Narrative:

We departed nzy en route to brown field. Leaving nzy's airspace, I changed frequencys and our headsets went dead. I had the student circle outside class D airspace while I troubleshot the radios, turning other electrical equipment off, recycling the radio, and switching to overhead speaker and hand microphone. The overhead speaker produced a loud squeal, but I was able to intermittently hear nzy tower over the squeal. I tried transmitting on 121.5 and nzy tower frequencys. Tower finally responded, clearing me to land via a straight-in to runway 29 before the squeal again drowned out their xmissions. I entered the lost communications transponder code and told tower I was losing my radio. I received 1 transmission garbled and barely readable, apparently asking me if I was squawking the lost communications code. I replied 'affirm.' inbound to the runway, I was busy searching for other traffic, including the S3 I'd seen enter the pattern mins before, and trying to adjust the volume on the radio to listen over the squeal. I was also monitoring the VOR frequency for voice xmissions. I made a straight-in to runway 29 as cleared, making gear down and position calls in the blind. After landing, I looked for a light signal to taxi. Both myself and my student observed a faint flashing white light, so we taxied to parking. Upon reaching parking, I was met by the base police, and told to contact tower on the land line. Tower informed me that I'd been squawking the hijack code, and I explained I thought I'd been squawking the lost communications code. Recommendations: this was an easy mistake to make, especially in light of the fact the lost communications and hijack codes are only 1 digit apart. A hijack code of 7555 would make it easier to keep them apart. I was pretty busy, between trying to listen to tower over the squeal, troubleshoot the radio, clear for other traffic, and monitor my pre-solo student who was flying the aircraft while I troubleshot the radios. I never looked at my transponder after initially setting the code. A call from tower, clarifying that I was squawking code 7500 and not lost communication would have alleviated the problem, but they are very restr in what to say in that situation. Tower also informed me they gave me a flashing red light, not a flashing white light. More training from both sides of the signal lights might help alleviate that situation. It's very hard to see ATC light signals from the cockpit, even on the ground when the aircraft is far from the tower.

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Original NASA ASRS Text

Title: AN INSTRUCTOR PLT DIALS IN THE WRONG XPONDER CODE WHEN HE HAS A PARTIAL RADIO FAILURE AND DIVERTS BACK TO NZY. THE POLICE MEET THE ACFT AT THE RAMP. HE HAD TAXIED IN TO THE RAMP WITH WHAT WAS PERCEIVED AS A WHITE LIGHT. IT WAS RED.

Narrative: WE DEPARTED NZY ENRTE TO BROWN FIELD. LEAVING NZY'S AIRSPACE, I CHANGED FREQS AND OUR HEADSETS WENT DEAD. I HAD THE STUDENT CIRCLE OUTSIDE CLASS D AIRSPACE WHILE I TROUBLESHOT THE RADIOS, TURNING OTHER ELECTRICAL EQUIP OFF, RECYCLING THE RADIO, AND SWITCHING TO OVERHEAD SPEAKER AND HAND MIKE. THE OVERHEAD SPEAKER PRODUCED A LOUD SQUEAL, BUT I WAS ABLE TO INTERMITTENTLY HEAR NZY TWR OVER THE SQUEAL. I TRIED XMITTING ON 121.5 AND NZY TWR FREQS. TWR FINALLY RESPONDED, CLRING ME TO LAND VIA A STRAIGHT-IN TO RWY 29 BEFORE THE SQUEAL AGAIN DROWNED OUT THEIR XMISSIONS. I ENTERED THE LOST COMS XPONDER CODE AND TOLD TWR I WAS LOSING MY RADIO. I RECEIVED 1 XMISSION GARBLED AND BARELY READABLE, APPARENTLY ASKING ME IF I WAS SQUAWKING THE LOST COMS CODE. I REPLIED 'AFFIRM.' INBOUND TO THE RWY, I WAS BUSY SEARCHING FOR OTHER TFC, INCLUDING THE S3 I'D SEEN ENTER THE PATTERN MINS BEFORE, AND TRYING TO ADJUST THE VOLUME ON THE RADIO TO LISTEN OVER THE SQUEAL. I WAS ALSO MONITORING THE VOR FREQ FOR VOICE XMISSIONS. I MADE A STRAIGHT-IN TO RWY 29 AS CLRED, MAKING GEAR DOWN AND POS CALLS IN THE BLIND. AFTER LNDG, I LOOKED FOR A LIGHT SIGNAL TO TAXI. BOTH MYSELF AND MY STUDENT OBSERVED A FAINT FLASHING WHITE LIGHT, SO WE TAXIED TO PARKING. UPON REACHING PARKING, I WAS MET BY THE BASE POLICE, AND TOLD TO CONTACT TWR ON THE LAND LINE. TWR INFORMED ME THAT I'D BEEN SQUAWKING THE HIJACK CODE, AND I EXPLAINED I THOUGHT I'D BEEN SQUAWKING THE LOST COMS CODE. RECOMMENDATIONS: THIS WAS AN EASY MISTAKE TO MAKE, ESPECIALLY IN LIGHT OF THE FACT THE LOST COMS AND HIJACK CODES ARE ONLY 1 DIGIT APART. A HIJACK CODE OF 7555 WOULD MAKE IT EASIER TO KEEP THEM APART. I WAS PRETTY BUSY, BTWN TRYING TO LISTEN TO TWR OVER THE SQUEAL, TROUBLESHOOT THE RADIO, CLR FOR OTHER TFC, AND MONITOR MY PRE-SOLO STUDENT WHO WAS FLYING THE ACFT WHILE I TROUBLESHOT THE RADIOS. I NEVER LOOKED AT MY XPONDER AFTER INITIALLY SETTING THE CODE. A CALL FROM TWR, CLARIFYING THAT I WAS SQUAWKING CODE 7500 AND NOT LOST COM WOULD HAVE ALLEVIATED THE PROB, BUT THEY ARE VERY RESTR IN WHAT TO SAY IN THAT SIT. TWR ALSO INFORMED ME THEY GAVE ME A FLASHING RED LIGHT, NOT A FLASHING WHITE LIGHT. MORE TRAINING FROM BOTH SIDES OF THE SIGNAL LIGHTS MIGHT HELP ALLEVIATE THAT SIT. IT'S VERY HARD TO SEE ATC LIGHT SIGNALS FROM THE COCKPIT, EVEN ON THE GND WHEN THE ACFT IS FAR FROM THE TWR.

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.