Narrative:

CFI (myself) was making takeoff for currency. As we taxied up #2 for takeoff behind an air carrier (fokker F100), I called ready to go. Tower queried air carrier if he was ready, but he told tower they were waiting for weight and balance information. We waited a couple of mins and I told tower I could back taxi for intersection takeoff. Shortly thereafter, aircraft called ready and tower cleared him for takeoff. We got a position and hold, then cleared for takeoff shortly thereafter. I planned takeoff on upwind side of runway (about 500 ft right quarter half way) and liftoff before F100 rotation point to avoid wake. As we started takeoff roll, tower cautioned about wake turbulence. I lifted off, climbed steeply, and about 1/2 way down runway decided to turn out early to our assigned heading of 320 degrees to make sure I avoided wake turbulence. I had about 500 ft AGL and went between passenger terminal and tower (about 1/2 mi between). Before our takeoff, tower had been talking to other landing traffic and I think had cleared them to land, so I had hurried takeoff to get out of the way (ie, get off quickly). That traffic was apparently a couple of mi out and perhaps on a wide downwind/base, and asked tower where departing traffic was. Tower advised him that his traffic had turned a bit early, so I wondered if tower was upset I had turned early without advising. Tower never said any more, but I felt perhaps I should have called prior to turn since I didn't go to departure end of runway before turn. It was a quick judgement call, and I didn't ask first due to concentrating on takeoff. I didn't want a 4 min delay for wake turbulence after waiting behind F100 to get his weight and balance data and figured his wake would drift and settle. Tower apparently didn't see a problem either, except for a slightly delayed wake turbulence warning. No dangerous stuff really occurred in this case, and a simple call on my part would have prevented the issue arising.

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Original NASA ASRS Text

Title: A C172 PLT MADE A PREMATURE TURNOUT CONTRARY TO NORMAL ARPT PROCS.

Narrative: CFI (MYSELF) WAS MAKING TKOF FOR CURRENCY. AS WE TAXIED UP #2 FOR TKOF BEHIND AN ACR (FOKKER F100), I CALLED READY TO GO. TWR QUERIED ACR IF HE WAS READY, BUT HE TOLD TWR THEY WERE WAITING FOR WT AND BAL INFO. WE WAITED A COUPLE OF MINS AND I TOLD TWR I COULD BACK TAXI FOR INTXN TKOF. SHORTLY THEREAFTER, ACFT CALLED READY AND TWR CLRED HIM FOR TKOF. WE GOT A POS AND HOLD, THEN CLRED FOR TKOF SHORTLY THEREAFTER. I PLANNED TKOF ON UPWIND SIDE OF RWY (ABOUT 500 FT R QUARTER HALF WAY) AND LIFTOFF BEFORE F100 ROTATION POINT TO AVOID WAKE. AS WE STARTED TKOF ROLL, TWR CAUTIONED ABOUT WAKE TURB. I LIFTED OFF, CLBED STEEPLY, AND ABOUT 1/2 WAY DOWN RWY DECIDED TO TURN OUT EARLY TO OUR ASSIGNED HDG OF 320 DEGS TO MAKE SURE I AVOIDED WAKE TURB. I HAD ABOUT 500 FT AGL AND WENT BTWN PAX TERMINAL AND TWR (ABOUT 1/2 MI BTWN). BEFORE OUR TKOF, TWR HAD BEEN TALKING TO OTHER LNDG TFC AND I THINK HAD CLRED THEM TO LAND, SO I HAD HURRIED TKOF TO GET OUT OF THE WAY (IE, GET OFF QUICKLY). THAT TFC WAS APPARENTLY A COUPLE OF MI OUT AND PERHAPS ON A WIDE DOWNWIND/BASE, AND ASKED TWR WHERE DEPARTING TFC WAS. TWR ADVISED HIM THAT HIS TFC HAD TURNED A BIT EARLY, SO I WONDERED IF TWR WAS UPSET I HAD TURNED EARLY WITHOUT ADVISING. TWR NEVER SAID ANY MORE, BUT I FELT PERHAPS I SHOULD HAVE CALLED PRIOR TO TURN SINCE I DIDN'T GO TO DEP END OF RWY BEFORE TURN. IT WAS A QUICK JUDGEMENT CALL, AND I DIDN'T ASK FIRST DUE TO CONCENTRATING ON TKOF. I DIDN'T WANT A 4 MIN DELAY FOR WAKE TURB AFTER WAITING BEHIND F100 TO GET HIS WT AND BAL DATA AND FIGURED HIS WAKE WOULD DRIFT AND SETTLE. TWR APPARENTLY DIDN'T SEE A PROB EITHER, EXCEPT FOR A SLIGHTLY DELAYED WAKE TURB WARNING. NO DANGEROUS STUFF REALLY OCCURRED IN THIS CASE, AND A SIMPLE CALL ON MY PART WOULD HAVE PREVENTED THE ISSUE ARISING.

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.