Narrative:

Taking off runway 13L at bfi at 50 ft I noticed a slight vibration. I leaned the mixture slightly and it smoothed out. Continuing my climb at 300 ft the engine began to run rough and sputter. Continuing to climb straight ahead I called the tower and requested an immediate return to the runway. I did not at this time specify which runway because I intended to climb for as long as I could first. Probably from the sound of my voice the tower told a B767 on final for runway 13R to 'go around for an emergency in the area.' I did not declare an emergency but I'm sure the tower could hear the fear in my voice. The engine continued to produce some power and at approximately 500 ft I began a left crosswind turn to avoid the B767 on the right and told the tower I would land on runway 13L. The tower told me I was cleared to land on any runway (they said this twice) and I responded that I would land on runway 13R (the long runway). I landed without incident (further) and upon request, I was cleared to taxi to parking, where a police officer took my name and address. I thanked the tower, the fire department and the police for their quick action and state of readiness. Because of everyone's professionalism further problems did not arise. Everyone in my opinion did what they needed to do.

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Original NASA ASRS Text

Title: SMA ACFT ON INITIAL CLB. RPTR PLT FELT VIBRATION AND ROUGH RUNNING ENG AND REQUESTED AN IMMEDIATE RETURN TO ARPT. THOUGH RPTR DIDN'T DECLARE AN EMER, THE TWR DID FOR HER.

Narrative: TAKING OFF RWY 13L AT BFI AT 50 FT I NOTICED A SLIGHT VIBRATION. I LEANED THE MIXTURE SLIGHTLY AND IT SMOOTHED OUT. CONTINUING MY CLB AT 300 FT THE ENG BEGAN TO RUN ROUGH AND SPUTTER. CONTINUING TO CLB STRAIGHT AHEAD I CALLED THE TWR AND REQUESTED AN IMMEDIATE RETURN TO THE RWY. I DID NOT AT THIS TIME SPECIFY WHICH RWY BECAUSE I INTENDED TO CLB FOR AS LONG AS I COULD FIRST. PROBABLY FROM THE SOUND OF MY VOICE THE TWR TOLD A B767 ON FINAL FOR RWY 13R TO 'GAR FOR AN EMER IN THE AREA.' I DID NOT DECLARE AN EMER BUT I'M SURE THE TWR COULD HEAR THE FEAR IN MY VOICE. THE ENG CONTINUED TO PRODUCE SOME PWR AND AT APPROX 500 FT I BEGAN A L XWIND TURN TO AVOID THE B767 ON THE R AND TOLD THE TWR I WOULD LAND ON RWY 13L. THE TWR TOLD ME I WAS CLRED TO LAND ON ANY RWY (THEY SAID THIS TWICE) AND I RESPONDED THAT I WOULD LAND ON RWY 13R (THE LONG RWY). I LANDED WITHOUT INCIDENT (FURTHER) AND UPON REQUEST, I WAS CLRED TO TAXI TO PARKING, WHERE A POLICE OFFICER TOOK MY NAME AND ADDRESS. I THANKED THE TWR, THE FIRE DEPT AND THE POLICE FOR THEIR QUICK ACTION AND STATE OF READINESS. BECAUSE OF EVERYONE'S PROFESSIONALISM FURTHER PROBS DID NOT ARISE. EVERYONE IN MY OPINION DID WHAT THEY NEEDED TO DO.

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.