What happened
On May 4, 2013, a Zenair 600 Zodiac ultralight, registration 26-ACS, was performing a banner towing operation at the Valence Chabeuil aerodrome. The pilot departed from an unpaved runway to tow a 60 m² banner. The banner was positioned ahead of the aircraft, fully deployed on the ground and connected to the aircraft by an 80-meter cable.
During the initial climb, the banner dragged through tall grass, which had not been mown for several weeks. This contact created significant drag, causing the aircraft to decelerate abruptly. The sudden loss of airspeed led to a stall, resulting in a collision with the ground. The aircraft sustained heavy damage.
The investigation
The investigation examined the takeoff technique, the airfield conditions, and the pilot's experience. The pilot utilized a method where the banner is attached prior to takeoff to minimize ground drag, requiring a specific pitch attitude during the climb to lift the banner off the surface. The pilot held a valid competency declaration for banner towing and had 1,000 total flight hours, including 500 hours on this specific type.
Investigators found that the airfield operator had not requested mowing for the runway, and no specific grass height threshold existed to trigger such a request. While the operator's manual included provisions for banner towing, it did not specify a particular takeoff procedure. The pilot noted that the takeoff was performed on the unpaved runway to avoid occupying the paved runway for an extended period and admitted to underestimating the impact of the grass height.
Findings
- The primary cause of the accident was the pilot's decision to perform the towing operation on a runway with tall grass.
- The pilot maintained an insufficient pitch attitude during the initial climb, which caused the banner to remain in contact with the vegetation.
- The high grass (exceeding 30 cm) created enough drag to cause a sudden deceleration and subsequent stall.