How the Sikorsky S-42 Changed Aviation History

DALLAS - The statement that the Sikorsky S-42 was the "airliner that changed aviation history" will undoubtedly spark debate.

However, the role it played with Pan American World Airways presents a very strong case. Indeed, in Pan Am: An Airline and Its Aircraft, author Ron Davies notes “it [was an] airliner . . . the effects and influence of which on the world of air transport were more immediate” than those of the DC-2, which had gone into service at about the same time.

First, the airliner epitomized Pan Am founder Juan Trippe’s ‘Nautical Airline’ theme (see Airways May 2015, "The ‘Nautical Airline'"). Second, the airliner was a chess piece in Juan Trippe’s transoceanic ambitions.

And finally, because of its superior capabilities, the S-42 might have very well sowed the seeds for the Chicago Convention of 1944, which created the political environment and regulatory scheme under which all airlines operate today.

The Aircraft

At lunchtime on November 19, 1931, aboard a Sikorsky S-40 flying boat, pilot Charles Lindbergh turned the controls over to Basil Rowe and went aft into the passenger cabin to sit next to the most important passenger on board, aircraft designer Igor Sikorsky. According to Robert Daley in An American Saga: Juan Trippe and His Pan Am Empire, the meeting between the two would be characterized as “one of the most important fights in the history of aviation.”

What Lindbergh and Sikorsky discussed was “the next step," writes Daley. What Lindbergh wanted was a “really new airplane, something completely clean in design, with no external bracing, no outriggers, no fuselage hanging from the wing by struts, no engines stuffed amid the struts like wine bottles in a rack. All those struts and bracings only meant wind resistance to Lindbergh, and wind resistance meant a loss of range and speed.”

Sikorsky countered that what Lindbergh wanted was “two steps ahead in development, and Sikorsky wanted to take one step at a time . . . because lives were at stake . . . [and] they could not afford to make mistakes.” So, what was the next step? Both men began to work it out while eating lunch. Lindbergh drew something on the menu. The S-42 had been conceived.

Trippe had had a similar vision of an aircraft able to span oceans. His new design would provide for increased lifting capacity, the ability to carry enough fuel for a 2,500-nautical-mile (4,000km) nonstop flight against a 30 mph (48 kph) wind, and cruise far above the average operating speed of any flying boat at the time. Based on his requirements, Glenn Martin drew up plans for such an aircraft. But it would be Sikorsky’s S-42 that would be delivered first, almost a year before the Martin M-130 reached completion.

The S-42 made its maiden flight on March 30, 1934, and, according to Davies, “incorporated many technical refinements, such as large wing flaps, extensive flush riveting, engine synchronization indicators (also present on the S-40), propeller brakes and automatic carburetors.

Its wing loading was higher than that of any previous airliner and was not exceeded by any other type until 1942, eight years after it had gone into service. Had it been a landplane, concrete runways would have been needed at airports (that then normally just operated grass, gravel, or cinder strips) to support the wheel loads.

The S-42 could carry a full payload of 32 passengers over a range of 750 nautical miles, permitting nonstop trans-Caribbean flights to Colombia and the omission of several en-route points on the way to Brazil. The S-42 could carry more passengers at least as fast and twice as far as the DC-3.

The “Nautical Airliner”

When in full passenger configuration, the S-42 truly epitomized Trippe’s ‘Nautical Airline’. The passenger windows were round, like a ship’s portholes. The interior furnishings resembled the trappings of a luxury passenger liner or yacht.

An advertising brochure highlighted the maritime nature of the service by employing the term ‘cruises’ and depicting the flight deck, which looked like the bridge of a ship.

Pan American inaugurated passenger service with the S-42 in 1934, operating out of Miami to Barranquilla, Colombia, and also through the Caribbean and down the East Coast of South America to Rio de Janeiro (passengers traveling to Buenos Aires were transferred to either a DC-2 or DC-3).

In 1935, the S-42A entered service with its improved aerodynamics and a slightly longer wingspan. The engines were also upgraded, enabling a longer range. These aircraft were used in the Caribbean and South America.

In 1936, the long-range S-42B came online. On June 18, 1937, the Bermuda Clipper began flying between Baltimore and Bermuda. The S-42B also started service to the South Pacific on December 23, 1937. Sadly, however, the run was temporarily suspended when the Samoan Clipper, an S-42B commanded by Captain Musick, suffered a deadly fire, killing both him and his crew.

The S-42B was also used on the Manila- Hong Kong route in 1937 and the Seattle-Ketchikan-Juneau route in 1940.

Because of its range, the S-42B was used extensively on survey routes for Pan American. In 1937, Pan American Clipper III made five survey flights over the Atlantic, originating in New York. The first was a round trip to Shediac, New Brunswick, followed by a round trip to Botwood, Newfoundland.

Then came two trips to Southampton, England, via Foynes, Ireland (the northern route). The last trip was over the southern route to Southampton via Bermuda, the Azores, Lisbon, and Marseilles. But the most important of all was the transpacific survey of 1935.

Juan Trippe´s Transoceanic Ambitions

Trippe had initially sought to inaugurate trans-oceanic operations across the Atlantic to England. But these were not meant to be; not before 1937, at least. Most of the reasons were political, but the main one was the S-42 itself, then the most advanced aircraft in the world.

At the time, the British had nothing even approaching its technical superiority. And that superiority, for all intents and purposes, blocked Pan American from inaugurating transatlantic service to the United Kingdom. The British would not let the United States (Pan American) show off their technical superiority until they had an aircraft of similar capabilities.

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The S-42 was not originally designed for transpacific flight. It had been designed for the Atlantic. With 32 passengers, a crew of five, and 2,500 pounds of mail and cargo, the S-42 could cover 1,250 nautical miles; not enough for the Pacific.

But the Martin M-130, slated for Pacific duty, was not yet ready for delivery, and Trippe wanted to start operations in the Pacific ‘now’. It was thus decided to use the S-42 for the survey flights, and NC 823M, the West Indies Clipper, was sent back to the factory, stripped of its interior, and fitted with extra fuel tanks to give it a range of 3,000 nautical miles. Renamed the Pan American Clipper, the aircraft flew off to San Francisco for its historic assignment.

The critical element of this was flying the California-Hawaii sector, which, according to Davies, “was and still is the longest significant air route segment in the whole world. Any aircraft that could perform adequately on this critical leg could fly any commercial overseas route.” The Pan American Clipper did.

The British finally developed an airliner that could compete with the S-42: the Shorts S.23. With that, they opened the door to Pan American. Atlantic service was inaugurated in 1939 with the Boeing 314.

Sowing the Seeds for Chicago?

While to claim that the S-42 sowed the seeds for the Chicago Convention of 1944 might be considered an overstatement, it should be remembered that, because of the aircraft’s superiority, the British had balked at allowing Trippe access to the UK during the mid-1930s.

Note, too, that Trippe was doing the negotiating for the landing concessions (as he had done in the past). In this case, he was dealing with Imperial Airways (the predecessor of BOAC and British Airways), which was a creature of its own government, as opposed to a private enterprise like Pan American.

In a sense, Trippe was negotiating with the British government. This prompted the British to ask why the US government wasn’t doing the bidding for Pan Am. This set the stage for US government involvement in negotiating with its foreign counterparts for landing rights—and ended Trippe’s role as a 'shadow foreign minister for aviation'.

Government-to-government negotiations for landing rights became US policy toward the end of World War II.

As the war was winding down, there was no doubt that the US was by far the strongest aviation power in the world, prompting significant worries from the British. The source of the imbalance may have been planted in an agreement reached during the war between US President Franklin Roosevelt and British Prime Minister Winston Churchill: the US would focus on the development of long-range bombers and transports while its Allies would concentrate on fighters and light bombers.

By the war’s end, the US had a definite advantage in both capacity and range.

The British, however, held control of one end of a large number of international journeys, something that was of great interest to Pan American, which had visions of operating flights to the European continent and Asia. Nevertheless, the US was in a position similar to that of the proverbial elephant, who, while dancing through a chicken yard, cried, “Everyone for himself!”

With the war coming to an end, it became increasingly clear that a meeting should be held to resolve issues of international aviation—most importantly, those between the US and Great Britain. Eventually, the US sent invitations to the Allied Nations and the neutral countries of Europe and Asia to meet in Chicago on November 1, 1944.

All of this because of the S-42; an airliner created during a Pan American flight on the back of a menu by Charles Lindbergh and Igor Sikorsky.

As a postscript, it should be noted that the landmark Chicago Convention on International Civil Aviation, which established the framework for today’s rules of international air travel, ended with some of the economic issues between the US and Britain remaining unresolved.

The US (Pan Am) wanted the authority to pick up passengers in Britain for travel beyond (‘beyond rights’ as sought in the Fifth Freedom of the Air, promulgated at Chicago). The British balked. The issue was finally settled with the US getting the coveted rights in the Bermuda Agreement of 1946, which became the model for future air services agreements the world over.

Published first in the August 2015 issue of Airways Magazine

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Featured image: Sikorsky S-42, aircraft registration NC-822M, "Brazilian Clipper," Pan American Airways, 1934. Photo: By Anonymous-L'Illustration, volume 92, issue 4785, page 387, 1934-11-17, Public Domain, https://commons.wikimedia.org/w/index.php?curid=12738668