Narrative:

Had iad ATIS information, XA51Z, wind 310 degrees 12 mi, visibility 10 mi, 3900 ft scattered, ceiling 6000 ft broken, temperature 1 degree, dewpoint 7 degrees, altimeter 30.04, departing runway 1L or runway 30, windshear advisories. I had taxied for departure runway 30. After reporting ready, I was cleared to taxi into position and hold runway 30. At the time there was a B777 on short final runway 1L. The extended centerline of runway 1L crosses the centerline of runway 30 approximately 1250 ft from the southeast end of runway 30, about 1000 ft along the runway from where I was lined up, and that crossing point is about 1/2 mi from the gp touchdown point on runway 1L. On gp, the B777 would have been about 150 ft AGL and that checked visually. As the B777 crossed the centerline of runway 30 I received a clearance for takeoff. I cannot remember whether or not tower issued a wake turbulence caution, but I was perfectly aware of the probability of its presence in any case. With the prevailing wind and the fact that runway 30 is some 10000 ft long, I elected to roll relatively slowly along the runway to a point where I considered wake turbulence would no longer be a factor before applying takeoff power. I applied limited power, probably less than 2000 RPM and started to move along runway 30. After having proceeded perhaps 500 ft, not more, and having noticed the airspeed indicator still not registering any speed, I was surprised to find myself airborne, fortunately wings level. I quickly added a little more power, still intent on not taking off just yet, and was able to control the aircraft to a wings level soft touchdown perhaps 5 seconds later. I estimate I had reached a ht of about 10 ft above the runway. There was continuous buffeting throughout this time. But I was more intent on controling the aircraft with reference to the ground than noticing airspeed, so I never did see any airspeed registered on the airspeed indicator. I have concluded that this premature liftoff was due to a combination of the prevailing 12 KT headwind together with the outflowing wake vortex as it reached the ground combining to create a local wind in excess of that required for flight in this aircraft. I consider that my normal recovery from the premature liftoff was probably attributable to the wake vortex flowing almost perpendicularly to the centerline of runway 1L, ie, straight down runway 30. I telephoned the dulles tower watch supervisor shortly afterwards to advise him of this event. He stated that as far as he was aware, this hazard had not been recognized previously, but he would initiate steps to have the problem brought to the notice of the procedures designers and other controllers. The potential for a much less satisfactory ending to this event is obvious. Fortunately all factors involved had presented themselves in a very convenient manner. This type of event could well happen to any small aircraft even parked in the vicinity of the flight path of heavy aircraft, and could well present the pilot of that small aircraft with a total surprise. Awareness of the hazard is the only remedy. Remaining well clear of the descending wake of heavy aircraft is the only safe solution. Perhaps the use of runway 30 by small aircraft when heavy aircraft are landing on runway 1L is to be avoided. Perhaps this restr should be extended to any runway confign where this situation could occur.

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Original NASA ASRS Text

Title: PLT OF PA28R-201 IS CLRED FOR TKOF AS A B777 COMPLETES APCH AND LNDG ON A RWY OF WHICH THE FLT PATH CROSSES OVER THAT OF THE RPTR'S DEPARTING RWY. RPTR SLOWLY ADVANCES PWR TO MOVE FORWARD BEYOND THE POINT OF POSSIBLE WAKE TURB BUT FINDS HIMSELF UNEXPECTEDLY AIRBORNE.

Narrative: HAD IAD ATIS INFO, XA51Z, WIND 310 DEGS 12 MI, VISIBILITY 10 MI, 3900 FT SCATTERED, CEILING 6000 FT BROKEN, TEMP 1 DEG, DEWPOINT 7 DEGS, ALTIMETER 30.04, DEPARTING RWY 1L OR RWY 30, WINDSHEAR ADVISORIES. I HAD TAXIED FOR DEP RWY 30. AFTER RPTING READY, I WAS CLRED TO TAXI INTO POS AND HOLD RWY 30. AT THE TIME THERE WAS A B777 ON SHORT FINAL RWY 1L. THE EXTENDED CTRLINE OF RWY 1L CROSSES THE CTRLINE OF RWY 30 APPROX 1250 FT FROM THE SE END OF RWY 30, ABOUT 1000 FT ALONG THE RWY FROM WHERE I WAS LINED UP, AND THAT XING POINT IS ABOUT 1/2 MI FROM THE GP TOUCHDOWN POINT ON RWY 1L. ON GP, THE B777 WOULD HAVE BEEN ABOUT 150 FT AGL AND THAT CHKED VISUALLY. AS THE B777 CROSSED THE CTRLINE OF RWY 30 I RECEIVED A CLRNC FOR TKOF. I CANNOT REMEMBER WHETHER OR NOT TWR ISSUED A WAKE TURB CAUTION, BUT I WAS PERFECTLY AWARE OF THE PROBABILITY OF ITS PRESENCE IN ANY CASE. WITH THE PREVAILING WIND AND THE FACT THAT RWY 30 IS SOME 10000 FT LONG, I ELECTED TO ROLL RELATIVELY SLOWLY ALONG THE RWY TO A POINT WHERE I CONSIDERED WAKE TURB WOULD NO LONGER BE A FACTOR BEFORE APPLYING TKOF PWR. I APPLIED LIMITED PWR, PROBABLY LESS THAN 2000 RPM AND STARTED TO MOVE ALONG RWY 30. AFTER HAVING PROCEEDED PERHAPS 500 FT, NOT MORE, AND HAVING NOTICED THE AIRSPD INDICATOR STILL NOT REGISTERING ANY SPD, I WAS SURPRISED TO FIND MYSELF AIRBORNE, FORTUNATELY WINGS LEVEL. I QUICKLY ADDED A LITTLE MORE PWR, STILL INTENT ON NOT TAKING OFF JUST YET, AND WAS ABLE TO CTL THE ACFT TO A WINGS LEVEL SOFT TOUCHDOWN PERHAPS 5 SECONDS LATER. I ESTIMATE I HAD REACHED A HT OF ABOUT 10 FT ABOVE THE RWY. THERE WAS CONTINUOUS BUFFETING THROUGHOUT THIS TIME. BUT I WAS MORE INTENT ON CTLING THE ACFT WITH REF TO THE GND THAN NOTICING AIRSPD, SO I NEVER DID SEE ANY AIRSPD REGISTERED ON THE AIRSPD INDICATOR. I HAVE CONCLUDED THAT THIS PREMATURE LIFTOFF WAS DUE TO A COMBINATION OF THE PREVAILING 12 KT HEADWIND TOGETHER WITH THE OUTFLOWING WAKE VORTEX AS IT REACHED THE GND COMBINING TO CREATE A LCL WIND IN EXCESS OF THAT REQUIRED FOR FLT IN THIS ACFT. I CONSIDER THAT MY NORMAL RECOVERY FROM THE PREMATURE LIFTOFF WAS PROBABLY ATTRIBUTABLE TO THE WAKE VORTEX FLOWING ALMOST PERPENDICULARLY TO THE CTRLINE OF RWY 1L, IE, STRAIGHT DOWN RWY 30. I TELEPHONED THE DULLES TWR WATCH SUPVR SHORTLY AFTERWARDS TO ADVISE HIM OF THIS EVENT. HE STATED THAT AS FAR AS HE WAS AWARE, THIS HAZARD HAD NOT BEEN RECOGNIZED PREVIOUSLY, BUT HE WOULD INITIATE STEPS TO HAVE THE PROB BROUGHT TO THE NOTICE OF THE PROCS DESIGNERS AND OTHER CTLRS. THE POTENTIAL FOR A MUCH LESS SATISFACTORY ENDING TO THIS EVENT IS OBVIOUS. FORTUNATELY ALL FACTORS INVOLVED HAD PRESENTED THEMSELVES IN A VERY CONVENIENT MANNER. THIS TYPE OF EVENT COULD WELL HAPPEN TO ANY SMALL ACFT EVEN PARKED IN THE VICINITY OF THE FLT PATH OF HVY ACFT, AND COULD WELL PRESENT THE PLT OF THAT SMALL ACFT WITH A TOTAL SURPRISE. AWARENESS OF THE HAZARD IS THE ONLY REMEDY. REMAINING WELL CLR OF THE DSNDING WAKE OF HVY ACFT IS THE ONLY SAFE SOLUTION. PERHAPS THE USE OF RWY 30 BY SMALL ACFT WHEN HVY ACFT ARE LNDG ON RWY 1L IS TO BE AVOIDED. PERHAPS THIS RESTR SHOULD BE EXTENDED TO ANY RWY CONFIGN WHERE THIS SIT COULD OCCUR.

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.