Bay City, MI, USA
N796AB
Piper PA18
The commercial pilot had completed one banner tow flight and was dropping the banner and picking up a second banner when the accident occurred. The operator reported that the pilot could not recall the events of the accident; however, witnesses saw the pilot conduct the banner drop from about 250 ft above ground level. After dropping the banner at an idle or nearly idle engine power setting, the airplane pitched up and abruptly banked left, impacting the ground about 180° from its previous heading. The operator suggested that the pilot's attention may have been diverted following the drop, and while operating at a low engine power setting, the airplane slowed and experienced an aerodynamic stall. The operator reported no preimpact mechanical malfunctions or failures with the airframe, engine, banner, or the tow equipment that would have precluded normal operation. It is likely that the pilot failed to maintain adequate airspeed during the banner drop and pick-up procedure and exceeded the airplane's critical angle of attack. This resulted in an aerodynamic stall and subsequent loss of control at an altitude that precluded recovery.
On July 6, 2019, about 2038 eastern daylight time, a Piper PA-18-150, N796AB, sustained substantial damage when it was involved in an accident near Bay City, Michigan. The commercial pilot sustained serious injuries. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 banner tow flight. After the completion of the three-hour flight, the pilot was scheduled for a half hour banner tow flight before ceasing flight activities for the day. After successfully dropping the banner and preparing to pickup another banner stationed on the ground by the runway, the operator reported the airplane remained level to slightly nose up. The pilot never added power and the airplane was observed to pitch up and abruptly bank to the left. Witnesses reported hearing the pilot apply full power during the loss of control sequence. The airplane impacted the ground in a direction 180° from the direction of flight. The airplane was not connected to a banner at the time of the accident. For the commencing pickup operation, the banner, the tow rope, and the tow hook were all connected and staged properly in the drop zone. The operator stated that the airplane "slowed to a[n] airspeed to slow to sustain controlled flight and a stall crash followed." The operator reported that due to the pilot's injuries, he was unable to recall the events of the accident flight. The operator further reported the pilot conducted the banner drop without adding any or enough power to sustain controlled flight and that after the banner was released from the airplane, the pilot's attention was diverted for unknown reasons. The airplane sustained substantial damage to the fuselage, both wings, and the empennage. The operator reported no preimpact mechanical malfunctions or failures with the airframe, the engine, the banner, and the tow equipment that would have precluded normal operation. The airplane was equipped with vortex generators mounted on the wings just aft of the leading edge and on the underside of the horizontal stabilizer via Micro AeroDynamics Supplemental Type Certificate SA00530SE. The airplane was not equipped with a stall warning system or an angle of attack indicator, nor was it required to be. The Federal Aviation Administration (FAA) publication Information for Banner Towing Operations FS-I-8700-1, discusses the banner pickup procedure, and states in part: Stalls during the banner pickup procedure constitute one of the more frequent causes of banner towing operational accidents. A stall occurs when an airfoil reaches a critical angle of attack and is a function of wing loading, independent of airspeed. This document further suggests procedures for the banner drop procedures and states that upon reaching the drop zone, the minimum airspeed should be 1.2 times the stall speed of the airplane. For the banner pickup process, this document states that the airplane's approach speed toward and through the pickup poles should be 1.6 times the airplane's stall speed. The operator's checklist states that for the banner drop procedure to maintain 60-70 mph while flying into the wind. For the banner pickup process, this document states to have an approach speed of 80 mph while flying into the wind. Air America Aerial Ads, LLC, is a banner tow and aerial advertising operator based in Genoa, Ohio, and operates in conjunction with the FAA-issued Certificate of Waiver J550 Banner Towing Operations. The company conducts banner tow operations throughout the country using various single-engine airplanes.
The pilot's failure to maintain airspeed and his exceedance of the airplane's critical angle of attack during a banner drop and pickup, which resulted in an aerodynamic stall and a subsequent loss of control.
Source: NTSB Aviation Accident Database
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