What was found
SEA - FLT 23 - STATIC INTERFERENCE HEARD FROM OVERHEAD SPEAKER/HEADSET AT WHICH TIME THE NR 1 F/D, NR 1 FMA, AND NR 1 GPS WENT BLANK. AFTER STATIC STOPS, F/D, GPS RETURN TO NORMAL, FMA STAYS BLANK. WHEN MODE TEST SWITCH IS DEPRESSED, FMA RETURNS TO NORMAL. OCCURRED 3 TIMES ON FINAL. UNABLE TO DUPLICATE STATIC ON NR 1 OVERHEAD SPEAKER/HEADSET. OPS CHECK OK ON GROUND. OK FOR SERVICE. (M)