Narrative:

IFR flight rdu to pne, 28 NM southwest of pxt VOR at 7000' MSL. IMC existed: visibility 0, light rain, turbulence. I heard a loud noise from the engine, then a banging noise which persisted until I landed. I also experienced engine vibration. All engine gauges were normal and there wasn't any discernable loss of power. Magnetos were checked, alternate air applied and fuel tanks shifted, yet to no avail. I declared an emergency. I informed the controller that I didn't have approach charts for the area (they were in my bag located on the back seat). I made 2 missed approachs at st mary's county airport during which I was below MDA for a short period of time; this I corrected. The MDA at st mary's is 540', I was at 500'. However, because of turbulence, I decided to fly at 600' on the recommendation of the controller. I next tried the cambridge dorchester airport, where I successfully landed. An inspection of the aircraft revealed that the right side aft cylinder exhaust pipe which is normally connected between the cylinder and the muffler had broken off. It fell beneath the engine. It banged between the engine and the bottom engine cover during the flight. Hot exhaust gas from the cylinder was being exhausted inside the engine housing near fuel lines and other combustible materials. The mechanic who inspected the aircraft at dorchester airport was amazed that there wasn't a fire. The pipe broke at a weld joint. I feel it wasn't welded properly. The only inaction on my part was I failed to get the transponder to 7700., I had conducted a preflight inspection of the aircraft and noted no problem. Thank god for good air traffic controllers; I had one of the best.

Google
 

Original NASA ASRS Text

Title: SMA PLT AT 7000' HEARS LOUD NOISE FROM ENGINE, THEN BANGING SOUNDS AND ENGINE VIBRATION. MADE EMERGENCY LNDG WITH ASSISTANCE OF ATC.

Narrative: IFR FLT RDU TO PNE, 28 NM SW OF PXT VOR AT 7000' MSL. IMC EXISTED: VISIBILITY 0, LIGHT RAIN, TURB. I HEARD A LOUD NOISE FROM THE ENG, THEN A BANGING NOISE WHICH PERSISTED UNTIL I LANDED. I ALSO EXPERIENCED ENG VIBRATION. ALL ENG GAUGES WERE NORMAL AND THERE WASN'T ANY DISCERNABLE LOSS OF PWR. MAGNETOS WERE CHKED, ALTERNATE AIR APPLIED AND FUEL TANKS SHIFTED, YET TO NO AVAIL. I DECLARED AN EMER. I INFORMED THE CTLR THAT I DIDN'T HAVE APCH CHARTS FOR THE AREA (THEY WERE IN MY BAG LOCATED ON THE BACK SEAT). I MADE 2 MISSED APCHS AT ST MARY'S COUNTY ARPT DURING WHICH I WAS BELOW MDA FOR A SHORT PERIOD OF TIME; THIS I CORRECTED. THE MDA AT ST MARY'S IS 540', I WAS AT 500'. HOWEVER, BECAUSE OF TURB, I DECIDED TO FLY AT 600' ON THE RECOMMENDATION OF THE CTLR. I NEXT TRIED THE CAMBRIDGE DORCHESTER ARPT, WHERE I SUCCESSFULLY LANDED. AN INSPECTION OF THE ACFT REVEALED THAT THE RIGHT SIDE AFT CYLINDER EXHAUST PIPE WHICH IS NORMALLY CONNECTED BTWN THE CYLINDER AND THE MUFFLER HAD BROKEN OFF. IT FELL BENEATH THE ENG. IT BANGED BTWN THE ENG AND THE BOTTOM ENG COVER DURING THE FLT. HOT EXHAUST GAS FROM THE CYLINDER WAS BEING EXHAUSTED INSIDE THE ENG HOUSING NEAR FUEL LINES AND OTHER COMBUSTIBLE MATERIALS. THE MECH WHO INSPECTED THE ACFT AT DORCHESTER ARPT WAS AMAZED THAT THERE WASN'T A FIRE. THE PIPE BROKE AT A WELD JOINT. I FEEL IT WASN'T WELDED PROPERLY. THE ONLY INACTION ON MY PART WAS I FAILED TO GET THE XPONDER TO 7700., I HAD CONDUCTED A PREFLT INSPECTION OF THE ACFT AND NOTED NO PROB. THANK GOD FOR GOOD AIR TFC CTLRS; I HAD ONE OF THE BEST.

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.