorious advance of the Red Army on other fronts created the necessary, although insufficient, condition for the start of the transfer of industry to peaceful "rails". One of the first who realized this was the team of KB S.V.Ilyushin. The war was in full play, but the government thought about the peaceful sky. The DC-3 and LI-2 Aircraft were completely old, and a plane with outstanding characteristics was needed. Ilyushin Design Bureau started to design a new aircraft in 1943, and in victorious 1945 a test model flew to the sky, which further got a name IL-12. It was a solid middle-range passenger aircraft.
In 1943, long before the Victory, realizing that after the war the country would need a civilian passenger plane better than the LI-2 (DS-3), Ilyushin starts work on the IL-12. In 1946 the Il-12 was launched by Aeroflot. So in the Soviet Union appeared the first domestic aircraft for mass passenger transportation, and in the OKB a new direction of work - passenger aircraft. Il-12 was also produced in the military transport variant.
The initial project of the future IL-12 had pressurized crew and passenger cabins, as it provided for a long flight at altitudes of about 7000 m (i.e., in the substratosphere). The machine was designed to carry 29 passengers, and the flight range was planned up to 5000 km, although with less load. Such an aircraft required a powerful propulsion system of four high-altitude M-88V engines.
The project was approved at the very beginning of 1944, but it was soon demanded to be processed for seemingly promising diesel engines. The design change for two ACh-31 (2000 hp) caused a change in the fuel system and the abandonment of pressurized cabs. The contours of the nose of the fuselage have changed, which in the first draft were calculated for overpressure. Now the car could accommodate 27 passengers; for this, three seats were placed in a row across the flight direction in a cabin that was more spacious than that of the most massive Aeroflot Li-2 aircraft.
Much attention in the development of the machine was given to the creation of effective anti-icing and fire fighting equipment, as well as to ensuring a long horizontal flight on one engine. The controllability of the aircraft was facilitated by the use of a servo trimmer on the steering wheel, which worked both as a servo compensator and in the mode of trimmers controlled by pilots.
An innovation on the IL-12 was also a three-leg landing gear with a nose strut, which allowed not only to simplify control of the aircraft on takeoff and landing, but also to increase passenger comfort, since the cockpit floor was now parallel to the ground. For the cargo version of the machine, this made loading and unloading easier.
The first take-off of IL-12 with diesel aircraft engines ACh-31 piloted by Vladimir and Konstantin Kokkinaki took place on August 15, 1945. It soon became clear that diesels would require a long refinement period. In 1947, the ACh-31 engine was just being finalized at 50 hours. Experimental IL-12 with a mass of 16,000 kg was accelerated in horizontal flight at an altitude of 5000 m to 445 km / h. The cruising speed was -325 km / h, but the capricious and unreliable ACh-31, in aviation did not take root. In this situation S.V. Ilyushin decided to replace diesels with ASh-82FN engines (1850 hp) tested during long operation. The engines intended for the passenger aircraft did not mount the second stage of the supercharger. Flight data, especially range, decreased significantly, but reliability increased significantly.
The new motors pulled along with them the alteration of the means of mechanization of the wing and the main landing gear with a change in the mechanism of their cleaning and the replacement of single wheels with twin wheels, which increased the passability of the car at unpaved airfields. The alteration of the aircraft took less than four months, and on January 9, 1946, it was reborn, and the IL-12 took off. Do not assume that from this day the tests were easy. As before, the motors presented a lot of trouble, but these were other difficulties that they quickly dealt with. The tests confirmed the calculated characteristics, and therefore, even before the end of the tests, the serial production of the passenger IL-12 began to be launched at the aircraft factory No. 30.
The February decision of the Council of People's Commissars OKB-240 instructed to build a transport IL-12, designed for 3500 kg of cargo and a passenger version with engines ASh-93 of greater power. The task provided for the transportation of 27 passengers at a range of up to 2000 km. The maximum speed was expected 450 km / h.
In July of the same year, state tests of the 27th local IL-12 began at the Scientific Research Institute of Civil Air Fleet. Leading pilots were G.A. Taran (during the war years he commanded the air transport regiment of the Civil Air Fleet) and A.I. Voskanov. The new modification had a cruising speed of 344-350 km / h when flying at an altitude of up to 3000 m. One engine could fly at a speed of 273-289 km / h, which is almost 100 km / h higher than that of a Li-2 . Tests that took place with a flight weight of 16,300 kg showed the possibility of a further increase in this indicator, and this is an additional commercial load and flight range. Pilots A.I. Voskanov and I.P. Mazuruk conducted a study of the stability and controllability of an aircraft with a flight weight of 16800 kg, as well as in the reloading version up to 17500 kg in the event of failure of one of the engines.
For operational tests, 25 aircraft were manufactured, including several cargo ones, which were sent to the Vnukovo air squad. Several machines performed flights with a take-off weight of 18,200 kg. Pilots noted that this made it difficult to take off the plane and fly to a speed of 175 km / h, and the approach due to a sufficiently large drawdown during leveling. According to the results of the tests, the flight weight was limited to 17,250 kilograms, in this case, the IL-12 became available for operation to intermediate pilots.
Excellent operational characteristics were confirmed by a non-stop flight on the Moscow-Tashkent route with a total length of 2820 km, as well as flights at altitudes of up to 6500 m, which were carried out through the mountain ranges of the Caucasus and Central Asia. IL-12 had to take off from high mountain airfields.
After the completion of the operational tests, improvements the new aircraft in June 1947 entered the passenger lines, gradually replacing the obsolete Li-2. The main option was for 27 passengers, but other modifications to the cabin were made. For example, on domestic short-range lines it accommodated up to 32 passengers, and up to 4,000 km in an airplane 11 passengers were more comfortable.
The popularity of the aircraft was affected not only by good speed characteristics and comfortable seating of passengers, but also by the fact that the aircraft provided quick and easy mastering of the flight crew. IL-12 used the same airfields and landing sites as the Li-2. By the end of 1947, the 30th plant delivered to the customer 188 Ilov, which allowed expanding the geography of the machine. Now it was possible to meet it not only on intra-union, but also on international (since the fall of 1948) routes. IL-12 received a residence permit in the Polar Aviation of the Glavsevmorput. It seemed that for the IL-12 and OKB everything was working out perfectly, but less than a year later a storm struck. Aeroflot quickly discovered that after 150 hours of flight, the aircraft needed to be repaired, with the elimination of structural and manufacturing defects, which the operators could not do.
The machine, once again, had to be finalized. And only after that, the IL-12 became the owner of the airways. On this machine pilot V.A. Filonov achieved the highest flight performance - 863 t / km in one hour, and since 1953, after the start of their operation by interchangeable crews, the flight of aircraft has increased even more. This became possible only due to the high reliability of the IL-12.
In 1947, in strict accordance with the government decree of March 16, the landing transport IL-12D (the first flight took place on August 29) was developed on the basis of the passenger, which was supposed to carry up to 3,500 kg of cargo. The cargo compartment floor was covered with metal panels and 36 hinged landing seats were installed on the sides of the fuselage. A cargo door appeared on the left side of the fuselage, opening outwards and to the sides. These improvements made it possible to transport guns of caliber up to 85 mm, 120 mm mortars, a GAZ-67 car and an M-72 motorcycle with a sidecar. On the fuselage provided a device for towing airborne gliders. Subsequently, the aircraft, modified according to the requirements of the Air Force, allowed transporting up to 37 paratroopers or 27 wounded on a stretcher with a crew of two pilots, a navigator, a flight radio operator and a flight engineer military equipment with a total weight of up to 4000 kg, as well as towing Ts-25 and Yak-14 gliders. The transshipment weight of the IL-12D reached 18500 kg.
Outdated radio equipment and scanty engine life caused a lot of complaints. At a meeting at the Ministry of Civil Aviation in August 1947, it was reported that the minaviaprom increased the resource of ASh-82FN engines within 200-300 hours and should have clarified it by October. Aeroflot management was worried not only about the low resource of engines, but also their reliability.
By the way, an interesting experiment on towing an IL-32 glider at the Air Force Research Institute is associated with the IL-12D. It was an attempt to “save” the super-heavy glider, for the towing of which the strength of the four-engine IL-18 (the first with the same name) was not enough. In order to haul IL-32 weighing 9600 kg, they "harnessed" it to two IL-12s flying a bearing system. Officially, the topic was called "Fan", and among the people - "Swan, cancer and pike." But, as it turned out pretty quickly, a simple idea at first glance required the highest qualification of towing pilots and was not successful.
Another feature of the "Il" was the use of it as a bomber. To do this, bombs were made on both sides of the wing center wing, installing cluster bomber holders for 16 high-explosive bombs of 100 or 250 kg caliber in the fuselage. Under the center section, there were three beam holders designed for both the suspension of landing containers and bombs of caliber up to 1500 kg. For bombing and dropping loads, the OPB-1R sights and the NKPB-7 night collimator sights were used. The latter was located in the blister cabin navigator. To protect against an air opponent, the UTK-1M fuselage installation with a 12.7 mm UBT machine gun was provided.
Georgy Filippovich Baidukova, quickly understanding the situation around the IL-12, actively took up the fine-tuning of the machine. In particular, in a letter to the Chief of the General Staff Vasilevsky dated March 26, 1948, he said: “IL-12 aircraft manufactured by the industry to date have a large number of manufacturing defects and structural deficiencies, in particular: they do not have anti-icing devices, the engines are started in the most technically backward way - compressed air, equipped with outdated radio equipment and with a wave range, not allowing to communicate with terrestrial radio stations of foreign airports, heating the passenger cabin is not reliable and often refuses to work ... "
IL-12T aircraft, and then IL-12D, were launched in a series. In 1948, the de-icing system was finalized. Now for this purpose, instead of the exhaust gases of the engines, outside air was used, heated by special heat exchangers. De-icing devices of this type protected both the wing and the stabilizer (previously an electrothermal device was used).
After one of the disasters, the reasons for which remained undetermined, in 1949 the flight weight of the Il was limited to 16,100 kg, while the number of passenger seats was reduced to 18 (the first three rows of seats were removed). At the end of the year, propellers were replaced with a modification that excluded their inadvertent unwinding in flight. As such, the IL-12 was operated for almost five years, and only in 1954 the restrictions were partially lifted, bringing the load to 21 passengers.
But in the first months of operation an incident happened at Vnukovo airdrome, which showed Achilles’ heel of two-engine passenger aircraft. One of engines broke down during run of the new aircraft, which was carrying children to Adler. The flight had been stopped immediately. No accident happened due to nose gear, and the nosing –over didn’t happen. The aircraft was short of power for guaranteed take-off with only one engine.
In aviation, as well as in technology in general, often disasters contribute to the identification of previously undetected defects in aircraft. So, at the cost of the death of the Norwegian female delegation returning to Il-12 from Stalingrad to Moscow, it was possible to eliminate a defect in the design of the seemingly comprehensively tested ASh-82FN engine. On the way to Stalingrad, an overspending of oil was discovered, but the crew, in violation of all the instructions, limited itself to only refueling the oil tank. On the way back, the oil ran out pretty quickly, and the engine, having worked "dry", ignited. As a result, the back cover of the engine, made of magnesium alloy, burned out, and the incoming air stream, raising the temperature of the fire stream, turned it into a gas cutter, easily destroying the wing's power elements.
After this incident, all the details of the ASH-82FN, which were previously made from magnesium alloys, began to be made of aluminum and the fire extinguishing system was improved, protecting the car and people on board.
In 1950, a modified rudder equipped with a spring servo compensator was installed on the plane. This innovation has reduced the load on the pedals, especially in the event of failure of one of the engines. Gradually, the "childhood illnesses" of the liner passed, and by the mid-fifties of the twentieth century, the IL-12 became as popular as the Li-2 once. In October 1958, the Il-12 under the flag of Polar Aviation (USSR-N440), piloted by pilot V. Petrov, flew over the planet’s South Pole for the first time, once again confirming its reliability. At the same time, the maximum range of the IL-12 with an additional fuel reserve reached 4000 km, and the flight altitude was not lower than 4500 m.The full length of the Mirny-South Pole-McMurdo route (US base) and back reached about 7000 km.
Serial production of the IL-12 ended in 1949. In four years, the P30 plant built 663 aircraft. Until 1948, the IL-12 flew on the main lines of Aeroflot. In the same year, flights began to Helsinki, Sofia and Warsaw. A year later, an export modification of the IL-12B appeared. The first to begin to develop it in the Czechoslovak airline "CSA", where they were operated until the mid-1960s.
In the spring of 1948, the IL-12 was exhibited at an exhibition in Poznan, and from the next year, the IL-12B began to enter the Polish LOT, and the IL-12D - to the Air Force. Then these machines appeared in the Bulgarian airline "TABSO".
Deliveries started in 1947. The total production of IL-12 more than 2000 aircraft. By the time it was withdrawan from the production in 1953 in favor of IL-14, it had received the NATO code name Coach. The later modification IL-14 became the workhorse of Soviet Aeroflot in the 1950's, until 1959 when the IL-18 started its flights.
From 1946 to 1949, Plant No. 30 produced 663 Il-12 aircraft of various modifications. IL-12 was widely used in the armed forces, both in transport (IL-12T) and in the landing (IL-12D) versions. The military had to solve problems aimed not only at ensuring the combat readiness of the troops, but also transporting the transportation of various goods, equipment and personnel of the units.
In China, both passenger IL-12B and airborne transport IL-12D were operated. In the last years of the aircraft’s life, the Chinese installed AS-82T engines with IL-14 on the “Ilya”. In China, the IL-12 were in operation longer than in other countries. Passenger aircraft on-board No. 505 continued flying until October 27, 1985, and aircraft No. 503 was decommissioned only on October 6, 1988. The last two IL-12s were operated in the army until October 1993. Later on they supplemented the exposition of the Datan-Shan Museum. Thus, the "hard worker" IL-12 was in service for 45 years. Such a long life can be envied by many aircraft in the world.
The maximum speed at an altitude of 2500 meters (8200 feet) of 407 kilometers per hour (253 miles / hour), a practical ceiling 6700 meters (22,000 feet); range 2000 kilometers (1250 miles). Weights: empty curb - 9000 kg (19,800 lbs) maximum takeoff 17,250 kg (38,000 pounds). Dimensions: wingspan 31.7 meters (104 feet) length of 21.31 meters (69 feet 11 inches); area 100 sq. meters (1076.43 square. ft).
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