C172RG PLT ENTERED MAF CLASS C AFTER BEING DISTRACTED BY THE LNDG GEAR WARNING HORN.

Narrative

I WAS TRAINING FOR MY CFI; THE C172RG WAS A RENTAL ACFT AND THE ACFT IN WHICH I HAD RECEIVED MY COMMERCIAL LICENSE IN 2000. THE C172RG HAD BEEN IN THE SHOP FOR REPAIR OF THE LNDG GEAR; BUT IT HAD BEEN FLYING A COUPLE OF WKS; AND I WAS AWARE OF THIS FACT. ON TKOF; AFTER DETERMINING THAT I COULD NO LONGER LAND ON THE RWY; I PLACED THE GEAR LEVER IN THE UP POS. AT THIS POINT THE GEAR WARNING HORN ACTIVATED. I WAITED UNTIL I TURNED XWIND AND THEN DOWNWIND AT WHICH POINT I RECYCLED THE GEAR AND AS SOON AS THE GEAR CAME BACK UP THE HORN BEGAN AGAIN. AT THIS POINT KNOWING CLASS C AIRSPACE (MAF) BEGAN AT 4400 FT I DID A QUICK CHK OF MY ALTIMETER WHICH INDICATED 4200 FT; SO I USED DOWN TRIM AND CLOSED THE THROTTLE A 'BIT.' AT THIS POINT I RECYCLED THE GEAR AGAIN AND THE PROB PERSISTED AT WHICH POINT I DECIDED TO TURN BASE AND RETURN TO THE ARPT. AT THIS POINT I WAS BTWN 2-3 MI FROM THE ARPT (MDD). AS I TURNED BASE; I NOTED I WAS HIGH IN RELATIONSHIP TO THE RWY AND LOOKED AT THE ALTIMETER WHICH READ JUST UNDER 4500 FT; SO I IMMEDIATELY PULLED PWR TO IDLE AND BEGAN APPLYING DOWN PRESSURE AND TRIM TO GET UNDER CLASS C AIRSPACE. I BELIEVE I WAS AT 100 FT OVER FOR ABOUT 1-2 MINS. THE RETURN TO THE ARPT AND THE LNDG WERE UNEVENTFUL. EVEN THOUGH I HAD PLANNED ON CONTACTING MAF FOR THE PERIOD OF TIME I WOULD BE IN THE 'PRACTICE AREA;' I HAD NOT CONTACTED THEM BECAUSE I HAD NEVER LEFT THE TFC PATTERN AT MDD AND HAD NOT INTENDED ON INVADING THEIR AIRSPACE. I BELIEVE THAT IN ADDITION TO WORKING THE PROB WITH THE WARNING HORN; THE FACT THAT I'VE BEEN FLYING C172 WITH AT 150 HORSEPOWER AND HAD JUST GOTTEN BACK IN THE C172RG AT 180 HORSEPOWER; HELPED CONTRIBUTE TO THIS EVENT. EVEN THOUGH I'D MADE NOTE OF MY ALT INITIALLY; DID AN ADJUSTMENT IN AN ATTEMPT TO STAY UNDER CLASS C; I BELIEVE WITH THE DIFFERENCE IN THE PERFORMANCE OF THE 2 ACFT THAT IN THE C172 I WOULD HAVE BEEN OKAY; BUT I SIMPLY DID NOT MAKE ENOUGH OF A CORRECTION FOR THE RG AND DID NOT CHK IT AGAIN UNTIL TURNING BASE; WHICH WAS PROBABLY ONLY A PERIOD OF LESS THAN 1 MIN.