Narrative:

The first officer was flying to bwi. Captain was 'radio man.' we were descending toward sabbi at 1000 FPM on the nottingham 5 arrival. We were given a frequency change to the last washington center controller prior to potomac approach. When I acknowledged the frequency change, I knew my 'microphone' was stuck. Neither the first officer nor I could transmit or hear. First, I checked the yoke switch -- no help. I unplugged my headset -- no help. I checked the hand-held microphone -- no help. I failed to notice that the right/T - I/C switch on the #1 communication panel was stuck in the right/T position. That made us 'NORDO.' it's strange that I had just discussed the function of the 'altitude' switch on the communication panel. We selected 'altitude' on the first officer communication panel and set the ATC frequency on the #2 radio. I gave the first officer the radio job. Now he is flying and talking. I used the auxiliary headset, selected #2 radio on the overhead panel and monitored. I had little confidence in my communication - so I elected to let the first officer fly as well as talk. I monitored. Another complication was the bwi WX was over 200 ft overcast, 1.5 visibility, -RA, ILS 10. I had potomac approach pass on we were having radio difficulty so they wouldn't be surprised if they saw code 7700 followed by 7600 and a landing at bwi. The first officer did a great job. Compliments to him. Still another complication was communications with the flight attendants. I didn't want to leave the ATC frequency, so we didn't give a PA. Things were happening pretty fast so I relied on the 'ding' leaving 10000 ft. I later explained the situation on the ground. They were concerned, but figured it out. On the ground, like usual, everything worked again. We called for maintenance anyway. I again checked all the switches and found that the right/T - I/C switch would stick when pushed to the right/T position. That was the culprit. I am not pleased with myself for not catching the switch malfunction earlier. I looked in the QRH. There is no help. Had this situation happened en route, we would have had more time to figure out the problem. I don't know of any place to prepare for this situation other than experience. I know that every little problem can't be reference to the QRH, but it would have helped in this situation. Some things to include: 1) yoke switch, 2) hand set (maybe unplug), 3) right/T - I/C switch (could break internally) (jammed), 4) headset (maybe unplug), 5) use of communication panel altitude/normal switch -- some panels don't have this, 6) circuit breakers, 7) may have to inoperative a radio if not appropriate for the QRH, a discussion of somewhere in the books might be worthy.

Related reports:

Google
 

Original NASA ASRS Text

Title: B737 300 CREW LOST COM WITH ATC BECAUSE OF A STUCK PUSH TO TALK SWITCH IN THE CAPT'S COM SYS.

Narrative: THE FO WAS FLYING TO BWI. CAPT WAS 'RADIO MAN.' WE WERE DSNDING TOWARD SABBI AT 1000 FPM ON THE NOTTINGHAM 5 ARR. WE WERE GIVEN A FREQ CHANGE TO THE LAST WASHINGTON CTR CTLR PRIOR TO POTOMAC APCH. WHEN I ACKNOWLEDGED THE FREQ CHANGE, I KNEW MY 'MIC' WAS STUCK. NEITHER THE FO NOR I COULD XMIT OR HEAR. FIRST, I CHKED THE YOKE SWITCH -- NO HELP. I UNPLUGGED MY HEADSET -- NO HELP. I CHKED THE HAND-HELD MIC -- NO HELP. I FAILED TO NOTICE THAT THE R/T - I/C SWITCH ON THE #1 COM PANEL WAS STUCK IN THE R/T POS. THAT MADE US 'NORDO.' IT'S STRANGE THAT I HAD JUST DISCUSSED THE FUNCTION OF THE 'ALT' SWITCH ON THE COM PANEL. WE SELECTED 'ALT' ON THE FO COM PANEL AND SET THE ATC FREQ ON THE #2 RADIO. I GAVE THE FO THE RADIO JOB. NOW HE IS FLYING AND TALKING. I USED THE AUX HEADSET, SELECTED #2 RADIO ON THE OVERHEAD PANEL AND MONITORED. I HAD LITTLE CONFIDENCE IN MY COM - SO I ELECTED TO LET THE FO FLY AS WELL AS TALK. I MONITORED. ANOTHER COMPLICATION WAS THE BWI WX WAS OVER 200 FT OVERCAST, 1.5 VIS, -RA, ILS 10. I HAD POTOMAC APCH PASS ON WE WERE HAVING RADIO DIFFICULTY SO THEY WOULDN'T BE SURPRISED IF THEY SAW CODE 7700 FOLLOWED BY 7600 AND A LNDG AT BWI. THE FO DID A GREAT JOB. COMPLIMENTS TO HIM. STILL ANOTHER COMPLICATION WAS COMS WITH THE FLT ATTENDANTS. I DIDN'T WANT TO LEAVE THE ATC FREQ, SO WE DIDN'T GIVE A PA. THINGS WERE HAPPENING PRETTY FAST SO I RELIED ON THE 'DING' LEAVING 10000 FT. I LATER EXPLAINED THE SIT ON THE GND. THEY WERE CONCERNED, BUT FIGURED IT OUT. ON THE GND, LIKE USUAL, EVERYTHING WORKED AGAIN. WE CALLED FOR MAINT ANYWAY. I AGAIN CHKED ALL THE SWITCHES AND FOUND THAT THE R/T - I/C SWITCH WOULD STICK WHEN PUSHED TO THE R/T POS. THAT WAS THE CULPRIT. I AM NOT PLEASED WITH MYSELF FOR NOT CATCHING THE SWITCH MALFUNCTION EARLIER. I LOOKED IN THE QRH. THERE IS NO HELP. HAD THIS SIT HAPPENED ENRTE, WE WOULD HAVE HAD MORE TIME TO FIGURE OUT THE PROB. I DON'T KNOW OF ANY PLACE TO PREPARE FOR THIS SIT OTHER THAN EXPERIENCE. I KNOW THAT EVERY LITTLE PROB CAN'T BE REFERENCE TO THE QRH, BUT IT WOULD HAVE HELPED IN THIS SIT. SOME THINGS TO INCLUDE: 1) YOKE SWITCH, 2) HAND SET (MAYBE UNPLUG), 3) R/T - I/C SWITCH (COULD BREAK INTERNALLY) (JAMMED), 4) HEADSET (MAYBE UNPLUG), 5) USE OF COM PANEL ALT/NORMAL SWITCH -- SOME PANELS DON'T HAVE THIS, 6) CIRCUIT BREAKERS, 7) MAY HAVE TO INOP A RADIO IF NOT APPROPRIATE FOR THE QRH, A DISCUSSION OF SOMEWHERE IN THE BOOKS MIGHT BE WORTHY.

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.