What happened
On January 13, 2018, a Dauphin SA 365 N3 helicopter, registration VT-PWA, was performing an offshore mission for the Oil and Natural Gas Commission (ONGC). The flight departed from Juhu, bound for the NQO installation. During the cruise phase at approximately 3,000 feet, the aircraft failed to maintain its selected heading and entered a right bank.
As the aircraft drifted, the pilot flying experienced spatial disorientation due to hazy weather and a lack of a visible horizon. While the pilot flying attempted to manually stabilize the aircraft after disengting the autopilot, the pilot monitoring attempted to intervene to correct the excessive bank. This led to conflicting control inputs, causing the aircraft to enter an unusual attitude and plummet into the sea at high velocity. All seven people on board, including the two crew members and five passengers, sustained fatal injuries.
The investigation
AAIB India examined the wreckage, flight data recorder (FDR) readouts, and maintenance records. The investigation involved technical advisors from Airbus and Safran. Investigators analyzed the behavior of the Automatic Flight Control System (AFCS) and the maintenance history of the aircraft, which had recently undergone a 600-hour inspection and a test flight. The inquiry also reviewed the organizational safety management systems of both the operator, Pawan Hans Ltd., and the client, ONGC.
Findings
- The primary cause of the accident was the pilot flying's spatial disorientation during poor visibility, triggered by a known malfunction in the AFCS heading mode.
- The pilot flying failed to hand over control to the pilot monitoring despite the latter's attempts to correct the excessive bank.
- There was a lack of adherence to standard cockpit checklists and callout procedures.
- The AFCS heading mode was malfunctioning, a defect that had been observed during a recent test flight but was not officially documented or reported for rectification.
- Critical components had been cannibalized between aircraft, an unsafe maintenance practice.
- Inadequate weather information was provided to the crew, as the visibility and cloud base beyond 25NM were unknown at takeoff.
Safety action
- The operator must implement a more robust Safety Management System (SMS) to proactively identify hazards and encourage the reporting of technical snags.
- Maintenance procedures must be improved to prevent the unsafe practice of component cannibalization.
- Flight crew training should emphasize Crew Resource Management (CRM), specifically regarding assertiveness and adherence to Standard Operating Procedures (SOPs).
- Procedures for obtaining and transmitting accurate meteorological data to flight crews must be established.