What was found
ON DEPARTURE OUT OF BOS, THE LANDING GEAR FAILED THE UPLATCH CHECK. THE LANDING GEAR WAS CYCLED THREE TIMES WITH THE SAME RESULT, WITH THE LANDING GEAR LEVER IN THE UPLATCH CHECK POSITION, THE UNSAFE LIGHT WAS ILLUMINATED WITH NO APPARENT GEAR EXTENSION. INSPECTION ON THE GROUND IN TOL REVEALED A MALFUNCTIONING LEFT MLG UPLATCH SWITCH. THE SWITCH WAS REPLACED, AND THE AIRCRAFT RETURNED TO SERVICE. (M)