What happened
On July 6, 1995, at approximately 12:45 local time, a Bell BH-206B helicopter, registration PT-HKJ, operated by Riana Táxi Aéreo, experienced an engine failure while flying near Ji-Paraná, Rondônia. The mission involved transporting technicians from the United Nations Development Programme (UNDP) to observe indigenous and extractive reserves in the region.
The flight originated in Porto Velho, with an initial plan to fly via Guajará-Mirim to Ji-Paraná. During the flight, the pilot performed a landing to refuel using 50 liters of reserve fuel carried in the baggage compartment. Following this refueling, the engine ceased operation as the aircraft approached its final destination. The pilot attempted an emergency landing in a cultivated field, but the aircraft struck trees and the ground, resulting in the total loss of the aircraft.
During the impact, the floor of the aircraft fractured, causing the seatbelts of the pilot and two passengers to detach. These occupants were thrown from the cabin and sustained serious injuries. One passenger, who was not wearing a seatbelt while filming the flight, was thrown from the aircraft and sustained fatal injuries.
The investigation
CENIPA investigators examined the engine components, finding that the compressor and combustion chamber were rotating freely without signs of foreign object ingestion or internal technical damage; any observed damage was consistent with the impact. The investigation focused on two primary hypotheses regarding the engine failure: either a loose electrical terminal on a booster pump caused the failure by increasing unusable fuel, or the engine failed due to fuel exhaustion.
Investigators noted that the aircraft was operating at the very limits of its fuel autonomy. While the pilot reported 10 gallons remaining on the fuel gauge, calculations suggested that the flight duration and consumption rates left almost no margin for error. Additionally, a terminal bolt on the main wire of one of the booster pumps was found to be improperly secured, though it was unclear if this occurred during flight or upon impact.
Findings
- Deficient planning: The flight was conducted at the extreme limits of the aircraft's fuel autonomy, representing an error in flight preparation and fuel calculations.
- Deficient supervision: Inadequate oversight was identified regarding maintenance practices, specifically concerning the improper securing of the booster pump terminal.
- The aircraft was within weight and balance limits, and the engine damage was determined to be a result of the impact rather than a pre-existing mechanical failure.
Safety action
- The Brazilian Department of Civil Aviation (DAC) was directed to conduct a special flight safety inspection of the Riana Táxi Aéreo maintenance sector.
- The operator was instructed to implement procedures to ensure effective maintenance supervision and to disseminate the findings of this accident to all crew members, emphasizing the risks of deficient flight planning.