What was found
ACFT MADE GEAR UP LANDING AFTER ALTERNATE GEAR EXTENSION PROCEDURES FAILED TO EXTEND GEAR. PILOT REPORTED HEARING GEAR HYD PUMP RUNNING AT ALL TIMES. JUST PRIOR TO TOUCHDOWN, PILOT TURNED OFF MASTER POWER, AND GEAR ATTEMPTED TO EXTEND. TWO DC POWER SOLENOIDS CONTROL PUMP DIRECTION (GEAR UP/GEAR DOWN). FOUND ''UP'' SOLENOID HAD ARCED CONTACT, SENDING DC POWER TO ''UP'' DIRECTION OF HYD PUMP. SUBMITTER SUSPECTED SOLENOID HAD STUCK, KEEPING GEAR RETRACTED. SUBMITTER RECOMMENDED PERIODIC REPLACEMENT OF SOLENOIDS, PIPER PN 484-373, TO PRECLUDE POSSIBILITY OF GEAR UP LANDINGS. (X)