What happened
On August 30, 2015, a Cessna 172H, registration CS-AHQ, was conducting a banner towing flight near Cascais, Portugal. The flight, operated by Aero Vip, was intended for training purposes, with the right-seat pilot undergoing qualification for banner towing operations. After approximately 35 minutes of flight, while flying at 600 feet near Cova do Vapor, the crew identified abnormal noises and signs of power loss.
Following troubleshooting attempts that failed to restore power, the pilot decided to release the banner over the left shore of the Tagus River and maneuver toward a beach near the Trafaria silos. Shortly after releasing the banner, the engine suffered a complete failure following a loud impact. Due to the loss of energy and increased drag from the full flaps (40°) configuration, the pilot was unable to complete a 180-degree turn to reach the beach. Consequently, the pilot performed an emergency ditching in the river.
The investigation
The GPIAAF investigation focused on the mechanical failure and the circumstances of the ditching. The wreckage was recovered from the riverbed at a depth of approximately 25 meters. The investigation examined the engine components and the flight crew's actions during the emergency. The investigation also noted that the aircraft's components were found grouped together, and the aircraft had been submerged and moved by the river current before being located.
Findings
Technical analysis of the engine revealed that the crankshaft failure near cylinder #2 caused the #2 connecting rod to separate and displace, subsequently striking the engine case wall and causing the engine case to break. The investigation also found that the aircraft's impact with the water was consistent with a low-speed, near-level ditching with a left-wing-down tendency.
Regarding the crew, both pilots sustained minor injuries. The right-seat pilot was able to exit through the unlocked right door, while the left-seat pilot had to exit through a rear window, breaking the transparency in the process. Notably, the pilots were not wearing life jackets, nor were such devices available on board. The investigation also highlighted that significant deformation to the left wing root and fuel tank may have contributed to the difficulty the left-seat pilot faced when attempting to open his door.
Safety action
The operator has since implemented several risk mitigation measures for banner towing operations, including:
- Enhanced pre-flight inspections with a focus on fuel tank condensation.
- Mandatory use of safety vests.
- Implementation of ditching maneuvers within the training program.
- Procedures to maintain a safe distance from the coastline and attempt ditching near boats rather than beaches.