DC9 CREW SUSPECTS PAX CELL PHONE INTERFERING WITH NAV RECEIVER DURING FLT IN ZHU AIRSPACE.

Narrative

THE LEAD FLT ATTENDANT RPTED A CELL PHONE IN USE ON THE GND AT THE GATE. LATER; WHILE AT CRUISE; THE #1 NAV RECEIVER WAS NOTED TO BE BEHAVING ABNORMALLY. THE TO/FROM FLAG WOULD PARTIALLY RETRACT AFTER INITIAL DEPLOYMENT ON ANY FREQ; BUT WOULD WORK FINE IN THE 'FROM' MODE. THE ANOMALY CEASED AFTER WE HAD DSNDED THROUGH FL180 (THE ALT AT WHICH THE FLT ATTENDANTS MAKE THE DSCNT PAX ELECTRONIC DEVICE ANNOUNCEMENT) AND WORKED FINE THROUGH THE APCH AND AT THE GATE ON THE VOT. WE WROTE IT UP IN THE LOGBOOK AS A SUSPECTED PAX ELECTRONIC DEVICE INTERFERENCE INCIDENT AND A VOR SENSITIVITY CHK WAS PERFORMED ON THE #1 NAV RECEIVER; WHICH WAS SATISFACTORY. SINCE THE LEAD FLT ATTENDANT'S PAX ELECTRONIC DEVICE WALK HAD NOT TURNED UP ANYTHING ELSE OF NOTE; I SUSPECT THAT THE PAX HAD LEFT HIS CELL PHONE SWITCHED ON INFLT AND THAT THIS MAY HAVE CONTRIBUTED TO OUR NAV RECEIVER PROB. P.S. OUR AIRLINE RECENTLY CHANGED ITS PAX ELECTRONIC DEVICE POLICY TO PERMIT CELL PHONE OP ON THE GND WITH THE DOOR OPEN. I HAVE EXPERIENCE; LIKE THIS INCIDENT; WHICH LEADS ME TO BELIEVE THAT SUCH A POLICY MAY NOT BE WISE.