SHORTLY AFTER TKOF ON AN IFR TRAINING FLT; THE PA28 SUFFERS A PARTIAL LOSS OF PWR. WHEN THE STUDENT TRIES TO ADVISE ATC THE INSTRUCTOR DISABLES THE XMISSION AND TELLS THE STUDENT SUCH A XMISSION WAS NOT NECESSARY.

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MY CFII AND I DEPARTED ON AN IFR FLT PLAN TRAINING FLT. WE RECEIVED OUR CLRNC AND WERE TOLD TO CONTACT DEP WHEN AIRBORNE. AT 350 FT AGL; I CONTACTED DEP AND THEY GOT US ON RADAR. AT ABOUT 900 FT MSL; THE ENG STARTED TO SPUTTER AND TO ME; ENG FAILURE SEEMED IMMINENT. I IMMEDIATELY TURNED BACK TO THE ARPT ON THE PWR WE HAD LEFT. THE ENG WAS STILL RUNNING; BUT GIVEN OUR ALT AND DISTANCE FROM THE ARPT; I THOUGHT IT WAS NECESSARY TO NOTIFY ATC OF THE PROB AND WHY WE WERE DEVIATING. I STARTED MY RADIO CALL SAYING 'WARRIOR XXX EXPERIENCING ENG TR...' AND THAT'S ALL MY INSTRUCTOR LET ME DO; SWITCHING FREQ RIGHT AWAY SO THAT THE REST OF MY CALL WOULDN'T BE HEARD. HE STATED THAT THE CALL WAS NOT NECESSARY SINCE THE ARPT WOULD BE MADE AND WE WOULDN'T CRASH (WHICH I WAS STILL UNSURE OF). WE LANDED; TAXIED ON THE LITTLE PWR WE HAD AND ONLY THEN WAS I TOLD TO CONTACT CLRNC AND TELL THEM WE WERE OK. THE CTLR INFORMED ME THAT SINCE THEY LOST COMS WITH US; SAW A RAPID DSCNT; AND IMMEDIATE SHARP TURN; THEY THOUGHT WE CRASHED AND HAD RESCUE SQUADS ON ALERT. AFTER ALL WAS EXPLAINED; I APOLOGIZED AND THE CTLR SAID GOOD-BYE. AT THIS POINT; I AM STILL UNSURE OF WHY A RADIO CALL SHOULD NOT BE MADE SINCE WE DEVIATED FROM OUR CLRNC AND WERE EXPERIENCING ENG TROUBLE. IN MY OPINION; IT IS FAR BETTER TO TELL SOMEONE AND LAND SAFELY WITH RESCUE SQUADS ON ALERT THAN TO STAY QUIET AND BE IN THE TREES. WANTED TO HAVE THIS ON RECORD BECAUSE THERE IS A RADIO CALL THAT HAS THE BEGINNING OF MY XMISSION. IN THE FUTURE; BETTER CRM AND CREW COM WOULD LEAD TO BETTER DECISION MAKING.