Narrative:

I launched a 50' x 100' banner from the airport. Before this launch; I had talked to other banner tow pilots; who had towed signs of this size; under the same conditions; with the same make and model aircraft; with the same horsepower and had no trouble. The aircraft was a cessna 305C; also called an L-19 birddog with 213 horsepower; a very capable banner towing aircraft. In the past; I have towed a 40' x 120' sign; with this aircraft; several times in humid; 85 degree weather. I believed I would have no trouble towing this 50' sign. Just in case a problem arose at the launch; I set up the sign with over 3500 feet of grass area in front of the launch site; I could drop the banner safely on the airport property. The launch went well and I found the aircraft climbing at about 200-300 feet per minute. The engine was developing full power and all looked fine. I circled the airport several times and climbed to about 1000 AGL with no problems. I then headed east with the sign. I encountered several up drafts and down drafts that would make the aircraft climb about 100-200 feet and descend about 100-200 feet at the rate of about 100 feet per minute. This was normal in towing a banner; so I wasn't concerned. When I reached the intended viewing area I encountered an extremely strong downdraft that made the aircraft descend; at the rate of over 500 feet per minute; from about 1000 AGL to about 600 AGL in less than a minute. I made the decision that if things continued at this rate; I could not climb out of the strong downdraft; the banner would drag through the trees or hit something on the ground and I might crash the aircraft. I decided the best course of action would be to drop the banner now in a safe location; rather than let it hit something where I could not control the outcome. I looked ahead and saw a golf course and then looked just off my left wing and saw a large; field made up of about 6 soccer fields with no one in the field. I turned to the left and dropped the sign as close to the middle of the field as I could. The aircraft began to climb and I turned back to see the banner land in the middle of the field. Having over 20 years experience in banner towing; my main concern was for the people on the ground and the safe operation of the aircraft. I think this was the best decision for a safe outcome.

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Original NASA ASRS Text

Title: C305 banner tow pilot reports dropping his banner in a soccer field when aircraft began to loose altitude due to high temperatures and down drafts.

Narrative: I launched a 50' x 100' banner from the airport. Before this launch; I had talked to other banner tow pilots; who had towed signs of this size; under the same conditions; with the same make and model aircraft; with the same horsepower and had no trouble. The aircraft was a Cessna 305C; also called an L-19 Birddog with 213 horsepower; a very capable banner towing aircraft. In the past; I have towed a 40' x 120' sign; with this aircraft; several times in humid; 85 degree weather. I believed I would have no trouble towing this 50' sign. Just in case a problem arose at the launch; I set up the sign with over 3500 feet of grass area in front of the launch site; I could drop the banner safely on the airport property. The launch went well and I found the aircraft climbing at about 200-300 feet per minute. The engine was developing full power and all looked fine. I circled the airport several times and climbed to about 1000 AGL with no problems. I then headed east with the sign. I encountered several up drafts and down drafts that would make the aircraft climb about 100-200 feet and descend about 100-200 feet at the rate of about 100 feet per minute. This was normal in towing a banner; so I wasn't concerned. When I reached the intended viewing area I encountered an extremely strong downdraft that made the aircraft descend; at the rate of over 500 feet per minute; from about 1000 AGL to about 600 AGL in less than a minute. I made the decision that if things continued at this rate; I could not climb out of the strong downdraft; the banner would drag through the trees or hit something on the ground and I might crash the aircraft. I decided the best course of action would be to drop the banner now in a safe location; rather than let it hit something where I could not control the outcome. I looked ahead and saw a golf course and then looked just off my left wing and saw a large; field made up of about 6 soccer fields with no one in the field. I turned to the left and dropped the sign as close to the middle of the field as I could. The aircraft began to climb and I turned back to see the banner land in the middle of the field. Having over 20 years experience in banner towing; my main concern was for the people on the ground and the safe operation of the aircraft. I think this was the best decision for a safe outcome.

Data retrieved from NASA's ASRS site as of April 2012 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.