What happened
On March 24, 2015, an AW139 helicopter, registration PR-SEO, was performing an offshore transport flight from Macaé Aerodrome (SBME) to platforms in Campos Bay, Brazil. The aircraft was carrying two crewmembers and nine passengers. Approximately ten minutes into the flight, while cruising at 4,000 feet and a speed of 13/0 KIAS, the emergency window on the copilot's side unexpectedly detached from the airframe. The crew immediately initiated a return to the origin aerodrome and landed safely without further incident. There were no injuries to the crew or passengers, though the aircraft sustained minor damage.
The investigation
CENIPA investigators examined the maintenance records and the physical condition of the window frame. The investigation revealed that a recent maintenance task involving the replacement of the cockpit door windows had been performed just two days prior to the incident. Field inspections identified a layer of primer remaining on the window frame and evidence that the sealant (Adhesive RTV 732) had not fully cured at the time of the flight.
Furthermore, the investigation found that the maintenance team was working with a Temporary Maintenance Instruction (TMI) obtained informally from another operator rather than through the company's official database. The investigation also noted that the mechanic responsible for the task lacked specific training on the AW139 and was not proficient in English, which hindered the ability to correctly interpret the technical instructions. The time taken to complete the task—approximately two hours per window—was significantly lower than the industry average of four hours, suggesting the work was rushed and improperly executed.
Findings
- Inadequate maintenance: The window installation was performed incorrectly due to a failure to follow the specific requirements of the TMI, specifically regarding the removal of paint/primer from the window frame edges.
- Improper sealant application: The sealant used in the installation had not fully vulcanized/cured before the aircraft returned to service.
- Training deficiencies: The maintenance personnel, including the mechanic, inspector, and supervisor, lacked specific training on the TMI and the AW139 model.
- Organizational failures: The operator's management failed to ensure that updated technical publications were available at the Macaé base and did not provide necessary English language training or specialized technical oversight.