Narrative:

Shortly after reaching cloww I detected a very faint 'engine odor;' however; all system were operating normally and engine gauges showed normal indications. I attributed the odor to slight aspiration of exhaust odor due to a possibly ajar landing gear door. At a point approximately 5 mi southwest of cloww; at approximately XA30Z; I noted a minimal 'fog' on the windscreen; symmetrically affecting both left and right sides of the windscreen. As it was now night; this 'fog' was detected with difficulty. 1 passenger asked about the possibility of ice causing this. I responded that this was unlikely as we were in VFR conditions and theorized it was due to poor operation of the aircraft heater; which allowed water vapor to condense on the interior surface of the windscreen. We had experienced this phenomenon prior to departure from hfd that morning. To confirm this; I wiped the interior of the windscreen and noted no improvement in forward visibility; which was still acceptable. Re-evaluate of the engine gauges a moment later revealed normal indications with the exception of the oil pressure gauge; which now indicated oil pressure at the very bottom of the green band; slightly lower than the normal indication of perhaps 1 needle width into the green band. Again looking back at the windscreen it was now clear that forward visibility was impeded and I noted there was a differential in the degree of this impediment from side-to-side; with the right side significantly more impeded than the left. The oil pressure remained at the yellow-green interface; however; I was no longer comfortable with continuing the flight. I contacted bradley approach control on the previously assigned frequency; explained my situation and requested priority handling to the nearest airport. They gave me at least 3 choices; however; worcester regional airport (orh); a twred field; was just 8 NM distant; and has a 7000 ft runway. I turned left from my assigned heading of 210 degrees after cloww to 080 degrees as suggested by bradley and proceeded towards orh at 6000 ft. I was soon able to see an airport but unsure if it was orh; I queried bdl regarding my position relative to a normal left traffic pattern for runway 29 at what appeared to be orh. They confirmed my position as 45 degrees to the left downwind at orh and I initiated a descent. I noted I still had oil pressure with the needle on or just slightly left of the yellow-green arc interface. As I entered the runway 29L downwind; I was now at approximately 4000 ft. I noted the oil pressure indication was now nil. I executed an expedited descent while on downwind; to 2200 ft; just above pattern altitude. I landed normally; but with minimal forward visibility; as the windscreen was now completely occluded with what was now very obviously engine oil. The runway centerline lights were partially visible straight ahead despite the oil and I had visual references out the side windows as well.

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Original NASA ASRS Text

Title: PA28 PLT HAS LOW ENG OIL PRESSURE WITH POSSIBLE OIL LEAK; DIVERTS FOR LNDG.

Narrative: SHORTLY AFTER REACHING CLOWW I DETECTED A VERY FAINT 'ENG ODOR;' HOWEVER; ALL SYS WERE OPERATING NORMALLY AND ENG GAUGES SHOWED NORMAL INDICATIONS. I ATTRIBUTED THE ODOR TO SLIGHT ASPIRATION OF EXHAUST ODOR DUE TO A POSSIBLY AJAR LNDG GEAR DOOR. AT A POINT APPROX 5 MI SW OF CLOWW; AT APPROX XA30Z; I NOTED A MINIMAL 'FOG' ON THE WINDSCREEN; SYMMETRICALLY AFFECTING BOTH L AND R SIDES OF THE WINDSCREEN. AS IT WAS NOW NIGHT; THIS 'FOG' WAS DETECTED WITH DIFFICULTY. 1 PAX ASKED ABOUT THE POSSIBILITY OF ICE CAUSING THIS. I RESPONDED THAT THIS WAS UNLIKELY AS WE WERE IN VFR CONDITIONS AND THEORIZED IT WAS DUE TO POOR OP OF THE ACFT HEATER; WHICH ALLOWED WATER VAPOR TO CONDENSE ON THE INTERIOR SURFACE OF THE WINDSCREEN. WE HAD EXPERIENCED THIS PHENOMENON PRIOR TO DEP FROM HFD THAT MORNING. TO CONFIRM THIS; I WIPED THE INTERIOR OF THE WINDSCREEN AND NOTED NO IMPROVEMENT IN FORWARD VISIBILITY; WHICH WAS STILL ACCEPTABLE. RE-EVAL OF THE ENG GAUGES A MOMENT LATER REVEALED NORMAL INDICATIONS WITH THE EXCEPTION OF THE OIL PRESSURE GAUGE; WHICH NOW INDICATED OIL PRESSURE AT THE VERY BOTTOM OF THE GREEN BAND; SLIGHTLY LOWER THAN THE NORMAL INDICATION OF PERHAPS 1 NEEDLE WIDTH INTO THE GREEN BAND. AGAIN LOOKING BACK AT THE WINDSCREEN IT WAS NOW CLR THAT FORWARD VISIBILITY WAS IMPEDED AND I NOTED THERE WAS A DIFFERENTIAL IN THE DEGREE OF THIS IMPEDIMENT FROM SIDE-TO-SIDE; WITH THE R SIDE SIGNIFICANTLY MORE IMPEDED THAN THE L. THE OIL PRESSURE REMAINED AT THE YELLOW-GREEN INTERFACE; HOWEVER; I WAS NO LONGER COMFORTABLE WITH CONTINUING THE FLT. I CONTACTED BRADLEY APCH CTL ON THE PREVIOUSLY ASSIGNED FREQ; EXPLAINED MY SITUATION AND REQUESTED PRIORITY HANDLING TO THE NEAREST ARPT. THEY GAVE ME AT LEAST 3 CHOICES; HOWEVER; WORCESTER REGIONAL ARPT (ORH); A TWRED FIELD; WAS JUST 8 NM DISTANT; AND HAS A 7000 FT RWY. I TURNED L FROM MY ASSIGNED HDG OF 210 DEGS AFTER CLOWW TO 080 DEGS AS SUGGESTED BY BRADLEY AND PROCEEDED TOWARDS ORH AT 6000 FT. I WAS SOON ABLE TO SEE AN ARPT BUT UNSURE IF IT WAS ORH; I QUERIED BDL REGARDING MY POS RELATIVE TO A NORMAL L TFC PATTERN FOR RWY 29 AT WHAT APPEARED TO BE ORH. THEY CONFIRMED MY POS AS 45 DEGS TO THE L DOWNWIND AT ORH AND I INITIATED A DSCNT. I NOTED I STILL HAD OIL PRESSURE WITH THE NEEDLE ON OR JUST SLIGHTLY L OF THE YELLOW-GREEN ARC INTERFACE. AS I ENTERED THE RWY 29L DOWNWIND; I WAS NOW AT APPROX 4000 FT. I NOTED THE OIL PRESSURE INDICATION WAS NOW NIL. I EXECUTED AN EXPEDITED DSCNT WHILE ON DOWNWIND; TO 2200 FT; JUST ABOVE PATTERN ALT. I LANDED NORMALLY; BUT WITH MINIMAL FORWARD VISIBILITY; AS THE WINDSCREEN WAS NOW COMPLETELY OCCLUDED WITH WHAT WAS NOW VERY OBVIOUSLY ENG OIL. THE RWY CTRLINE LIGHTS WERE PARTIALLY VISIBLE STRAIGHT AHEAD DESPITE THE OIL AND I HAD VISUAL REFS OUT THE SIDE WINDOWS AS WELL.

Data retrieved from NASA's ASRS site as of January 2009 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.