by Robert Gandt
At Barranquilla, Colombia, a giant crowd had swarmed over the airfield, making it impossible to land. Darkness was falling, and the S-38 was nearly out of fuel. Lindbergh tossed notes asking the police to clear the crowd. The crowd remained. Lindbergh climbed the S-38 to seek another landing spot. At that moment, both engines sputtered, then fell silent.
The occupants of the cabin kept their silence while Lindbergh calmly glided the S-38 away from the airfield. He had spotted a lagoon about two miles away, and he dead-sticked the S-38 toward the narrow channel. Smoothly, Lindbergh skimmed the hull of the amphibian onto the lagoon. As the S-38 rocked to a stop in the darkening water, the tension broke. Laughter erupted inside the cabin.
They were picked up by natives in dugout canoes who took them to shore. They then transferred to an automobile where they were taken, late but unruffled, to yet another a gaudy reception. An illuminated sign greeted them: WELCOME LINDY.
10
The Flying Forest
She was the largest airplane ever constructed in the United States. On 19 November 1931, when she took off from Miami for her inaugural journey to the Canal Zone, the age of the great flying boats had officially begun.
The Sikorsky S-40 was the culmination of a design effort that began in early 1930. Igor Sikorsky had signed a contract with Pan American to build two giant, four-engined, oceangoing aircraft. A third ship would be optioned. Each would cost $125,000. The S-40 would be the first airplane ever to be built to a particular airline’s specifications.
That winter Sikorsky made numerous trips down from his Stratford plant to Juan Trippe’s little three-room New York office at 100 West Forty-second Street. There, around a long table, he huddled with Trippe, Lindbergh, and Priester over the drawings of the new flying boat.
European conservatism often clashed with American impatience. Lindbergh wanted the S-40 to reflect the newest aeronautical technology—clean lines, a sleek airframe, cantilevered wings, fully cowled engines mounted integrally into the wings. He was disappointed when he first saw the S-40’s maze of struts, braces, flying wires, and outriggers. She resembled nothing so much as an overgrown S-38, still featuring the boat hull slung beneath the wing, tail surfaces appended by twin booms to the wing and supported by braces from the stubby aft fuselage. Lindbergh could not resist calling the new amphibian a “flying forest.”
Sikorsky held his ground. In his view, giant strides in aircraft development came in a layered, incremental process. The design of an aircraft as advanced as the S-40 ought to be an outgrowth of proven concepts, he thought. Such a concept was the already successful S-38.
Sikorsky believed in the “art of the possible.” He was also being realistic. The refinements urged by Lindbergh were costly in terms of structural weight. The luxury of cantilevered wings and empennage and integrally mounted engines added massive thickness and weight, upping the aircraft’s basic operating weight and lowering available payload. Such penalties could only be offset by additional power, which, in 1930, was a scarce commodity. The S-40’s four Hornet engines would deliver a total of no more than 2,300 horsepower.
Andre Priester shared Sikorsky’s beliefs. Performance in Priester’s book was always second to safety and reliability. He saw the S-40 as a building block toward more ambitious aircraft.
Lindbergh eventually let himself be persuaded. The two Europeans were, he thought, “a remarkable combination—the dynamic and demanding Priester with his Dutch accent and the imperturbable Igor and his Russian accent.”1
Trippe, as impatient as Lindbergh, sided with the conservatives, but for pragmatic reasons. Pan American needed the S-40—and its huge payload capacity—without delay. There was no time on Trippe’s agenda for protracted experiments with aircraft design. For now, Sikorsky would proceed with the “flying forest.”
Lindbergh had other concerns, mostly about maintenance of the Sikorsky boats. Salt water was the curse of seaplanes. He complained to Sikorsky that the S-38 had been fitted with brass nuts on an aluminum framework, a match which, almost overnight, caused electrolysis, with white powder forming where the two metals met. Sikorsky agreed to make the changes.2
There was the matter of cockpit placement, always an issue with flying boats. In the original plans, the cockpit had been located high up in the center section of the wing, where it resembled the bridge of a ship. Lindbergh thought that the pilots’ compartment belonged forward, about one-third of the distance from the bow to the leading edge of the wing. This would improve crash survivability and enhance the pilots’ visibility. An inherent problem with the S-38 was the deluge of water that sprayed from the propellers onto the windshield during takeoff and landing.
The S-40, like the smaller S-38, was to be configured as an amphibian. This was an anachronistic notion, which still persisted in 1930, that just as it was deemed safer to fly over bodies of water with float-equipped airplanes, so it was equally prudent to equip seaplanes with wheels to fly over land. Since the S-40 was intended to fly over great stretches of Latin American land masses, so she would be burdened with a massive, retractable landing gear. Because no landing gear hardware existed for an aircraft of such dimensions, Sikorsky searched a railroad yard to find shock absorber springs of sufficient size. The springs he eventually installed on the S-40 had been designed for a medium-sized railway car.3
Sikorsky and his Russian engineers had a talent for “cut and try” methods to find correct solutions. To find the proper hull design, they tested different shapes by constructing miniatures and towing them behind a boom attached to a motorboat. These model hulls, about six feet long, were dragged about the Housatonic River at various speeds for around two thousand runs, a total of two hundred hours of testing.
By the spring of 1931 the S-40 neared completion. When the aircraft rolled out of her hangar, Sikorsky shared his pride with his employees. “Once again,” he wrote, “we could feel gratified in watching one more ambitious dream materialized. It was grand to stand before a nearly completed airplane, and to attempt to recall the impressions created by the early ideas and sketches of the ship before it was built, or even designed.”4
She possessed a size and presence unlike any aircraft on earth. Her wings, towering some twenty-three feet above the ground, spanned 114 feet and had a chord of sixteen feet. They had required 1,740 square yards of fabric in their covering. From bow to tail she measured nearly seventy-seven feet. Empty, she weighed 24,748 pounds, and when fully loaded she weighed 34,000 pounds. Her big, thick wings carried a load of just over eighteen pounds per square foot of wing area.
The cabin of the S-40 was designed to carry forty passengers, four abreast, in unprecedented comfort over a distance of 500 miles. With only twenty-four passengers, her range was extended to about 950 miles. Her four 575-horsepower Hornet engines would give her an advertised cruise speed of 115 miles per hour.
Flown by Sikorsky’s chief test pilot and countryman, Boris Sergievsky, the S-40 underwent all her test series. After minor modifications, she went back to the hangar to be painted in Pan American colors. She had exceeded all expectations. As a pure flying boat, without the railroad springs and heavy wheels, her payload could be increased by 1,800 pounds. Even as an amphibian, she could climb to 6,500 feet on three engines and fly level at 2,000 feet on only two.5
On 25 September, Captain Basil Rowe and a Pan Am team arrived to perform the acceptance tests. Rowe liked everything about the airplane except for the heaviness in the aileron control. “We discussed several corrective measures,” he recalled, “and finally decided upon a greater gear ratio. This was far from the ideal solution, but it was the best we could do at that stage of completion. The trouble with our compromise was constant winding of the wheel, but it was better than doubtful control in rough conditions.”
On 10 October 1931, Basil Rowe and his crew ferried the S-40 to Anacostia for her formal christening. The day, appropriately, was Columbus Day. Twelve thousand people watched the ceremony. While Navy and Marine Corps bands pla
yed, two radio networks reported the proceedings. Juan Trippe made a short speech. Mrs. Herbert Hoover swung a bottle of what was declared to be Caribbean seawater against the S-40’s bow. The new ship became, officially, the American Clipper.6
She lived a glamorous life. For the inaugural trip, her captain was America’s premier hero, Charles Lindbergh. As with all Lindbergh’s travels, the flight was attended by worshipful crowds, clamoring press, and the usual gaudy send-off from the Pan American base in Miami. With veteran Basil Rowe as first officer, the American Clipper took off with thirty-two passengers on board, bound for Kingston, Jamaica, then onward to Barranquilla, Colombia, and Cristóbal in the Canal Zone. Among the passengers was Igor Sikorsky.
During the overnight stops, Sikorsky sat at the dinner table with the crew. The discussions dwelt, inevitably, on the new clipper and the “next step.” A creative chemistry had by now developed between Lindbergh and Sikorsky. “Lindbergh and I would take the menu,” recalled Sikorsky, “turn it upside down and make sketches for a long-range flying boat. We both believed that scheduled transatlantic flying was possible, and at that time a flying boat seemed to be the right solution. At those dinners we laid down the basic principles around which to design a transoceanic flying boat. The problem was to combine speed with long range and a payload which would make transoceanic airline routes practical and economical.”7
The inaugural flight continued to Barranquilla without trouble, arriving precisely on schedule. But on the following day the expedition nearly came to grief. While the aircraft lay tied to her dock, Lindbergh stood atop the wing supervising the refueling operation. A fuel tank overflowed, spilling gasoline over the wing and into the water. Lindbergh suddenly realized that a number of the spectators on the pier were smoking.
“Stop smoking!” he called from the wing. To his horror, he saw the obedient smokers extinguish their cigarettes—by tossing them into the gasoline-covered water.
It might have been disaster. Several tense seconds ticked past. The cigarettes fizzled, then snuffed out. Happily for the American Clipper, and Lindbergh, there was no inferno.
Lindbergh waited in Barranquilla while Rowe and First Officer Charles Lorber took the S-40 on down to Cristóbal and back again. Then he resumed command for the return journey to Miami.
The transit in Kingston resulted in a delay, which Lindbergh calculated would put them into Miami just before nightfall. The S-40 had no provisions for night flying and, in any case, there would be no lights on Biscayne Bay for a night landing. But Lindbergh took off, thinking that if all went well, they would arrive with still enough light left to make a normal landing.
He was wrong. Darkness came, and the American Clipper was still airborne. In the blackness, Lindbergh could not even determine the wind direction. When he finally settled the big ship onto the darkened water, it smacked the surface, porpoised, then lurched hard to the left, tossing a few unfastened passengers out of their seats.
Chagrined, Lindbergh apologized for the rough landing. Sikorsky, ever the nobleman, took personal blame for the landing. It wasn’t at all Lindbergh’s fault, he insisted. It must have been a problem with the design of the hull.
Lindbergh smiled. For the rest of their lives the two men would remain staunch friends.8
Over the years, Basil Rowe spent many hours in the cockpits of the S-40s. On one occasion during a flight to Colombia, he again had as a passenger the ship’s builder, Igor Sikorsky. When Rowe went back to the cabin to pay his respects, he found the little Russian on his knees, feeling about the cabin floor, a worried expression on his face. The other passengers looked on with alarm. Rowe asked what the matter might be.
“I keep hearing a peep, peep, squeak, squeak.”
Rowe listened, then assured him that a mechanic would attend to the matter when the Clipper landed in Kingston. Sikorsky, in the meantime, was upset. It was unthinkable that the American Clipper—his dreamship—should be afflicted with peeping and squeaking.
On the next leg of the journey, Rowe returned to the cabin. “Well, Mr. Sikorsky, do you still hear that peep, peep, squeak, squeak?”
“No, it’s gone—what was it?”
“It was a thousand baby chickens in the cargo department. We unloaded them in Kingston.”
Understanding, then relief, flooded Sikorsky’s face. He turned to the window and laughed.9
On another occasion Rowe became involved in a publicity stunt. He was to race the American Clipper from Havana to Miami against an ancient cart drawn by oxen. The oxen were to plod along a four-mile route through the center of Havana to the outskirts of the city. The winner would be whichever vehicle arrived at its destination first.
Rowe didn’t like the odds. “It proved much too wild because of three factors. The first and foremost was the method used by the Cubans in handling oxen: goading them along with a nail in the end of a pole. The second factor was a northeaster that I had to buck. The third was the Cuban himself and his inherent love of gambling.”
Along the way Rowe was kept informed by radio of the oxen’s progress. He heard that the crowds were betting heavily against the clipper and had begun pushing the cart until the beasts were moving at about ten miles an hour. When he was only halfway to Miami, he heard that the oxen were within a mile and a half of their goal.
Rowe decided to dispense with ethics. “I pulled the throttles closed and set the big flying clipper down on a smooth stretch of protected water in the lee of the Keys. I radioed ‘Just landed,’ planed along on the step for half a mile or so, then pulled up and continued the flight. It was a dirty trick, but so is sticking nails in oxen.”
In 1931 Pan American posted its first annual profit—$105,452 on a revenue of $7,913,587. With the increase in passenger and mail revenues afforded by the capacious S-40s, the airline, at the height of the depression, would continue to show profits.
The American Clipper and her two sister ships, the Caribbean Clipper and the Southern Clipper, flew the routes to Central and South America, ranging as far south as Buenos Aires, Argentina, and Santiago, Chile, stopping regularly at ports like Rio de Janeiro, Brazil; Bogota, Colombia; and Lima, Peru. In 1936 their capacity was increased to forty passengers with the installation of the more powerful 660-horsepower Hornet TB1 engines.
The sturdy S-40s provided a decade of faithful service to Pan American. After Pearl Harbor day they were requisitioned by the U.S. Navy and served as training ships until their retirement in 1943. The three aircraft logged an estimated ten million miles of flight, never experiencing a crash—a remarkable record for flying boats.
The S-40 was never a transocean flying boat. She was a lumbering truck of a transport aircraft, short-legged but sturdy, designed for the Latin American route system. She was a mammoth for her day, exceeded in size only by the less successful mammoth, the German Do X.
In her original configuration, the S-40’s load-to-tare ratio (maximum payload versus empty weight of the aircraft) was 28:72, a far cry from the efficient numbers (nearly 50:50) of the next generation of over-ocean boats. But even this modest performance would have been impossible had Sikorsky incorporated the weighty streamlining features that Lindbergh had originally urged.
With the S-40, Sikorsky had practiced the “art of the possible.” Now it was time for the next step. From the building block of the S-40 he would construct the world’s most advanced flying boat.
11
The Next Step
The S-42 flying boat, in penciled outline, first appeared on the back of a hotel restaurant menu in Cienfuegos, Cuba. During the inaugural flight of the American Clipper, Lindbergh and Sikorsky had sketched the features of a new flying boat. By the time the inaugural trip returned to Miami, their menu-sketching had become a proposal for a transoceanic flying boat.
Lindbergh, it was agreed, would promote the idea to Pan American, whom he served as a technical consultant. Sikorsky would sell the plan to United Aircraft, the parent corporation of Sikorsky Aircraft Co.1
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p; The S-42 proposal matched the ambitions of Juan Trippe, whose eye was now firmly fixed on the oceans. In Trippe’s vision, Pan American was to become America’s maritime service of the air. The historic Atlantic and Pacific trade routes, if Trippe had his way, would be plied by Pan American’s flying merchant ships.
The competition had already begun. In the South Atlantic the adventurous French airline, Aéropostale, was sending mail from Africa to South America aboard their Latécoère flying boats. In the North Atlantic, the Germans had placed the Graf Zeppelin in regular service. In 139 flights across the Atlantic, the airship had carried an impressive total of 17,591 passengers without mishap. The age of transatlantic air travel was nearly at hand.2
On 1 October 1932 Pan American placed an order for three S-42 flying boats with options for seven more. The order specified features unprecedented in an airliner, including the technological advances sought by Lindbergh in the S-40 and the evolutionary “next step” development espoused by Andre Priester and Igor Sikorsky.
* * *
The final configuration underwent several alterations. In its original concept, the S-42 was a twin-engined, long-range flying boat. Early in the planning stage, the twin-engine concept gave way to a three-engine design. This idea, installing the engines on struts above the wing and fuselage, eventually yielded to a four-engine arrangement with the engines mounted directly into the leading edge of the wing which, in turn, was fixed atop a streamlined cabane in the upper fuselage.
The development of the S-42 became a collective effort. Priester and Lindbergh were the Pan American overseers of the project. Sikorsky’s co-subsidiaries at United Aircraft—Pratt and Whitney, and Hamilton Standard—were to supply the engines and propellers. Although the new Pratt and Whitney Twin Wasp engine was the initial choice to power the S-42, it was later decided to stay with the upgraded, 700-horsepower versions of the reliable Pratt and Whitney Hornet engine instead of the unproven new Twin Wasp. The performance required in Pan American’s specifications could only be achieved with a new device recently developed by Hamilton’s brilliant engineer, Frank Caldwell—the controllable-pitch propeller.