Helicopter S-55 I. Sikorsky | MODEL CONSTRUCTION

Helicopter S-55 Sikorsky Aircraft company, part of United Aircraft Corporation, was designed and built in the late 1940-ies, during the period of rapid progress in the global helicopter industry, becoming a significant success of its designer, Igor Sikorsky. By this time, the aircraft designers and military ceased to consider helicopters as merely exotic aircraft. Before them were staged combat missions of a wide range of: supplying troops in remote areas, landing, fight enemy submarines, aerial photography, rescue of crews of downed aircraft, setting smoke screens, laying communication lines, and aerial surveillance.

The helicopter could be also essential when conducting amphibious operations in a nuclear war, when most airfields and military bases could be destroyed in a nuclear exchange. In these conditions it was assumed before the attack of the enemy secretly to disperse the landing force and their subsequent concentration in the landing place, using for this purpose a large number of transport rotary wing vehicles.

To implement these ideas needed a reliable car, capable of carrying 10 to 20 men, or about a ton of cargo. Held also armed search and rescue double and triple helicopters on the role of transport workers was not good.

In 1946, the firm Beil has developed a helicopter Model 48A with two-bladed propeller, capable of carrying up to eight infantrymen with weapons. For military tests built ten prototypes under the designation YR-12, but technical problems did not allow to run “48A” in the series. At that time, have spread the view that to design a heavy helicopter single-rotor design is impossible. The most realistic prospects for the creation of such devices was associated with a twin screw apparatus of the longitudinal scheme, which was developed by the firm American aircraft designer Frank PIASECKI (by the way, the son of the Russian citizen who immigrated to America before the revolution). In 1945 he created according to this scheme the biggest helicopter of the time PV-3 (HRP-1), which could be carried in the cabin for eight troops or 900 kg of cargo. The laws of aerodynamics dictated that the long fuselage PV-3 small midsection needs to have a reasonable drag, and a good longitudinal stability will be ensured in a wide range of alignment due to the location of the cargo compartment between the rotors.

Igor Ivanovich Sikorsky

Advantages of the scheme PIASECKI to illustrate, imagine a picture when a heavy bag carry handles for two people. Regardless of the shape and placement of cargo in the bag, both have approximately equal load, as the bag itself is in relative peace and almost swinging.

Sikorsky, despite the visible advantages of the longitudinal scheme, believed that heavy single-rotor helicopter possible and more promising. The own funds of the company, the designer started to create a ten-machine S-55. In this work were taken into account all the experience of the construction and operation of helicopters, analyzed the advantages and disadvantages of already tested aerodynamic designs and constructive solutions.

The layout scheme of the previous Sikorsky helicopters S-51, S-52 and S-53 for the new project was not good because the engine they were placed on the axis of the rotor, and the cab at the front – its weight is balanced by the tail boom. However, to provide the necessary centering of heavy transport vehicles with the location of the load ahead of the axle screws was very difficult. Returning to our illustration with the bag, it turns out that if one of the porters to leave his pen, the stability of the whole system will be disturbed. The logical way out of this situation is to hold both handles in one hand. Did Sikorsky.

On the S-55 cargo cabin located on the site of the engine, directly on the axis of the rotor, and the power plant in bow, where she balanced the tail boom. To ensure the equilibrium of the apparatus when the layout was much easier. A two-seat cockpit mounted above the engine, which provided a good overview and a high level of crew safety in case of a rough landing, the helicopter crash or fire from the ground.

Sikorsky H-19 Chickasaw

The eight-cylinder radial piston engine was mounted at an angle of 45°. With the main gear it was connected by the long shaft located in the plane of symmetry of the cab. For better cooling of the front of the motor mounted fan. Hot air is output through the grille cutouts on the sides of the forward fuselage. Part of this air can be directed into the cabin for heating it in winter or when flying at high altitudes. This engine had another advantage – ease of access for maintenance or replacement.

Two-stage planetary main gearbox mounted on the ceiling of the cargo compartment separated from the engine compartment the firewall and connected to the cockpit by a narrow passage. Inside the cargo cabin could accommodate up to ten Marines or eight wounded on stretchers. For ease of loading and unloading on the starboard side of the cabin provided a large sliding door.

The world’s first helicopter S-55 was equipped with a four-channel fully powered control.

Instrumentation was provided by flying at night and in poor weather conditions. The radio equipment consisted of a radio altimeter, radio compass and radio stations were installed in the rear cargo compartment.

The rotor is three-bladed. The propeller hub had combined horizontal and vertical joints. The blades are all-metal. The blade spar was a extruded hollow D-shaped profile. Its caudal portion, consisting of shell with honeycomb core, glued to the spar. For the first time screws this design was used si-korskim record helicopter S-52.

The possible occurrence of fatigue cracks in the spar was diagnosed by controlling a pressure of the injected gas inside the cavity. If the gas coming out through the crack, the pressure in the cavity of the spar fell, and from the butt of the blade has been pin red.

The tail rotor is two-bladed, high. He was rotated from the end of the gearbox, which by means of transmission shafts, through another intermediate gearbox connected to the main gearbox.

The fuselage – semi-monocoque, was assembled from parts made of aluminum and magnesium alloys.

Fuel tanks with a total capacity of 723 l were located beneath the floor of the cargo compartment. There was a possibility of installation of additional fuel tanks inside the cargo compartment, to thereby increase the flight range up to 1600 km.

Heavy and oversized cargo S-55 could carry on the external sling. And to raise on Board a light cargo and people during rescue operations on Board there was a small winch.

Four-post wheel chassis wasn’t cleaned. The main landing wheel had a braking system that is controlled by pedals. A-pillars – equally fluent.

To balance the helicopter in flight at cruising speed the tail boom was fitted with a small adjustable stabilizer.

The design of the new helicopter took less than a year. The first flight of the S-55 was held on 10 November 1949, and he was immediately submitted, the U.S. air force, which required a rescue helicopter for the Strategic air command.

In terms of competition, the car had to have a sufficient number of places in order for one flight to take on Board the entire crew of crashed b-36. Note that the competition of the firm were obliged to provide equipment in a condition suitable for flight tests.

The first phase of testing of the helicopter S-55 was conducted at Eglin air force base (Florida), where there was a Command of testing new aircraft. A leading test pilot appointed major of Bedford brown and his assistant, captain Joseph D. Cooper. The helicopter was evaluated in normal weather conditions. Testing consisted of flying the determination of the maximum load and confirmation of the declared performance.

Helicopter Sikorsky S-53

Helicopter Sikorsky S-52

Helicopter Sikorsky S-55 had an unusual layout-its engine positioned in the front, freeing up space for the cargo compartment under the gearbox. Photo – British helicopter modification WS-55 “Whirlwind”

The main concerns of pilots related to poor stability of the machine and the lack of rigidity of the tail boom that is dangerous fluctuated during landing. Problems decided to install in the rear fuselage of triangular ribs-bracket – he supported the tail boom, improving rigidity and structural strength and improved aerodynamic performance of the helicopter. In addition, the tests revealed the futility of the adjustable stabilizer, and Sikorsky the production version of the S-55 was limited to the installation of a fixed stabilizer, to enhance directional stability fastened it to the inverted-V

After successful completion of the first stage of testing the aircraft was assigned the military designation of uh-19A and handed it to the custody of the headquarters of the 5th air army force in Korea, where for three months the pilots checked it in a combat situation. During this time, Cooper and co-pilot Russell Uiharu managed to evacuate from the front line 99 wounded and rescue the five pilots. In one of the missions in S-55 has set a record – the pilots of the helicopter were taken from the environment 11 seriously wounded soldiers.

The helicopter had to participate in special operations delivery in the rear of the subversive groups and the removal of structural elements and equipment of the MiG-15. The latter task was entrusted to the crew in case “Moment” will be hit by 200-km zone off the West coast of North Korea. When Cooper and Figaro reported that it discovered the downed MiG, they immediately flew to the place of their fall. In flight at low altitude, S-55 was covered fighters S-51 “Mustang”, the average F – 80 “Shuting Old”, and on the big F – 86 “sabre”.

The downed fighter was found on a remote mountain ledge. After planting in the case entered a specially trained team that dismembered “MiG” with the help of saws and hand grenades. All disassembly and loading of the parts took about 45 minutes. On the way back the pilots went straight over the fortified area of the Koreans, which opened on machine a heavy fire from all weapons. The helicopter was damaged, but continued flying. When they reached the coast, the pilots landed, on their own eliminated damages and reloaded some precious cargo on a flying boat SA-16.

Upon arrival in the United States, brown wrote a report in which he commented on the helicopter. The paper noted that S-55 can be used to solve the problem by saving and transportation of goods. But the role of machines for targeting and control the actions of tactical aviation helicopter handled badly. Control officers complained of great vibration and low speed S-55. Technical staff noted frequent failures of windshield wipers, brakes, wheels and system heat the cabin.

Returning from Korea, the helicopter was delivered to Eglin air force base. Now he was tested in extreme conditions in a special climatic hangar. This miracle of technology was used by the Americans in 1941. Structurally, the hangar consisted of several compartments. In main with the size 61×76 m rolled the aircraft, and in other compartments were cooling devices, pumps for water, fans, etc test cycle was two days in which the temperature is first lowered to -53° C, then raised to +74°, simultaneously increasing humidity, thus simulating the tropical climate.

Identified during the testing deficiencies, the firm has eliminated, and in the winter of 1950/51 year, the helicopter ferried to Alaska. Joseph Cooper had to make a few flights for the transfer of cargo. In particular, S-55 and took away the property with two crashed military aircraft and rescued the pilot of a light plane that made an emergency landing in a remote area because of loss of orientation. Once again, Cooper scored, rescuing a group of staff a bombing range – house of this group were burned and people were left homeless in the dead of winter.

Despite its obvious successes, the machine Sikorsky was defeated in the contest. Adopted Strategic air command took the helicopter of the longitudinal scheme PIASECKI PV-22 (H-21), although it was submitted to the competition much later. The fact that the capacity of the S-55 it seemed to the customer is insufficient, while on Board-36 could take a double set of pilots and navigators, which increased the number of seats available in the helicopter to 22, a S-55 that the number of passengers was not calculated.

However, he loved the military, and in 1950 he ordered the Army, air force, Navy and U.S. Coast guard. In December of the same year under the designation H-19A Chickasaw began mass production and delivery of S-55 to the troops. The name of the helicopter given in honor of an Indian tribe of Chickasaw (Chickasaw), who lived near the Mississippi river. In the troop transport variant for the marine corps “Chickasaw County” had the designation of HRS-1, and rescue variant for the Navy -HO4S-1.

Almost immediately after adopting the helicopters sent to Korea, where difficult combat rotorcraft well proven.

Given the experience of the Korean war, the serial production of S-55 was only increased, and orders for it every year. Simultaneously, the machine is constantly modernized. By 1955 the army H-19B received a new engine R-1300-3D 700 HP, the rotor was increased to 16.5 m diameter and rejected 3° down tail boom. To tilt the beam decided after several accidents in which she was cut off by the rotor. In the same period, called H-19D began to produce and assault variant of the S-55, armed units with unguided rockets and heavy machine gun.

In March 1952, the helicopter received a certificate, and the company “new York Airways” started to use S-55 for regular freight traffic, and a year and passengers.

In just 12 years of serial production the plant in Bridgeport was built 1281 (257 civilian and military 1024) S-55 valued at $ 150,000 each.

Since 1952, the British firm Westland Aircraft Ltd started the construction of S-55 under license under the designation WS-55 Whirlwind (eng. – vortex). The first licensed flight of the machine took place on 12 November of the same year. For eleven years the British built 485 machines.

In 1952 the S-55 was the first helicopter in the world, flew across the Atlantic ocean, and embodied in the reality of the American dream about the transfer of helicopters to Europe on their own, similar aircraft on the route Labrador – Greenland -Iceland – Scotland – Germany. The flight was performed two search-and-Spa-stalnyh N-19A, is fitted with three additional fuel tanks.

The morning of July 15 of the machine rose into the air with a military air base near Springfield, to the North from the helicopter plant in Bridgeport. Pilots first with its own name Hopalong (“leap”) were captains Vincent Mak Govern and Harry Jeffers; the second, called Whirl a way (“Whirlwind, rushing into the distance”), was piloted by captain George Hembry and first Lieutenant Harold Moore.

July 31 at 16 hours after the most difficult in aviation history of flight in adverse weather conditions, the helicopters landed in Scotland. Length of the route amounted to 6375 km. Intermediate landing was carried out in paragraphs Westover (USA), Presque EIL (USA), goose Bay (Canada), Narsarsuaq (Greenland), keflavík (Iceland), Prestwick (Scotland), the Hague (Holland) and Wiesbaden (Germany). In total they spent in the air 51 hours and 55 minutes. The average speed record flight was equal to 130 km/h, height – 230 m. the length of the last continuous area amounted to 1508 km, thus, the S-55 set a new world distance record, previously owned car Sikorsky S-48.

The first production helicopters S-55 differed stabilizer inverted V. On photos Australian S-55

“PIASECKI” PVS-22, won the competition for the rescue helicopter for the Strategic air command of the United States

Historic flight proved the principal possibility of transporting helicopters on their own across the ocean. Unfortunately, to date, the two legendary machines are not preserved, and the Museum of the U.S. air force is N-19V (tilted beam), painted Hopalong. The flight was widely publicized and contributed to the increase in sales S-55.

Following Britain, a license to manufacture S-55, acquired the French. Firm NCASE “Sud-Aviation” built 87 copies called E Iéphant Joyeux (“Joyous elephant”).

71 machine type S-55 made under license from Japanese company “Mitsubishi”.

S-55 served as a platform to conduct various experiments. In one of them the blades of the rotor of a standard helicopter of the marine corps НRS-2 was equipped with a small liquid rocket engines (LRE), working on hydrogen peroxide. The approximate weight of one LPRE -0,4 kg. the Fuel tank is dome-shaped is secured on the propeller hub and the pipelines to LRE laid in the cavity of the spar. Stock rocket fuel does not exceed 30 kg and can provide three LRE for seven minutes. The main purpose of such extraordinary additional power – plant- to increase takeoff power, thereby giving the rotary-wing apparatus the ability to land a helicopter in the event of failure of the main motor.

Tests showed a dramatic improvement in characteristics of the helicopter when you turn on a rocket engine. For example, if earlier НRS-2 at sea level were able to evacuate six people and at an altitude of 5000 m is only three, it is now at any height could take one more person, and still take off vertically. However, concentrated hydrogen peroxide was a serious danger for the machine and its crew, and the military decided that this system is unusable in normal field conditions.

Helicopter United States coast guard H-19A with a float landing gear is landing on water

A helicopter from the U.S. coast guard H-19A with a float landing gear is landing on the water

Helicopters S-55 was used by the air forces of Argentina, Australia, Belgium, Brazil, Brunei, UK, Venezuela, Ghana, Greece, Guatemala, Honduras, Dominican Republic, France, Israel, Italy, Spain, Qatar, China, Colombia, Canada, Kuwait, Nicaragua, Nigeria, Pakistan, Portugal, USA, Taiwan, Thailand, Uruguay, the Philippines, Sri Lanka, South Korea, Japan and Yugoslavia.

Large orders in S-55 and other helicopters allowed Sikorsky to improve the financial position of the company and to start developing a new rotary-wing vehicles.

S-55 was to have an enviable fate. Some of them fly so far. Created in the middle of the last century with the use of many new technical solutions, which has become a classic today, these machines are able to argue in its characteristics with the modern “classmates”.

In March 1951 the first production S-55 entered service with the squadron of heavy transport helicopters marine corps НMR-161 under the command of Colonel John herring, which became the first in the history of aviation division of this kind. By the way, in the Marines they had the designation НRS-1.

After retraining and resupply crews the squadron was sent to Korea and August 31, landed in Pusan, and pilots began to fly for yourself area.

In early September НМR-161 was tasked to support the 1st marine regiment, which was in a difficult position, being in a mountainous region without a stock of weapons and food. In the cargo compartments of helicopters has put an additional fuel tank 270 liters of fuel.

13 September at 15 o’clock 20 minutes we began loading ammunition and food for the Marines. At the same time, the helicopter was taken to the location of the Marines, the branch of fighters to support at the place of unloading. After 30 minutes, seven loaded cars up in the air. The flight route passed through a deep ravine, providing good cover from anti-aircraft weapons. At the exit of the hollow, equipped with a landing area the size of 6×12 meters, lined with glowing stripes. Planting was directed by the Manager in a well visible from the air a white jacket. Next to the Playground established a high pole with a red flag; the flag signaled that the area is under enemy fire.

In 16 hours 10 minutes appeared first helicopter with a load suspended on a ventral hook. Leaving the cargo it took on Board seven wounded (two on stretchers) and went back. The flight continued for three hours, rotorcraft during this time made 28 vertoleta-departures, while they delivered 8560 kg of cargo and evacuated 74 wounded soldier.

Two days later, the squadron НМR-161 has completed a new assignment, which is subsequently commented on the pages of all American Newspapers of the time. The helicopters were to deliver a unit of Marines on one of the most difficult areas of the mountain regions of Korea. The first was to drop off the soldiers of the reconnaissance company. The landing was a tall, with two suitable for planting sites for 50 square meters each. It was supposed to pull the fighters hanging from helicopters with the help of a 9-meter rope with knots. For the landing of the first four people took a minute and a half. In other cases, the time of descent of one soldier took about 20 seconds. In four hours the helicopter landed 224 fighter and brought 8 tons of cargo. At the end of the operation one of the machines with suspended coil of telephone wire laid for paratroopers line. In the official report on the operation said: “These initial startling success showed how largely the helicopter can contribute to the solution of tactical problems related to transfer and supply the attacking troops.”

At the end of September was accomplished, perhaps the only one in the history of the Korean war, night helicopter landing – “operation Blackbird”. The task required to deploy a reinforced infantry company to cover the exposed flank of the American troops in 8 km from the front edge. According to the order, the day before the operations conducted daily exercises in similar conditions of the landing area.

Combat landing began in complete darkness. Each helicopter was carrying five soldiers. To avoid clashes, took off with an interval of three minutes, and the flights there and back were carried out at different heights. The operation took place with considerable difficulty. Thus, the electric lights were too weak, and to indicate the boundaries of the landing site had to kindle fires and use of signal fireworks. Fires repeatedly zadavalis air stream from the propellers, and bright fireworks dazzled the pilots. But, despite all this, two hours of turntables delivered to the space 233 of the paratrooper.

Helicopter S-55 designs and.Sikorski:

1 – rotor hub 2 – blade rotor; 3 – them; 4 – float; 5 – reflector; 6 – the cockpit glazing; 7 – keel; 8 – the tank of jet fuel; 9 – grid cooling of the engine; 10 – sliding load compartment door; 11 – towing hook; 12 – supporting beams; 13 – rod hook; 14 – fixing unit rod; 15 – exhaust pipe; 16 – hinged engine hood; 17 – blades tail rotor; 18 – absorber; 19 – tail safety heel; 20 – shock absorber main landing gear; 21 – stabilizer

In October the Sikorsky helicopters were deployed for a whole battalion. This time the military has developed efficient methods for rapid loading and unloading soldiers. The transfer, which involved 12 helicopters, began October 11th at 10 am. For five hours the helicopters transported 958 people and 104 tons of cargo.

15 Oct six НRS-1 evacuated from the environment unit of the South Korean troops and 24 wounded, for which he received a commendation from the commander of the 9th army corps major-General of Vöhrenbach.

The next task was the struggle against partisans in the occupied territories. According to the plan, October 20, provided for the landing of the soldiers in different places of the woodland and mopping up the territory. Bad weather delayed the flight for one day. 22 Oct still it was drizzling and the wind was blowing, but the helicopters rose into the air. Of the ten two cars rolled over during takeoff, and the third fell while in hover, and suffered serious damage. In these accidents, due to the high strength of the fuselage structure, injured only one person. Some time later, a few helicopters managed to take out the engines and main parts of the crashed cars.

October 26 began operation “Husbander I” the destruction of villages in the rear of American troops in order to deprive guerrillas of shelter during the winter. Two helicopters deployed a group of four soldiers with explosives, grenades and flamethrowers. One car flew over a target village in the cordon, and on the other tried a flamethrower to set fire to the house and to throw their grenades. But a powerful stream of air from the helicopter rotor is not allowed to use the flamethrowers. It was decided to plant a demolition near the village.

On the following day participated in the operation for four НRS-1. They made 20 sorties, destroyed 113 houses and huts. For the whole operation only once helicopters came under fire of guerrillas, while receiving minor damage.

In 1952, the helicopters were still used to transport troops and cargo, and participated in counterinsurgency operations. Equipment transportation on an external sling has been improved by major Cornwell. He first used for this purpose, strong rope mesh, securing them with a rope under the fuselage.

In six months of fighting technique has worked almost flawlessly. The trouble began only on October 24, when near Seoul at the car of captain Irwin broke the bracket that supports the tail boom. Four days later a similar incident occurred with НRS-1 captain Al, who first thought his helicopter was shot down. Further flights were banned. Only after delivery to Korea 15 new vehicles modified with a reinforced bracket the flights resumed.

When performing combat missions, the Americans were extremely cautious, fearing the capture of enemy helicopters. So, in early February, Lieutenant Colonel Mitchell and captain Warren flew out to rescue a fighter pilot shot down behind enemy lines 65 km from the front line. However, the “vane” was not able to accomplish the task.

Then the sailors turned to “land” the helicopter. Mitchell went to the “Rochester”. Taking it a doctor and one assistant with a machine gun, he flew to the rear of the Koreans. Seven fighters carrier-based aircraft covered his helicopter while he circled over the crash site of a fighter. After a few laps, the pilots decided to land, especially as neither of the downed pilot or his parachute was nowhere to be seen. Had Mitchell come back with nothing.

New unofficial record for rotorcraft Sikorsky was the operation “Pronto” to transport troops and equipment to the distance of about 90 km. In 5 hours 45 minutes to nine НRS-1 was transported 620 soldiers and 4.5 tons of cargo. Seven of them were flown by pilots-beginners, who has just arrived in Korea.

Each operation to transport troops carefully prepared and thought over. For example, on 19 April, the helicopters were transporting a battalion of South Koreans to a new location, the route lay over the river. Just in case the pilots wearing lifejackets, and the doors of the cargo cabin were left open. On the river at this time were on duty for two amphibious ready in which case proceed to the rescue.

At the end of April in the actions of division came a forced break. Flights on all the S-55 was forbidden to get a new driveshaft tail rotor. Vices of the same part on several machines caused a number of accidents and disasters.

In the summer of 1952 the number НRS-1 at the front has grown exponentially, and now they were armed with not only Marines but also the US army.

In August of the same year, the helicopter squadron НМR-161 was used for the transfer of 114-mm rocket launchers, rocket launchers from one position to another. The fact that when shooting these installations raised huge plumes of dust and smoke than unmasked its position, causing the return fire of the enemy. The use of helicopters for rapid change firing positions gave the Americans a huge advantage. The rotorcraft was able to raise a single unit and up to 22 rockets with fuses. For interaction between calculations and pilots conducted exercises and practice the skills often used in such a tandem in a real fight.

The power plant of the helicopter – R1340 piston engine power 600 HP

Mi-4 – the Soviet equivalent of the helicopter S-55

12 Feb 1953 in helicopters under mysterious circumstances, there have been two disasters. The first victims were the pilot, captain Ragless and mechanic Sergeant Brand. Their car was heading to the aircraft carrier, which was supposed to deliver it to Japan. НRS-1 to the carrier flew and fell into the sea 40 km South of Busan. Neither the wreckage nor the bodies of the crew could not be found. March 25, 10 km from Cinchona there was a similar case – the pilot and two mechanics were missing… Assumed that the reason was a problem in the power plant.

Since the beginning of the war until the conclusion of peace in the summer of 1953 helicopters S-55 made 18 607 sorties, transported 60 046 people and 3,400 tons of cargo. The evacuation of the wounded was considered a secondary task, but, nevertheless, this figure is very significant – just helicopters rescued about 2748. Another important event for the S-55 in the same year became a test of their nuclear explosion during the exercise, “Desert rock V”, which was held in Nevada at the site of the atomic energy Commission of the United States.

The day before the start of the exercise 39 S-55 flew to the area of a polygon on a dirt airfield Yuka. They had to land troops close to the epicenter of the explosion.

Half an hour before the explosion was set to radio silence. A minute before the explosion, the crew sat in the cockpit and started the engines. At exactly 3 a.m. all around lit up with a flash of bright light, in half a minute on the Playground, passed the shock wave. And immediately rose into the air two helicopter reconnaissance that went to the epicenter. Four minutes later, they landed a kilometer away from the mushroom clouds and landed dosimetrists. After measuring levels of radiation, they gave permission to take off the main group. 37 cars headed out from the staging area and landed paratroopers in 1.5 km from the epicenter. In a report to the head of the exercises, Brigadier General bullock said that S-55 and brilliantly distinguished himself in this operation, and confirmed its ability to move troops in the application of enemy nuclear weapons.

The success of the S-55 has led to the fact that a single-rotor scheme Sikorsky seriously pressed, and in consequence almost supplanted all other schemes of helicopters. Moreover, it happened not only in the United States – although attempts to designers in other countries to build similar aircraft ended in failure.

The layout is similar to the S-55, used in OKB M. L. Mil at the creation of the Mi-4 with the only difference that his fuselage did the double hatch for loading self-propelled machinery.

We can say that a wide spread transport helicopter single-rotor design, the S-55 design I. Sikorsky became a powerful stimulus for the development of the helicopter in many countries.

THE MAIN PERFORMANCE CHARACTERISTICS OF THE HELICOPTER S-55

BASIC FLIGHT CHARACTERISTICS OF THE HELICOPTER S-55

A. CHECHIN, N. Food reserve was

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