Military Factory logo

Hughes H-4 Hercules (Spruce Goose)

United States (1945)
Picture of Hughes H-4 Hercules (Spruce Goose) Heavy-Lift Transport / Flying Boat Prototype
Picture of Hughes H-4 Hercules (Spruce Goose) Heavy-Lift Transport / Flying Boat Prototype Picture of Hughes H-4 Hercules (Spruce Goose) Heavy-Lift Transport / Flying Boat Prototype
+ Images
This entry's gallery contains additional pictures.

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
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
LON
 
  PAR
PAR
 
  BER
BER
 
  MOS
MOS
 
  TOK
TOK
 
  SYD
SYD
 
  LAX
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
Pie graph section
Pie graph section
Pie graph section
Pie graph section
Pie graph section
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
1
1


  * Commercial Market High belongs to Cessna 172.

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


Altitude Visualization
Small airplane graphic
  Compare this entry against other aircraft using our Comparison Tool  
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 Flag Graphic
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".