The Spruce Goose Is a Wooden Wonder

As an aviator, Howard Hughes was a man of records. In the decades following the first flight of the Wright Brothers, aviation could still bear the mark of a single individual’s obsession, and for a time, Hughes’s obsession was for speed. While still in his 20s, the multimillionaire businessman had helped design the streamlined H-1 racer, intended to be the world’s fastest aircraft. In 1935, Hughes flew it himself in to set a speed record at 352 miles per hour—28 miles per hour faster than the previous record holder. Over the course of the next 18 months, Hughes set multiple aviation records, including flying from Los Angeles to Newark in less than seven and a half hours. 

In 1938, Hughes and four other men flew a Lockheed plane around the world in just 91 hours, cutting the previous record, held by aviation pioneer Wiley Post, in half.

But his biggest, most audacious, most life-consuming, most fought-for, and most lasting record was for the construction and—spoiler alert—brief flight of the massive seaplane known as the H4 Hercules, née the HK-1, what his enemies called a flying lumberyard, what he called his Flying Boat, known to the world as the Spruce Goose. The aircraft was, and is, 284,000 pounds, eight stories tall from wheelbase to tail tip, and has a football field of a wingspan—with the wingtips extending well into the endzones. 

“It was so ginormous,” said Katherine Huit, a historian and previous director of collections at the Evergreen Aviation Museum in McMinnville, Ore., which has displayed the plane—an ASME Engineering Landmark—for more than 30 years. “Imagine looking up at a skyscraper and seeing this thing at eight stories. I don’t know how else to put it in perspective. It’s like taking a Tonka truck and putting it next to a semi. That’s how it feels. You feel so tiny when you’re standing next to it, it’s crazy.”

But size is just the most obvious innovation of the most jumbo of jumbo planes. In designing, constructing, and experimenting with it, Hughes and his engineers set many firsts before its flight, with its flight, and, also, after its flight.
 

Ships of the skies

The Spruce Goose was a concept arising from dire necessity. The United States had entered World War II in December 1941, and almost immediately, U.S. shipping in the Atlantic Ocean had come under attack by German U-boats. By May 1942, the losses had become unsustainable, prompting F.H. Hoge, Jr., a member of the War Production Board’s planning committee, to write a memo suggesting that instead of delivering cargo to Europe via ships on the water, we could do it with giant flying boats in the air.

It was an outlandish idea, but one taken up by industrialist Henry John Kaiser. Kaiser, never a boat man before the war, had managed to figure out how to mass produce the cargo-carrying Liberty Ship at an unprecedented speed and scale. (The design was so simplified that a shipyard could construct a Liberty Ship in a few weeks, or in the case of the SS Robert E. Peary, four and a half days.) Kaiser didn’t know how to build airplanes, either, but he believed he could do for flying cargo ships what he had done with the floating kind. 

Kaiser pitched his idea to Washington and the press with hyperbole. His flying ships would be “beyond anything Jules Verne could ever have imagined,” and would carry first 200 tons and eventually 500 tons. He claimed he could have a prototype tested and flying in 10 months, and, soon after, he would be producing 500 a year. Despite the bravado, potential partners in the aviation industry remained unconvinced that such a plane could fly. And with wartime restrictions on the availability of aluminum for building a prototype and engineers for designing it, Kaiser couldn’t get the OK to build a single flying ship, let alone a fleet.

Kaiser needed more than an idea. He needed Howard Hughes.

Hughes was more than a daring aviator. After inheriting a fortune and petroleum-technology company from his father, Hughes moved to Hollywood to produce and direct movies, including the 1930 aerial combat movie Hell’s Angels. His interest in aviation led him to found Hughes Aircraft Company and purchase control of TWA. Unlike Kaiser, Hughes knew airplanes. 

However, Hughes was notoriously hard to reach. Kaiser heard from Hughes’ engineer, Glenn Odekirk, that Hughes was in San Francisco to promote his film The Outlaw but was hiding out in a hotel with a cold. Kaiser tracked him down and within days they had agreed that Hughes would design the giant seaplane and Kaiser would build it. With Hughes onboard, Kaiser eventually wore down the government’s naysayers and they agreed to let the project go forward, provided they did not siphon materials or engineers from the aircraft industry.
  

Design and testing

Hughes involved himself in every aspect of every aircraft his company built—from nose to tail and everything in-between. The HK-1 (a designation that recognized both Hughes and Kaiser) would be no different. Hughes insisted on a single-hull craft with a wingspan a good 50 percent wider than the largest seaplane in the world at that time, the Martin Mars. Hughes Aircraft quickly submitted drawings to the government.

But even after Kaiser and Hughes won an $18 million contract ($336 million at today’s value) to produce three planes for testing purposes, skeptics—including Grover Loening, chief consultant to the War Production Board and developer of the first seaplane in 1923—continued to question the viability, flyability, and efficiency of an aircraft of that size. To prove them wrong, Hughes set out to create a half-scale model of the plane. 

Since even a half-scale HK-1 would be huge, the model couldn’t be built from scarce aluminum, which was needed for other military aircraft. Hughes instead turned to Duramold—a process of laminating wood with heat, pressure, and resin—developed by Hughe’s friend in aviation, Sherman Fairchild. Hughes had used the process to create his D-2 bomber (never flown in combat) and he purchased from Fairchild the rights to use the Duramold technique on all aircraft over 20,000 pounds. 

After testing the Duramold model in the National Advisory Committee for Aeronautics (NACA) wind tunnel, John Parkinson, the assistant chief of the Hydrodynamics Division, said that it “had probably the largest Reynolds number I’ve ever heard of.” Further tests were done on an even smaller model with a four-foot wingspan. 

But successes in modeling and testing did nothing to lessen the tension between Hughes and would be meddlers. One area of contention between the NACA and Hughes was the size and placement of the step, essentially the distance between the keel on the bottom of the seaplane and the rest of the hull. Hughes insisted that it should be two feet—much larger, proportionally, than other seaplanes. Smaller steps meant less drag but more difficult takeoffs and landings. To determine the best place for the step, Hughes experimented taking off and landing his Sikorsky S-43 flying boat roughly 6,000 times, according to engineer Odekirk. (Hughes crashed the S-43 in May 1943, killing two of the men onboard).
 

Under construction

The flying boat is known universally as the “Spruce Goose,” though there was little actual spruce in it (though there was some in the wing spars) because the evergreen doesn’t grip hardware as well as harder options. Instead, the bulk of the wood used was birch. The massive size of the plane meant many of the parts were longer than lumber could provide, so shorter pieces had to be scarfed together. At the scale they were working at, that meant inventing new tools to press the wood. And the aeronautical-grade tolerances were exacting: All glue lines were inspected and any over one-thousandth of an inch were rejected.

The size of the vehicle and its undertaking produced some astonishing numbers. The skin of the hull was glued on and held in place with eight tons of nails (for superior efficiency, guns to put the nails in and nail pullers to pull them were invented). Eight 3,000 horsepower Pratt & Whitney R-4360 Wasp Major engines, with 28 cylinders each, gave the plane 24,000 horsepower. They would draw their power from 14 1,000-gallon fuel tanks, consuming, together, 800 gallons an hour. A 120-volt DC electric system allowed them to reduce the weight of the miles of wiring by 75 percent. For the Flying Boat, Hughes and his engineers pioneered hydraulic control systems, redundant systems, and a fire suppression system.

In April of 1943, after the Duramold wings and hull had long been underway, Loening wrote that it was no longer necessary that the HK-1 be made of wood—aluminum was no longer scarce and was lighter and superior. Hughes should switch to metal. 

Controlling and contrarian, Hughes refused, but the pressure to switch to metal would continue for months. Loening visited the hangar where the flying boat was being constructed and reported that there was no way of knowing how the wooden joints would stand up to the stresses of flight, and this lent the plane an “element of unreliability that is definitely ‘scary’ for aircraft.”

Loening’s report ushered in a months-long battle about whether the project should continue. Whatever the reliability of the plane’s joints, as the war wore on and American ships wrested control of the Atlantic and Pacific oceans, the need for a flying cargo craft of that size diminished. But Hughes used his domineering personality to wear down resistance, and eventually had the contract reinstated, with Kaiser out of the picture, and the plane renamed the H-4 Hercules.
 

A race against time

Construction continued so long that eventually the war the H-4 was designed to support ended. Even so, Hughes was determined to continue the project and decided, in 1946, that it was time to move the plane from Culver City to its place of final assembly, Long Beach Harbor’s Terminal Island.

The cost and apparent needlessness of the flying boat caught the attention of the Senate Special Committee to Investigate the National Defense Program, a panel formed by then-Senator Harry S. Truman in 1941 to look into corruption and waste in the military. With the war over and Truman in the White House, the committee began to investigate Hughes’s flying boat in 1947. The race was on: Could Hughes assemble the plane and get it in the air before the committee put the kibosh on its further development?

The move itself was of unprecedented size. The planning for the journey took two years. Roads were closed, trees were trimmed, and police escorted the trucks with their massive loads of wings, hull, and fins. Twenty-one utility companies cut and reattached more than 2,000 power lines as the caravan moved toward its destination at two miles per hour. 

Even as investigation into spending on the plane continued, the plane moved toward completion. Its wings were attached to the hull, the nose of which rested just feet from the water. The hull had 12 water-tight compartments filled first with beach balls, and later with Styrofoam balls, to improve floatation if there were a leak. 

The investigation into the long-delayed delivery of the H-4 Hercules began in late July of 1947. With political deftness and maneuvering, Hughes managed to play the oppressed and win public sympathy. After five days of testimony the hearings were adjourned—to be resumed in November. Hughes returned to Terminal Island, determined to test the plane before he had to go back to Washington. 

Hughes worked with his engineers during the day—and then by himself till the wee hours of the morning—testing the engines, control, and electrical systems, and obsessing about the layout of controls on the flight deck. 

On November 2, 1947, Hughes took the controls and edged the H-4 Hercules into Long Beach Harbor, carrying engineers, crew, and journalists on board ostensibly for the purposes of “taxi tests.” 

When asked directly, that day, whether he intended to fly the plane, Hughes insisted that he did not. But he managed to make sure there was no trained co-pilot sitting with him. If he did take off, all the credit would be his.

After making a few actual taxi runs, Hughes asked for the flaps to be lowered into takeoff position. Then he pushed the throttle and soon had the H-4 hurtling beyond taxi speed. At 80 mile-per-hour, the flying boat earned its adjective, took off, and flew for half a minute 25 feet above the water.

“If you listen to the recording of the James McNamara radio broadcast, you will hear the audible silence,” Huit said, “because you can hear the engines and you can hear the plane bouncing along the water, and then, all of a sudden, it gets enormously silent, quiet, and everybody realizes that they’ve cleared the sea and they are actually in the air.”
 

Record breaker

That short, ground-effect-enhanced jaunt was the first and last time the Hercules would be airborne. But it was enough to set the record for the largest plane (by wingspan) ever flown, a record it held until Scaled Composites’ Stratolaunch jet with its 385-foot-wingspan beat it more than 70 years later.

The short flight was indeed the culmination of years of engineering and innovation, but Hughes would continue to improve on its systems for years. In 1948 he built a $1.75 million, climate-controlled hanger to house the flying boat. 

“During the years it was cloistered away Hughes completely redid the flight deck,” Huit said. “They added equipment and tested the propellers and the hydraulics and the fire suppression systems and all the electrical controls.” 

Did Hughes ever intend to fly the Spruce Goose again? Perhaps for a time. But in 1953 the hangar was flooded, the plane floated, and the tail was mangled against the ceiling. By then, the era of seaplanes had come to an end, and Hughes was turning his attention to space exploration. 

“I don’t think he intended to fly it again because he knew its time had passed,” Huit said.

Ownership of the seaplane was disputed for decades, and then it spent the 1980s on display under a dome in Long Beach Harbor. Eventually, the plane would make its second big move, again in pieces, to the Evergreen Museum in Oregon, where after a careful reassembly it is on display. 

And, who knows, maybe someday some enterprising, flight-obsessed mogul will set out to get the flying boat in the air again.

“I’ll go out on a limb and say it probably could fly again, with a lot of attention to mechanical soundness and testing the wood for durability,” Huit said. “That said, the wood is dang strong. It is super strong. So, you know, who knows?”

Michael Abrams is a technology writer in Westfield, N.J.