A cargo plane belonging to a U.S.-based company crashed shortly after takeoff from Bagram Air Base in Afghanistan on Monday, killing seven crew members. The Taliban claimed it shot the plane down, but many others speculated that the cargo was improperly loaded or shifted during takeoff. How do you load a cargo plane?
With positions, locks, and a load master. The inside of a cargo plane is divided into positions where freight can be loaded. Each position has a maximum weight, which is stenciled onto the inside of the plane, and the positions are separated by tracks on the floor. Locks located along the tracks and side rails hold the cargo in place. Most cargo is packaged in either pre-formed containers that fit into the positions or onto pallets and secured by nets. Some types of freight, such as cars or other large vehicles, can take up more than one space, but they still must be secured by locks and rails. (The plane that crashed in Afghanistan on Monday was reportedly carrying vehicles.)
The load master is in charge of cargo placement. He makes sure that each piece of freight has been weighed prior to loading the plane and that the total weight stays beneath the aircraft’s carrying capacity. (The Boeing 747-400 that crashed in Afghanistan has a cargo capacity of around 125 tons.) He also ensures that the plane is properly balanced. Although lateral balance can be an issue in extreme situations, the more important concern is ensuring that the cargo doesn’t shift the plane’s center of gravity too far forward or backward.
The load master provides the pilot with a report of the total load and balance data prior to takeoff and inspects cargo placement. In some operations, the load master stays on the plane during flight and checks that nothing has shifted prior to landing.
Cargo pilots worry about freight breaking free from the locks and sliding around in the back. Shifting freight can make the plane either nose-heavy or tail-heavy, and the pilot has no way of knowing whether that has happened until after the plane is airborne, when it may be too late. That scenario played out in 1997, when boxes of denim broke loose in the belly of a DC-8 operated by the now defunct Fine Air cargo airline. Several empty positions allowed the freight to shift a great distance toward the back of the plane. The suddenly tail-heavy aircraft plummeted to the ground immediately after takeoff, skidding through a busy part of Miami and killing a man on the ground along with several crew members. Load masters are now required to place all locks on cargo planes in the up position—even if there is no freight in the space—to prevent loose cargo from sliding through empty positions. Critics, however, contend that the oversight of cargo operations remains lax, putting the lives of both flight crews and bystanders at risk.
Commercial passenger jets must also remain balanced, but they don’t require as precise a loading operation as freighters. Airlines typically place luggage into containers before loading them into wide-bodied planes, but the bags are simply tossed into smaller jets. Rather than dividing the cargo hold into a series of positions, there is simply an aft belly and a fore belly. Baggage handlers have to keep those divisions roughly in balance and under the plane’s capacity, keeping in mind the distribution of passengers. On the average commercial flight, the airlines can get away with assuming each passenger is of average weight. On smaller planes, however, which have less margin for error, passengers have to report their precise weight for proper balancing.
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Explainer thanks former cargo airline employee George Paul.
747 Crash at Bagram Air Base (Warning: video contents may be disturbing.)