What was found
DURING DESCENT WITH THRUST LEVERS AT IDLE, THREE RED GEAR WARNING INDICATORS WERE OBSERVED AND WARNING HORN WAS MOMENTARILY HEARD TWICE THEN WENT AWAY. THE GEAR LEVER WAS IN THE UP POSITION. THE AIRCRAFT WAS GROUNDED. DOWNLOADED THE FDR AND FOUND THAT BOTH RADIO ALTIMETERS HAD A MOMENTARY SPIKE IN ALTITUDE FROM GREATER THAN 5,000FT. TO LESS THAN 800FT. CAUSING THE WARNING LIGHTS AND HORN TO COME ON. REPLACED NR 2 FWD RADIO ALTIMETER IAW 34-33-21. OPS CHECK NORMAL..