In 1947, the H-4 Hercules, then the largest aircraft ever built and made of wood, made its first and only flight off the coast of California.
The H-4 Hercules seaplane on its first and only flight off the coast of California. Image: FAA
In 1942, the United States participated in World War II and faced the problem of transporting large numbers of troops, weapons, and supplies across the Atlantic to England. At that time, hundreds of Allied ships passing through this sea were sunk by German submarines.
To solve this, construction and shipbuilding tycoon Henry J. Kaiser proposed to the US government to build a new type of seaplane larger than anything before. However, a plane that can carry 68,000 kg, 750 fully equipped soldiers, or two 30-ton M4 Sherman tanks across the Atlantic sounds crazy.
To design and build such a special vehicle, Kaiser collaborated with Howard Hughes, who was famous for his exploits in aviation, filmmaking, and eccentric life. However, this is not a long-term cooperation. Before long, Hughes and the Hughes Aircraft company, with characteristic enthusiasm, took over the entire project, leaving Kaiser largely as a spectator.
From its inception, the H-4 Hercules aircraft project was very strange. Because there was a shortage of strategic materials and the H-4 Hercules was a low priority project, Hughes and his company were not allowed to use metal to build the aircraft. Instead, they had to use as much wood as possible. This gave the plane the nickname Spruce Goose, even though it was actually made from birch wood.
The H-4 Hercules is made from an advanced layered Duramold plywood shaped to special molds and fabricated by gluing multiple layers of birch wood with urea-formaldehyde adhesive. These layers are sealed under heat and pressure, then treated with high-frequency electronic radio waves. Workers continue to sand the outside of the material, paper wrap, coat, paint and polish.
Even the heavy beams and beams to create the airframe were made from plywood because suitable solid wood could not be found. These forced the project team to develop new tools, new molds, and new glues.
An airplane three times larger than anything before required a lot of creative thinking, and Howard Hughes encouraged it. Unlike many technology entrepreneurs, Hughes was interested in every aspect of design and manufacturing, even flying hundreds of hours himself in a specially modified seaplane to test new design ideas. . He also took care of both the motor and the control panel, spending many hours placing each piece of equipment exactly where he wanted it, regardless of the electrician’s opinions about the wiring.
“Hercules is a huge project. It’s the largest plane ever built. It’s over five stories tall with a wingspan longer than a football field, longer than a block,” Hughes said.
Construction of the H-4 Hercules was lengthy, partly due to Hughes’s perfectionism. World War II ended before the plane was completed. By 1947, the US government spent 22 million USD to build the plane, Hughes himself spent 18 million USD.
With its massive size and wooden materials, the H-4 Hercules still took off successfully. Video: Alex the Historian
On November 2, 1947, the H-4 Hercules launched in the waters off Long Beach, California. With a smooth surface that doesn’t look like wood, the plane is 66.65 m long, has a wingspan of 97.51 m and is 24.18 m high, with an unladen weight of 113,398 kg.
Along the giant wings are eight 28-cylinder air-cooled Pratt & Whitney R-4360 Wasp Major engines, each generating 3,000 horsepower (2,200 kW) to turn the four-bladed propellers. The plane is so large that engineers can walk inside the wings and service the engines while in flight. The control surfaces are so large that a custom-designed hydraulic system is needed for the pilot to control them. There’s even a new high-voltage wiring system that makes the wires thinner to reduce weight.
Hughes sat in the pilot’s seat while a number of reporters were also on the plane. Hughes knew the plane better than anyone and was the most experienced in flying it. Reporters were informed that this was just a water test and the first flight was still in the future.
However, things did not turn out that way. After a few operations on the water, Hughes suddenly opened the throttle, reaching a speed of 129 km/h and the giant seaplane flew into the air, reaching a maximum speed of 217 km/h, flying 1.6 km in 26 seconds. The maximum flight altitude is 21 m. The short journey attracted great attention and proved that this giant machine could take off.
In 1948, after the first and only flight of the H-4 Hercules, Hughes spent $1.75 million to build a humidity-controlled warehouse just to store the H-4 Hercules. There, the aircraft were under 24-hour guard by a staff of 300 personnel (reduced to 50 by 1962). This team was responsible for ensuring the plane was always in flying condition, even starting the engines once a week until a special rotary device was invented. Through floods, earthquakes and subsidence, the plane was cared for at a cost of $1 million per year until Hughes died in 1976.
A legal dispute ensued years later because Hughes did not leave a will and a dispute over who owned the H-4 Hercules erupted. After much discussion, the plane is still intact and on display at the Evergreen Aerospace Museum in McMinnville, Oregon.