Narrative:

I was cleared to taxi from the FBO to runway 10L at pdx via the outer taxiway (alpha). I was almost to the departure end of the runway when I felt the right wing dip sharply. I thought I had a flat tire or damaged gear strut and was contemplating my course of action when the plane suddenly returned to a level condition. My passenger pointed out a widebody transport jet on the adjacent ramp which we had just passed behind. It had been pushed back to the edge of the ramp, perpendicular to the taxiway. I would estimate the distance from the tail of the jet to the taxiway as 200-300'. The jet was apparently using breakaway thrust just as I passed behind it.

Google
 

Original NASA ASRS Text

Title: PLT OF SMA TAXIING ON TXWY ADJACENT TO TKOF RWY ENCOUNTERED JET BLAST CREATED BY WDB STARTING TKOF ON RWY.

Narrative: I WAS CLRED TO TAXI FROM THE FBO TO RWY 10L AT PDX VIA THE OUTER TXWY (ALPHA). I WAS ALMOST TO THE DEP END OF THE RWY WHEN I FELT THE RIGHT WING DIP SHARPLY. I THOUGHT I HAD A FLAT TIRE OR DAMAGED GEAR STRUT AND WAS CONTEMPLATING MY COURSE OF ACTION WHEN THE PLANE SUDDENLY RETURNED TO A LEVEL CONDITION. MY PAX POINTED OUT A WDB JET ON THE ADJACENT RAMP WHICH WE HAD JUST PASSED BEHIND. IT HAD BEEN PUSHED BACK TO THE EDGE OF THE RAMP, PERPENDICULAR TO THE TXWY. I WOULD ESTIMATE THE DISTANCE FROM THE TAIL OF THE JET TO THE TXWY AS 200-300'. THE JET WAS APPARENTLY USING BREAKAWAY THRUST JUST AS I PASSED BEHIND IT.

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.