Abstract: An air conditioner refrigerant compressor driving and mounting apparatus for a helicopter of the type having a free rotating power output shaft, which rotates within a power take-off pad includes a compressor drive assembly drive shaft housing supported by the power take-off pad. A compressor drive assembly drive shaft is connected with the engine power output shaft, extends linearly through the compressor drive assembly housing, and is supported therein by bearing means. A compressor drive assembly drive shaft pulley is attached to the compressor drive assembly drive shaft and rotated thereby. Bracket means are provided for mounting an air conditioner refrigerant compressor on an outer surface of the compressor drive assembly housing such that a compressor drive shaft for driving the compressor is generally parallel with the compressor drive assembly drive shaft. A compressor pulley is attached to the compressor drive shaft and generally aligned with the compressor drive assembly drive shaft pulley.