What happened
On December 8, 1998, an Aeroboero AB-115, registration PP-GEA, was conducting a flight instruction check mission near Porto Alegre, Brazil. The flight, operated by Aeroclube do Rio Grande do Sul, involved an instructor and a student pilot. After completing several maneuvers, the crew attempted to return to the Belém Novo aerodrome when they noticed a significant loss of engine power.
During the emergency, the instructor remained focused on troubleshooting the engine and allowed the student to maintain control of the aircraft. As the engine power continued to diminish, the aircraft lost airspeed. The instructor eventually took control to perform an emergency landing in a wooded area near Bairro Lami. During the descent, the aircraft entered a stall, causing the right wing to strike a tree before the aircraft collided with a fence post. The impact resulted in two serious injuries to the crew and the total loss of the aircraft.
The investigation
CENIPA investigators examined the engine and the aircraft's maintenance history. Technical analysis by the Centro Técnico Aeroespacial determined that the engine itself was not responsible for the crash, though evidence of carbonization on four spark plugs was found. Investigators concluded that a deficiency in the fuel mixture distribution likely caused the gradual loss of power.
Regarding the human factors, the investigation focused on the instructor's decision-making. While the instructor was highly qualified, the investigation found that delegating control to the student during an active emergency compromised situational awareness. The student, attempting to maintain altitude, inadvertently allowed the airspeed to decay, leading to the stall.
Findings
- Excessive confidence in the student pilot led the instructor to delegate aircraft control during an engine power loss event.
- Deficient cockpit coordination and task sharing resulted in the student pilot managing a high workload, which led to a loss of airspeed.
- Inadequate emergency planning contributed to the lack of a pre-determined safe landing site once the power loss was identified.
- A deficiency in fuel mixture distribution caused the gradual loss of engine power.
- The flight school's flight safety doctrine at the time was primarily focused on maintenance rather than pilot and instructor operational safety.