The Evolution of a Dream: Igor Sikorsky’s Flying Boats

by Doug Miller

 PHOTO: IGOR SIKORSKY IN NEW YORK, 1919 (SIKORSKY ARCHIVES).

Today, the name Sikorsky is synonymous with helicopters. Building vertical lift aircraft was a goal the Russian aeronautical inventor pursued from his early years. But he had another dream that he would pursue as well – literally – from the time he was not yet a teenager. He was destined to create an ocean-going ship that could fly. It would take him several decades to arrive at the stage of real-world problem solving and trial and error at which he excelled before he could get to work on the concept in earnest.

As a young engineer in Russia he built the world’s first four engine aircraft before the First World War, and was largely responsible for that nation’s embryonic aircraft development during the conflict. But the coming of the Russian Revolution forced him to flee to the West, and after a stint in France, he eventually wound up in America in 1919 with not much more than his hopes for a career designing aircraft. He struggled to establish himself, making ends meet teaching while pursuing his real passion.

By 1924, with the help of fellow Russian émigrés, Sikorsky had established the Sikorsky Aero Engineering Corporation on Long Island. The first product, the twin-engine S-29, was almost wrecked on a test flight, but with an emergency infusion of cash from famed composer Sergei Rachmaninoff, the plane was made to fly successfully. After that, the way forward was much smoother. The following months saw Sikorsky Aero focusing on land planes, but it wasn’t lost on the designer that the market potential for long-range transports might favor designs that could alight on water. By 1927, that business opportunity seemed to be a real prospect. It would take Igor Sikorsky into a realm he had not explored before – except in a childhood dream.

But the beginning of Igor Sikorsky’s flying boat design journey was almost its finish. May 31st, 1927 was a mostly sunny and mild day on Long Island Sound when he and a small crew took his first flying boat, the S-34, out for a test flight. A headline the next day read “Sikorsky in Plane Falls into the Bay.” It had been a near thing. The right engine on the twin-engine flying boat had quit at 800 feet, not far from the Sikorsky factory at College Point, Long Island. Sikorsky, along with a mechanic and pilot Charles Collyer survived the resulting nosedive and crash, but the S-34, a one-off prototype, was a write-off. They were lucky to survive.

PHOTO: THE S-34 ONLY ONE WAS BUILT (SIKORSKY ARCHIVES).

Sikorsky’s initial flying boat design borrowed from a tested concept developed some years before by Glenn Curtiss, who had pioneered flying boats starting before World War I. The design approach that worked for Curtiss was a shortened hull, to reduce weight, and an empennage, or tail section, mounted behind on booms extending from and high above the hull. This feature kept the control surfaces high out of the water, but also well placed to maintain control in the aircraft’s slipstream. It was the same approach Curtiss had used on his design for the NC-4 flying boat, with which the US Navy had crossed the Atlantic in 1919. It was a formula that would serve Sikorsky for half-a-dozen years..

PHOTO: TAIL SURFACES ASSEMBLY ON A SIKORSKY S-38  AMPHIBIAN (NACA, NATIONAL ADVISORY COMMITTEE ON AERONAUTICS).

The demise of the ill-fated S-34 was hardly the end of Sikorsky’s evolving vision for water-borne aircraft. In a perfect example of what was his trait of dogged persistence, he soon was back with a greatly improved version of the same basic concept. The “next step” was already close to being released for public sale.

PHOTO: THE SIKORSKY S-36: THE NEXT STEP FORWARD (AERO DIGEST, 1927).

It was a similar design, but markedly improved – the S-36. This was a larger and heavier version of the S-34, now equipped with retractable landing gear – an amphibian or “amphibion” as Sikorsky called his design. Unlike the S-34, this aircraft had an enclosed cabin, and unlike the S-34, the two Wright J-5 Whirlwind engines were now mounted below, rather than on top of the wing -a much better aerodynamic arrangement. The S-36 was to be produced for two markets. One was a utility model while the other was a long-range version. In the event, only five were built. One went to the U.S. Navy, two to a Canadian oil firm operating in Colombia, and one to a new airline, Pan American Airways, which was interested in surveying potential routes down through the Caribbean and Central America.

PHOTO: THE DAWN: LOST WITHOUT A TRACE (PAHF COLLECTION).

The remaining S-36, christened the “Dawn,” was sold to an adventurous niece of President Woodrow Wilson, Mrs. Frances Grayson, who hoped to be the first woman to fly across the Atlantic (as a passenger). Her first attempt, in October 1927 was quickly cut short due to performance issues after takeoff. She was ready to try a second time that December. The Dawn was almost wrecked when landing after a test flight at Roosevelt Field in Garden City, Long Island, when the plane failed to brake properly on the wet runway and almost crashed into a hangar. A quick intentional ground loop by pilot Oskar Omdahl saved the plane for the next attempt on Christmas Eve. This time the heavily laden S-36 did get off the ground, but was fated to disappear and never be seen again. A Canadian wireless station reported receiving a partial message from the Dawn the next day, “Something wrong…” After that, only silence.

Certainly the road forward for Igor Sikorsky had not been free of setbacks. He had built a large aircraft for another transatlantic attempt in 1926 by French aviator Rene Fonck. That plane, dubbed the S-35, crashed on takeoff from Roosevelt Field on September 21 when a tire blew out and precipitated the disintegration of the landing gear. The plane lurched into a ditch and started to burn furiously. Fonck and his copilot barely escaped but two other crew members perished in the ensuing conflagration.
Igor Sikorsky was not aloof or distant as far as the costs paid for progress. He, along with almost all of the Sikorsky Engineering Corporation’s employees went to the funeral mass held for the French radio operator who had died in the S-35 crash.
The aircraft designer was ready to provide another S-35 for a second attempt by Fonck, it was reported. Sikorsky was nothing if not resourceful, patient, and up to facing long odds. Perhaps this quality stemmed from his deep religious faith and spiritual beliefs. But Sikorsky had also overcome a great many obstacles in pursuing his path to success, so he was not easily put off by real-world challenges. His was a classic American story of an immigrant making good through vision and hard work.

PHOTO: THE SIKORSKY FACTORY FLOOR, c. 1928 (NACA, PRECURSOR TO NASA).

The S-36 was only another step on the way towards Sikorsky’s vision. It was just a few months later that the Sikorsky Aero was ready to offer customers a bigger more powerful variant, the S-38. This airplane boasted double the horsepower of the S-36, with the Wright J-5’s being replaced with Pratt and Whitney “Wasp” engines of 450 H.P. each which were now cleanly suspended below the wing. The single tail boom of the S-36 was replaced by a set of two booms to attach the tail section with its twin rudders.

PHOTO: LINE DRAWING OF THE S-38 (NACA, 1928).

Pan Am’s S-36, delivered on a leased basis starting on December 7, 1927 was returned to Sikorsky after only a few weeks, in February of 1928. At that point the airline was making do with its small fleet of Fokker tri-motor aircraft. Throughout 1928, Pan Am kept operations to a minimum, flying only between Key West and Havana (with the route extended north to Miami in September of that year). For the moment, there was no real need for flying boats and/or amphibian aircraft – yet. That was about to change.
By the start of 1929, thanks to new Foreign Airmail contracts won with the passage of the Foreign Airmail Act of 1928, Pan Am was going to be flying much farther over longer routes to places throughout the Caribbean and Central America. A great deal of this flying was over water between islands or to places along coastlines where the only place to land was on water. There were some places where airports were to be found too, and the S-38 fit in perfectly in this operational environment, as it could land on water or terra firma both. The landing gear was exceptionally capable it was said, supposedly able to lift the plane’s hull off the ground unaided – like a push-up! Another “feature” was the emergency braking option offered by retracting the landing gear if the wheel brakes were proving insufficient. (Most landing fields had grass runways in those days so dragging the hull’s bottom was not a catastrophic event.)

PHOTO: A PAN AM S-38 AT WORK (PAHF, JAHNCKE COLLECTION).

The S-38 could carry a crew of three and eight passengers. Cruising at the most economical speed of 90 miles per hour, it would go three miles on a gallon of fuel. With normal fuel capacity of 180 gallons, this gave the S-38 very adequate range for the average 300-mile flights between stops on Pan Am’s routes, with a reserve. And of course, as Andre Priester, Pan Am’s Chief Engineer had noted, “flying boats carried their own airports on their bottom” should the need for an emergency water landing occur..
The amphibian configuration was perfect for the mix of land and water landings on the routes down through the Caribbean, Central America and down the South American coast that made up Pan Am’s routes in the early years.
The success of the S-38 prompted the development of smaller variant, the single-engine S-39, which addressed the needs of smaller operations and sport aircraft owners.

But of course, as in the past, Igor Sikorsky foresaw the way towards future development, and he was ready when Pan Am’s Juan Trippe reached out to him at the end of 1929 with a request for a bigger transport. After the S-38 (of which Pan Am ended up with 38 of the 111 built) he came up with what looked like a giant variation on the theme – the S-40. This was dubbed the “flying forest” by some, due to the elaborate external bracing and struts that supported the same style of twin-boom tail structure as the S-38. The four engines were also hung below the wing. The original design was also that of an amphibian configuration, but this arrangement was undone later, due to the weight of the landing gear. The S-40 could carry 40 passengers – five times the capacity of the S-38. It was also much longer-legged, with a range of 900 miles.

PHOTO: THE S-40: THE “FLYING FOREST” (PAHF COLLECTION).

This was almost literally, Igor Sikorsky’s “dream boat.” As a youngster growing up in Russia, as he recounted in his autobiography, “The Story of the Winged S” courtesy of the Sikorsky Archives :

“ …at the age of about 11 years, I had a wonderful dream… I saw myself walking along a narrow, luxuriously decorated passageway. On both sides were walnut doors, similar to the state room doors of a steamer. The floor was covered with an attractive carpet. A spherical electric light from the ceiling produced a pleasant bluish illumination. Walking slowly, I felt a slight vibration under my feet and was not surprised to find that the feeling was different from that experienced on a steamer or on a railroad train. I took this for granted because in my dream I knew that I was on board a large flying ship in the air.”

PHOTO: S-40 CABIN: A BOYHOOD DREAM REALIZED (PAHF, ZAVADA COLLECTION)

This dream became reality in 1931, when Igor Sikorsky actually flew in his new creation, the S-40. He had, he realized, brought his own dream to life. The American Clipper, as the first S-40 was christened, was the embodiment of his youthful vision, right down to the walnut paneling, the carpeted floor, and the blue lights above. It was a remarkable life experience. The S-40 also represented something special for Pan Am: it was first aircraft the airline would call “Clipper,” starting a 60-year-long tradition that lived on as long as Pan American Airways did.

The S-40 was a big plane – it weighed over 17 tons, and was designed to carry larger payloads over long over-water routes, like the 600-mile stretch from Kingston, Jamaica to Barranquilla, Colombia. But even before the premiere of the big plane, Sikorsky developed the S-41, helping to fill a gap on Pan Am’s shorter haul routes. This plane, essentially an enlarged version of the successful S-38, came online in September 1930. Pan Am bought three.
Sikorsky continued on with the evolution of flying boats. After the S-40 (three were built), his next “boat” was the truly evolutionary S-42, in 1934. This aircraft incorporated many aeronautical advances and was a far more capable flying machine than any of his previous designs. Pan Am again was the sole launch customer and bought all ten, which by the end of production had developed into the S-42B.

The new clipper, designed with the active participation of Pan Am’s Technical Advisor Charles Lindbergh, was a sharp break from earlier Sikorsky flying boat design. Gone was the awkward-looking boom and tail section approach – the empennage was mounted directly on top of the fuselage. Now, thanks to the use of controllable-pitch propellers and engine brakes that could eliminate the hazard of out of control “windmilling” propellers in the case of in-flight engine failures, the S-42’s engines were faired directly into the wing, not hanging below, a far cleaner aerodynamic arrangement.

PHOTO: THE S-42: AN EVOLUTIONARY DESIGN (CLYDE SUNDERLAND PHOTO, PAHF COLLECTION).

The plane had trailing-edge flaps, which helped both to reduce takeoff runs and landing speeds. The wing design was very innovative and efficient, making possible high wing loading, comparable to that of contemporary racing plane design. Improvements in materials and engines made for a continuing evolution of the S-42, which by 1936 was being built as the S-42B. The range and payload of this aircraft had been improved by about ten percent over the first models. All in all, Pan Am acquired ten S-42’s. Equipped for long-range fuel endurance, they made it possible for Pan Am to initiate surveys of transoceanic routes – the opening of the door to truly global commercial air transport.

The S-42 was followed by the S-43 in early 1936 – known as the “Baby Clipper.” This twin-engine amphibian was well adapted for the short haul routes of South America, where the type saw most of its service for Pan Am and partner airline Panair do Brasil. Altogether Pan Am bought 12 of the 53 built by Sikorsky. Another, once owned by Howard Hughes, is now restored and is in Kermit Weeks’ collection in Florida (along with an S-38 and an S-39 too!) One, acquired by the US Marine Corps, survived the attack at Pearl Harbor in 1941 and is being restored at the National Air and Space Museum in Virginia. The Pima Air and Space Museum in Tucson has the third extant model.

PHOTO: A PAN AM S-43 "BABY CLIPPER" ON THE STEP (PAHF COLLECTION).

By the close of the1930’s, Igor Sikorsky was nearing the culmination of his flying boat design journey. The final product was the VS-44. (Since 1929,Sikorsky’s company had been a part of United Aircraft, which merged the company with another subsidiary, Vought Aircraft. Hence the prefix “VS.”) The civil flying boat design had emerged from an earlier 1937 prototype patrol bomber that had been passed over by the US Navy. Although Igor Sikorsky had hopes for recapturing Pan Am’s business with the VS-44, (and another, larger design which was never built named the VS-45), the airline had already committed to Boeing and its B-314. Although the Boeing had greater payload, the Sikorsky could fly faster and farther. It was a serious contender, but the market was small, and Pan Am had found other answers to its flying boat needs. In the event, there were three VS-44’s built for, and flown by American Export Airlines (AEA), a subsidiary of the American Export Steamship Company wth hopes of competing in the transatlantic airline business. Although ordered in 1939, the VS-44’s didn’t see service on the route to Europe until 1942 (in part due to objections raised by competitor Pan Am).

PHOTO: THE VS-44 THE FINAL FLYING BOAT (PAHF, ZAVADA COLLECTION).

Even though they never flew for Pan Am, the VS-44’s had a tangential familial connection. AEA became American Overseas Airlines (AOA) when the company was absorbed by American Airlines after WWII. Then in 1950, AOA itself became part of Pan Am, although the flying boats were a fading memory by then. The sole surviving VS-44 is now on display at the New England Air Museum near Connecticut’s Bradley International Airport (BDL), having been carefully restored by former Sikorsky employees in the 1990’s. A few other models of earlier Sikorsky flying boats also survive as well, although no S-40’s or S-42’s remain.

The Sikorsky flying boat legacy was complete with the VS-44. The visionary designer would soon be moving on to pursue another dream of his youth – a successful vertical flight machine. As with flying boats, he would achieve amazing success. His flying boats remain as a handful of museum pieces and memories, but the skies are filled with his helicopters.

A note: In the interests of simplicity, we have treated both Sikorsky amphibian aircraft (“amphibions”) and pure flying boats as a single class of aircraft for this article.