What happened
On February 3, 1975, at approximately 15:00 local time, a Piper PA-25-260 Spruce Strike (registration CS-AGD), operated by SANAGRI (Serviços Aéreos de Sanidade Agrícola), was conducting aerial pesticide application in the Freixo Redondo area, near Évora, Portugal. The aircraft was flying at very low altitude over an orchard containing holm oaks (azinheiras). During a pass, the pilot momentarily looked down to observe signals from a ground marker directing the operation. Upon looking back up, the pilot realized too late that the left wingtip had struck the upper branches of one of the taller trees. The pilot immediately banked right and pulled up to avoid further contact.
The aircraft sustained damage to the leading edge of the left wing and associated structural components. Despite the impact, the aircraft remained controllable. The pilot continued the flight to Evora Aerodrome, dumping the remaining pesticide load over uncultivated land as a precautionary measure before landing safely without further incident.
The investigation
The GPIAAF (Gabinete de Prevenção e Investigação de Acidentes com Aeronaves) investigated the incident following a report submitted by SANAGRI. The aircraft, registered CS-AGD, had 1,206.15 total flight hours, with 13 hours and 20 minutes since its last 50-hour inspection. The engine, a Lycoming O-540-G1A5, had 728.15 total hours. The pilot held a valid license and had logged 2,215 total flight hours, including 142 hours specifically in aerial spraying operations.
Meteorological conditions at the time included overcast skies with high clouds, light winds from the northwest, visibility of 20 km, and a temperature of 14°C. The aircraft was loaded with 1,293 kg of payload, which was within the center of gravity limits. Post-incident inspection by the repair facility ALAR in Tires confirmed partial damage to the left wing's leading edge (approximately 90 cm in length), six rib tips, six false ribs, and denting on the aileron trailing edge.
Findings
The investigation concluded that the primary cause was the pilot's momentary distraction while observing ground signals during low-altitude operations. The presence of trees within the operational zone required extraordinary attention, which was compromised by looking away from the flight path. Contributing factors included the specific nature of crop dusting over wooded terrain and the need for constant situational awareness.
The damage sustained did not critically impair the aircraft's airworthiness to the point of immediate failure, but it necessitated grounding for repairs. The GPIAAF noted that the aircraft was flown from the incident site to Tires for repair without prior inspection by DGAC experts, which was deemed irregular. The investigation recommended stricter adherence to post-incident inspection protocols and emphasized the need for rapid commission action in such cases to minimize operational disruptions.
Safety action
The GPIAAF issued recommendations urging that operators and pilots be warned against operating aircraft with unverified airworthiness status after an incident. It also recommended that inquiry commissions act more swiftly in future incidents to reduce prejudice to stakeholders.