Narrative:

After takeoff and climbing to 2;100 ft; the tower transferred us to departure. Departure told us to turn to a heading of 180 degrees and climb to an altitude of 5;000 ft. While passing through approximately 4;000 to 4;200 ft; departure called traffic at 12 o'clock; a B747 crossing right to left; descending to 6;000 ft and advised us on possible wake turbulence. At this point; I was still hand flying the plane. I slowed my ascent and pulled back the power slightly. I thought that if I were more than 1;500 below the crossing B747; we would cross under the wake. I did not believe that the wake would descend at a rate that would affect our flight. The TCAS indicated that the B747 was still descending at the point where we would cross. I estimate the crossing to be a 90 degree intercept. As we passed under the path of the B747; our altitude was about 4;600 ft. It was then that our plane entered one sudden and severe downward push. There was no roll movement. Before and after the wake encounter; we were in smooth air. I called ATC and told them we encountered wake turbulence and that we were slowing to check the aircraft. The plane responded normally to all inputs and the engine gauges also indicated no problems. I asked my co-pilot to check our one passenger within approximately 15 seconds of the encounter. The passenger said that he bumped his head but he was ok. I believe that our aircraft hit the bottom of the wake turbulence since we were only pushed down. There was no roll or upward movement.

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Original NASA ASRS Text

Title: PC-12 Captain reported encountering wake turbulence during climb from a B747 crossing their path about 1;500 FT above them.

Narrative: After takeoff and climbing to 2;100 FT; the Tower transferred us to Departure. Departure told us to turn to a heading of 180 degrees and climb to an altitude of 5;000 FT. While passing through approximately 4;000 to 4;200 FT; Departure called traffic at 12 o'clock; a B747 crossing right to left; descending to 6;000 FT and advised us on possible wake turbulence. At this point; I was still hand flying the plane. I slowed my ascent and pulled back the power slightly. I thought that if I were more than 1;500 below the crossing B747; we would cross under the wake. I did not believe that the wake would descend at a rate that would affect our flight. The TCAS indicated that the B747 was still descending at the point where we would cross. I estimate the crossing to be a 90 degree intercept. As we passed under the path of the B747; our altitude was about 4;600 FT. It was then that our plane entered one sudden and severe downward push. There was no roll movement. Before and after the wake encounter; we were in smooth air. I called ATC and told them we encountered wake turbulence and that we were slowing to check the aircraft. The plane responded normally to all inputs and the engine gauges also indicated no problems. I asked my co-pilot to check our one passenger within approximately 15 seconds of the encounter. The passenger said that he bumped his head but he was ok. I believe that our aircraft hit the bottom of the wake turbulence since we were only pushed down. There was no roll or upward movement.

Data retrieved from NASA's ASRS site 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.