DC9 FLC EXPERIENCES MULTIPLE ELECTRONIC EQUIP FAILURES IN FLT.

Narrative

WHILE AT CRUISE FLT FL310 WE NOTED THE ONSET OF MULTIPLE ANOMALIES WITH INDEPENDENT AND INTERRELATED ONBOARD ELECTRONIC SYS. THE RADAR ALTIMETER BEGAN FLAGGING AND SWEEPING; THE GPWS AND TCASII ANNUNCIATED 'FAIL;' THE VORS FLAGGED; DESPITE GOOD IDENTS AND; BY AND LARGE; RATIONAL SIGNALS. TESTS OF THE EQUIP WERE OTHERWISE SATISFACTORY SO WE MADE ANNOUNCEMENTS REQUESTING THAT CERTAIN PED'S (CELLPHONES; PAGERS; TVS AND RADIOS) BE VERIFIED IN A DEPOWERED CONDITION; AND THE FLT ATTENDANTS DID A 'PED WALK' IN THE CABIN. THE PROB INITIALLY VANISHED BUT THEN REAPPEARED; AND WE REPEATED THE PROCESS THIS TIME REQUESTING THAT ALL PED'S BE DEPOWERED. THE 3RD AND FINAL PED WALK REVEALED THAT SEVERAL PAGERS HAD TO BE DEPOWERED BY BATTERY REMOVAL; AND THERE WAS A COMPUTER IN USE WITH AN EXTERNAL BATTERY PACK. (NO INCOMING CALLS TO THE PAGERS WERE ADMITTED TO.) AFTER THIS; THE ANOMALOUS INDICATIONS VANISHED FOR GOOD AND ALL SYS OPERATED NORMALLY (INCLUDING ON THE GND VOT SIGNALS). WE WROTE UP THE INDICATIONS FOR MAINT TO VERIFY NORMAL INDICATION OF AFFECTED UNITS.