Narrative:

I was cleared to land on runway 35. The tower requested that I vacate the runway as soon as possible because traffic was on final for runway 17. I observed the traffic coming toward me and left the runway. I considered this situation to be somewhat inconvenient, as well as unusual. After dropping off a passenger I contacted clearance for departure instructions, then ground control. Following the airport chart in my manual I taxied toward runway 17 to the runup area. Tower cleared me for takeoff at this time. My right seat passenger (a pilot for 25 yrs--both military and civil) and I commented that a short field takeoff would be necessary due to traffic at the other end. In light of the landing situation, my right seat passenger and I assumed this was PAR for the course in phl. The entire takeoff roll also included keeping an eye on the jet landing on runway 27R. At wilmington I was given a message to call phl approach, which I did immediately. I was asked if I knew that I took off from the taxiway (U) next to runway 17, which was reported to the tower by an light transport. I told the tower that I (as well as my passenger) were totally unaware. Upon analyzing how this error occurred, the following mitigating circumstances came into play. The taxiway area was not clearly marked from the runup area. The actual runway was not visible from the runup area. Why didn't the tower stop my takeoff roll? Why did the light transport pilot see it first? In light of my landing on runway 35 with opposing traffic landing next in sequence on 17, my takeoff error was not evident.

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Original NASA ASRS Text

Title: GA SMA MADE TKOF ON TXWY U INSTEAD OF RWY 17 AS CLEARED.

Narrative: I WAS CLRED TO LAND ON RWY 35. THE TWR REQUESTED THAT I VACATE THE RWY ASAP BECAUSE TFC WAS ON FINAL FOR RWY 17. I OBSERVED THE TFC COMING TOWARD ME AND LEFT THE RWY. I CONSIDERED THIS SITUATION TO BE SOMEWHAT INCONVENIENT, AS WELL AS UNUSUAL. AFTER DROPPING OFF A PAX I CONTACTED CLRNC FOR DEP INSTRUCTIONS, THEN GND CTL. FOLLOWING THE ARPT CHART IN MY MANUAL I TAXIED TOWARD RWY 17 TO THE RUNUP AREA. TWR CLRED ME FOR TKOF AT THIS TIME. MY RIGHT SEAT PAX (A PLT FOR 25 YRS--BOTH MIL AND CIVIL) AND I COMMENTED THAT A SHORT FIELD TKOF WOULD BE NECESSARY DUE TO TFC AT THE OTHER END. IN LIGHT OF THE LNDG SITUATION, MY RIGHT SEAT PAX AND I ASSUMED THIS WAS PAR FOR THE COURSE IN PHL. THE ENTIRE TKOF ROLL ALSO INCLUDED KEEPING AN EYE ON THE JET LNDG ON RWY 27R. AT WILMINGTON I WAS GIVEN A MESSAGE TO CALL PHL APCH, WHICH I DID IMMEDIATELY. I WAS ASKED IF I KNEW THAT I TOOK OFF FROM THE TXWY (U) NEXT TO RWY 17, WHICH WAS RPTED TO THE TWR BY AN LTT. I TOLD THE TWR THAT I (AS WELL AS MY PAX) WERE TOTALLY UNAWARE. UPON ANALYZING HOW THIS ERROR OCCURRED, THE FOLLOWING MITIGATING CIRCUMSTANCES CAME INTO PLAY. THE TXWY AREA WAS NOT CLEARLY MARKED FROM THE RUNUP AREA. THE ACTUAL RWY WAS NOT VISIBLE FROM THE RUNUP AREA. WHY DIDN'T THE TWR STOP MY TKOF ROLL? WHY DID THE LTT PLT SEE IT FIRST? IN LIGHT OF MY LNDG ON RWY 35 WITH OPPOSING TFC LNDG NEXT IN SEQUENCE ON 17, MY TKOF ERROR WAS NOT EVIDENT.

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.