What happened
On January 13, 1995, at approximately 15:00, a Cessna 170, registration PT-AUD, was performing an aerial advertising mission, towing a banner along the southern coast of São Paulo. While maneuvering around the Ponta das Gadelhas area, the aircraft suddenly entered a rapid right-hand descending spiral.
Another aircraft from the same operator, PT-IER, was flying approximately 300 meters behind the Cessna 170 at an altitude of 300 feet. The pilot of the trailing aircraft observed the Cessna 170 drop its right wing and nose, exhibiting characteristics of a stall, before entering a spiral dive that ended in a 90-degree impact with the sea. The aircraft remained afloat for approximately two minutes before sinking. The pilot sustained one fatality and did not attempt to abandon the aircraft before it submerged.
The investigation
CENIPA investigators were unable to examine the wreckage due to the aircraft being submerged in deep, difficult-to-access waters. However, the investigation established that the aircraft's maintenance was up to date, with the last 50-hour inspection having been performed recently. Meteorological conditions at the time were satisfactory, with no restrictions on visibility or ceiling.
Investigators focused on two primary hypotheses: a sudden physiological incapacitation of the pilot or an operational error during the maneuver. The investigation noted that the pilot had experienced a traumatic brain injury in a car accident in December 1994. While the pilot held valid licenses and a medical certificate, no specific health evaluation had been conducted following that recent head trauma. Additionally, the investigation noted that the pilot lacked extensive experience in banner-towing operations, having only 71:50 hours in that specific mission type.
Findings
- Incapacitation or operational error: The sudden change in flight attitude following a medium-bank turn suggests either a sudden physiological event or an improper control input, such as a failure to adjust engine power, leading to a stall.
- Lack of experience: The pilot's limited experience in banner-towing maneuvers may have contributed to an inadequate response during the turn.
- Environmental stress: High cockpit temperatures and the nature of low-altitude, low-speed operations may have increased pilot stress.
- Survival factors: The pilot was not wearing a life jacket, and the aircraft's seat harness lacked shoulder straps, which likely contributed to head injuries during the impact.
Safety action
- The operator was advised to evaluate the use of life jackets for pilots operating over the sea and to establish operational procedures for maritime emergencies.
- Recommendations were made to alert operators and crews regarding the necessity of medical re-evaluations following significant health events or accidents.