Piper PA 25-235 N4519Y accident near Northglenn, Colorado

Probable cause

The pilot's decision to operate the banner-tow flight below the minimum safe altitude specified by federal regulation, which likely limited his ability to recover from a potential loss of airspeed due to a gusting wind condition. Also causal was the pilot’s delayed decision to release the banner, which allowed the airplane to exceed its critical angle-of-attack and resulted in an aerodynamic stall/spin from which he was unable to recover.

NTSB analysis

The pilot reported that the purpose of the banner-tow flight was to tow an advertisement billboard over a ballpark. He stated that, despite the engine operating normally, the airplane had little to no climb performance as he flew southbound toward the ballpark; therefore, he decided to make a 180-degree turn and return to the departure airport. He released the banner after the airplane developed an excessive descent rate during the turn. The pilot reported that he was unable to recover sufficient airspeed after releasing the banner and that the airplane encountered an aerodynamic stall/spin at a low altitude. The airplane then descended, inverted, into a house where a postimpact fire ensued. A postaccident examination of the airplane revealed no preimpact mechanical failures or malfunctions that would have precluded normal operation. At the time of the accident, the low-level surface winds were from the south between 5 and 10 knots with gusts reaching 20 to 30 knots.

A review of radar track data confirmed that the accident airplane flew over a congested area at altitudes below 1,000 ft above ground level (agl). The final portion of the accident flight included an S-turn maneuver below 500 ft agl. According to radar data, during the S-turn, the airplane flew within 1,000 ft laterally and 200 ft vertically of the pilot's personal residence. Additionally, radar data revealed that the pilot made a tight 360-degree turn near his residence, between 600 and 700 ft agl, during another recent banner-tow flight. Based on the available radar evidence, the pilot, on at least two occasions, flew below the minimum safe altitude required by federal regulation 91.119(b), which prohibited operating an airplane, over a congested area, at an altitude below 1,000 ft above the highest obstacle within a horizontal radius of 2,000 ft.

The pilot's intentional flight below the required minimum safe altitude likely limited his ability to recover from a potential loss of airspeed due to a gusting wind condition during the banner-tow flight. Additionally, his delayed decision to release the banner allowed the airplane to exceed its critical angle-of-attack, which resulted in an aerodynamic stall/spin from which he was unable to recover.

Text from the NTSB. Open the NTSB docket for CEN14FA230 for the full record.