What happened
On May 7, 2021, an Adventure ultralight aircraft, registration PU-ATZ, was conducting an instructional flight from Atibaia Airport (SDTB) in Brazil. The flight, carrying an instructor and a student, included traffic pattern procedures at a nearby airfield before returning to the home base.
During a go-around maneuver at approximately 270 feet above the runway, the engine suddenly failed. The instructor took control of the aircraft and attempted an emergency landing on the BR 381 highway. Shortly before impact, the pilot attempted to maneuver the aircraft to avoid a box truck traveling on the road; however, the aircraft collided with the vehicle before striking the ground. The aircraft sustained substantial damage. The instructor sustained minor injuries, while the student was uninjured.
The investigation
CENIPA investigators examined the aircraft's maintenance records and the mechanical state of the ignition system. The investigation focused on the cause of the engine flameout and the flight profile during the go-around.
Investigators discovered that the aircraft had been washed with soap and water the previous day. The aircraft was equipped with an instructor-specific emergency ignition cutoff switch, intended to prevent student errors during engine starts. The investigation found that this switch lacked an effective seal or drainage system. Testing confirmed that contaminated water had entered the switch housing, creating an electrical path to the engine ground, which provided enough current to shut down the engine.
Findings
- The primary cause of the engine failure was water ingress into the emergency ignition cutoff switch, which created an electrical short.
- The design of the ignition switch did not provide adequate protection against moisture, humidity, or vibration.
- The operator's maintenance and cleaning instructions were not robust enough to prevent sensitive electrical components from being affected by water during cleaning.
- A lack of standardized procedures for go-around maneuvers and risk management for engine failures was noted.
- The flight profile—a low-altitude, level-flight pass followed by a go-around—reduced the aircraft's ability to regain altitude and return to the runway after the engine failure.