AN MLG ACR EXPERIENCED A STUCK MIKE; WHILE ON A PROVING RUN; BLOCKING AN ATC FREQ FOR ABOUT 15 MINS.

Narrative

FLT WAS AN FAA PROVING RUN IN AN MLG; FLL TO ACY. FAA INSPECTOR IN COCKPIT JUMPSEAT; ANOTHER IN CABIN. JUST AFTER LEVEL OFF; CABIN INSPECTOR GAVE FLT ATTENDANT A SCENARIO INPUT CARD FOR A LOUD SQUEAL AND AIR NOISE AROUND GALLEY DOOR FLT ATTENDANT CALLED ME ON INTERPHONE JUST AFTER I HAD TALKED TO JAX CTR CTLR. REALIZED ABOUT 15 MINS LATER THAT MY MIKE SWITCH ON THE YOKE HAD STUCK OPEN. WE (I) HAD THE ENRTE FREQ BLOCKED THE ENTIRE TIME WHILE WE DISCUSSED WHAT WE WOULD DO IN THAT SITUATION (DOOR SEAL LEAK; STRUCTURAL DAMAGE ETC) AND THEN PULLED OUT THE MEL AND ACFT OPERATING MANUAL TO CHK ALLOWABLE DIFFERENCE IN PLTS' ALTIMETERS WHICH WE HAD FOUND TO BE RUNNING 130-150 FT AT LEVELOFF. (140 ALLOWABLE LISTED IN OPERATING MANUAL). THIS WAS THE FIFTH DAY OF THESE FLTS; AND WE HAD ALL OBSERVED ABOUT 120 FT DIFFERENCE IN PREVIOUS DAYS. AS I SAID; THIS ROUTINE CONSUMED ABOUT 15 MINS; FAA MAN ON JUMPSEAT; FINALLY REMARKED THAT THE RADIO HAD BEEN VERY QUIET. THAT WAS WHEN I REALIZED MY XMIT SWITCH WAS STUCK; AND WE HAD BLOCKED JAX CTR FREQ FOR A CONSIDERABLE TIME; WHEN THEY WERE IN FACT QUITE BUSY.