Small Aircraft
Flight Crew Commercial; Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Flight Instructor
Flight Crew Last 90 Days 94; Flight Crew Total 2143; Flight Crew Type 1210
Situational Awareness
Deviation / Discrepancy - Procedural FAR; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Weather / Turbulence
Flight Crew Became Reoriented
Human Factors; Weather
I have an aerial advertising company and was contracted to fly a total of 4 hour and 15 minute flight over a concert.  The FAA requirements are that aerial advertising aircraft are to be at a minimum of 1000 AGL while towing banners over populated areas.  There were continuous mild to moderate up and downdrafts over the venue area.  I was flying a 5 ft letter banner approximately 120 ft long.  Most of the time I was at 1100 to 1200 AGL to cushion any downdrafts that normally show up.  Probably 4 or 5 times in the 3 hours I was over the venue; I got into a moderate downdraft of 1000 feet per minute descent from a little more powerful downdraft and my initial power applications were not enough to stop the descent before dropping to 900 AGL.  I have a Garmin 496 GPS that has a very accurate Vertical Speed indicator that I use to detect downward vertical movement. Maybe two of those times I was also being directed by Approach Control to look for approaching aircraft that were in my general area and my attention was diverted for a little more outside time than my normal scan and I got a late start on the power application. Corrective actions would be to be a little more aggressive on power applications.  That being said we also have to consider the noise issues of the people we are flying circles around. The more power the more potential for complaints.  I will also try and be 50 to 100 ft higher to have a little more cushion on that 1000 ft minimum when we have the potential for stronger downdrafts.
Banner tow pilot reported operating below the FAR mandated floor of 1000 feet AGL while circling an outdoor event due to turbulence and downdrafts.