Narrative:

While working the west arrival position I accepted a handoff of a DH8 on the abc arrival from the center. The aircraft had no mode-C displayed but our LOA with the center requires propellers on the arrival to be at 11000 ft and jets at 12000 ft. When the aircraft checked in I confirmed his altitude and informed the pilot his mode-C was not working and asked him if any other controllers had mentioned this to him. The pilot stated that no one had informed him and they were trying to recycle the transponder. I instructed the pilot to descend and maintain 9000 ft and to report reaching. The pilot then informed me that he was getting an error message on the TCAS regarding lack of altitude. I issued the pilot an instruction and when he responded I heard the 1000 ft to go warning go off so I confirmed that he was leaving 10000 ft for 9000 ft. He responded yes and after about 90 seconds I asked the pilot if he was level at 9000 ft and he then stated he lost all avionics and he did not know his altitude. I declared an emergency for the pilot and then called the west departure controller as the aircraft was now in another controller's airspace and asked him to protect his airspace around the aircraft with the avionics failure as I did not know his altitude or heading. The pilot then called me to say he had an altimeter working and he was at 7500 ft and asked me if he wanted to go back up. I said no and to descend and maintain 6000 ft. I then switched the aircraft to the final controller and he landed without incident.

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Original NASA ASRS Text

Title: TRACON CTLR DECLARED EMER FOR INBOUND DH8 AFTER PLT STATED ALL AVIONICS WERE INOP; COORDINATING WITH ADJACENT SECTORS FOR AIRSPACE.

Narrative: WHILE WORKING THE W ARR POS I ACCEPTED A HDOF OF A DH8 ON THE ABC ARR FROM THE CTR. THE ACFT HAD NO MODE-C DISPLAYED BUT OUR LOA WITH THE CTR REQUIRES PROPS ON THE ARR TO BE AT 11000 FT AND JETS AT 12000 FT. WHEN THE ACFT CHKED IN I CONFIRMED HIS ALT AND INFORMED THE PLT HIS MODE-C WAS NOT WORKING AND ASKED HIM IF ANY OTHER CTLRS HAD MENTIONED THIS TO HIM. THE PLT STATED THAT NO ONE HAD INFORMED HIM AND THEY WERE TRYING TO RECYCLE THE XPONDER. I INSTRUCTED THE PLT TO DSND AND MAINTAIN 9000 FT AND TO RPT REACHING. THE PLT THEN INFORMED ME THAT HE WAS GETTING AN ERROR MESSAGE ON THE TCAS REGARDING LACK OF ALT. I ISSUED THE PLT AN INSTRUCTION AND WHEN HE RESPONDED I HEARD THE 1000 FT TO GO WARNING GO OFF SO I CONFIRMED THAT HE WAS LEAVING 10000 FT FOR 9000 FT. HE RESPONDED YES AND AFTER ABOUT 90 SECONDS I ASKED THE PLT IF HE WAS LEVEL AT 9000 FT AND HE THEN STATED HE LOST ALL AVIONICS AND HE DID NOT KNOW HIS ALT. I DECLARED AN EMER FOR THE PLT AND THEN CALLED THE W DEP CTLR AS THE ACFT WAS NOW IN ANOTHER CTLR'S AIRSPACE AND ASKED HIM TO PROTECT HIS AIRSPACE AROUND THE ACFT WITH THE AVIONICS FAILURE AS I DID NOT KNOW HIS ALT OR HDG. THE PLT THEN CALLED ME TO SAY HE HAD AN ALTIMETER WORKING AND HE WAS AT 7500 FT AND ASKED ME IF HE WANTED TO GO BACK UP. I SAID NO AND TO DSND AND MAINTAIN 6000 FT. I THEN SWITCHED THE ACFT TO THE FINAL CTLR AND HE LANDED WITHOUT INCIDENT.

Data retrieved from NASA's ASRS site as of January 2009 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.