What happened
On October 15, 1997, an Aeroboero AB-115, registration PP-GPW, departed from Campo de Marte (SBMT) bound for Jundiaí (SDJD) for an instructional flight. The crew consisted of a student pilot in the rear nacelle and an instructor in the front nacelle. During the initial climb, the aircraft failed to exceed 200 feet in altitude and began to descend after crossing runway heading 12.
As the aircraft struggled to maintain altitude, the instructor took control and executed a left turn to avoid an obstacle (a hill) located ahead. Despite applying full power, the aircraft maintained a descent rate of 50 feet per minute. In an attempt to reduce drag and increase airspeed, the instructor retracted the flaps; however, this maneuver caused an immediate further reduction in lift and an increased rate of descent.
Attempting an emergency landing in the Tietê River, the aircraft struck a utility pole along the Marginal do Tietê highway, subsequently colliding with two vehicles (a Fiat Palio and a Volkswagen Kombi) before coming to rest against a roadside barrier. The aircraft sustained severe damage.
The investigation
CENIPA investigators examined the engine, which was found to be in normal operating condition with no mechanical abnormalities. The investigation focused on the environmental conditions at the time of takeoff. Meteorological data indicated a temperature of 36°C and an atmospheric pressure of 1008 hPa.
Post-accident flight tests with the same aircraft model demonstrated that under these specific high-temperature and low-pressure conditions, the Aeroboero AB-115 exhibits a significantly reduced climb gradient. Furthermore, the investigation noted that the terrain at Campo de Marte, specifically the area near runway 30, is subject to wind shifts and downdrafts caused by nearby hills. The investigation also reviewed the instructor's decision-making process regarding flap retraction and the psychological impact of the dual roles (student/instructor) being performed during the flight.