The Cold Chain

Temperature Control During Air Shipment

Like any means of transportation, air transportation can encounter significant changes in temperature. For example, about 47% of air shipped perishables comes from countries having a warm or tropical climate. Containers, when waiting to be loaded on the aircraft, are exposed to environmental conditions and become sensitive to heat gain. However, since air transportation is characterized by its speed, many quick measures can be taken to minimize the effects of such detrimental conditions.

The most vulnerable part in an airport to airport shipment is the airside operations portion. Since most of the time perishables come from a warm climate to a cold or moderate one, it means that a load can be exposed to both high and low temperatures in a matter of few hours. Obviously most of the time, shippers will protect their goods for either high or low temperature. Rarely will a load be packed to deal with both extremes. Furthermore, it is almost impossible to predict the temperature at departure and arrival at the airport since many factors can affect it. When exposed to the sun for example, a typical load can increase its temperature by many degrees in a matter of few hours. For this reason, good collaboration between all parties involved throughout the airport operations is critical to ensure success.

Another important part is the flight phase. Contrary to the common myth in air transportation, temperatures in the cargo holds are not necessarily cold. In fact, they are in many cases quite high despite the fact that at 10000m altitude the aircraft structure is exposed to very cold air of about -55°C. During the flight, temperature of cargo holds of certain aircraft can be controlled but in many cases the capacity of the refrigeration system does not allow for the cooling down of the temperature of warm perishables. Each type of aircraft, hold and packaging has its own temperature pattern. So it is important to know the type of aircraft, its configuration as well as the available locations in the aircraft (e.i. forward, aft, main or lower deck compartments) beforehand. The following figures present temperature patterns recorded on different flights with a wide body, narrow body and a commuter type aircraft.
 

Air Temperature in a 747-300 AFT Compartment near Thermostats During a 7 Hours Trip

Source: IATA & Air Cargo Transportation Research Group