On May 2, 1999, about 1430 eastern daylight time, a Piper PA-18A-150, N6894B, operated by High Exposure, Inc, on a banner towing flight, was substantially damaged while landing at Cross Keys Airport (17N), Cross Keys, New Jersey. The certificated commercial pilot and pilot rated passenger received minor injuries. Visual meteorological conditions prevailed for the flight which had departed from 17N about 1315. No flight plan had been filed for the flight that was conducted under 14 CFR Part 91. The pilot ran a banner towing business. He had contracted to perform a banner flight over Veterans Stadium, Philadelphia, during a Philadelphia Phillies baseball game. A trainee pilot in the rear seat was along for familiarization of banner towing. The pilot reported that the trainee pilot did not handle the flight controls. At the completion of the flight, the banner was dropped, and the airplane maneuvered to enter the traffic pattern for landing on Runway 9 at Cross Keys. The pilot reported that he observed the wind sock which indicated the winds were from 100 degrees, and the air was smooth. On the final approach, he used a speed of 80 MPH with one notch of flaps. The pilot also stated: "...Approximately 150 feet from the runway threshold, with the aircraft on a stabilized approach profile, the aircraft made a sudden and uncommanded RH [right hand] bank to 45 degrees, and a simultaneous abrupt descent. Immediate control inputs to counter the bank and descent had no response, and an immediate increase to full power also had no response. Upon realizing that RH wing impact was imminent, I cut the power. The RH wing struck the ground approximately 50 feet from the runway threshold and thereafter the plane came to rest 20 feet from the runway in an upright position, and just to the right of the runway centerline perpendicular to the runway...." The pilot reported that the fuselage was twisted, both wings were bent, the engine mounts were bent down, and the floor was buckled up. The pilot reported that he obtained a weather briefing in the morning. The Federal Aviation Administration Flight Standards District Office at Philadelphia was requested to obtain a copy of the briefing. However, the data was not requested and it was lost. Cross Keys did not have recorded weather. However, a check was made of several area airports including Wilmington, Delaware (ILG); Philadelphia, Pennsylvania (PHL); Northeast Philadelphia, Pennsylvania (PNE); Trenton, New Jersey (TTN); McGuire Air Force Base (WRI), Wrightstown, New Jersey; Atlantic City, New Jersey (ACY); and Millville, New Jersey (MIV). Between the hours of 0900 and 1500, the majority of observations had gusts. The basic winds ranged from a low of 11 knots to a high of 25 knots, with an average of 17 knots. The gusts ranged from a low of 19 knots to a high of 31 knots, with an average of 25 knots. The direction ranged from 030 to 090, with the preponderance from 050 through 070 degrees. The minimum difference between steady state winds and gusts ranged from 3 knots to 12 knots, with the average about 8.5 mph. The pilot reported that he conducted an earlier flight from Cross Keys with a 1030 departure. A check of the area airports revealed the weather at the 1030 departure was similar to the weather when the pilot departed Cross Keys at 1315, and when he returned at 1430. According to the Piper PA-18A-150 flight manual: "The gross weight power off stall speed with full flaps in the Super Cub 150 is 43 M.P.H.; with flaps up the stalling speed increases about 4 M.P.H."