B747-400 LOSES RADIO CONTACT WITH ATC DURING APCH AT NRT; JAPAN. ACFT HAD A STUCK MIKE CAUSED BY ONE OF THE FLC.

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WE WERE AT 4000 FT; ESTIMATED 230 KIAS; HDG 340 DEGS MAGNETIC. APPROX 10 MI SE OF YOKOSHIBA NDB 'YQ' BEING VECTORED FOR AN ILS RWY 34 APCH AT NARITA; JAPAN. WE WERE ON APCH CTL FREQ AND LOST VHF COMS. WE IMMEDIATELY SQUAWKED 7600 IN THE XPONDER AND THE FO SWITCHED THE #2 RADIO TO NARITA TWR FREQ WHILE I STAYED ON APCH CTL FREQ. I WAS THE PF. WE WERE ON A VECTOR TO YOKOSHIBA NDB AT THE TIME OF THE INCIDENT. ALMOST IMMEDIATELY I COULD HEAR NARITA APCH AGAIN AND ATTEMPTED UNSUCCESSFULLY TO CONTACT THEM. THE FO WAS UNABLE TO CONTACT TWR SO HE SWITCHED BACK TO APCH CTL AND THEN I WAS UNABLE TO HEAR APCH CTL AGAIN. BOTH THE FO AND I WERE USING MINITEL MIKES. ON THIS B747-400 ACFT; THE FO ALSO HAS A HAND-HELD MIKE WHICH HANGS NEAR HIS FLT BAG ON THE R SIDE WALL. HE DETERMINED THAT HIS BOOK OF APCH PLATES WAS PRESSING AGAINST THE MIKE AND BLOCKED THE FREQ SELECTED BY HIM. HE UNKEYED THE MIKE AND WE RE-ESTABLISHED COMS WITH APCH CTL. WE WERE ASSIGNED A NEW XPONDER SQUAWK AND VECTORED FOR ANOTHER APCH AND LANDED UNEVENTFULLY AT NARITA.