Narrative:

We were inside the final approach fix, cleared for an ILS approach and I believe cleared to land. This was next to the last landing we were to do for the completion of FAA proving runs. We were trying, of course, to do a thorough job and we advising our 'FAA passenger' on short final to double check seat belts for landing. We had also always briefed these passenger to fasten thier seat belts during our initial descent. On approximately a 3 mi final on the ILS to las, I, sitting on the right seat and working with the radios, turned the transmitter selector switch to the 'passenger advisory' (PA) position to tell the passenger to double-check seat belts. When the selector switch is in the PA position, no outside communication will come over my system. In other words, my system will not receive. Normally this would present no problem for 2 reasons: 1)the other pilot's system would pick up normal ATC communication , and 2) I would normally be in the PA position for only 3 to 5 seconds. However this time I neglected to turn my selector switch back to the normal position for ATC communication. Therefore I was not receiving any outside communication on my side and the other pilot was not receiving any communication on his side either. His communication panel was set properly but he was not picking up any reception either. For the last 1000 feet on the ILS we were not in communication with ATC. I noticed upon landing that it was very quiet on the radio. I checked my selector switch and, sure enough, it was still in the PA position. I turned it to the #2 transmitter and immmediately I heard normal communications between the tower and other airplanes. I called the tower and told them we were exiting the runway to the right. Nothing was said to us about not being in contact. The left communication panel had had a history of trouble. It was, I beleive, turned in for maintenance before this trip and corrected. However there were scattered incidents throughout the proving runs where nothing would come over the captain's side without fiddling with the switches. Upon arrival at home base, we returned the airplane to radio maintenance to have the problem re-corrected.

Related reports:

Google
 

Original NASA ASRS Text

Title: FLC OF AN LTT LOST COM DURING FINAL DUE TO THE FO NOT RETURNING TO THE COM RADIO SELECTOR POS AFTER MAKING A 'PA' ANNOUNCEMENT

Narrative: WE WERE INSIDE THE FINAL APCH FIX, CLRED FOR AN ILS APCH AND I BELIEVE CLRED TO LAND. THIS WAS NEXT TO THE LAST LNDG WE WERE TO DO FOR THE COMPLETION OF FAA PROVING RUNS. WE WERE TRYING, OF COURSE, TO DO A THOROUGH JOB AND WE ADVISING OUR 'FAA PAX' ON SHORT FINAL TO DOUBLE CHK SEAT BELTS FOR LNDG. WE HAD ALSO ALWAYS BRIEFED THESE PAX TO FASTEN THIER SEAT BELTS DURING OUR INITIAL DSCNT. ON APPROX A 3 MI FINAL ON THE ILS TO LAS, I, SITTING ON THE R SEAT AND WORKING WITH THE RADIOS, TURNED THE XMITTER SELECTOR SWITCH TO THE 'PAX ADVISORY' (PA) POS TO TELL THE PAX TO DOUBLE-CHK SEAT BELTS. WHEN THE SELECTOR SWITCH IS IN THE PA POS, NO OUTSIDE COM WILL COME OVER MY SYS. IN OTHER WORDS, MY SYS WILL NOT RECEIVE. NORMALLY THIS WOULD PRESENT NO PROB FOR 2 REASONS: 1)THE OTHER PLT'S SYS WOULD PICK UP NORMAL ATC COM , AND 2) I WOULD NORMALLY BE IN THE PA POS FOR ONLY 3 TO 5 SECONDS. HOWEVER THIS TIME I NEGLECTED TO TURN MY SELECTOR SWITCH BACK TO THE NORMAL POS FOR ATC COM. THEREFORE I WAS NOT RECEIVING ANY OUTSIDE COM ON MY SIDE AND THE OTHER PLT WAS NOT RECEIVING ANY COM ON HIS SIDE EITHER. HIS COM PANEL WAS SET PROPERLY BUT HE WAS NOT PICKING UP ANY RECEPTION EITHER. FOR THE LAST 1000 FEET ON THE ILS WE WERE NOT IN COM WITH ATC. I NOTICED UPON LNDG THAT IT WAS VERY QUIET ON THE RADIO. I CHKED MY SELECTOR SWITCH AND, SURE ENOUGH, IT WAS STILL IN THE PA POS. I TURNED IT TO THE #2 XMITTER AND IMMMEDIATELY I HEARD NORMAL COMS BTWN THE TWR AND OTHER AIRPLANES. I CALLED THE TWR AND TOLD THEM WE WERE EXITING THE RWY TO THE R. NOTHING WAS SAID TO US ABOUT NOT BEING IN CONTACT. THE L COM PANEL HAD HAD A HISTORY OF TROUBLE. IT WAS, I BELEIVE, TURNED IN FOR MAINT BEFORE THIS TRIP AND CORRECTED. HOWEVER THERE WERE SCATTERED INCIDENTS THROUGHOUT THE PROVING RUNS WHERE NOTHING WOULD COME OVER THE CAPT'S SIDE WITHOUT FIDDLING WITH THE SWITCHES. UPON ARR AT HOME BASE, WE RETURNED THE AIRPLANE TO RADIO MAINT TO HAVE THE PROB RE-CORRECTED.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.