POTENTIAL CONFLICT DURING MISSED APCH PROC.

Narrative

CAVU DAY WITH JUST A FEW SCATTERED CLOUDS. I WANTED TO SHOOT SOME APCHS WITH MY INSTRUCTOR AS I WAS BEHIND ON HOOD TIME. TKOF FROM CONCORD; CA WAS NORMAL. FIRST VOR RWY 19R APCH WAS GOOD. TRAVIS AFB CTLR TURNED US OVER TO CCR TWR. RWY 32 WAS IN USE SO I FLEW ONLY 1 MIN 20 SECONDS FROM VOR TO VISUAL DSCNT POINT AS WE WOULD CIRCLE TO LAND. INFORMED TWR OF MISSED APCH AT 2 MINS 20 SECONDS AND AT 80 KTS AND TWR GAVE US BACK TO TRAVIS. SECOND VOR APCH ALSO WENT WELL; INITIALLY. TRAVIS INFORMED US THAT WE WERE FOLLOWING A HELI ON APCH. I SLOWED TO 70 KTS TO MAINTAIN SEPARATION WITH A COPTER WE COULDN'T SEE. LOTS OF TFC IN PATTERN; SO AT VISUAL DSCNT POINT I TOLD TWR WE WOULD MISS AGAIN AND I WENT BACK TO TRAVIS FREQ WITHOUT TWR TELLING US TO DO SO. TRAVIS CAME UP AND TOLD US THERE HAD BEEN A CONFLICT WITH TFC (MY SAFETY PLT; INSTRUCTOR WITH 16000 PLUS HRS; NEVER SAW A CONFLICT OF ANY SORT). I MADE A REAL ERROR IN CHANGING FREQS WITHOUT TWR TELLING ME TO CHANGE. MANY REASONS - RUSTY ON HOOD TIME; VERY BUSY FOLLOWING HELI; LOTS OF TFC IN PATTERN. STILL; I MADE AN ERROR WHICH COULD HAVE BEEN VERY SERIOUS. I LEARNED A GREAT DEAL FROM THIS; AND WILL BE MORE CAREFUL IN THE FUTURE TO STAY WITH TWR UNTIL TOLD TO GO BACK TO APCH.