Narrative:

On feb/sat/03, I was on an IFR flight plan from cll to lch when I experienced a sudden loss of engine RPM. I applied carburetor heat, put the mixture full rich, and checked my magnetos. The oil pressure and temperature were normal and there was no smoke from the engine. My efforts had no effect in restoring the RPM to normal. I contacted beaumont approach and notified them I had partial loss of power from my engine and that I needed to land. I asked for bmt and then bpt when I realized there was IMC below me and the ILS at bpt might be needed. En route to bpt, I saw bmt through a break in the clouds. I asked ATC for clearance to land at bmt informing them that I had that airport in sight. I said I wanted to circle down through the clouds and land at bmt. During this time my engine RPM was varying and I was afraid I could lose all power. I was given clearance to bmt but given 3000 ft altitude assignment and then apparently a 1600 ft altitude assignment. I understood that I was cleared to land at the airport but when I reached 1500 ft, beaumont approach said I busted my assigned altitude. I was able to climb to 1600 ft again and then was cleared to change frequency and land. I did not declare an emergency. On the ground, I discovered that 4 of my spark plugs had severe lead fouling.

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Original NASA ASRS Text

Title: C152 PLT HAS MALFUNCTIONING ENG, REQUESTS CLRNC TO NEAREST ARPT, HAS ALT EXCURSION AND LANDS AT BMT.

Narrative: ON FEB/SAT/03, I WAS ON AN IFR FLT PLAN FROM CLL TO LCH WHEN I EXPERIENCED A SUDDEN LOSS OF ENG RPM. I APPLIED CARB HEAT, PUT THE MIXTURE FULL RICH, AND CHKED MY MAGNETOS. THE OIL PRESSURE AND TEMP WERE NORMAL AND THERE WAS NO SMOKE FROM THE ENG. MY EFFORTS HAD NO EFFECT IN RESTORING THE RPM TO NORMAL. I CONTACTED BEAUMONT APCH AND NOTIFIED THEM I HAD PARTIAL LOSS OF PWR FROM MY ENG AND THAT I NEEDED TO LAND. I ASKED FOR BMT AND THEN BPT WHEN I REALIZED THERE WAS IMC BELOW ME AND THE ILS AT BPT MIGHT BE NEEDED. ENRTE TO BPT, I SAW BMT THROUGH A BREAK IN THE CLOUDS. I ASKED ATC FOR CLRNC TO LAND AT BMT INFORMING THEM THAT I HAD THAT ARPT IN SIGHT. I SAID I WANTED TO CIRCLE DOWN THROUGH THE CLOUDS AND LAND AT BMT. DURING THIS TIME MY ENG RPM WAS VARYING AND I WAS AFRAID I COULD LOSE ALL PWR. I WAS GIVEN CLRNC TO BMT BUT GIVEN 3000 FT ALT ASSIGNMENT AND THEN APPARENTLY A 1600 FT ALT ASSIGNMENT. I UNDERSTOOD THAT I WAS CLRED TO LAND AT THE ARPT BUT WHEN I REACHED 1500 FT, BEAUMONT APCH SAID I BUSTED MY ASSIGNED ALT. I WAS ABLE TO CLB TO 1600 FT AGAIN AND THEN WAS CLRED TO CHANGE FREQ AND LAND. I DID NOT DECLARE AN EMER. ON THE GND, I DISCOVERED THAT 4 OF MY SPARK PLUGS HAD SEVERE LEAD FOULING.

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.