Cargo Aircraft

A class of cargo aircraft, designed to meet the special needs of certain types of military operations, has evolved since the end of World War II. These aircraft are used to transport various type military cargo such as trucks, tanks, jeeps, and artillery pieces, as well as troops. The size and shape of the fuselage is dictated by the number and type of vehicles to be carried, and some important aspects of the overall configuration are strongly influenced by the requirements for cargo handling and loading.

A number of highly successful turboprop aircraft have been developed for use as cargo carriers. The largest of these aircraft is the Russian Antonov AN-22, which weighs over 550 000 pounds and is equipped with four 15 000-horsepower engines. The Lockheed C-130 is perhaps the best known of the turbo prop-powered cargo aircraft and the one that has been produced in the greatest numbers. The C-130 is used by all branches of the United States military forces and by the military forces of dozens of foreign governments. A commercial cargo version of the aircraft is also available.

In order to minimize weight and complexity, the landing gear is retracted into blisters located on either side of the fuselage, rather than into the wing or engine nacelles. The high wing position is advantageous for a cargo aircraft because it allows trucks and other types of equipment to move beneath the wing, and the fuselage can be brought close to the ground without causing interference with the engines and propellers. A rear loading door may be deployed from the bottom of the upswept, aft portion of the underside of the fuselage. The proximity of the forward portion of the fuselage to the ground results in an aft-loading ramp with only a small inclination to the ground so that vehicles can be readily driven or pushed into the aircraft.

Three jet-powered cargo aircraft that employ many of the configuration features embodied in the C-130 design have been developed in the United States. These are the Lockheed C-141 StarLifter, the Lockheed C-5A Galaxy, and the Boeing C-17 Globemaster III. The Soviet Ilyushin Il-76 military transport is similar in appearance and has a gross weight of 350 000 pounds. The high-wing position employed on these aircraft is advantageous for a cargo aircraft because it allows trucks and other types of equipment to move beneath the wing, and the bottom of the fuselage can be brought close to the ground for easy cargo loading without causing interference with the engines. A rear door, which serves as a loading ramp when lowered, is deployed from the bottom of the upswept aft portion of the fuselage. The proximity of the bottom of the fuselage to the ground results in a ramp with only a small inclination to the ground; thus, vehicles can be readily driven or pushed into the aircraft. The rear door is also used for aerial deployment of vehicles and equipment by parachute.

The larger aircraft are provided with a forward loading door in the nose of the aircraft. The door is like a visor and lifts up and over the flight deck (somewhat like that for the Boeing 747 freighter). The entire cross-section of the cargo compartment is exposed when the nose visor is raised.

Most modern jet airliners have some type of cargo-carrying capability. Even those aircraft configured primarily for passengers usually carry a limited amount of cargo, along with baggage, in the hold below the passenger deck. Many jet transports are also available in convertible form and may be changed quickly from a passenger to an all-cargo configuration. In this case, the passenger seats are removed and cargo is carried in the space usually occupied by the passengers as well as in the hold. The floor of the passenger cabin is usually strengthened to allow for the higher unit floor loadings likely to be encountered with cargo. A large cargo door is also provided on convertible passenger-cargo aircraft.

Some jet transports are available in dedicated cargo versions. In addition to special cargo doors and strengthened floors, these aircraft have no facilities for attending to passenger needs and may even be constructed with no cabin windows. A crew rest compartment is sometimes located immediately behind the flight deck. The visor-type loading door located in the nose of a 747 freighter, and a large rear cargo door.

The basic unit for transporting goods has been the truck. Being the basic unit, the truck has defined limitations on intermodal containers that can typically be transported by ships, trains and trucks. Much of commerce today for which intermodal containers are most convenient are high volume, low weight products, computers being one example. Thus, volume instead of weight creates the limiting factor in the design of intermodal containers. As such, containers have grown to the maximum volume capacity of the basic unit, the truck. As such, intermodal containers are limited by the dimensions allowed by highway infrastructures.

Intermodal containers have greatly facilitated and lowered the cost of cargo transportation. However, air cargo has generally been excluded from participation in intermodal cargo systems. Aircraft of a size capable of carrying substantial cargo have typically been designed first as passenger aircraft. Cylindrical fuselages and lack of large access ports thereto in such passenger aircraft limit the use of such aircraft for truly intermodal cargo systems. Rather, the aircraft must become the basic unit with odd shaped and smaller sized containers. As a result, even with containerized cargo, a truck must be loaded with multiple individual containers for efficient distribution of air cargo. Such aircraft are also designed to be efficient at high speeds which is costly. Military transports are also not particularly compatible with intermodal cargo systems as they are designed for oversized cargo such as rolling equipment, e.g., tanks and trucks, and palletized, irregularly shaped cargo. Most aircraft specifically designed for the military also are mission directed and overall efficiency for competitive cargo transportation is not a first priority.

The commercial cargo market has not historically purchased large numbers of new aircraft. The reasons run the gamut from poor balance sheets to cheap substitutes in the form of used, converted passenger aircraft. The first response of most carders to the increase in demand for cargo services will not be to purchase new cargo aircraft, but to better utilize current capacity. The second likely response will be to purchase excess belly-hold capacity from the passenger carriers. The last strategic response will be the purchase of new cargo aircraft by both existing carders and new entrants to the air cargo industry.

The widest possible definition of cargo is goods transported by ship, aircraft, truck, or other vehicle. Air cargo represents a small subset that is transported on aircraft. Air cargo has the highest value per pound of any freight shipped in the United States. It also is the least used method of shipping in terms of both tonnage and ton-miles. According to the U.S. DOT, Bureau of Transportation Statistics, in the 1990s the tonnage and ton-miles of air cargo accounted for approximately one-tenth of 1 percent of the United States total cargo weight, but account for seven-tenths of 1 percent of the total value of United States shipped goods. The arrival of the Boeing 747 jumbo jet was both a boon and a bane to the air cargo business. They were a boon because as all-cargo aircraft they provided the capacity to carry both large containers and over 100 tons per trip. But they were also a bane because the capacity available in the bellies of passenger aircraft could accommodate most of the air cargo tonnage available, and--by virtue of the byproduct nature of space--at a considerably lower cost than dedicated freighter aircraft. The combination of expanded belly capacity and lower freight rates permitted by deregulation proved to be the death knell for freighter operations by the U.S. passenger airlines.TWA operated its last freighter in December 1978, followed in later years by American, United, and PanAm.

After most U.S. carriers phased out their operations of freighters, the promotion of air cargo devolved upon the freight forwarders, who had been the airlines' best customers. Some of the largest forwarders, such as Emery, Burlington Air Express and Airborne, later began to fly their own aircraftto provide the cargo lift they needed, at the times of day they needed it, and they became major cargo carriers in their own right.

Since the average fleet replacement rate, which is given by the inverse of the average aircraft life span, is just above 2 percent per year, the prospects for a new all-cargo aircraft in the absence of demand growth are dismal. However, additional aircraft acquired to meet new demand growth can effectively double, triple, or even quadruple the aircraft fleet requirements above the replacement rate. Another important issue is the historical tendency of cargo operators to purchase a large portion of their aircraft fleet as converted passenger aircraft as opposed to new all-cargo aircraft. This trend is not surprising given the high acquisition costs of new aircraft and the difficulty of securing financial resources by smaller carriers.

The role of aircraft capital costs are critical to the success of this industry. Smaller passenger and all-cargo carriers may not wish to pay the huge capital costs associated with owning new all-cargo aircraft. For some carriers, cargo is only profitable by owning older aircraft, where the effects of the capital costs have been minimized. Improved balance sheets and large profits will undoubtedly attract new competitors to the marketplace, forcing a status quo type of equilibrium, where a set of carriers consistently generate above normal profits, another set barely break even, and a third set consistently lose money and exit the marketplace.