ACFT EQUIP PROB RADIO MGMNT PANEL (RMP) FREQ AUTO CHANGED TO AN ERRONEOUS FREQ.

Narrative

AFTER ALREADY CHKING ON THE APCH CTL AND BEING VECTORED FOR ILS RWY 23R WE NOTICED WE WERE ABOUT TO CROSS THROUGH THE LOC. WHEN CAPT QUERIED ATC AND GOT NO RESPONSE; HE LOOKED DOWN AND NOTICED WE HAD LOST THE FREQ WE'D BEEN TALKING ON; AND THE RADIO HAD BY ITSELF REVERTED BACK TO TAMPA GND CTL! (WE'D LEFT THERE OVER AN HOUR AND 1/2 AGO!) HE IMMEDIATELY RE-DIALED APCH CTL FREQ AND CHKED IN WITH THEM. THEY GAVE US A TEAR DROP TURN AND WE INTERCEPTED AND FLEW THE ILS APCH TO RWY 23L WITHOUT FURTHER INCIDENT. WE WROTE UP WHAT HAD OCCURRED IN THE ACFT LOGBOOK AND INFORMED MAINT AND THE OUTBOUND CREW. APPARENTLY A SIMILAR INCIDENT HAD OCCURRED WITH ANOTHER CREW IN THIS ACFT. AFTER SWITCHING TO GND IN RDO; THE ACFT'S RADIOS REVERTED TO THE GND FREQ OF THE PREVIOUS DEP. ALL WITHOUT INPUT FROM THE CREW. OURS WAS THE FIRST INCIDENT TO OCCUR WHILE AIRBORNE. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE ILS APCH WAS INSERTED ON THE APCH PAGE; ALL RADIO MGMNT PANELS WERE NORMAL; THE NAV SWITCH WAS IN THE COVERED (NORMAL) POS AND THE FREQ WHICH AUTO-TUNED WAS NOT CLOSE TO THE PRESENT OR RECENTLY USED FREQS. ENRTE THE FLC HAD CHANGED FREQ MANY TIMES; SO THE TAMPA GND CTL FREQ HAD NOT BEEN LEFT IN THE RADIO MGMNT PANEL 2 AND THE RPTR SAYS THERE WAS NO INADVERTENT TRANSFER FROM STANDBY TO THE ACTIVE. ALSO; THE ACFT HAD ONE PREVIOUS WRITE UP THAT A FREQ AUTO-CHANGED; BUT IT WAS ON THE GND AND THIS WAS INFLT. RPTR HAS HAD NO FEEDBACK FROM MAINT; AND SINCE THE COMPANY IS IN THE PROCESS OF CHANGING ACFT; THERE WAS NOT MUCH INTEREST. APPARENTLY; THIS PARTICULAR ACFT IS BEING REMOVED FROM SERVICE AND SOLD.