What happened
On November 24, 2015, at approximately 4:00 p.m., an Airbus AS350 BA helicopter, registration N-355RH, was performing a private flight from Toussaint Louverture International Airport in Haiti to Santo Domingo's Dr. Joaquin Balaguer International Airport. While en route, the aircraft experienced engine malfunctions that forced the pilot to perform an emergency landing in a banana plantation in Hatillo, Azula, Dominican Republic.
The impact was high-energy, with the aircraft descending vertically into the terrain. Despite the severity of the impact, the pilot and the three passengers were uninjured and were able to evacuate the aircraft on their own. The helicopter sustained significant damage, including a partially detached tail boom, broken landing skids, a deformed nose, a broken lower windshield, and damage to the main rotor blade.
The investigation
The CIAA investigation focused on the mechanical condition of the Arriel 1B engine and the maintenance history of the aircraft. Physical inspections of the wreckage and a subsequent teardown of the engine at the manufacturer's facility (SAFRAN) in Dallas, Texas, revealed critical internal failures.
Investigators found that the engine's power control lever was improperly adjusted, causing the engine to operate consistently above normal parameters. This resulted in advanced, progressive deterioration caused by excessive operating temperatures. Specifically, the engine's temperature sensors (thermocouples) showed signs of heat damage, and the exhaust cone featured multiple perforations and impacts caused by debris from within the engine. Furthermore, the magnetic particle detectors were found to be heavily laden with metallic particles.
Findings
- The engine suffered from advanced internal deterioration due to prolonged operation at excessively high temperatures.
- Maintenance failures were a primary contributing factor, as the operator failed to perform required borescope inspections of the first-stage turbine. While a technical concession allowed for extended intervals, the required inspection had been overdue by 783 hours.
- There was no evidence that the operator had complied with Mandatory Service Bulletin #A292 72 0809 regarding the second-stage turbine wheel.
- The engine was operating outside of standard parameters due to an improper setting on the power control lever.