Definition: Cargo aircraft are aircraft dedicated to hauling freight rather than transporting passengers. Any airplane, regardless of size, is considered a freighter if carrying cargo rather than people is its primary use.
Significance: In the Western industrialized world, most food, newspapers, and mail is transported by air. Because air freighters often have separate terminals, fly primarily at night, or utilize different airports than passenger traffic, it is easy to overlook how vital air freight has become to the modern economy. Air freight companies, such as Federal Express, DHL, and United Parcel Service, operate thousands of cargo aircraft daily, most of which go totally unnoticed by the general public. DHL Worldwide Express alone operates 358 aircraft out of thirty-six regional hubs around the world.
Cargo aircraft, also called freighters, transport fresh flowers from Africa, grapes from Chile, and many other items that in previous decades would have traveled by ship or truck, or not at all. While much of the commercial freight traffic in many countries still travels by land routes, cargo aircraft handle ever-increasing amounts of material. In the United States and Europe, for example, catalog companies and Internet merchants rely on freight companies such as Federal Express to deliver orders to customers quickly. Without air freighters, the overnight delivery of packages and documents over thousands of miles, which is now taken for granted, would be impossible.
Although the general public often thinks of cargo air-craft as hauling freight that is small, light, or perishable, air freighters are just as likely to be hauling oversize materials as they are to be transporting perishable cargoes that must reach customers quickly. Items too large in weight, length, width, or height to be shipped by truck or rail are now flown to their destinations on oversize aircraft such as the civilian Super Guppy and the U.S. military’s C-5. Until recently, railway freight cars could not carry items exceeding 60 feet in length. The C-5, in contrast, has a cargo bay 143 long.
The Beginning of Cargo Flight
Using aircraft for hauling cargo was not an immediate priority in the aviation industry. For the first several decades of the twentieth century, aircraft remained relatively small. Following the Wright brothers’ success in 1903, aviation pioneers focused first on increasing speed, distance, and number of passengers before contemplating using aircraft to carry freight. Any cargo hauled was highly specialized and lightweight, such as medical supplies. The United States Post Office began airmail service in 1918, but the service was limited almost entirely to letters. Writers were urged to use thin onionskin paper to reduce the weight of individual pieces of correspondence.
As the size and range of aircraft increased, however, aviation’s potential for hauling freight became more apparent. In the mid-1920′s, the U.S. military acknowledged the divergence of freighters from transport aircraft and began numbering the former with a “C” designation, to indicate cargo. The Douglas C-1 was the first airplane so designated, in 1925. The airplane, a single-engine biplane, had an enclosed passenger compartment that could transport six people. With the seats removed, it became a freighter. This remains typical of military freighters, as many aircraft bearing a “C” designation are used as troop transports as well as for carrying cargo.
On the civilian side, United Parcel Service (UPS), founded in Seattle in 1907 as a messenger firm, began shipping packages by air in 1929. For many years, however, the company restricted that service to the West Coast. In 1953, UPS expanded its air delivery system nationally. Companies such as UPS generally use conventional aircraft that have been converted for use as freighters. This is nothing new in aviation history. Many aircraft designed for transporting passengers have been pressed into service as freighters, while numerous passenger aircraft carry some freight in addition to their human cargo. The rear bulkhead in the main cabin of many aircraft is movable, which gives airlines the flexibility to increase or decrease the size of the passenger compartment and the baggage compartment behind it if necessary. Most commercial airlines, for example, have contracts with the U.S. Postal Service to transport mail. Ironically, one of the aircraft most closely associated in the public’s mind with long-distance passenger transport,the Boeing 747, was designed originally to maximize its cargo capacity.
Passenger/Cargo Craft
When Boeing company aerospace engineers began planning the 747 in the early 1960′s, industry analysts believed the future of air passenger service would lie in the area of supersonic transports (SSTs), such as the Concorde airliner then being developed in Europe. Although the 747 was initially designed as a jumbo jet with a double-decker passenger compartment, the price of aviation fuel in the 1960′s was so low—barely 10 cents per gallon—that many experts believed SSTs would be economical to operate despite their high fuel requirements and relatively small passenger cabins. The Concorde, for example, has a maximum passenger capacity of 144 persons, in comparison with the 747′s high-density 624. The energy crisis of the 1970′s combined with public concerns about negative side effects of SSTs, such as noise, proved the experts’ predictions wrong. With the 747 being highly useful for either passenger transport or as a freighter, it is not surprising that by the twenty-first century, the SST had become a curiosity, while the Boeing 747 dominates international air traffic. Boeing ultimately chose not to use the double-deck concept for the passenger cabin of the 747. Instead, they placed the cockpit above the main cabin, giving 747′s used as freighters an exceptionally roomy cargo compartment. When configured as a passenger plane, a 747 will seat passengers in rows of ten persons across. When configured as a freighter, two 8-foot wide cargo containers can be placed side by side.
Noted cargo aircraft over the years have included the Ford Tri-Motor and the Douglas DC-3. Both aircraft were developed primarily for use in transporting passengers, but were quickly pressed into service as freighters. The Ford Tri-Motor, introduced in 1926, was notable for its all-metal construction, an aviation first. One of the first aircraft designed to be inherently stable, the Tri-Motor could fly well on only two engines and maintain a level flight path with only one. The aircraft was manufactured for only seven years, from 1926 to 1933, with a total of 199 being built. The Tri-Motor was a rugged aircraft capable of surviving a great deal of rough use. As recently as 1998, a few Tri-Motors remained in service, including one being used by a sightseeing company in Ohio to fly daily tourist excursions.
The venerable DC-3 made its debut in 1935. Within a short time it gained a reputation for being virtually indestructible. It has been estimated that by 1944, over 90 percent of the aircraft being used by commercial airlines were DC-3′s. The Douglas Aircraft Company built a total of 18,000 aircraft before discontinuing production. During World War II, the military version of the DC-3, the C-47, saw wide use in both the European and Pacific theaters. General Dwight D. Eisenhower was quoted as saying that the DC-3 was one of the four “weapons,” which also included the jeep, the bazooka, and the atomic bomb, that helped the Allies win the war. Over one thousand DC-3′s remained in service as of 200l, with the majority being used for transporting cargo.
Specialized Freighters
The DC-3 was typical of many freighters in that it was designed initially to serve as a passenger plane. In 2001, many commercial freighters are civilian aircraft, such as Boeing 737′s or McDonnell Douglas DC-10′s, that have exceeded the maximum number of hours allowed for use as a passenger plane, although a few specialized cargo aircraft have emerged in the civilian market. These specialized freighters include the Super Guppy, a modified Boeing Stratocruiser, developed by Aero Space-lines in the early 1960′s. The diameter of the upper portion of the fuselage was increased, giving the aircraft the ability to transport oversized items such as sections of the Saturn rockets used in the U.S. space program. The rocket sections were too large in diameter to be transported via rail or truck. The resulting rather bloated profile earned the Super Guppy its nickname. The Super Guppy has a sideways-hinged nose for straight-in loading. Other freighters may be hinged so the nose swings up, or feature a large rear cargo door with a ramp. The military’s C-5 Galaxy has both a hinged nose and a ramped rear cargo door.
Some military freighters do share an airframe design with a civilian equivalent, but the manufacturer modifies the aircraft at the factory with specialized cargo doors and other features. The C-131 used for many years by the U.S. Air Force was a cargo transport version of the Convair 340 used by civilian airlines. Military freighters, such as the C-5 Galaxy developed by Lockheed, are generally built specifically to be used as cargo aircraft. The C-5 is the United States’ largest military freighter. The cargo hold of a C-5 is large enough to carry six Apache helicopters. The aircraft has a payload capacity of 270,000 pounds, which is less than that of its Russian counterpart, the Antonov AN-124, but still sufficient to transport two M-1 battle tanks weighing 135,000 pounds each. Fact sheets on the C-5 Galaxy point out that the aircraft’s cargo bay, at 143 feet long, is a greater distance from end to end than that which Wilbur and Orville Wright covered in their first powered flight at Kitty Hawk. The C-5 is remarkable in its ability to land and take off from very short runways. The aircraft’s landing gear has twenty-eight tires, giving it the high flotation necessary for landing on dirt runways. The landing gear are hydraulically hinged, allowing the plane to “kneel” to bring the level of the cargo bay down to truck-bed height, making loading and unloading easier and faster.
Just as U.S. aerospace engineers developed the C-5 to transport oversized military equipment such as tanks, engineers in the Soviet Union designed the Antonov AN-124. The AN-124 made its first public appearance outside the Soviet Union at the May, 1985, Paris air show. The aircraft has a maximum payload of 330,700 pounds. Like the C-5, the AN-124 is notable for its twenty-four-wheel landing system, which enables it to land on dirt runways and even hard-packed snow, despite being possibly the heaviest aircraft in the world.
