Fly Wheels

Fly Wheels

The Sikorsky VS-44 Flying Boat

The VS-44, having had both military and civil application, had been Sikorsky's largest—and last—flying boat, but had had a meager production run of only four.

Tracing its lineage to several previous amphibious designs, it had its first spark in the S-38.  Powered by two 420-hp Pratt and Whitney Wasp engines, the ten-passenger biplane, first flying in 1928 and attaining cruise speeds of about 100 mph, had been ordered by the US Navy and Pan American Airways.  Lindbergh inaugurated airmail service with the type between the US and the Panama Canal Zone the following year.  Operated by several other carriers, it enjoyed a production run of 110.

The succeeding, quad-engined, high-wing, boat-hulled S-40, ordered by Pan American in 1929 and destined to become the then-largest US aircraft, accommodated 40 passengers on 500-mile sectors, the first, designated "American Clipper," inaugurating service on November 19, 1931.  Its eventual fleet of three enabled it to pioneer Caribbean and South American routes.

The S-41, a larger version of the S-38 with a capacity of 14, had a production run of just seven.

Intended for transoceanic routes, the S-42, powered by four Pratt and Whitney engines driving reversible-pitch Hamilton Standard propellers, was designed to fill requirements for a larger-capacity, 2,500-mile, amphibious airliner cruising at 150 mph, although a reduced, 1,500-pound payload significantly increased its range capability.  First flying in 1934, it enabled Pan American to serve previously uncoverable Atlantic and Pacific segments with its fleet of ten.

The largest—and last—Sikorsky flying boat, incorporating technology developed by these earlier designs, arose from the Navy's requirement for a 3,450-mile patrol bomber to eclipse the range of its current PBY Catalinas.  The specification, detailed by the US Navy Bureau of Aeronautics' Design Proposal #137, stipulated a 200-mph speed, a crew complement of six, and four machine gun turrets.

The design, sequentially designated "S-44" by Sikorsky, and the only one which closely met the Navy's requirements, incorporated a high, all-metal, cantilever wing; four Pratt and Whitney, 700-hp Twin Wasp radials which drove constant-speed Hamilton Standard propellers; a .50-caliber machine gun in both its bow and tail turrets; and a .30-caliber machine gun in its two center turrets.  Although it could equally accommodate 4,000 pounds of bombs, the later specified, and more powerful, 1,050-hp R-1830-68 engines, coupled with 12-foot-diameter props, doubled this capacity.

A single prototype, for which a contract had been awarded on June 25, 1936, first flew a year later on August 13 from the Housatonic River near the Sikorsky factory in Stratford, and featured a 47,142-pound gross weight in bomber configuration and a 49,059-pound maximum weight in patrol guise.

The two-month flight test program, entailing 26.9 airborne hours, revealed several performance parameters, including a 640-fpm initial climb rate, a 62-mph stall speed, a 225-mph maximum speed at 10,000 feet, a 23,100-foot service ceiling, and a 4,545-mile range.

Delivered to Norfolk Naval Air Station on October 12, 1937, the XPBS-1 accumulated an additional 53.5 hours of test flying, during which rudder control force deficiencies were experienced, necessitating a return to the manufacturer for modifications.  Yet, despite the fact that Navy pilots expressed overall aircraft handling and performance satisfaction, the Navy itself abruptly canceled any further orders for the design, replacing it with the Coronado instead.  No reason was subsequently specified.

Thus relegated to transporting government officials and priority cargo, the single XPBS-1 operated for five years until it was damaged while landing in San Francisco Bay in 1942, incurring a log strike.  It was removed from Navy inventory with 1,367.5 hours in its logbook.

The design, however, had commercial application.  Pan American Airways' competitor, American Export Airlines (AEA), seeking a long-range, amphibious airliner for its own transatlantic passenger services, signed a contract for a civil version of the XPBS-1 designated "VS-44", the "VS" prefix reflecting the combined, but temporary, Chance Vought and Sikorsky factory operations, both divisions of United Aircraft Corporation.  Pending its receipt of Civil Aeronautics Board passenger route rights, it intended to purchase three VS-44As, whose names reflected its American Export shipping—and original—division of vessels—namely, "Excalibur," "Excambian," and "Exeter"—while Pan American itself ordered the competing Martin M-130 flying boat.

Several design modifications were first required to bring it up to commercial standard.  The nose turret, first and foremost, had to be replaced with a solid, rounded, cone made of metal, while the windows, doors, and hatches were relocated.  In order to transform the patrol bomber into an airliner, an altogether different interior had to be installed, bulkhead-divided into six smaller, watertight sections with appropriate passenger seating, galleys, lavatories, heating, ventilation, and soundproofing.  A larger horizontal tail, featuring ten degrees of dihedral, was retrofitted to augment longitudinal control, while aileron and tail cables were rerouted.

The interior configuration included a five-person cockpit controlled by a pilot, copilot, flight engineer, navigator, and radio operator; a galley located immediately below it and equipped with an oven, an electric stove with two hot plates, a sink, hot and cold water, a refrigerator, and storage cabinets; crew sleeping accommodations; mooring equipment; a baggage compartment; and two men's rooms.  Passenger capacity varied between 32 in day and 16 in sleeper configuration.  Forty-inch-wide seats were convertible into both upper and lower berths, and each was provided with a window, a reading light, and heating and ventilation vents.  The aft cabin contained the ladies' room, a second baggage compartment, and cabin crew accommodation.

Upon completion, the VS-44A, with a 79.3-foot overall length, sported a high, thick, 124-foot wingspan from which projected the four three-bladed, 12.6-foot-diameter propellers driven by 1,200-take off horsepower Pratt and Whitney Twin Wasp S13C-G piston engines and below which hung two, water surface-skimming floats near its wingtips.  Two dual-wheeled main beaching gear units and a single, twin-wheeled tail unit permitted nonaquatic ground taxiing.  The tailplane spanned 31 feet.  With a 3,820-gallon fuel capacity, the aircraft offered a 59,534-pound gross weight and a 211-mph maximum speed.

Draped in Navy camouflage livery, the first aircraft, named "Excalibur," was completed on December 30, 1941, but was redirected by the necessities of World War II.  AEA, operating it with its own flight crews, commenced weekly, war transport transatlantic service on June 20 to Faynes, Ireland.  "Excambian" and "Exeter" were delivered on May 4 and June 23.

Operating the world's first nonstop westbound transatlantic crossing on June 22, 1942, aircraft "Excalibur" flew from Faynes to New York in 25 hours, 40 minutes with 16 passengers aboard.

The airframe's service life, however, would span little more than three months.  Executing a long, water-purposing take off from Botwood, Newfoundland, on October 3, 1942, it attained a ten-foot altitude before settling back into the water.  Re-emerging, it angled into an excessive, 30-degree nose-high attitude, during which time it climbed to 35 feet, but subsequently barreled earthward, impacting with the ocean's surface and breaking apart.  Five of the 11 crew members and six of the 26 passengers perished.  Although the actual cause had never been pinpointed, it is believed that the pilot had attempted to use an excessive, drag-producing, take off procedure-deviating trailing edge flap setting.

Because the remaining two airframes had constituted the world's longest-range commercial types, able to fly 3,100-mile or greater sectors with full payloads, and because the war dictated the need for such transports, their ownership was transferred to the US government on January 26, 1943 for operation in the Navy's transoceanic passenger, cargo, and mail ferry service to the Caribbean and Europe.  American Export Airlines, under contract to them, continued to maintain and fly the aircraft.

Repainted in AEA's livery in January of 1945, the two VS-44As recommenced scheduled, civilian service in June, but a later merger with American Overseas Airlines (AOA) and the prevalence of war-sparked runway construction obviated their need, transatlantic routes now increasingly served by land planes, such as the Douglas DC-4.

The "Excambian" and "Exeter" were therefore acquired by Tampico Airlines from the War Assets Corporation on February 27, 1946, at which time they were subserviced to other carriers for charter operations.  But Tampico's own financial difficulties resulted in their onward sale to Skyways International the following April.

Hull-losing accidents, hitherto characteristic of the design's history, struck once again—and only four months after the acquisition, on August 15, 1947.  Attempting to land on the River Plata near Montevideo, Uruguay, during black of night, in nonexistent visual reference conditions and without updated altimeter settings, aircraft "Exeter," already overloaded, impacted with the water surface, shedding its hull plates and severing half of its left wing.  Flooded with gushing water, the aircraft sank, taking nine of the 12 souls on board with it.  Only "Excambian," one of the four XPBS-1 and VS-44A airframes, now remained.  Its longevity would usurp them all.

After Skyways' liquidation and intermediate ownership by Seaboard Commercial Finance Corporation, the Aviation Exchange Corporation acquired the aircraft with the intention of transporting cargo to the Amazon River, but its plan, upon reconsideration, was not economically viable.  As a result, Avalon Air Transport, which provided steamship-competitive air service on the 27-mile sector from Long Beach, California, to Catalina Island, acquired it on June 14, 1957, but relocated the engine controls to a position between the forward two cockpit seats; removed the flight engineer's panel, and rendered the navigator and radio operator functions redundant.  Seating capacity increased to 47.  Operating under an FAA supplemental type certificate, the single VS-44A ultimately made 8,172 trips to Catalina Island during its decade of service, carrying more than 211,000 passengers, along with 68 trips to San Clemente under Navy contract.

Continuing in this island-hopping role, the "Excambian" provided inter-Caribbean connections, particularly between St. Thomas and St. Croix, when Antilles Air Boats purchased it on January 9, 1968 for $100,000.  However, the short-lived operation, almost ending the way the lives of the other three airframes had, was abruptly cut short when the aircraft ran aground after landing in St. Thomas the following year.  Although there had been no injuries and little more than wet feet in the forward cabin, repair costs, particularly due to corrosion, proved prohibitive, and it therefore remained in situ for another six years.

With its service life thus effectively terminated, Antilles Air Boats donated the aircraft to the Naval Air Museum in Pensacola, Florida, in 1976, and they concluded a long-term loan agreement with the New England Air Museum in 1983.  During its subsequent, ten-year restoration, conducted in a temporary, $150,000 Rubb hangar at Sikorsky Memorial Airport in Stratford, it was transformed into its original, 1942, American Export Airlines configuration, requiring the replacement of 97 percent of its aluminum skins, 35 percent of its airframe structure, the relocation of the engine controls to the flight engineer's panel, and the installation of its transoceanic flying boat passenger cabin.

The project, under National Air and Space Museum guidance, was completed by a team of volunteers from Sikorsky, Textron Lycoming, the airline industry, and technical schools.

Relocated in sections, including the wings, engines, and control surfaces, to the Windsor Locks New England Air Museum, it was reassembled and painted in AEA livery during the latter half of the year before being displayed in its Harvey H. Lippincott Civil Aviation Hangar.

Having transported passengers, cargo, and mail in both military and commercial configurations for more than a quarter of a century, the latter entailing scheduled airline, charter, and air taxi operations, the "Excambian," the last of the remaining four XPBS-1 and VS-44A airframes, equally represents the end of the long-range, transoceanic, elegantly-appointed, flying boat era, and remains on display, dominating the hangar, to tell its story.

About the Author

A graduate of Long Island University-C.W. Post Campus with a summa-cum-laude Bachelor of Arts Degree in Comparative Languages and Journalism, I have subsequently earned the Associate in Applied Science Degree in Aerospace Technology at the State University of New York - College of Technology at Farmingdale.  I have also earned the Continuing Community Education Teaching Certificate from the Nassau Association for Continuing Community Education (NACCE) at Molloy College, the Travel Career Development Certificate from the Institute of Certified Travel Agents (ICTA) at LIU, the Art and Science of Teaching Certificate at Long Island University, and completed a Multi-Genre Writing Program at Hofstra University.  At SUNY Farmingdale Aerospace I completed some 30 hours of Private Pilot Flight Training in Cessna C-152 and -172 aircraft.

Having amassed almost three decades in the airline industry, I managed the New York-JFK and Washington-Dulles stations at Austrian Airlines, created the North American Station Training Program, served as an Aviation Advisor to Farmingdale State University of New York, and devised and taught the Airline Management Certificate Program at the Long Island Educational Opportunity Center.

A freelance author, I have written some 70 books of the short story, novel, nonfiction, essay, poetry, article, log, curriculum, training manual, and textbook genre in English, German, and Spanish, having principally focused on aviation and travel, and I have been published in book, magazine, newsletter, and electronic Web site form. I am a writer for Cole Palen's Old Rhinebeck Aerodrome in New York. I have made some 350 lifetime trips by air, sea, rail, and road.

Are dirt bike crank fly wheels hollow on the newer machines to make them rev faster ?

They aren't hollow, but they make the ignition rotor very small and put it on the inside of the coils for exactly the reason you asked.

The first bike they did this with was the Honda 125 Elsinore in '73 and those motors did rev quicker than the old external rotor motors, beyond a doubt.

Rc Fly Wheels