Narrative:

Class B and C training flight with student pilot. Landed oak for class C departure communications procedures (ATIS, clearance del, ground, tower, etc). Off 27R taxied back to run-up area runway 27R to use radio in 7ECA. Radio was old. It worked fine in flight through landing and taxi. Received ATIS. Switched to clearance del and could not communication with many tries from both microphone position. Same problem using ground frequency. Switched back to tower (local) frequency, explained problem and asked for clearance to pao. Reception was fair and controller gave class C departure clearance and transponder code and taxi clearance to runway 27R. I read back clearance with position and heading runway 27R (I thought I had heard 'onto runway 27R.') the controller had made some 'nonstandard' ATC clrncs since our arrival, so with the combination of a bad radio, non-standard ATC communications, I heard 'taxi on to runway 27R.' so we (me and student) did. The controller told us he had not cleared us onto the runway, but to runway 27R (no 'hold short of'). He then cleared us for takeoff on 27R and, evidently, to make a right 270 degree overhead 'departure' which I never heard. So I called him on upwind at approximately 500 ft AGL asking for further clearance. He told me he had said to make a 270 degree overhead departure. No conflicts from any of this as we cleared the approach path visually before and as we taxied into position. With the distraction of a bad radio, a student, and a non- standard controller, I could have easily misunderstood the controller's communications/intentions. As soon as we were airborne, the radio worked fine. It is scheduled to be repaired with a higher performance mode in 7 days.

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Original NASA ASRS Text

Title: INSTRUCTOR WITH SPI HAS RWY EXCURSION AND POOR DEP DUE TO MALFUNCTIONING RADIO.

Narrative: CLASS B AND C TRAINING FLT WITH STUDENT PLT. LANDED OAK FOR CLASS C DEP COMS PROCS (ATIS, CLRNC DEL, GND, TWR, ETC). OFF 27R TAXIED BACK TO RUN-UP AREA RWY 27R TO USE RADIO IN 7ECA. RADIO WAS OLD. IT WORKED FINE IN FLT THROUGH LNDG AND TAXI. RECEIVED ATIS. SWITCHED TO CLRNC DEL AND COULD NOT COM WITH MANY TRIES FROM BOTH MIKE POS. SAME PROB USING GND FREQ. SWITCHED BACK TO TWR (LCL) FREQ, EXPLAINED PROB AND ASKED FOR CLRNC TO PAO. RECEPTION WAS FAIR AND CTLR GAVE CLASS C DEP CLRNC AND XPONDER CODE AND TAXI CLRNC TO RWY 27R. I READ BACK CLRNC WITH POS AND HDG RWY 27R (I THOUGHT I HAD HEARD 'ONTO RWY 27R.') THE CTLR HAD MADE SOME 'NONSTANDARD' ATC CLRNCS SINCE OUR ARR, SO WITH THE COMBINATION OF A BAD RADIO, NON-STANDARD ATC COMS, I HEARD 'TAXI ON TO RWY 27R.' SO WE (ME AND STUDENT) DID. THE CTLR TOLD US HE HAD NOT CLRED US ONTO THE RWY, BUT TO RWY 27R (NO 'HOLD SHORT OF'). HE THEN CLRED US FOR TKOF ON 27R AND, EVIDENTLY, TO MAKE A R 270 DEG OVERHEAD 'DEP' WHICH I NEVER HEARD. SO I CALLED HIM ON UPWIND AT APPROX 500 FT AGL ASKING FOR FURTHER CLRNC. HE TOLD ME HE HAD SAID TO MAKE A 270 DEG OVERHEAD DEP. NO CONFLICTS FROM ANY OF THIS AS WE CLRED THE APCH PATH VISUALLY BEFORE AND AS WE TAXIED INTO POS. WITH THE DISTR OF A BAD RADIO, A STUDENT, AND A NON- STANDARD CTLR, I COULD HAVE EASILY MISUNDERSTOOD THE CTLR'S COMS/INTENTIONS. AS SOON AS WE WERE AIRBORNE, THE RADIO WORKED FINE. IT IS SCHEDULED TO BE REPAIRED WITH A HIGHER PERFORMANCE MODE IN 7 DAYS.

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.