The Birth of Rotor Technology: The Development of the Helicopter During the Second World War (Part 1)

The Second World War marked a significant turning point in the development and practical application of helicopters in aviation history. During this period, visionary engineers such as Igor Sikorsky, Frank Nicholas Piasecki, Arthur Young, and Stanley Hiller, Jr. exerted considerable effort to realise vertical flight despite the limited technological capabilities of the time. The urgent demands of the war rapidly revealed the potential of these new aircraft in both military and civilian fields, providing them with opportunities to prove themselves in various roles such as search and rescue, medical evacuation, logistical support, and reconnaissance.

Igor Sikorsky and Pioneer Helicopters (VS-300, XR-4, XR-5, XR-6)

Igor Sikorsky was a pioneering engineer who laid the foundations for modern helicopter design in aviation history. He established the standards for helicopter design as we know it today, particularly by using a single main rotor and single tail rotor configuration.

Igor Sikorsky attempted to design a helicopter as early as 1908, but engine technology was not yet advanced enough to enable rotorcraft flight. He shelved this design endeavour, but as engine technologies matured in the 1930s, he found an opportunity to revisit the helicopter concept.

Cover image: Igor Sikorsky conducting experimental flights with the VS-300 model

Igor Sikorsky completed his first helicopter plans in early 1939 and built the VS-300 model. On 14 September 1939, with him in the cockpit, the aircraft made its first vertical take-off. This prototype, which was tethered to the ground and weighted down for stability and safety during the initial tests, had a small open cockpit and a four-cylinder, 75 horsepower Lycoming engine. The engine drove the three-bladed main rotor and the torque-compensating tail rotor, located at the end of a narrow tail boom, via a belt transmission. The pilot sat in front of the engine, and the instrument panel contained only a tachometer, oil pressure gauge, and engine temperature gauge. Sikorsky's control system included cyclic pitch control for the main rotor and pedals for the tail rotor.

After initial limited test flights, the VS-300 underwent various modifications and attracted the interest of the US Army Air Corps. On 13 May 1940, the redesigned VS-300 took flight unweighted and unshackled. In this version, an open-framed steel tube fuselage was used instead of a closed tail boom, and Sikorsky added two horizontal thrust struts to the rear of the aircraft to increase roll and pitch control. The Lycoming engine was replaced by a more powerful 90-horsepower Franklin engine. Captain H. F. Gregory, who was evaluating the VS-300 on behalf of the US Army Air Corps and was inexperienced in helicopter flight, managed to land near the take-off point after a flight of approximately eight minutes.

Gregory's short flight led to a joint financing and development agreement between the government and Vought-Sikorsky for the Army XR-4. In December 1940, various government departments agreed to fund Vought-Sikorsky for the XR-4 prototype. The initial contract called for a helicopter nearly identical to the VS-300, which was flying at the time, but subsequent test flights necessitated numerous changes to both the helicopter and the contract before the XR-4 was delivered, and the final product bore only a slight resemblance to the helicopter in the original contract.

Sikorsky remained dissatisfied with the machine's flight characteristics, despite it being successfully flown by an amateur pilot, and continued to make gradual improvements. Through meticulous flight series, he extended the VS-300's airborne duration. On 15 April 1941, Sikorsky broke the national endurance record with a flight lasting one hour, five minutes, and fourteen seconds. On 6 May 1941, the VS-300 surpassed the world endurance record held by the Fa-61, remaining airborne for one hour, thirty-two minutes, twenty-six and one-tenth of a second.

Between 1940 and 1941, the VS-300 crashed several times, and Sikorsky made various modifications to improve its reliability. In June 1941, one of the most significant changes was made by replacing the three rear outer struts with a short vertical pylon supporting a single vertical tail rotor. During testing, the helicopter exhibited a tendency to suddenly lift its nose during slow hovers; Sikorsky discovered that the downwash from the main rotor was negating the effectiveness of the auxiliary horizontal tail rotors. This change not only improved the aircraft's controllability but also improved the helicopter's performance by eliminating the extra weight. In December, he replaced the unsatisfactory main rotor cyclic pitch control with a new system. Another significant change was the renewal of the landing gear, replacing the skids with nose and tail wheels. On 17 April 1941, after fitting pneumatic floats to the main wheels, it successfully took off from water. In its final form, the VS-300 featured a Franklin engine with 150 horsepower in a fabric-covered fuselage with an open cockpit and a three-wheel landing gear. Sikorsky's determination and flexibility ultimately produced a stable, practical, and highly versatile flying machine that set the standard for subsequent helicopters.

The modifications made to the XR-4, designated S-48 by its manufacturer, mirrored those made to the VS-300. Shortly after the December 1941 attack on Pearl Harbor, Sikorsky employees rolled the first XR-4 out of its secret hangar in Bridgeport, Connecticut. The helicopter's forward fuselage was covered in fabric, while the rest of the tubular frame skeleton remained exposed. A single tail rotor was connected to a 165 horsepower Warner engine, mounted just behind the two-person cockpit, via a long shaft and gearboxes. The engine drove three 18-metre fabric-covered main rotor blades. Just behind the cockpit were the engine oil and fuel tanks. Among the pilot controls were a cyclic stick, rudder pedals, and a collective (pitch) stick with throttle control at its end. Plexiglass windows provided excellent visibility and some protection for the pilot and observer. Three balloon-tyred main landing gear wheels were mounted on the ends of hydraulic shock absorbers.

A small wheel supported the rear of the aircraft. On 14 January 1942, in front of a crowd of government officials and company executives, the XR-4 took to the air for the first time. Tests of the final version of the VS-300 continued for several more months before the Vought-Sikorsky helicopter was officially retired.

The VS-300 flew throughout 1942, even as development of the S-47 or XR-4, Sikorsky's first production helicopter, continued at full speed. In 1943, Vought-Sikorsky delivered the VS-300 to the Henry Ford Museum in Dearborn, Michigan, where it is on display today.

The S-47/XR-4 underwent several minor modifications and test flights before the first prototype was accepted by the US Army Air Corps on 30 May 1942. Sikorsky expanded the instrument panel to include a rotor tachometer, a wing pitch indicator, and the basic flight instruments found on most aircraft of the era. Additionally, he added Plexiglas to the front section of the floor to improve downward visibility. During a test flight in April, the pilot hovered in the air around a pole with a brass ring attached, held by the ground crew. Like a carnival carousel, the pilot passed the pitot tube through the ring and lowered the prize to the inventor of the S-47. In another flight, to prove the aircraft's versatility, the XR-4 lifted a net full of eggs suspended beneath the aircraft by a thin rope. The pilot circled around and lowered the net to the ground so gently that none of the eggs broke. An engineer proved the eggs were not boiled by smashing one against a rock. Demonstrating its ability to communicate while suspended in the air, an observer lowered a telephone receiver to an officer on the ground and made a brief conversation; radios, of course, soon replaced the telephone. Sikorsky pilots demonstrated the helicopter's unique rescue capability by lowering a 25-metre rope ladder to the ground, picking up a man on the ladder, and flying away with him. By reversing this operation, a helicopter could deliver critical personnel to isolated units. In addition to military applications, the helicopter could be used to spot forest fires and drop firefighters into otherwise inaccessible locations, allowing fires to be extinguished before they became uncontrollable disasters.

With a gross weight of 2,700 pounds, the XR-4 travelled at 70 miles per hour at an altitude of 5,000 feet and, with some modifications, proved useful for the US Navy. Equipped with inflatable rubber flotation devices, dubbed ‘big sausages,’ the helicopter made several take-offs and landings from both land and water, even from the choppy surface of Lake Erie. Navy officers immediately envisioned various uses for the helicopter: search and rescue, convoy and anti-submarine patrol (the machine could carry a depth charge without an observer) and naval gunfire spotting. On 6 and 7 May 1943, in Long Island Sound, an Army test pilot made several take-offs and landings on a cargo ship named USS Bunker Hill, which had a landing platform mounted between the superstructure and the cranes. The helicopter's 38-foot rotor left very little room for error, and approaches had to be made alongside the ship, but the pilot successfully completed twenty-four landings and take-offs from both the anchored and moving ship. Following the demonstrations, the pilot transported several important individuals from the ship to Stratford Airport—another first for the Sikorsky helicopter, transferring passengers from ship to shore by aircraft. In July, an XR-4 and an R-4 conducted a successful three-day ship landing trial using a platform built onto the stern of the USS James Parker, a luxury passenger ship converted into a fast troop carrier. These fast ships were operating alone, not in convoy, and military planners hoped that the rocket-equipped R-4 could protect the ships from submarines. Unlike previous ship landings, these were conducted on the open ocean, onto a swaying ship and in 40-knot winds. With its hovering and ship-landing capabilities, the XR-4 looked perfect for both the Navy and the Army. The Navy designated the first version HNS-1.

During the 761-mile cross-country journey from the Vought-Sikorsky Stratford, Connecticut factory to Wright Field, Ohio, and subsequent flights, the XR-4 broke all existing records for endurance, altitude, and airspeed. The XR-4 flew for 100 hours without incident, climbed to a demonstrated service ceiling of 12,000 feet, and reached a maximum speed of 90 miles per hour. US Army test pilots effectively demonstrated the helicopter's military and civilian versatility by pushing it to the limits of its flight envelope. On 5 January 1943, the Army ordered twenty-nine XR-4s to be produced.

On 16 May 1943, one of the first production R-4s became the first helicopter to carry the US postal service. An R-4 took off from the Capitol terrace, delivering a small airmail package to a passenger plane waiting at Washington, D.C. Municipal Airport. The helicopter made its historic flight in terrible weather conditions – fog and drizzle reducing visibility to one-eighth – in which a normal aeroplane could not fly. A few weeks later, Lowell Thomas, a nationally recognised news commentator, made the first radio broadcast from an R-4 hovering in the air.

Although similar in appearance to the prototype, the production R-4 incorporated several improvements. The exhaust pipe was repositioned to exit from the side of the aircraft rather than underneath, preventing accidental fires when hovering over flammable materials such as dry grass and leaves. The tail rotor was moved further back on the tail boom to protect it during automatic landings. Engineers repositioned the air ducts to draw engine cooling air from the front of the helicopter rather than the rear. The previous 165 horsepower model was replaced by a 180 horsepower Warner air-cooled engine. A one-metre extension to the rotor blades increased the rotor diameter to 38 feet and provided greater lift. Increasing the fuel capacity by 5 gallons extended the machine's range, and the radio installation provided the previously lacking air-to-ground communication. The aircraft bore the traditional US Army olive drab colour on its upper surfaces; the underside was painted battleship grey.

Before deploying the R-4 worldwide, military planners ordered the helicopter to be tested in extreme weather conditions. On 6 November 1943, an R-4 began a long journey to Ladd Field near Anchorage, Alaska. In Bridgeport, Connecticut, mechanics dismantled an R-4 and loaded it onto a C-46 transport aircraft. After arriving in Alaska, the R-4 was reassembled and underwent a series of cold weather tests. Nicknamed the ‘Arctic Jitterbug,’ the helicopter performed satisfactorily in every test after being serviced with oil and hydraulic fluid designed for cold weather operations. The programme test personnel fabricated a metal frame that was attached to the side of the R-4. They attached a standard Army stretcher, protected by a canvas cover, to the frame. Several flights demonstrated that casualties placed in sleeping bags could be easily evacuated from the battlefield to field hospitals in cold weather. However, programme managers quickly discovered that freezing damaged the fabric covering the rotor blades and ordered special covers to protect the blades from the elements. Pilots also determined that flying in icy conditions would shatter the rotor blades. Interior Department personnel observing the helicopter trials quickly recognised the machine's utility in wildlife and forest management. Although the R-4 never saw combat, it had nevertheless flown in an operation under adverse conditions.

In the photo above, Igor Sikorsky is lifted by a rescue winch system operated by the Coast Guard HNS-1 (R-4B) aircraft during a demonstration in 1944. Commander Erickson is operating the helicopter.

Ongoing tests of the XR-4 revealed several issues with certain components, but close cooperation between Vought-Sikorsky engineers and Army personnel overcame all obstacles. The helicopter's transmission overheated and required more frequent gear changes than anticipated. Just four days before Army Air Forces Chief General Henry H. ‘Hap’ Arnold was due to arrive on a special trip to see the capabilities of this marvellous new machine, mechanics discovered that the helicopter required a new transmission. No spare parts were available at Wright Field. Following a frantic telephone call to Connecticut, company engineers assembled the necessary machine operators over the Fourth of July holiday. Sikorsky personnel rushed the large box of hastily produced gears to the airport and, as a wartime emergency measure, placed the repair parts in the seats of two disgruntled TWA passengers, who carried the box to Dayton in the passenger cabin. On 7 July 1944, after a hasty revision, the XR-4 performed flawlessly and impressed Arnold so much that he ordered the supply of the larger and more powerful Vought-Sikorsky XR-5, the first helicopter to be ordered in bulk by the US Armed Forces.

As early as 1942, Sikorsky built a detailed mock-up of a more advanced rotorcraft that would become the R-5. Although still a two-seater, the R-5 was much larger, more powerful, and more capable than the R-4, which was often assigned to pilot training. The mock-up, designed for universal capabilities, included attachment points for four stretchers (two on each side) carried in protected pods and the ability to mount bomb racks on the R-5's fuselage. The preliminary plans met the Army's requirements for an airspeed of over 125 miles per hour, efficient operation above 5,000 feet, endurance of over three hours, and a payload of over 1,100 pounds. On 13 June 1943, the War Department sent a letter to Sikorsky requesting four XR-5s, two for the US and two for the UK, to be paid for with Lend-Lease funds.

The XR-5 was radically different from its predecessor. For example, wartime shortages forced Sikorsky engineers to construct some components from moulded plastic-impregnated plywood instead of aluminium. The three-bladed rotor system had a 48-foot diameter, with blades made of laminated plywood and canvas trailing edges mounted on steel tube spars. The new helicopter was powered by a vertically mounted, nine-cylinder, air-cooled 450 horsepower Pratt & Whitney Wasp Junior radial engine. The XR-5's 40-foot fuselage consisted of three sections. The cockpit area was enclosed in Plexiglas and constructed from an aluminium alloy frame mounted on an aluminium monocoque floor. The tandem seating arrangement, with the observer in front and the pilot behind, provided almost unrestricted visibility. Dual controls allowed both to fly the aircraft. The middle section, containing the engine, was constructed from welded steel tubes covered with plastic-impregnated plywood. The rear section was a solid wooden monocoque tail cone supporting the 7-foot tail rotor and drive shaft. The two-person crew sat in front of the main wheels of the conventional landing gear.

In the photograph above, Vought-Sikorsky chief test pilot Les Morris, together with Captain Jsck Beighle of the US Air Force, is seen taking off in a Sikorsky YR-5A, 43-46603, with ten passengers on board, in Bridgeport on 29 November 1945.

On 18 August 1943, the XR-5 flew for the first time, but experienced severe vibrations and unacceptable bending of the main rotor blades. After stiffening the blade tips and adding counterweights, the test engineers tried again and achieved greater success. On 13 September, the XR-5 carried ten people in the air, with two in crew positions and four suspended on either side of the landing struts. Vought-Sikorsky produced significant numbers of the R-5 for both the Army and Navy (HO5S), and some saw military service during World War II in the Pacific and China-Burma-India (CBI) theatres of operations. The company also produced sixty-five company-funded R-5Bs, modified with a cockpit that could accommodate three passengers behind the front pilot's seat.

Engineers and pilots quickly realised the R-4's inadequate power-to-weight ratio, especially after the addition of radio equipment and bomb racks. This realisation sparked ideas for a more powerful, aerodynamic helicopter, leading to the XR-6 design. Lack of funding nearly killed the XR-6 before the project even began, but the US Navy saved the new helicopter. Navy planners, anticipating the need for a larger and more powerful helicopter in the future, agreed to finance half of the XR-6's development costs.

The image above shows the Sikorsky R-6A Hoverfly II at the US Air Force National Museum in Dayton, Ohio. (Image source: USAF)

Like its predecessor, the XR-6 consisted of three main sections: the cabin, the centre section and the tail boom. However, it differed in that the airframe was lightened and strengthened with lightweight alloys and newly discovered composites. An aluminium alloy monocoque floor extended from the cockpit rearward and beneath the centre section, like the keel of a boat. An aluminium frame covered with Plexiglas and fibreglass formed the forward cockpit area. Inside the moulded plastic centre section, a steel alloy tubular frame supported an air-cooled, six-cylinder, 245-horsepower Franklin engine, along with transmission, fuel and oil tanks. The engine intakes and exhaust stacks, designed for enhanced aerodynamics, were embedded in the fuselage. Aluminium alloy sections, covered with a robust magnesium coating, also formed the tail boom, which housed the drive shaft for the three-bladed, 7-foot 10-inch tail rotor. The helicopter had a conventional landing gear with a small nose wheel to protect the aircraft in the event of a nose-down landing and to improve forward taxiing. The pilot and observer sat side by side, and the controls were identical to those on the R-4. A shelf immediately behind the crew seats held standard military radio equipment. The designers had also added special pocket holders for maps and other aviation supplies. The rotor blades were the same size as those on the R-4 and were interchangeable, but the R-6 had a newly designed, aerodynamic rotor head.

Improved performance also characterised the R-6. Air speeds in excess of 100 miles per hour and endurance of over five hours gave the R-6 the longest range of any helicopter to date. With an operating weight of approximately 2,600 pounds, the R-6 could easily cross the Rocky Mountains. The aircraft could carry a closed stretcher on either side or bomb racks instead of stretchers.

The XR-6 made its maiden flight on 15 October 1943. Excessive vibrations, control feedback, and other issues limited flight duration and restricted altitude to approximately 1 foot, forcing designers to find solutions. As with the R-4, the transmission overheated, particularly during hover flight. Despite the best efforts of Sikorsky's engineers, vibrations continued to shake the helicopter, increasing with airspeed, but those associated with the new rotorcraft accepted these as minor growing pains. On 27 November, despite some issues, the XR-6 lifted six personnel, including the crew, and hovered for several minutes. By early 1944, engineers had managed to correct most of the vibrations, and test pilots flew in snowy conditions without experiencing any damage to the rotor blades. Encouraged, the pilots began to believe they could fly in ‘helicopter weather,’ when most aircraft would have been grounded.

By the spring of 1944, the XR-6's performance justified the time and effort spent on its construction. On 2 March, Colonel H. F. Gregory of the US Air Force, accompanied by a civilian observer, flew the aircraft non-stop from Washington National Airport to Wright Field, Ohio. This journey of approximately 387 miles took four hours and fifty-five minutes and unofficially broke three world records, including the helicopter's longest non-stop flight. The aircraft's ground speed against headwinds also surpassed all previous records. The XR-6's heated, soundproofed cockpit significantly reduced engine and transmission noise, impressing everyone who flew the helicopter.

Although the shortcomings and limited capabilities of the R-4, R-5, and R-6 hindered their performance, the government purchased 130 R-4s and over 300 R-5s and R-6s. Each helicopter type served with the US Army, Navy, and Coast Guard, as well as the British Royal Navy and Royal Air Force, achieving historic successes; the British nicknamed their R-4s ‘Hoverfly’. On 3 January 1944, an R-4 carried out the first helicopter rescue mission, delivering blood plasma to survivors of an explosion aboard the USS Turner. On the night of 31 December 1943, a mysterious explosion rocked the destroyer, killing many crew members and injuring others. Coast Guard vessels rescued survivors from the icy water, evacuated the wounded to emergency hospitals set up on the Sandy Hook, New Jersey shore, and made an urgent call for blood plasma. Commander Frank A. Erickson, commander of the Coast Guard Air Unit at Floyd Bennett Field on Long Island, landed a Coast Guard HNS-1 (R-4) in a small grassy area at Battery Park in lower Manhattan amid a swirling snowstorm, picked up the vital plasma, and delivered it to medical personnel at Sandy Hook fourteen minutes later. No other mode of transport could have responded so quickly to the life-saving plasma.

Coast Guard R-4s also assisted in civilian disasters. On 1 April 1944, Lieutenant (jg) W. C. Bolton, during a routine patrol from Floyd Bennett Field, spotted a lone individual on an isolated sandbar in Jamaica Bay. He landed and rescued a fifteen-year-old boy who had been trapped on the islet by the rising tide. Also in April, a fire in the ties on the Long Island railway threatened to destroy the viaduct over Jamaica Bay. Firefighters battling the blaze could not reach it with the necessary equipment. A Coast Guard helicopter from Floyd Bennett Field flew to the scene, hovered over the burning viaduct, and dropped hand-held extinguishers to the firefighters.

In November 1944, while searching for a sunken P-51 fighter plane in a lake near Orlando, Florida, US Army Captain McGuire, flying a Sikorsky XR-5, received a radio communication that a C-47 cargo plane had crashed 50 miles away. McGuire flew to the area to search for the downed plane's crew. He picked up an injured chaplain from the C-47 and evacuated the wounded man to a military hospital.

The first combat rescues of downed airmen and wounded soldiers were carried out by Sikorsky R-4s in the CBI Theatre. In April 1944, Lieutenant Carter Harman proved the noisy, cumbersome R-4's lifesaving capabilities; he rescued three wounded British soldiers and American pilots, T/Sgt. Edward Hladovcak, whose aircraft had been shot down behind enemy lines. Despite high altitude, humidity, and tropical temperatures reducing the helicopter's performance, Harman extracted all four, almost from under the Japanese's noses, two at a time from a rice paddy. This was a unique rescue, as the R-4 was designed to carry only one passenger.

Throughout May 1944, R-4s participated in various other evacuations in the CBI Theatre. During the Allied airborne invasion of Burma, paratroopers suffered heavy casualties, some combat losses, some not. US Army pilots evacuated many wounded, including stretcher cases attached to the outside of the helicopters.

At midnight on 23 January 1945, the Tenth Air Force Air Forest Rescue Detachment received a call reporting that a soldier at an air station high in the Naga Hills of northern Burma had accidentally shot himself in the hand. The wound was infected and required urgent medical attention. The station commander wondered if the ‘egg beater’ could descend to the high altitude and extract the man. Captain Frank W. Peterson flew an R-4 to the mountain station and, taking off at a run, managed to airlift the wounded man to a hospital.

Lieutenant Raymond F. Murdock performed one of the most dramatic rescue operations in the CBI Theatre of Operations when he used an R-4 to extract a seriously injured pilot from the dense Burmese jungle. On 19 March 1945, an Air Transport Command C-46 crashed due to icing while attempting to transport supplies over the Himalayas. Captain James L. Green and a Naga tribal chief, who claimed to know the location of the downed crew, took off from Burma's Shingbwiyang Airfield in a Fairchild PT-19 trainer aircraft. After a fruitless two-hour search, Green returned to the airfield. Just five miles from the airfield, the PT-19's engine failed, and Green crashed into 150-foot-tall trees covering the last steep ridge line before the airfield. At dusk, another aircraft spotted the jumbled wreckage of Green's plane. The next day, a ground rescue team began a two-day trek to reach the crash site. The rescue team found Green, seriously injured, and the dead tribal chief. The flight surgeon accompanying the rescue mission determined that Green would not survive the return journey to Shingbwiyang. However, the doctor believed that Green could be kept alive for several days with the medical supplies dropped from the air. A helicopter rescue request was sent to the Air Forest Rescue Detachment in Myitkyina; there was no hope that any other aircraft could land near Green. Volunteers carried hand tools, electric saws, and dynamite up the steep slope and, within two weeks, cut a hole in the trees and built a small platform on a ledge extending from the ridge line.

On the night of 3 April, a violent rainstorm threatened to end the entire operation, but by dawn on 4 April, the bamboo-reinforced landing strip remained intact. Thick fog kept Murdock grounded until 10:00 a.m.; he then started the R-4 and took off for the rescue, hoping that rising temperatures would not reduce the helicopter's performance to the point where it could not lift two people from the small landing area. To complicate matters further, winds were buffeting the helicopter as it approached the ridge line. Murdock thought, ‘This is going to be like landing in a windy well,’ but he managed to navigate the R-4 through the trees and onto the runway. When he reduced power, the helicopter began rolling down the runway. Several men ran to hold the R-4 in place while others carried Green to the waiting helicopter. They strapped Green to a board placed in the right seat, and Murdock prepared for the most challenging part of the mission. He started the engine and throttled up to maximum power. When he raised the collective stick, the R-4 jumped about four feet off the ground but couldn't climb higher with two men on board. Murdock swallowed hard and turned the helicopter downhill, moving forward. With maximum power, forward airspeed, and the downward slope of the terrain, Murdock barely cleared the trees and dropped Green off at Shingbwiyang hospital. However, the small helicopter could not return to its base in Myitkyina. The long-overdue engine replacement failed en route, forcing Murdock to make an emergency landing on the Burma Road. The R-4 completed its journey in the back of a truck. Sikorsky helicopters continued their valuable service rescuing soldiers and airmen in the CBI Theatre for the remainder of the Second World War.

In November and December 1944, RAF Wing Commander Brie announced that Sikorsky helicopters were also serving with the British armed forces in the Atlantic Ocean and Europe. The British attached R-4Bs to the decks of warships escorting cargo ships to Britain. The British used the helicopters to search for submarines and locate survivors in the event of submarine attacks. He also noted that R-4Bs equipped with floats rescued several downed pilots from the mud flats stretching along the English Channel and the English coast.

On 30 January 1945, a Coast Guard R-4 performed a unique rescue mission by lowering a breathing apparatus to a merchant ship in New York harbour. A crew member had fallen into icy waters, and attempts to revive the sailor had failed. Harbour ice prevented the ship's crew from bringing the man ashore, and the captain radioed for help. Responding to the call, a Coast Guard helicopter hovered over the ship in less than half an hour and lowered the breathing apparatus onto the ship's deck.

In April 1945, a US Air Transport Command C-54 cargo plane transported a Coast Guard R-4 floatplane over 1,000 miles from Floyd Bennett Field to Labrador. Nine crew members of a Royal Canadian Air Force aircraft that crashed in the inaccessible wilderness of Labrador were stranded and in need of urgent assistance. On 2 May, after the ground crew reassembled the R-4 at Goose Bay, the pilot battled winds, blizzards and blinding sun to reach the crash site and successfully rescued all the downed airmen in successive flights. The pilot reported severe sunburn after flying for hours in the glare of the reflected sunlight.

Sikorsky helicopters also supported the logistical component of the war towards the end of the Second World War. On 22 May 1945, the US Navy announced that helicopters had been assigned to logistics support ships in the Pacific Theatre of Operations. The “floating aviation depots” on modified Liberty ships, equipped with aircraft repair and maintenance workshops, accompanied the Allies' advance into Japanese-occupied territories. Sikorsky R-4B helicopters operated from small flight decks on these ships, transporting parts to shore or other ships to keep warplanes flying.

Towards the end of World War II, helicopters skilfully demonstrated the impact they would have in the civilian world after hostilities ended. In July 1945, a Sikorsky helicopter sprayed insecticide at the Yale Bowl. Prior to the New Haven Symphony Orchestra's first open-air concert at the Yale Bowl, a Coast Guard helicopter sprayed the stadium and adjacent grounds with DDT insecticide, developed during the war. The Connecticut Agricultural Experiment Station and the USDA Entomology and Plant Quarantine Bureau collaborated with the Coast Guard to complete the project. That same month, US and Mexican Army pilots flew various scientists over the Paricutin volcano near Mexico City, which had become active in 1943, using Sikorsky helicopters. The missions offered opportunities to both scientifically observe an evolving volcano and test flight conditions. Although the flight was very similar to those experienced in the CBI Theatre of Operations, US Army Captain Colchagf noted that the pilots discovered information of vital interest to the Engineering Department at Wright Field. Professor L. C. Graton of Harvard's Department of Geology stated that there was no doubt that observations made from slow-flying helicopters provided scientists with information about the volcano's activity that could never be obtained from the ground or from conventional aircraft.

On 29 November 1945, an S-51 (R-5) achieved another aviation first. Responding to a distress call to assist the Coast Guard in rescuing the crew of an oil barge that had broken apart in severe weather, Sikorsky test pilot Dimitry ‘Jimmy’ Viner and an Army Air Corps officer took off from the Sikorsky factory despite strong winds and heavy rain. They flew low over the choppy waters off Fairfield, Connecticut, and spotted the sinking tanker. While Viner hovered over the stricken vessel, the Army officer used the helicopter's winch system to secure two crew members, marking the first time in history that a rescue operation had been carried out using this system.

This concludes the first part of our series. We will meet again in part 2. All references and sources will be presented under a single heading in the final part of the series.