What was found
SOON AFTER TAKEOFF (APPROX. 1 MINUTE), SMOKE WAS NOTICED COMING FROM THE RT SIDE OF THE COCKPIT. FLIGHT CREW DECLARED AN EMERGENCY AND RETURNED TO HPN, WHERE THEY LANDED WITHOUT INCIDENT. THIS AIRCRAFT HAD BEEN DE-ICED PRIOR TO DEPARTURE; BOTH THE APU AND ENGINES WERE NOT RUNNING AT THE TIME. MAINTENANCE COMPLETED A VISUAL INSPECTION OF THE AIRCRAFT, OPERATED THE APU AND WITH THE ASSISTANCE OF THE FLIGHT CREW, PERFORMED GROUND ENGINE RUNS AT TAKEOFF POWER; NO DEFECTS WERE NOTED (UNABLE TO DUPLICATE). A SUCCESSFUL CONFIDENCE FLIGHT WAS ACCOMPLISHED AND THE AIRCRAFT RETURNED TO SERVICE.