Narrative:

Runway 16R cleared for immediate takeoff. On takeoff I noticed a substantial loss of power. Reaching 100' power was intermittent. I immediately advised tower that I was aborting departure and was cleared to enter a low downwind for runway 16R. All other traffic was vectored away by tower. I entered a close in downwind left hand pattern for 16R. I endeavored to gain altitude at each power surge and achieved a maximum of 300' AGL. I discovered that I was too close to the runway to turn final and I did not wish to extend my downwind, or otherwise go out of gliding distance from the airport. I obtained permission to land on runway 16L and did so west/O further incident. Upon parking in the transient area a ramp attendant advised me that fuel was leaking from the left side of my engine cowling. He turned the fuel draincock and the leaking stopped. The draincock was part of my walk around inspection. I had checked it, thought I closed it, and went on. Before takeoff I noticed no leaks either around the draincock or anywhere else. Apparently the draincock has a 'half open' position, from which it can vibrate fully open. If the draincock is not turned to the lockout position where a spring holds it closed, opening, leaking, and loss of fuel pressure is a definite possibility. There should be a placard warning of this or the draincock should be flush mounted. The other draincocks on this aircraft are of the flush mounted type.

Related reports:

Google
 

Original NASA ASRS Text

Title: PLT OF SMA DEPARTING SMF HAS POWER LOSS AND CIRCLES BACK TO LAND. PLT LATER DISCOVERED THAT FUEL DRAIN WAS NOT FULLY CLOSED.

Narrative: RWY 16R CLRED FOR IMMEDIATE TKOF. ON TKOF I NOTICED A SUBSTANTIAL LOSS OF PWR. REACHING 100' PWR WAS INTERMITTENT. I IMMEDIATELY ADVISED TWR THAT I WAS ABORTING DEP AND WAS CLRED TO ENTER A LOW DOWNWIND FOR RWY 16R. ALL OTHER TFC WAS VECTORED AWAY BY TWR. I ENTERED A CLOSE IN DOWNWIND L HAND PATTERN FOR 16R. I ENDEAVORED TO GAIN ALT AT EACH PWR SURGE AND ACHIEVED A MAX OF 300' AGL. I DISCOVERED THAT I WAS TOO CLOSE TO THE RWY TO TURN FINAL AND I DID NOT WISH TO EXTEND MY DOWNWIND, OR OTHERWISE GO OUT OF GLIDING DISTANCE FROM THE ARPT. I OBTAINED PERMISSION TO LAND ON RWY 16L AND DID SO W/O FURTHER INCIDENT. UPON PARKING IN THE TRANSIENT AREA A RAMP ATTENDANT ADVISED ME THAT FUEL WAS LEAKING FROM THE L SIDE OF MY ENG COWLING. HE TURNED THE FUEL DRAINCOCK AND THE LEAKING STOPPED. THE DRAINCOCK WAS PART OF MY WALK AROUND INSPECTION. I HAD CHKED IT, THOUGHT I CLOSED IT, AND WENT ON. BEFORE TKOF I NOTICED NO LEAKS EITHER AROUND THE DRAINCOCK OR ANYWHERE ELSE. APPARENTLY THE DRAINCOCK HAS A 'HALF OPEN' POS, FROM WHICH IT CAN VIBRATE FULLY OPEN. IF THE DRAINCOCK IS NOT TURNED TO THE LOCKOUT POS WHERE A SPRING HOLDS IT CLOSED, OPENING, LEAKING, AND LOSS OF FUEL PRESSURE IS A DEFINITE POSSIBILITY. THERE SHOULD BE A PLACARD WARNING OF THIS OR THE DRAINCOCK SHOULD BE FLUSH MOUNTED. THE OTHER DRAINCOCKS ON THIS ACFT ARE OF THE FLUSH MOUNTED TYPE.

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.