Gas turbine engine with supplemental oil cooler airflow

A gas turbine engine (10) is provided with an oil cooler which receives cooling air from a turbo fan (14). At times when the turbo fan (14) is operating at lower speeds, the volume of cooling air is also lowered. At such times, a supplemental airflow is provided over heat exchangers (38) in the oil cooler. The supplemental airflow includes a supplemental airflow fan (42) and valve (40) for selectively controlling the supplemental airflow over the heat exchangers (38).