Narrative:

Flight taxied via taxiway C to runway 10L; intersection right. WX was moderate rain requiring use of windshield wipers for taxi. Pavement and markings were partially obscured by standing water. Upon receiving takeoff clearance; line-up checklist was completed and flight followed green taxiway centerline lights through 135 degree turn on taxiway right onto runway 10L. At end of taxiway centerline lights; yellow taxi line was no longer visible due to darkness and water on pavement. Pilot aligned aircraft with what appeared to be runway centerline lights and held in position. Upon receiving takeoff clearance; final engine checks (underspeed governor; hp limiters; nts check valve) were completed and takeoff roll commenced. At approximately 30-40 KTS; pilot heard a 'clunk' from left side of aircraft and aborted takeoff. Aircraft remained under control throughout with no perception of swerving and no abnormal engine sounds or vibrations. Aircraft was taxied back to ramp via txwys K and C. Inspection showed scratch marks on aft surface of one blade of #1 (left) propeller. No other damage was found. Sfo airport operations found one edge light on left edge of runway 10L broken; but advised pilot that it may have been broken prior to this event. Airport operations also found metallic debris unrelated to the broken light near the center of runway 10L at approximately the same location. Inspection revealed that this debris did not come from our aircraft. It is inconclusive whether the propeller strike was on a runway edge light or on debris near the center of the runway. After discussion with maintenance; the aircraft was flown back to its home base without incident. Contributing factors: while general area visibility was adequate; visibility immediately around the aircraft was compromised by rain. In particular; rain on the windshield and side windows impaired visibility. The pilot's side windshield wiper was relatively ineffective. Much of the pavement presented a 'black hole' appearance due to reflections and standing water obscuring taxi lines and other markings. While I was convinced that I had lined up the aircraft on the runway centerline; it is possible that I inadvertently lined up on the left edge lights; believing them to be the runway centerline lights due to reduced visibility through the rain-covered windshield. It is also possible that I lined up between the left edge and centerline; believing the centerline lights to be the right edge lights. In addition; I feel that the optical illusion caused by rain beginning to flow diagonally upward on the windshield at the beginning of the takeoff roll may have contributed to this incident; if; in fact; the propeller strike was on an edge light rather than on runway debris.

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Original NASA ASRS Text

Title: BE90 AT SFO IN MODERATE RAIN ABORTS TKOF AFTER A 'CLUNK' IS HEARD FROM THE L SIDE OF ACFT.

Narrative: FLT TAXIED VIA TXWY C TO RWY 10L; INTXN R. WX WAS MODERATE RAIN REQUIRING USE OF WINDSHIELD WIPERS FOR TAXI. PAVEMENT AND MARKINGS WERE PARTIALLY OBSCURED BY STANDING WATER. UPON RECEIVING TKOF CLRNC; LINE-UP CHKLIST WAS COMPLETED AND FLT FOLLOWED GREEN TXWY CTRLINE LIGHTS THROUGH 135 DEG TURN ON TXWY R ONTO RWY 10L. AT END OF TXWY CTRLINE LIGHTS; YELLOW TAXI LINE WAS NO LONGER VISIBLE DUE TO DARKNESS AND WATER ON PAVEMENT. PLT ALIGNED ACFT WITH WHAT APPEARED TO BE RWY CTRLINE LIGHTS AND HELD IN POS. UPON RECEIVING TKOF CLRNC; FINAL ENG CHKS (UNDERSPEED GOVERNOR; HP LIMITERS; NTS CHK VALVE) WERE COMPLETED AND TKOF ROLL COMMENCED. AT APPROX 30-40 KTS; PLT HEARD A 'CLUNK' FROM L SIDE OF ACFT AND ABORTED TKOF. ACFT REMAINED UNDER CTL THROUGHOUT WITH NO PERCEPTION OF SWERVING AND NO ABNORMAL ENG SOUNDS OR VIBRATIONS. ACFT WAS TAXIED BACK TO RAMP VIA TXWYS K AND C. INSPECTION SHOWED SCRATCH MARKS ON AFT SURFACE OF ONE BLADE OF #1 (L) PROP. NO OTHER DAMAGE WAS FOUND. SFO ARPT OPS FOUND ONE EDGE LIGHT ON L EDGE OF RWY 10L BROKEN; BUT ADVISED PLT THAT IT MAY HAVE BEEN BROKEN PRIOR TO THIS EVENT. ARPT OPS ALSO FOUND METALLIC DEBRIS UNRELATED TO THE BROKEN LIGHT NEAR THE CTR OF RWY 10L AT APPROX THE SAME LOCATION. INSPECTION REVEALED THAT THIS DEBRIS DID NOT COME FROM OUR ACFT. IT IS INCONCLUSIVE WHETHER THE PROP STRIKE WAS ON A RWY EDGE LIGHT OR ON DEBRIS NEAR THE CTR OF THE RWY. AFTER DISCUSSION WITH MAINT; THE ACFT WAS FLOWN BACK TO ITS HOME BASE WITHOUT INCIDENT. CONTRIBUTING FACTORS: WHILE GENERAL AREA VISIBILITY WAS ADEQUATE; VISIBILITY IMMEDIATELY AROUND THE ACFT WAS COMPROMISED BY RAIN. IN PARTICULAR; RAIN ON THE WINDSHIELD AND SIDE WINDOWS IMPAIRED VISIBILITY. THE PLT'S SIDE WINDSHIELD WIPER WAS RELATIVELY INEFFECTIVE. MUCH OF THE PAVEMENT PRESENTED A 'BLACK HOLE' APPEARANCE DUE TO REFLECTIONS AND STANDING WATER OBSCURING TAXI LINES AND OTHER MARKINGS. WHILE I WAS CONVINCED THAT I HAD LINED UP THE ACFT ON THE RWY CTRLINE; IT IS POSSIBLE THAT I INADVERTENTLY LINED UP ON THE L EDGE LIGHTS; BELIEVING THEM TO BE THE RWY CTRLINE LIGHTS DUE TO REDUCED VISIBILITY THROUGH THE RAIN-COVERED WINDSHIELD. IT IS ALSO POSSIBLE THAT I LINED UP BTWN THE L EDGE AND CTRLINE; BELIEVING THE CTRLINE LIGHTS TO BE THE R EDGE LIGHTS. IN ADDITION; I FEEL THAT THE OPTICAL ILLUSION CAUSED BY RAIN BEGINNING TO FLOW DIAGONALLY UPWARD ON THE WINDSHIELD AT THE BEGINNING OF THE TKOF ROLL MAY HAVE CONTRIBUTED TO THIS INCIDENT; IF; IN FACT; THE PROP STRIKE WAS ON AN EDGE LIGHT RATHER THAN ON RWY DEBRIS.

Data retrieved from NASA's ASRS site as of January 2009 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.