Hughes H-4 Hercules (Spruce Goose)

United States (1945)

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The Hughes H-4 Hercules, ridiculed as the Spruce Goose, remains the largest flying boat ever constructed and features the largest wingspan of any aircraft ever made.

Detailing the development and operational history of the Hughes H-4 Hercules (Spruce Goose) Heavy-Lift Transport / Flying Boat Prototype. Entry last updated on 5/11/2016. Authored by Staff Writer. Content ©www.MilitaryFactory.com

This famous Howard Hughes flying boat aircraft - formally designated by Hughes Aircraft as the H-4 "Hercules" - only ever achieved a single flight (with Hughes himself at the controls) and was only produced in a single working example. The folly of the project garnered the H-4 the nickname of "Spruce Goose" and largely termed a failure in the scope of World War 2-era aircraft design. The primary drive behind such a large airframe was in providing the United States military - then committed to war in Europe and the Pacific - with an oversized transport capable of airlifting large quantities of battlefield equipment to the front. This was strengthened by regular losses of Allied shipping from German U-Boats in the Atlantic and elsewhere, taking their toll on vital supplies attempting trying to reach forces in Europe. As such, a military requirement was put forth for a trans-Atlantic freighter-type aircraft capable of a considerable payload.

Despite the seemingly promising nature of the H-4 design, it simply arrived too late in the war to serve much of a purpose, additionally adding to the image of the project as a complete failure for Hughes. The H-4 also suffered from the defense spending drawn down once the war had officially come to a close - many projects were either suspended indefinitely or cancelled outright. Hughes was then forced to appear before a Senate committee to answer for government funds spent on his H-4.

Upon its completion, the H-4 became the world's largest aircraft and largest flying boat ever designed and produced to that point. Power was served through 8 x Pratt & Whitney R-4360 28-cylinder engines developing 3,000 horsepower each. Four engines were fitted to a wing. Each wing was high-mounted in its installation and straight in its general design with the engine nacelles fitted at the leading edges. Each wing itself was the full wingspan of just one competing Boeing B-29 "Superfortress" four-engined heavy bomber. To demonstrate the internal carrying capacity of the H-4, the hold could service up to 700 combat infantry or two M4 Sherman Medium Tanks. Endurance of the aircraft was estimated to be approximately 21 hours of flight time. Its flying boat qualities - aided by its boat-like hull and outboard-mounted pontoon legs - allowed the H-4 to take-off and land from just about any water source. Additionally, the aircraft was constructed of wood (birch) which helped buoyancy and would not require heavy use of metals in its construction (metal proving a critical wartime resource). The wood approach was also spanned into another Hughes wartime project - the D-2 heavy fighter (detailed elsewhere on this site). The "Spruce Goose" ridicule is related to the product's heavy use of wood in its construction.

The initial H-4 concept was drawn up by Henry Kaiser while the direct design was put together by engineer Glenn Odekirk. Howard Hughes served as the project's overseer and would be the hands at the controls during her one and only flight. The one and only prototype was saved in the post-war draw down and can be seen in its full glory at the Evergreen Aviation Museum of McMinnville, Oregon, USA.

As much as aviation technology has advanced to this day (November 2013), the Hughes H-4 Hercules still maintains the largest wingspan of any aircraft ever built, let alone considered for production. This claim to fame includes even the mammoth American Boeing 747 and the Soviet/Russian An-225 Mriya offerings. Additionally, no other flying boat design has bested her dimensions.

Picture of the Hughes H-4 Hercules (Spruce Goose) Heavy-Lift Transport / Flying Boat Prototype

Any available statistics for the Hughes H-4 Hercules (Spruce Goose) Heavy-Lift Transport / Flying Boat Prototype are showcased in the areas immediately below. Categories include basic specifications covering country-of-origin, operational status, manufacture(s) and total quantitative production. Other qualities showcased are related to structural values (namely dimensions), installed power and standard day performance figures, installed or proposed armament and mission equipment (if any), global users (from A-to-Z) and series model variants (if any).

Our Data Modules allow for quick visual reference when comparing a single entry against contemporary designs. Areas covered include general ratings, speed assessments, and relative ranges based on distances between major cities.

Image of collection of graph types

Relative Maximum Speed Rating

Hi: 200mph

Lo: 100mph

This entry's maximum listed speed (199mph).

Graph average of 150 miles-per-hour.

Relative Operational Ranges

NYC

LON

PAR

BER

MOS

TOK

SYD

LAX

NYC

Graph showcases the Hughes H-4 Hercules's operational range (on internal fuel) when compared to distances between major cities.

Aviation Era Impact

Useful in showcasing the era cross-over of particular aircraft/aerospace designs.

Unit Production Comparison

Comm. Market HI*: 44,000 units

Military Market HI**: 36,183 units

* Commercial Market High belongs to Cessna 172.

** Military Market High belongs to Ilyushin Il-2.

Altitude Visualization

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Supported Mission Types:

Air-to-Air

Interception

Unmanned

Ground Attack

Close-Air Support

Training

Anti-Submarine

Anti-Ship

Airborne Early Warning

MEDEVAC

Electronic Warfare

Maritime/Navy

Aerial Tanker

Utility/Transport

Passenger Industry

VIP Travel

Business Travel

Search/Rescue

Recon/Scouting

Special Forces

X-Plane/Development

National Origin: United States

Service Year: 1945

Classification Type: Heavy-Lift Transport / Flying Boat Prototype

Manufacturer(s): Hughes Aircraft - USA

Production Units: 1

Global Operators:
United States (cancelled)

Structural - Crew, Dimensions, and Weights:
Unless otherwise noted the presented statistics below pertain to the Hughes H-4 Hercules model. Common measurements, and their respective conversions, are shown when possible.

Operational
CREW

Personnel
3

Dimension
LENGTH

Feet
218.67 ft

Meters
66.65 m

Dimension
WIDTH

Feet
320.01 ft

Meters
97.54 m

Dimension
HEIGHT

Feet
79.33 ft

Meters
24.18 m

Weight
LOADED

Pounds
396,832 lb

Kilograms
180,000 kg

Installed Power - Standard Day Performance:
8 x Pratt & Whitney 28-cylinder R-4360 propeller engines developing 3,000 horsepower each.

Performance
SPEED

Miles-per-Hour
199 mph

Kilometers-per-Hour
320 kph

Knots
173 kts

Performance
RANGE

Miles
2,983 mi

Kilometers
4,800 km

Nautical Miles
2,592 nm

Performance
CEILING

Feet
20,899 ft

Meters
6,370 m

Miles
3.96 mi

Performance
CLIMB RATE

Feet-per-Minute
1,000 ft/min

Meters-per-Minute
305 m/min

Armament - Hardpoints (0):

None.

Variants: Series Model Variants
• HK-1 - Original Design Designation that reflects the collaborative efforts of design and concept from Henry Kaiser and Howard Hughes ("HK").
• H-4 - Base Designation with the wihtdrawal of Henry Kaiser from the project.
• HFB-1 - Another designation attributed as a recognition of "Hughes Flying Boat - First Design".

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