Narrative:

I have been a part time CFI for 2 yrs. Most training flts are to the practice area or cross-country to uncontrolled airports. I decided I needed to go out and fly in the ATC system to become more proficient. My solo flight was VFR using VOR/LORAN from L12-ont-cho-ral-hmt-L12. After landing at ral, I requested the VOR ground check located on the airport, then taxi back to runway 27 for takeoff. I was instructed to remain on the tower frequency. With the VOR check completed, I was approved to taxi to runway 27. While taxiing I asked the tower to contact socal departure for a clearance and transponder code for a departure to the southeast into march AFB class C, with a landing at hmt. When I had completed my preflight checklist and received the current ATIS information, I contacted the tower to tell them I was ready to depart runway 27. Ral tower gave me my transponder code and my clearance. I thought I heard sbound departure approved. With the clearance to depart I entered runway 27. Over the departure end of the runway the tower instructed me to contact socal departure. I made the standard left 15 degree heading change for ral's noise abatement program while checking in with socal. I then started to complete my turn to the south. It was then that the very angry socal controller asked me what I was doing. Why I had turned? That I was instructed to fly runway heading. I immediately turned back to comply with his instructions. I told him I had sidestepped over (noise abatement) and I was sorry for the confusion. I was about 1/4 mi south of the airport. The controller then cleared me to my southeast heading and to contact the next sector. I believe that the confusion came from the tower's use of the word 'approved' in my clearance and me expecting to hear that I was going to receive a clearance to depart to the southeast. I did not hear the tower clearance as maintain runway heading. I heard 'departure approved'. I think that when a request is made from an aircraft, that the word 'approved' should not be used in the instructions or reply from the controling facility if there is a difference between the request and what ATC wants that aircraft to do.

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Original NASA ASRS Text

Title: PLT INSTRUCTOR OF A CESSNA 150 FAILED TO MAINTAIN THE RWY HDG AFTER TKOF CAUSING DEP CTL TO INTERVENE TO ASSURE LEGAL TFC SEPARATION.

Narrative: I HAVE BEEN A PART TIME CFI FOR 2 YRS. MOST TRAINING FLTS ARE TO THE PRACTICE AREA OR CROSS-COUNTRY TO UNCTLED ARPTS. I DECIDED I NEEDED TO GO OUT AND FLY IN THE ATC SYS TO BECOME MORE PROFICIENT. MY SOLO FLT WAS VFR USING VOR/LORAN FROM L12-ONT-CHO-RAL-HMT-L12. AFTER LNDG AT RAL, I REQUESTED THE VOR GND CHK LOCATED ON THE ARPT, THEN TAXI BACK TO RWY 27 FOR TKOF. I WAS INSTRUCTED TO REMAIN ON THE TWR FREQ. WITH THE VOR CHK COMPLETED, I WAS APPROVED TO TAXI TO RWY 27. WHILE TAXIING I ASKED THE TWR TO CONTACT SOCAL DEP FOR A CLRNC AND XPONDER CODE FOR A DEP TO THE SE INTO MARCH AFB CLASS C, WITH A LNDG AT HMT. WHEN I HAD COMPLETED MY PREFLT CHKLIST AND RECEIVED THE CURRENT ATIS INFO, I CONTACTED THE TWR TO TELL THEM I WAS READY TO DEPART RWY 27. RAL TWR GAVE ME MY XPONDER CODE AND MY CLRNC. I THOUGHT I HEARD SBOUND DEP APPROVED. WITH THE CLRNC TO DEPART I ENTERED RWY 27. OVER THE DEP END OF THE RWY THE TWR INSTRUCTED ME TO CONTACT SOCAL DEP. I MADE THE STANDARD L 15 DEG HDG CHANGE FOR RAL'S NOISE ABATEMENT PROGRAM WHILE CHKING IN WITH SOCAL. I THEN STARTED TO COMPLETE MY TURN TO THE S. IT WAS THEN THAT THE VERY ANGRY SOCAL CTLR ASKED ME WHAT I WAS DOING. WHY I HAD TURNED? THAT I WAS INSTRUCTED TO FLY RWY HDG. I IMMEDIATELY TURNED BACK TO COMPLY WITH HIS INSTRUCTIONS. I TOLD HIM I HAD SIDESTEPPED OVER (NOISE ABATEMENT) AND I WAS SORRY FOR THE CONFUSION. I WAS ABOUT 1/4 MI S OF THE ARPT. THE CTLR THEN CLRED ME TO MY SE HDG AND TO CONTACT THE NEXT SECTOR. I BELIEVE THAT THE CONFUSION CAME FROM THE TWR'S USE OF THE WORD 'APPROVED' IN MY CLRNC AND ME EXPECTING TO HEAR THAT I WAS GOING TO RECEIVE A CLRNC TO DEPART TO THE SE. I DID NOT HEAR THE TWR CLRNC AS MAINTAIN RWY HDG. I HEARD 'DEP APPROVED'. I THINK THAT WHEN A REQUEST IS MADE FROM AN ACFT, THAT THE WORD 'APPROVED' SHOULD NOT BE USED IN THE INSTRUCTIONS OR REPLY FROM THE CTLING FACILITY IF THERE IS A DIFFERENCE BTWN THE REQUEST AND WHAT ATC WANTS THAT ACFT TO DO.

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.