What was found
AT 13000 MSL, 280 KIAS, WARNING AURAL GEAR, RED GEAR UNSAFE UP ILLUMINATED.. WARNING STOPPED AFTER 3 MINUTES, 10 MINUTES LATER AT 3000 MSL WARNING REOCCURRED. WHEN GEAR WAS PLACED DOWN ALL INDICATIONS WERE NORMAL. TROUBLESHOT TO A FAULTY RADAR ALTIMETER SYSTEM. REMOVED BOTH SUSPECT DEFECTIVE RADAR ALTIMETER ANTENNAS AND REPLACED WITH NEW. ANTENNA R & R PERFOMED IAW AMM 34-44-09. REMOVED SUSPECT RADAR ALTIMETER TRANSCEIVER IAW AMM 34-44-01. INSTALLED AN OVERHAULED REPLACEMENT RADAR ALTIMETER TRANSCEIVER IAW AMM 34-44-01. OPS CHECKED OF THE RADAR ALTIMETER SYSTEM SATISFACTORY WITH NO FURTHER DEFECTS NOTED.