Narrative:

I was flying an small aircraft in pao's traffic pattern, right-hand traffic for runway 30 with the option, except stop and goes. After my 3RD touch and go the engine began to run rough at about 400' AGL. I informed the tower that I was experiencing engine trouble and wanted to land as soon as possible. I was cleared to land on any runway. I informed the tower I would land on runway 12. During my right-hand turn from upwind to downwind heading I switched fuel tanks. Engine operation continued to be rough but I was able to make runway 12 with little difficulty. After landing I was able to taxi under normal power to the planes tie-down. During taxi I heard ground control direct the airport vehicle to my position to obtain my name, address and certificate number because I had declared an emergency. To the best of my knowledge I never used the term 'emergency, mayday' or any other phrase indicating a declaration of emergency. After securing the aircraft I went up to the tower to thank the controllers for their assistance. I was then informed that I was instructed to make a full stop landing during my last approach so ATC could clear departing aircraft for takeoff. I never copied this transmission and to the best of my knowledge never acknowledged this instruction. The cause of the engine malfunction has not yet been determined. It should be noted that there was 3 or 4 aircraft in the pattern and it was necessary for an small aircraft Y to abort his approach to allow a safe landing of my plane. In the future it will be necessary for me to confirm the type of landing when in the pattern in addition to the standard 'cleared to land' clearance.

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Original NASA ASRS Text

Title: GA SMA HAD ENGINE PROBLEM MAKING TOUCH AND GOES AT PAO.

Narrative: I WAS FLYING AN SMA IN PAO'S TFC PATTERN, RIGHT-HAND TFC FOR RWY 30 WITH THE OPTION, EXCEPT STOP AND GOES. AFTER MY 3RD TOUCH AND GO THE ENGINE BEGAN TO RUN ROUGH AT ABOUT 400' AGL. I INFORMED THE TWR THAT I WAS EXPERIENCING ENGINE TROUBLE AND WANTED TO LAND AS SOON AS POSSIBLE. I WAS CLRED TO LAND ON ANY RWY. I INFORMED THE TWR I WOULD LAND ON RWY 12. DURING MY RIGHT-HAND TURN FROM UPWIND TO DOWNWIND HDG I SWITCHED FUEL TANKS. ENGINE OPERATION CONTINUED TO BE ROUGH BUT I WAS ABLE TO MAKE RWY 12 WITH LITTLE DIFFICULTY. AFTER LNDG I WAS ABLE TO TAXI UNDER NORMAL POWER TO THE PLANES TIE-DOWN. DURING TAXI I HEARD GND CTL DIRECT THE ARPT VEHICLE TO MY POSITION TO OBTAIN MY NAME, ADDRESS AND CERTIFICATE NUMBER BECAUSE I HAD DECLARED AN EMER. TO THE BEST OF MY KNOWLEDGE I NEVER USED THE TERM 'EMER, MAYDAY' OR ANY OTHER PHRASE INDICATING A DECLARATION OF EMER. AFTER SECURING THE ACFT I WENT UP TO THE TWR TO THANK THE CTLRS FOR THEIR ASSISTANCE. I WAS THEN INFORMED THAT I WAS INSTRUCTED TO MAKE A FULL STOP LNDG DURING MY LAST APCH SO ATC COULD CLEAR DEPARTING ACFT FOR TKOF. I NEVER COPIED THIS XMISSION AND TO THE BEST OF MY KNOWLEDGE NEVER ACKNOWLEDGED THIS INSTRUCTION. THE CAUSE OF THE ENGINE MALFUNCTION HAS NOT YET BEEN DETERMINED. IT SHOULD BE NOTED THAT THERE WAS 3 OR 4 ACFT IN THE PATTERN AND IT WAS NECESSARY FOR AN SMA Y TO ABORT HIS APCH TO ALLOW A SAFE LNDG OF MY PLANE. IN THE FUTURE IT WILL BE NECESSARY FOR ME TO CONFIRM THE TYPE OF LNDG WHEN IN THE PATTERN IN ADDITION TO THE STANDARD 'CLRED TO LAND' CLRNC.

Data retrieved from NASA's ASRS site as of August 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.