Hughes H-4 Hercules: Inside The Largest Aircraft Ever Built That Could’ve Changed History!

Designed by Howard Hughes himself, and ridiculed as the “Spruce Goose” for its size and the material it was built out of, the Hughes H-4 Hercules should have had a long and storied service life. Yet it never took off as it was expected…

As the largest fixed-wing aircraft ever built (only the LZ 129 Hindenburg airship from the famed Hindenburg disaster is bigger), the H-4 was a behemoth for its time, and indeed in our own, being far larger than anything built before or after it.

So why did it go from one of the most anticipated aircraft of the 1940’s to something relegated to the pages of history in less than a decade?

Pre-Hughes H-4 Hercules

Having supplied the Allies (mainly Britain) with supplies since 1940, the US had realized its ships had become targets of German U-Boats, who often sunk these American vessels in the hopes of crippling Britain and forcing it to sue for peace.

With the US’s entry into the war in December 1941, attacks on US ships intensified, with ships being sunk much faster than new ones could be produced.

Realizing this, in 1942, US steel and shipbuilding magnate, Henry J. Kaiser, came up with the idea of using a much larger flying boat, which he called a “flying cargo ship” to replace his famed Liberty class of cargo ship.

Whilst he knew the idea was feasibly possible (thanks to the introduction of flying boats like the Boeing 314, Dornier Do X and Short Empire in the 1930’s) Kaiser lacked the infrastructure and knowhow to make his design a reality.

Luckily for Kaiser, his status as one of America’s richest industrialists had allowed him to meet many other industrialists, including Howard Hughes, the son of a Texas drill bit magnate, turned aviation pioneer.

Approaching Hughes, Kaiser set out the specs for his aircraft. Designed to be the largest aircraft ever built up until that point, Kaiser hoped the aircraft could 150,000 lbs (68,000 kg) of cargo, or about the same as seven and a half of his Liberty class cargo ships.

Beyond carrying cargo, Kaiser hoped it could also be used to transport 750 full-equipped troops or two M4 Sherman tanks over the Atlantic, depending on the military’s needs.

Whilst a massive undertaking, especially given the fact that Hughes Aircraft had not produced a large aircraft like this before, Hughes jumped at the opportunity and partnered with Kaiser to produce his aircraft, with development beginning that same year.

Recognizing both Kaiser and Hughes’ contribution to the aircraft, it was designated as the HK-1, with “HK” standing for “Hughes-Kaiser”.

Development

In 1942, Hughes-Kaiser received their development for three prototypes to be completed and ready for service by 1944. Receiving this, Hughes-Kaiser immediately got to work designing the behemoth.

Focusing on achieving certain specs above all else, a mixed group of Hughes Aircraft and Kaiser Shipyards engineers (led by Howard Hughes himself) worked on several designs, experimenting with twin-hull/fuselage and single-hull/fuselage designs, as well as with the number of engines.

After months of design and feasibility studies, the Hughes-Kaiser engineers settled on a single-hull/fuselage design with eight Pratt & Whitney R-4360 Wasp Major wing-mounted engines.

Originally designed to be made from industrial-grade aluminum, wartime shortages necessitated that all available aluminum be used to produce aircraft already in mass-production, with there being no aluminum spare for use on experimental aircraft.

Adapting to this, Howard Hughes came up with the idea of redesigning the HK-1 to be made out of wood (primarily birch), arguing that before they were made from metal, ships were made of wood, thus, so could the HK-1.

Whilst they were initially skeptical, the HK-1 was soon redesigned to be made from wood strengthened by lamination, in what’s known as the Duramold process, this made the wood as strong as metal, whilst also keeping it light.

By 1944, no prototype had been built as redesigning the HK-1 to be built out of wood (a much lighter material than aluminum) was time-intensive. And that’s not even factoring in building the prototype!

However, that year Henry J. Kaiser chose to abandon the project, ending the Hughes-Kaiser partnership before it ever took off.

Fueled by Kaiser’s frustrations with Howard Hughes, the numerous development delays, and his belief that the HK-1 was no longer necessary due to the first flight of the much cheaper Boeing C-97 Stratofreighter (a militarized Boeing 377) in November that year.

With Kaiser’s departure, Hughes re-designated the HK-1 as the Hughes H-4 Hercules, and the US military reduced its order to only one prototype for evaluation.

Operational History

Delay after delay pushed back the H-4’s evaluation date further and further. Alas, a working prototype was fully built by 1946, from here, the Hughes H-4 Hercules has had a rather interesting life…

Role in Senate Investigations

During WWII, the US government had given military contractors billions of dollars combined to produce new weapons for the war effort. Of this money, a considerable amount of it went towards the development of new aircraft like the H-4 Hercules.

Together with the XF-11 reconnaissance aircraft also under development by the company, Hughes Aircraft received a combined $40 million for development of these two aircraft. Even after the war’s end, neither aircraft were anywhere near entering service.

For the Hercules, this was mostly due to wartime shortages of aluminum resulting in a complete redesign.

However, it was also partly due to Howard Hughes needlessly redesigning large parts of the Hercules personally, so it could be “perfect”. Similarly, several other design and managerial issues caused delays in production.

Whilst this was the official reason given by Hughes Aircraft, the US government believed Hughes had actually done this to intentionally defraud the Federal Government and profit from the war.

To that end, Hughes was brought before a senatorial committee in 1947, that aimed to investigate the two aircraft and Hughes’ supposed war profiteering. Led by Republican Senator from Maine, Ralph Owen Brewster, the committee focused heavily on the H-4.

Repeatedly accusing Hughes of increasing costs to increase his already vast wealth, Senator Brewster focused specifically on the Hercules (which he mockingly referred to as the “Spruce Goose” or “Flying Lumberyard” to anger Hughes).

Unlike other investigations, the Hughes investigation was broadcast on national TV, with Brewster questioning almost every aspect of the H-4’s design and Hughes’ decisions when designing it, in the hopes of proving Hughes was a war profiteer.

Despite Brewster’s best efforts to prove otherwise, it was eventually ruled that Howard Hughes and Hughes Aircraft had not attempted to defraud the US during the war, and Hughes was cleared of all charges.

First Flight

During his investigation, Senator Brewster repeatedly question Hughes about why, if a prototype had already been built, had it not even attempted its first flight yet? Hughes argued he wanted to make sure it was perfect before risking people’s lives, but Brewster didn’t buy it.

Instead, he tried to spin it that a prototype had been built to justify why development of the H-4 Hercules was so high, as well as to hide Hughes’ war profiteering.

Rebutting him again, Hughes famously said:

The Hercules was a monumental undertaking. It is the largest aircraft ever built. It is over five stories tall with a wingspan longer than a football field. That’s more than a city block.

Now, I put the sweat of my life into this thing. I have my reputation all rolled up in it and I have stated several times that if it’s a failure, I’ll probably leave this country and never come back. And I mean it.

Hoping to take away Brewster’s ammunition, Hughes scheduled a few taxi runs of the Hercules for November 2 1947 and invited some of the press to watch from the shoreline.

Performing two of three taxi runs that were fairly uneventful, two members of the press left to publish their stories. Those that stayed, however, go to watch history be made.

On a whim, Hughes decided that the third and final taxi run would also be the Hercules’s first flight.

Taxiing down the water of Long Beach, California, the press watched as the Hercules took off, made it 70 feet in the air, and landed a few miles down the shore.

The next day, the H-4 Hercules’s first flight was all anyone could talk about, with it making both local and national news.

Beyond that, it also sealed Brewster’s fate, making his investigation into Hughes increasingly unpopular with the public, and taking away one of his key arguments for why Hughes was a war profiteer. Ultimately, this is what allowed Hughes to be cleared of all charges.

Secret Post-Life Maintenance

Ultimately, the H-4’s first flight proved to be its only flight, meaning that the aircraft’s service ceiling, maximum speed and lifting capacity were never properly tested, and thus, its specs (even today) only remain as an engineer’s best guess.

Despite having it placed in a hangar for long-term storage, Hughes refused to let the aircraft be dismantled, sold or destroyed in any way.

Instead, he actively wanted to maintain it, keeping it in a climate-controlled hangar (to prevent the wood from rotting) and paying a full-time maintenance crew of 300 out of his own pocket to maintain it.

Interestingly, all of them signed contracts that prevented them from speaking openly about the H-4’s maintenance, even after the maintenance crew was reduced from 300 people to only 50.

Due to the immense secrecy surrounding the H-4’s post-life maintenance, several theories have popped up to explain why it was done, and why it was so secretive.

The first (and most commonly accepted) theory is that the H-4 had a sentimental value to Hughes.

After all, Hughes had staked his reputation on the Hercules, it had briefly made him an enemy of the public and nearly landed him in prison, only for it to take off against all odds.

According to the theory, he simply couldn’t bear to see it fall into disrepair. So even if it costed him millions of dollars over the years, Hughes wanted to make sure it was still looked after if he ever wanted to go and see it and reminisce about the good old days.

The other main theory, which is less accepted, is that Hughes kept it maintained in case it was ever needed. Perhaps this was a failsafe in the event the Cold War went hot, and the US military needed a large cargo aircraft.

As the largest aircraft in the world, maintaining it for this purpose would’ve been smart, as had a nuclear war broke out, the US military wouldn’t have had enough time to get it back into an airworthy condition before the next lot of nukes landed.

War could start any minute, so keeping it maintained all the time was the only way to do it.

Others have suggested Hughes always dreamed of having a second flight in the Hercules, but never got round to it due to his failing health, but kept it maintained in the event his health improved.

But then again, we’ll probably never know the real reason. Hughes has been dead since 1976 and wasn’t exactly open about his decisions.

Museum Display

When Hughes died in 1976, his will didn’t leave any clear instruction on what should happen to the Hercules. As such, maintenance on the Hercules ceased the same year he died, with the Federal Government now claiming ownership of the enormous aircraft.

According to them, as they’d funded the majority of the aircraft’s development, they were now the owner of the Spruce Goose.

After years of legal battles between Hughes’ Summa Corporation and the Federal Government, a compromise was reached. Here, the Summa Corporation paid $700,000 for the Hercules and the Federal Government ceded all rights to the aircraft.

On top of this, part of the H-4’s wing went to the Smithsonian’s National Air & Space Museum, where it went on display alongside the museum’s Hughes H-1 Racer.

In 1980, the Hughes H-4 Hercules was acquired by the Aero Club of Southern California (based in Long Beach, California). Acquiring the aircraft, it was placed in its own circular building, just a stone’s throw away from the RMS Queen Mary ship exhibit.

On display there, the Hercules’s own building became not only an exhibit on the Hughes H-4 Hercules itself, but also Hughes Aircraft as a whole, as well as becoming one of the selling points of the museum.

Expanding their holdings into southern California, Disney acquired the museum in 1988.

Three years later, Disney informed the museum that they no longer wished the museum to display the Hercules so they could expand their real estate holdings further down the coast.

Unwilling to let this priceless piece of aviation history not be seen by the public, the museum spent two years searching for a suitable museum, eventually striking a deal with the Evergreen Aviation & Space Museum.

For an undisclosed lump sum payment and a portion of the museum’s profits, the H-4 Hercules was disassembled and shipped by land and sea to the museum. Once there, a team of volunteers spent eight years reassembling the H-4.

The H-4 Hercules was finally unveiled to the public in 2001, and has since become one of the most popular attractions at the museum!

Role in The Aviator

In 2004, director Martin Scorsese released The Aviator, a biopic of Howard Hughes’s life, starring Leonardo DiCaprio (as Hughes) Alec Baldwin (as Juan Trippe) and Alan Alda (as Senator Brewster).

Focusing heavily on the senate inquiry that made “Hughes” a household name, the Hughes H-4 Hercules is featured prominently in the film on several occasions

Unable to use the original as it’s considered by many to be a priceless and irreplaceable part of aviation history, Scorsese was forced to use a replica of the original.

Contacting California-based replica aircraft manufacturer, Aero Telemetry, Scorsese had them produce a 1/16 size replica (that could fly via remote control) and cockpit mockup alongside producing 1/4 replicas of the Hughes H-1 Racer and XF-11 reconnaissance aircraft.

Slightly larger than anticipated due to various parts of the Hercules needing to be redesigned (due to its smaller size), the H-4 replica was delivered in late November 2003, with filming beginning on November 24 2003.

Indeed, all exterior shots of the Hercules in the movie use the replica, whilst Aero Telemetry engineers flew the H-4 replica via remote control, with cameras on the ground and in the air (via a Bell JetRanger III helicopter) filmed the flight.

And footage from these flights are actually what you see in the movie!

Indeed, the Aero Telemetry H-4 Hercules looked and flew so realistically that it was featured prominently in the movie’s marketing material, and short clips of the H-4’s flight were played during the introduction of the Best Picture Oscar nominees at the 2005 Oscars.

Once filming of the movie ended, the Aero Telemetry H-4 Hercules was placed on display next to the original at the Evergreen Aviation and Space Museum.

Role in Other Media

Whilst its appearance in The Aviator is by far the H-4’s most famous appearance in pop culture, it is by no means its only appearance. Far from it actually.

Beyond its appearance in newspaper articles, magazines and newsreels since the 1940’s, the H-4’s first appearance in media was in the 1987 fantasy children’s film Yogi Bear and the Magical Flight of the Spruce Goose.

The film is set onboard the H-4 Hercules, the film depicts the characters (Yogi Bear and the other bears) as touring the H-4, when they accidentally lock themselves in the aircraft and it takes off, heading for the Queen Mary hotel.

In the 1988 biopic of automaker Preston Tucker, Tucker: The Man and His Dream, Preston Tucker has a conversation with Howard Hughes sometime in the 1940’s, at the Hughes Aircraft plant in front of the Hercules.

After finishing their prior conversation, Tucker mentions the Hercules, with Hughes responding about how he doesn’t really care if the Hercules flies or not, it’s just about circumventing the establishment (primarily Senator Fergusson).

During the 1991 adventure film, The Rocketeer, Cliff Secord is able to escape Howard Hughes himself and federal agents after gliding in a large scale-model of the H-4 Hercules, which inadvertently proves the H-4 will fly to Hughes.

In the 2011 neo-noir video game, L.A. Noir, the player is able to enter the Hercules. Similarly, if you are willing to pay for a DLC, one of the missions, “Nicholson Electroplating”, features interior and exterior views of the H-4 Hercules.

During the first episode of the fifth season of Leverage, the cons attempt to sell the Hercules by convincing their mark that Hughes secretly installed state-of-the art stealth technology onboard the H-4.

Specifications

Specifications	Hughes H-4 Hercules
Length	218 ft 8 in (66.65 m)
Wingspan	320 ft 11 in (97.82 m)
Height	79 ft 4 in (24.18 m)
Fuselage Height	30 ft (9.1 m)
Crew	3
Cruise Speed	250 mph (400 km/h; 220 kn)
Range	3,000 mi (4,800 km, 2,600 nmi)
Service Ceiling	20,900 ft (6,400 m)
Empty Weight	250,000 lb (113,398 kg)

Why Did The H-4 Hercules Not Fly Again?

By the time the Hughes H-4 Hercules had performed its first flight, it was considered surplus to requirement by many in the industry. Yet Hughes never flew it again, not even to try and prove the naysayers wrong.

The military deemed it surplus to requirement because it was a flying boat. Just as Henry J. Kaiser had predicted when he left in 1944, the arrival of the cheaper C-97 Stratofreighter had swayed the military’s postwar orders away from the Hercules.

And due to legal complications, Hughes couldn’t turn the Hercules into a passenger airliner and offer it to airlines.

Even if he had, it’s highly likely that most airlines would’ve simply laughed him out of the room. After all, they had orders for cheaper, conventional, long-haul airliners that could fly transatlantic flights quickly (for the time) and efficiently.

So many weren’t interested in purchasing what they saw as an antique.

Although cargo airlines and cargo aircraft existed at the time, those in private service were usually ex-airline passenger aircraft that were then modified for cargo use. With airlines not interested in even trying the Hercules, its cargo life never took off (no pun intended).

The immense size of the Hercules also prevented Hughes from offering it as a personal aircraft like Sikorsky had done to their S-43 flying boat. Had it been considerably smaller, the Hercules may have been produced in small numbers for the world’s elites.

A show of immense wealth and power in the 1930’s and 1940’s was to have your own flying boat (as it could land on both land and water). If it were smaller, Hughes could’ve offered it to his fellow businessmen and/or acting buddies.

Ultimately, no one seemed interested in flying the Hercules, so it’s never had its second flight Hughes so desperately wanted.

How Could The H-4 Hercules Have Changed History?

Had Hughes not been forced to redesign the HK-1 in 1944 due to aluminum shortages, the three HK-1 prototypes would’ve most likely been finished well before 1944, allowing the US military to evaluate it.

Although we’ll never know for sure, it’s highly likely that the US military would’ve purchased the three HK-1 prototypes and potentially some extra ones to reduce orders for smaller C-47 and C-54 cargo/troop carrier aircraft.

Entering service in late 1944 or early 1945, the HK-1 (assuming Henry Kaiser never left the project if the three prototypes had been built) would’ve entered into the war too late to have influenced the outcome of the war in any way.

Once the war was over, the US military would’ve probably kept their HK-1 fleet, or at least the bulk of it, instead selling off more of its smaller C-46, C-47 and C-54 aircraft than it did in our timeline, with the US keeping the HK-1 until the Korean War.

At the outbreak of the war, the US military’s HK-1 fleet would’ve been constantly flown by the USAF, performing as many flights per day/week as possible, with each flight transporting 750 soldiers each time.

These soldiers could’ve then caught North Korean and later Chinese troops of guard due to their sheer numbers.

Beyond transporting troops, some of its flights would’ve been transporting tanks and other supplies too.

Hughes may even have developed a bomber variant (somehow) of the HK-1, which could’ve quite easily overwhelmed the communist forces in Korea similarly due to their sheer numbers. Interestingly, this would mean no communist North Korea.

As a troop transport, the HK-1 may have even been kept until the outbreak of Vietnam, where the sheer number of American troops may have been enough to overwhelm the Viet Cong forces when the US first entered the war.

Alternatively, it may even have been retrofitted to release napalm, with its cargo hold being more than big enough to carry enough napalm to burn down several forests at once.

There’s also a chance that Hughes would’ve gained congressional approval to sell a civilian version to airlines after the war, where it would’ve likely been the (much) larger alternative to already large airlines like the Lockheed Constellation and Boeing 377 on transatlantic routes.

Had this happened, it’s likely that the HK-1 would’ve still been flying well into the 1970’s and 1980’s as a cargo aircraft, probably as an outsize cargo aircraft like the An-225, 747 Dreamlifter or Airbus Beluga is used today.

Supposing it was a commercial success, Hughes Aircraft in all likelihood would’ve continued to produce commercial aircraft, maybe even entering the jet age with some kind of jet-powered alternative to the HK-1/H-4 Hercules!

Legacy

Although only one was ever built, and it only flew once, the Hughes H-4 Hercules still left a rather large legacy, one that can still be seen today – assuming you know where to look!

Hughes Aircraft

Despite being an engineering masterpiece, the H-4 ultimately proved to be a failure, as only one was produced and it only ever flew once.

Combined with the failure of the XF-11 program, convinced Hughes that building fixed-wing aircraft simply wasn’t worth it. The industry was too consolidated, and demand wasn’t high enough to keep Hughes in the game.

Instead, Hughes began producing helicopters in 1948, missiles in 1949 and various spacecraft and satellites from the 1950’s onwards.

In effect, this would lead to the production of the TH-55 Osage and MD 500 (originally the Hughes 500) helicopters, as well as the development of several communications satellites – many of which are still used today!

Despite its commercial failure, Howard Hughes and Hughes Aircraft always maintained that it was his greatest achievement in the aviation field.

Aviation Industry

The failure of the H-4 Hercules was pretty much the end of the flying boat era.

Over the course of the 1940’s, our knowledge of aerodynamics increased monumentally. Combined with several major advancements in engine technology, there were aircraft that could cross the Atlantic Ocean without needing to stop to refuel.

Although a few other flying boats were built after the Hercules (I’m looking at you, Saunders Roe Princess) they were often canceled shortly after their first flight or had extremely short service lives, before being replaced by conventional airliners.

Even today, as hundreds of other aircraft have been built, the Hercules is still remembered for its size and the great “What if” of the service life it never got. Whenever there’s anything to do with the Hercules in the news, every major outlet covers it.

Regardless of what else is going on.

Despite being built in the 1940’s, the H-4 held the record for the longest wingspan of any aircraft for over 70 years, holding it from 1947 (when the prototype first flew) to 2019, when the Burt Rutan-designed Scaled Composites Stratolaunch first flew.

That’s 72 years!

What do you think of the Hughes H-4 Hercules? Tell me in the comments!

Featured image courtesy of RV1864 via Flickr.