A320 CREW HAD A STUCK MIKE XMIT SWITCH AT DCA.

Narrative

WHILE TAXIING FOR TKOF ON RWY 19 AT DCA; I BECAME SUSPICIOUS THAT THE PUSH-TO-TALK SWITCH ON MY JOYSTICK MIGHT BE STICKING IN THE XMIT POS. THIS WAS CONFIRMED WHEN THE ECAM CAUTION MESSAGE APPEARED INDICATING THAT THE #1 VHF RADIO HAD BEEN XMITTING MORE THAN 1 MIN; IE; STUCK MIKE SWITCH. I CYCLED THE SWITCH AND THE CAUTION MESSAGE SUBSIDED. WE ALSO BEGAN HEARING GND CTL AGAIN AND THE CTLR WAS ADVISING ALL ACFT TO CHK FOR A 'STUCK MIKE.' I THEN CHANGED FREQS TO TWR AND WE WERE CLRED INTO POS AND HOLD ON RWY 19; TFC LNDG (OR TAKING OFF; I DON'T RECALL WHICH) ON A XING RWY. WHILE HOLDING IN POS; WE AGAIN GOT THE ECAM CAUTION MESSAGE INDICATING A STUCK MIKE. I CYCLED MY PUSH-TO-TALK SWITCH AND ALSO CHANGED THE XMIT BUTTON ON MY AUDIO PANEL TO INTERCOM (TO MAKE CERTAIN THAT A STUCK MIKE WOULD NOT INTERFERE WITH ANY FREQ). AT THAT TIME; WE HEARD THE TWR CTLR ORDERING A GAR FOR AN ACFT LNDG RWY 19. WE SAW THE ACFT GO OVERHEAD. TWR THEN ADVISED US THAT THEY BELIEVED WE HAD A STUCK MIKE. WE SWITCHED TO HAND MIKE; DEPARTED AND CONTINUED TO DTW WITHOUT FURTHER INCIDENT WHERE; UPON ARR; WE MADE A MAINT ENTRY INTO THE ACFT LOGBOOK. THIS WAS A SIMPLE MECHANICAL FAILURE THAT LED TO A POTENTIALLY DANGEROUS SIT. AT THE LEAST; IT CAUSED 1 OR MORE ACFT TO HAVE TO GO AROUND; AT AN ARPT (DCA) WITH UNIQUE ATC PROBS. THIS PROB HAS BEEN STUDIED MANY TIMES AND FEW TECHNOLOGY SOLUTIONS EXIST TO HELP ELIMINATE IT. I GIVE CREDIT TO THE ENGINEERS OF AIRBUS TO INCLUDE A WARNING SYS THAT SIMPLY ISSUES A CAUTION MESSAGE AFTER 1 MIN OF CONTINUOUS VHF XMISSION. WITHOUT THAT FEATURE; THIS PARTICULAR SIT WOULD HAVE ALMOST CERTAINLY BEEN WORSE. THE REAL PROB WITH THIS PARTICULAR MECHANICAL FAILURE IS HOW INSIDIOUS IT IS. BOTH TIMES WE EXPERIENCED THE FAILURE; IT WAS DURING THE READBACK; THEREFORE ANY PERIOD OF SILENCE AFTER THE XMISSION DID NOT SEEM UNUSUAL. ABSENT THE AIRBUS MONITORING AND CAUTION SYS; THE ONLY INDICATION OF A STUCK MIKE PROB IS A PROLONGED PERIOD OF SILENCE OR NON RESPONSE TO A XMISSION; NEITHER OF WHICH ARE ALL THAT UNUSUAL. THE REAL LONG-TERM SOLUTION TO THIS PROB IS A BETTER COM SYS. FOR MANY REASONS; INCLUDING THIS INCIDENT; I HAVE FELT THAT A MORE TECHNOLOGICALLY ADVANCED COM SYS SHOULD BE IN PLACE FOR THE AIRLINE INDUSTRY. THE OBVIOUS CHOICE AT THIS POINT IS A DATA LINK SYS; POSSIBLY USING THE ACARS SYS.