by Robert Waldvogel

Created on: September 12, 2010

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,

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