What was found
AFTER ROTATION, VIBRATION OCCURRED. AFTER GEAR RETRACTION, NOSE GEAR DOOR DID NOT RETRACT. COMPLIED WITH QRH AND RETURNED BACK TO MIA.(<P ><SPAN>REMOVED AND REPLACED ALT SQUAT SWITCH S801 REFERENCE AMM 32-61-01. ADJUSTED SQUAT SWITCH TARGET GAP TO MID RANGE .15. OPERATIONAL NORMAL REFERENCING AMM 32-61-01. PERFORMED NOSE GEAR INSPECTION, NO FAULTS FOUND REFERENCING AMM 05-51-31 P1A. </SPAN></P> / <P> </P>)