What was found
DURING APPROACH TO SJU, SMOKE WAS NOTICED IN THE COCKPIT ABOUT 15 MINUTES AFTER THE HEATER WAS TURNED ON. THERE WAS ALSO A GREATER DEAL OF SMOKE COLLECTION IN THE AFT CABIN. AN EMERGENCY WAS DECLARED AN A FEW MINUTES LATER, THE LEFT WING OVERHEAT LIGHT ILLUMINATED. DURING APPROACH TO THE RUNWAY, THE WING OVERHEAT LIGHT WENT OUT AND THE AIRCRAFT LANDED WITHOUT FURTHER INCIDENT. MAINTENANCE INSPECTED AND DISCOVERED THAT THE COOLING TURBINE HAD SEIZED. THE COOLING TURBINE WAS DEFERRED AND THE AIRCRAFT WAS RETURNED TO SERVICE. (M)