What happened
On January 23, 1999, a Cessna 170B, registration PT-AUM, was conducting an aerial advertising flight (banner towing) near Rio de Janeiro when the pilot noticed smoke entering the cockpit. The smoke originated from the engine, which subsequently suffered an explosion.
During the emergency, the pilot initiated a turn toward the beach rather than toward the sea, as established by standard emergency procedures for banner towing. Due to the loss of power and insufficient altitude to clear the breaking waves, the pilot opted to land on the sand of Leblon Beach. During the landing, the aircraft struck the sand, causing the landing gear to collapse and the plane to settle on its back. The towed banner failed to release during flight and struck two people on the beach, resulting in one serious injury and one minor injury. The pilot escaped the wreckage uninjured.
The investigation
CENIPA's investigation focused on the mechanical failure and the operational decisions made during the emergency. Investigators examined the engine and found that cylinder number 3 had ruptured, with fragments found inside the crankcase. The investigation also revealed that several other cylinders showed signs of corrosion.
Furthermore, the investigation scrutinized the maintenance history and organizational oversight. It was noted that the aircraft's maintenance was inadequate, evidenced by the presence of corrosion and the use of an automotive battery instead of an aviation-grade battery. The investigation also found that the operator, Space Publicidade Aerea Ltda, lacked a formal training and operational oversight program specifically for banner towing operations.
Findings
- Engine Failure: The primary cause of the engine failure was the rupture and explosion of cylinder number 3, driven by defective maintenance that allowed corrosion to compromise the engine components.
- Operational Deviations: The pilot failed to follow established emergency procedures by turning toward the populated beach instead of the sea, which maximized the risk to third parties on the ground.
- Organizational Deficiencies: The operator lacked a structured training and monitoring program for banner towing, leading to a lack of proficiency in emergency handling and a disregard for safety norms.
- Maintenance Oversight: Inadequate maintenance practices and a lack of company supervision allowed the use of improper parts and unaddressed engine corrosion.