CFTT. LOW ALT CIVIL OP.

Narrative

PHOTO MISSION IN CONTACT WITH DAVIS MONTHAN AFB APCH CTL (TUS APCH) WHO CLRED ME TO MANEUVER FOR PHOTOS AT 5500 FT; THEN 4500 FT. I THEN ASKED FOR 1000 FT AGL (3500 FT MSL); FOR MY LOWER PHOTO. AFTER LEVELING OFF AT 3500 FT MSL; I SLOWED TO 80 MPH IAS FOR THE PHOTO RUN. WE MUST SLOW THE ACFT DOWN AS MUCH AS POSSIBLE FOR REDUCED BLURRING IN THE PHOTOS. THE ACFT BEGAN TO SETTLE RAPIDLY AND I ADDED APPROX 60 PERCENT PWR AT FIRST AND THEN WENT TO FULL PWR. BY THE TIME I HAD REESTABLISHED A CLB WE WERE DOWN TO APPROX 500 FT AGL OR 3000 FT MSL. I CALLED ATC TO RECHK THE ALTIMETER SETTING AND CONFIRMED THAT IT WAS CORRECT AT 30.01. ATC NEVER MENTIONED ANYTHING ABOUT THE LOW ALT AND I CONTINUED MY MISSION AT 3500 FT MSL AND DEPARTED FOR GYR. IN REVIEW I FEEL THE DOWNDRAFT WAS BOTH RARE AND UNEXPECTED. IN THE YRS THAT I HAVE BEEN MAKING THESE FLTS I HAVE NEVER ENCOUNTERED THIS DEG OF A PROB. THE DOWNDRAFT OCCURRED AT A VERY SLOW AND CRITICAL PORTION OF THE FLT WITH SLOW SPD AND MYSELF LOOKING OUTSIDE TO LINE UP THE RUN. IN THE FUTURE; I WILL MAINTAIN A HIGHER SPD FOR A LARGER MARGIN OF ERROR.