Mobile air conditioning and heating units are ground support equipment designed to supply conditioned air to heat or cool aircraft. Such units are capable of delivering a large airflow against static pressure at the end of a flexible duct or into an aircraft. Compared to the air conditioning capability, the heating capability is normally considered an optional accessory, but in some climates the heating capability is often as useful as the cooling.

Figure 11-4 shows a typical mobile air conditioner and heating unit. This unit is capable of delivering up to 3,500 cu ft of cooling air per minute. It is capable of dropping the interior temperature of a large aircraft from 115° F to approximately 76° F. Its heating capability provides an output of up to 400,000 Btu per hour. A single engine supplies power to the truck and the air conditioning equipment. This is accomplished by means of power takeoffs mounted on an

auxiliary transmission. By simple shifting of gear handles in various combinations of positions, an operator can drive the truck, operate the blower only, or operate the blower and the refrigeration equipment. All controls and switches for operation are in the cab.