Narrative:

Departed N54 (langhorne, PA) on IFR flight plan to alb. Was instructed by phl approach to climb to 6000 ft direct allentown. I got on the 157 degree radial (337 heading) and locked on autoplt. Aircraft shortly thereafter (still in climb) started turning to right. However, VOR needle stayed centered. I tuned second VOR and got same results. By the time I got to 030 degree heading I knew something was wrong but the needles were still centered. At that time phl approach asked my heading. I responded that I was on 337 radial of allentown (double wrong answer -- I was on 157 radial and he asked heading). Controller (angrily) responded -- answer my question! Say heading. I said 010 degree (I had turned back, VOR needles were now showing right of course). He said I had turned away from allentown and 'fly heading 330 degree' which I did. VOR reflected maximum of 3 dots deviation. I have not been able to duplicate this problem on subsequent flts. I attribute it to autoplt anomaly. Vigilance of instruments is important at all times. I probably was 30 seconds - 1 min slow in correcting the heading due to conflict of readings. A few mins later, having been handed off to allentown approach and cleared from 6000 to 7000 ft my engine got a sudden vibration. My engine instruments were not showing a problem (normal fuel flow, oil temperature, oil pressure, RPM, manifold pressure -- which was 25 inches at the time). A reduction in power stopped the vibration. I advised controller that I had a vibration and must get down immediately although I currently had partial power. I enriched mixture, increased RPM, and flew vector to quakertown airport which he gave as 8 mi away. He asked if this was emergency and I said yes. I had become concerned that not knowing the cause of the problem could result in a worse problem before reaching the airport. I concentrated on flying the vector and monitoring the instruments. When notified that I was still several (possibly 5 or less) mi from the airport, I noticed that I was flying over an airport with fixed distance markings which was probably not quakertown. I asked the controller about it. He responded pennridge. I said I wanted to land there. He said ok and called pennridge on telephone. I made successful landing -- end of emergency. A mechanic was available and worked on my problem. It was determined that 1 fuel injector had clogged causing the vibration. This mechanic and others have said to me there was nothing I could have done to prevent it, and the vibrating would have become worse over time due to over-richness on other 5 cylinders. Allentown FSDO requested an M and D report from the mechanic which he will supply. In retrospect, it might have been premature to go all the way and say 'emergency', but fear of the unknown was probably my main influence even though a successful outcome was very probable. In the future during such occurrences I will try my best to remain calm and in control (not go along for the ride) and work with ATC in a professional way. I am sure I would say 'emergency' again if I thought it necessary. I found the controllers eager to help and very cooperative but I wonder why they would have vectored me further away to an airport with a shorter runway.

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Original NASA ASRS Text

Title: HDG DEV OFF COURSE, THEN VIBRATION FROM ENG. PRECAUTIONARY LNDG.

Narrative: DEPARTED N54 (LANGHORNE, PA) ON IFR FLT PLAN TO ALB. WAS INSTRUCTED BY PHL APCH TO CLB TO 6000 FT DIRECT ALLENTOWN. I GOT ON THE 157 DEG RADIAL (337 HDG) AND LOCKED ON AUTOPLT. ACFT SHORTLY THEREAFTER (STILL IN CLB) STARTED TURNING TO R. HOWEVER, VOR NEEDLE STAYED CENTERED. I TUNED SECOND VOR AND GOT SAME RESULTS. BY THE TIME I GOT TO 030 DEG HDG I KNEW SOMETHING WAS WRONG BUT THE NEEDLES WERE STILL CENTERED. AT THAT TIME PHL APCH ASKED MY HDG. I RESPONDED THAT I WAS ON 337 RADIAL OF ALLENTOWN (DOUBLE WRONG ANSWER -- I WAS ON 157 RADIAL AND HE ASKED HDG). CTLR (ANGRILY) RESPONDED -- ANSWER MY QUESTION! SAY HDG. I SAID 010 DEG (I HAD TURNED BACK, VOR NEEDLES WERE NOW SHOWING R OF COURSE). HE SAID I HAD TURNED AWAY FROM ALLENTOWN AND 'FLY HDG 330 DEG' WHICH I DID. VOR REFLECTED MAX OF 3 DOTS DEV. I HAVE NOT BEEN ABLE TO DUPLICATE THIS PROBLEM ON SUBSEQUENT FLTS. I ATTRIBUTE IT TO AUTOPLT ANOMALY. VIGILANCE OF INSTS IS IMPORTANT AT ALL TIMES. I PROBABLY WAS 30 SECONDS - 1 MIN SLOW IN CORRECTING THE HDG DUE TO CONFLICT OF READINGS. A FEW MINS LATER, HAVING BEEN HANDED OFF TO ALLENTOWN APCH AND CLRED FROM 6000 TO 7000 FT MY ENG GOT A SUDDEN VIBRATION. MY ENG INSTS WERE NOT SHOWING A PROBLEM (NORMAL FUEL FLOW, OIL TEMP, OIL PRESSURE, RPM, MANIFOLD PRESSURE -- WHICH WAS 25 INCHES AT THE TIME). A REDUCTION IN PWR STOPPED THE VIBRATION. I ADVISED CTLR THAT I HAD A VIBRATION AND MUST GET DOWN IMMEDIATELY ALTHOUGH I CURRENTLY HAD PARTIAL PWR. I ENRICHED MIXTURE, INCREASED RPM, AND FLEW VECTOR TO QUAKERTOWN ARPT WHICH HE GAVE AS 8 MI AWAY. HE ASKED IF THIS WAS EMER AND I SAID YES. I HAD BECOME CONCERNED THAT NOT KNOWING THE CAUSE OF THE PROBLEM COULD RESULT IN A WORSE PROBLEM BEFORE REACHING THE ARPT. I CONCENTRATED ON FLYING THE VECTOR AND MONITORING THE INSTS. WHEN NOTIFIED THAT I WAS STILL SEVERAL (POSSIBLY 5 OR LESS) MI FROM THE ARPT, I NOTICED THAT I WAS FLYING OVER AN ARPT WITH FIXED DISTANCE MARKINGS WHICH WAS PROBABLY NOT QUAKERTOWN. I ASKED THE CTLR ABOUT IT. HE RESPONDED PENNRIDGE. I SAID I WANTED TO LAND THERE. HE SAID OK AND CALLED PENNRIDGE ON TELEPHONE. I MADE SUCCESSFUL LNDG -- END OF EMER. A MECH WAS AVAILABLE AND WORKED ON MY PROBLEM. IT WAS DETERMINED THAT 1 FUEL INJECTOR HAD CLOGGED CAUSING THE VIBRATION. THIS MECH AND OTHERS HAVE SAID TO ME THERE WAS NOTHING I COULD HAVE DONE TO PREVENT IT, AND THE VIBRATING WOULD HAVE BECOME WORSE OVER TIME DUE TO OVER-RICHNESS ON OTHER 5 CYLINDERS. ALLENTOWN FSDO REQUESTED AN M AND D RPT FROM THE MECH WHICH HE WILL SUPPLY. IN RETROSPECT, IT MIGHT HAVE BEEN PREMATURE TO GO ALL THE WAY AND SAY 'EMER', BUT FEAR OF THE UNKNOWN WAS PROBABLY MY MAIN INFLUENCE EVEN THOUGH A SUCCESSFUL OUTCOME WAS VERY PROBABLE. IN THE FUTURE DURING SUCH OCCURRENCES I WILL TRY MY BEST TO REMAIN CALM AND IN CTL (NOT GO ALONG FOR THE RIDE) AND WORK WITH ATC IN A PROFESSIONAL WAY. I AM SURE I WOULD SAY 'EMER' AGAIN IF I THOUGHT IT NECESSARY. I FOUND THE CTLRS EAGER TO HELP AND VERY COOPERATIVE BUT I WONDER WHY THEY WOULD HAVE VECTORED ME FURTHER AWAY TO AN ARPT WITH A SHORTER RWY.

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.