Medium large transport aircraft dtw to pit. #1 communication stuck on transmit, blocked frequencys.

Attributes
ACN	164488
Time
Date	199012
Day	Sun
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : pit
State Reference	PA
Altitude	msl bound lower : 4000 msl bound upper : 6000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zob tracon : pit
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Flight Phase	cruise other descent other landing other
Route In Use	arrival other enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : atp pilot : cfi pilot : commercial
Experience	flight time last 90 days : 120 flight time total : 6000 flight time type : 200
ASRS Report	164488
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : commercial pilot : instrument pilot : atp
Events
Anomaly	aircraft equipment problem : less severe other anomaly other
Independent Detector	other controllera other flight crewa
Resolutory Action	flight crew : overcame equipment problem
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other

Narrative:

Captain's audio panel faulty all trip from dtw to pit. On approach lost communication with ATC. Turns out that #1 communication was locked on transmit electrically. No stuck microphone. Captain's microphone stuck hot with no switch depressed. Trail and error to resolve problem. We were blocking ATC frequency and communication ability. Went to previous frequency, thus blocking it. Finally realized #1 communication stuck on transmit. Reacquired communication with ATC on #2 communication, but #1 still blocking other frequency causing high potential for midair sep's due to ATC inability to communicate. The audio panel totally malfunctioned. All receivers hot on in captain's headset, plus over passenger P/a. ATC frequencys being blocked and unable to receive ATC directions. Real mess. High potential for midair collision in approach pattern! Finally established communication reliability with #2 communication. Put #1 communication on 121.5 temporarily as not to block any ATC frequency needed for contact until on ground. Then pulled #1 communication circuit breaker to disable transmit (continuous). I don't know if any sep errors were caused by our continued flight on last given vector during malfunction or by other aircraft due to ATC frequencys temporarily being blocked. I don't, as of now, know what maintenance found wrong with my aircraft audio system, but obvious system fault is possible and should be looked into, as very dangerous results from system failure.

Original NASA ASRS Text

Title: MLG ACFT DTW TO PIT. #1 COM STUCK ON TRANSMIT, BLOCKED FREQS.

Narrative: CAPT'S AUDIO PANEL FAULTY ALL TRIP FROM DTW TO PIT. ON APCH LOST COM WITH ATC. TURNS OUT THAT #1 COM WAS LOCKED ON XMIT ELECTRICALLY. NO STUCK MIC. CAPT'S MIC STUCK HOT WITH NO SWITCH DEPRESSED. TRAIL AND ERROR TO RESOLVE PROB. WE WERE BLOCKING ATC FREQ AND COM ABILITY. WENT TO PREVIOUS FREQ, THUS BLOCKING IT. FINALLY REALIZED #1 COM STUCK ON XMIT. REACQUIRED COM WITH ATC ON #2 COM, BUT #1 STILL BLOCKING OTHER FREQ CAUSING HIGH POTENTIAL FOR MIDAIR SEP'S DUE TO ATC INABILITY TO COMMUNICATE. THE AUDIO PANEL TOTALLY MALFUNCTIONED. ALL RECEIVERS HOT ON IN CAPT'S HEADSET, PLUS OVER PAX P/A. ATC FREQS BEING BLOCKED AND UNABLE TO RECEIVE ATC DIRECTIONS. REAL MESS. HIGH POTENTIAL FOR MIDAIR COLLISION IN APCH PATTERN! FINALLY ESTABLISHED COM RELIABILITY WITH #2 COM. PUT #1 COM ON 121.5 TEMPORARILY AS NOT TO BLOCK ANY ATC FREQ NEEDED FOR CONTACT UNTIL ON GND. THEN PULLED #1 COM CB TO DISABLE XMIT (CONTINUOUS). I DON'T KNOW IF ANY SEP ERRORS WERE CAUSED BY OUR CONTINUED FLT ON LAST GIVEN VECTOR DURING MALFUNCTION OR BY OTHER ACFT DUE TO ATC FREQS TEMPORARILY BEING BLOCKED. I DON'T, AS OF NOW, KNOW WHAT MAINT FOUND WRONG WITH MY ACFT AUDIO SYS, BUT OBVIOUS SYS FAULT IS POSSIBLE AND SHOULD BE LOOKED INTO, AS VERY DANGEROUS RESULTS FROM SYS FAILURE.

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.