Narrative:

I am 1 of 2 owners of a 1978 baron E55 XXXX. On 04/sat/02, I departed ZZZ on an IFR flight. After I leveled off at 8000 ft, my low thrust indicator light and horn came on for the left engine, and I was concerned that I was losing power (only partially) in the left engine. I think I was talking to ZZZ center at the time. I was IMC and turbulence was moderate. With the threat of losing power in the left engine, I told center that I was experiencing partial loss of power in the left engine and requested vectors to an airport close by. The controller vectored me to ZZZ1. I did not declare an emergency. After descending to about 5000 ft, the low thrust indicator light and horn that had been on to that point stopped (the light went off and the horn silenced). Simultaneously, it felt as though I had full power back in the left engine. Nonetheless, I landed at ZZZ1 and was surprised to be met by an emergency vehicle (airport fire truck). Since it was saturday, the local maintenance shop was closed, but I called the owner and described what I had experienced. He recommended that I pull the propeller through on the left engine and ascertain if 1 or more of the 6 cylinders felt different. I did that and felt nothing was amiss. He also recommended that I restart and run up the engines. When I tried to restart the batteries were still weak (I had an APU start at ZZZ and I did not have enough battery power to restart the engines. Since it was getting late in the afternoon and the WX was questionable, I called my law firm's full-time professional pilot and had him fly from ZZZ2 and get me. I left the baron at ZZZ1 to be checked out and to have new batteries installed. On 04/thu/02, I directed our law firm pilot to take someone qualified to fly the baron, make sure it was proper and legal to fly, and to fly the baron home. They flew to ZZZ1 in the morning. WX was severely VFR. Firm pilot and mr X who flew the baron back to ZZZ2 started both engines and ran them up. They shut the engines down and talked with the a&P who opened that a 'slug of oil' had momentarily clogged the spark plugs causing a momentary partial los of power. The a&P assured both pilots that the plane was airworthy and that there was nothing else to do. The a&P made no logbook entry other than for the 2 new batteries, and the baron was restarted and took off. The baron XXXX flew home flawlessly. On apr/fri/02, I received a phone call from a ZZZ2 FAA representative stating that I violated an far by allowing the baron to depart ZZZ without having a proper logbook entry made by the a&P. When I called the owner of the shop, he told me there was nothing for the a&P to enter in the logbook because nothing was wrong with the engine.

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Original NASA ASRS Text

Title: A BEECH 55 AT 8000 FT DIVERTS DUE TO PARTIAL LOSS OF PWR ON THE L ENG BUT MAKES NO LOGBOOK ENTRY ON ENG PERFORMANCE.

Narrative: I AM 1 OF 2 OWNERS OF A 1978 BARON E55 XXXX. ON 04/SAT/02, I DEPARTED ZZZ ON AN IFR FLT. AFTER I LEVELED OFF AT 8000 FT, MY LOW THRUST INDICATOR LIGHT AND HORN CAME ON FOR THE L ENG, AND I WAS CONCERNED THAT I WAS LOSING PWR (ONLY PARTIALLY) IN THE L ENG. I THINK I WAS TALKING TO ZZZ CTR AT THE TIME. I WAS IMC AND TURB WAS MODERATE. WITH THE THREAT OF LOSING PWR IN THE L ENG, I TOLD CTR THAT I WAS EXPERIENCING PARTIAL LOSS OF PWR IN THE L ENG AND REQUESTED VECTORS TO AN ARPT CLOSE BY. THE CTLR VECTORED ME TO ZZZ1. I DID NOT DECLARE AN EMER. AFTER DSNDING TO ABOUT 5000 FT, THE LOW THRUST INDICATOR LIGHT AND HORN THAT HAD BEEN ON TO THAT POINT STOPPED (THE LIGHT WENT OFF AND THE HORN SILENCED). SIMULTANEOUSLY, IT FELT AS THOUGH I HAD FULL PWR BACK IN THE L ENG. NONETHELESS, I LANDED AT ZZZ1 AND WAS SURPRISED TO BE MET BY AN EMER VEHICLE (ARPT FIRE TRUCK). SINCE IT WAS SATURDAY, THE LCL MAINT SHOP WAS CLOSED, BUT I CALLED THE OWNER AND DESCRIBED WHAT I HAD EXPERIENCED. HE RECOMMENDED THAT I PULL THE PROP THROUGH ON THE L ENG AND ASCERTAIN IF 1 OR MORE OF THE 6 CYLINDERS FELT DIFFERENT. I DID THAT AND FELT NOTHING WAS AMISS. HE ALSO RECOMMENDED THAT I RESTART AND RUN UP THE ENGS. WHEN I TRIED TO RESTART THE BATTERIES WERE STILL WEAK (I HAD AN APU START AT ZZZ AND I DID NOT HAVE ENOUGH BATTERY PWR TO RESTART THE ENGS. SINCE IT WAS GETTING LATE IN THE AFTERNOON AND THE WX WAS QUESTIONABLE, I CALLED MY LAW FIRM'S FULL-TIME PROFESSIONAL PLT AND HAD HIM FLY FROM ZZZ2 AND GET ME. I LEFT THE BARON AT ZZZ1 TO BE CHKED OUT AND TO HAVE NEW BATTERIES INSTALLED. ON 04/THU/02, I DIRECTED OUR LAW FIRM PLT TO TAKE SOMEONE QUALIFIED TO FLY THE BARON, MAKE SURE IT WAS PROPER AND LEGAL TO FLY, AND TO FLY THE BARON HOME. THEY FLEW TO ZZZ1 IN THE MORNING. WX WAS SEVERELY VFR. FIRM PLT AND MR X WHO FLEW THE BARON BACK TO ZZZ2 STARTED BOTH ENGS AND RAN THEM UP. THEY SHUT THE ENGS DOWN AND TALKED WITH THE A&P WHO OPENED THAT A 'SLUG OF OIL' HAD MOMENTARILY CLOGGED THE SPARK PLUGS CAUSING A MOMENTARY PARTIAL LOS OF PWR. THE A&P ASSURED BOTH PLTS THAT THE PLANE WAS AIRWORTHY AND THAT THERE WAS NOTHING ELSE TO DO. THE A&P MADE NO LOGBOOK ENTRY OTHER THAN FOR THE 2 NEW BATTERIES, AND THE BARON WAS RESTARTED AND TOOK OFF. THE BARON XXXX FLEW HOME FLAWLESSLY. ON APR/FRI/02, I RECEIVED A PHONE CALL FROM A ZZZ2 FAA REPRESENTATIVE STATING THAT I VIOLATED AN FAR BY ALLOWING THE BARON TO DEPART ZZZ WITHOUT HAVING A PROPER LOGBOOK ENTRY MADE BY THE A&P. WHEN I CALLED THE OWNER OF THE SHOP, HE TOLD ME THERE WAS NOTHING FOR THE A&P TO ENTER IN THE LOGBOOK BECAUSE NOTHING WAS WRONG WITH THE ENG.

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.