What happened
On August 4, 2015, a Dauphin N3 helicopter, registration VT-PHK, was performing a non-scheduled passenger flight from Khonsa to Longding in Arunachal Pradesh. After departing from Khonsa, the crew reported climbing to higher altitudes. However, the aircraft failed to arrive at its destination, and subsequent attempts by air traffic control to establish contact were unsuccessful.
Following an extensive search operation involving Indian Air Force helicopters and ground teams from the Assam Rifles, the wreckage was located six days later in a deep gorge approximately six nautical miles south of the Khonsa helipad. The impact and subsequent fire resulted in three fatalities, including the pilot, the co-pilot, and one passenger. The aircraft was completely destroyed.
The investigation
AAIB India's investigation focused on the flight path, meteorological conditions, and organizational oversight. Investigators examined the wreckage, which was found scattered across a steep terrain, and reviewed the flight history and crew qualifications.
The inquiry established that the helicopter was operating under Special VFR conditions. While the aircraft was climbing, the investigation looked into the possibility of the crew attempting an alternate route to navigate around inclement weather. The investigation also reviewed the maintenance records, noting the aircraft had undergone a major inspection shortly before the accident, and evaluated the training and supervision protocols within Pawan Hans Limited.
Findings
- The crew likely attempted to fly an alternate route to avoid bad weather, which led to spatial disorientation.
- Sunlight striking thick clouds created glare, further reducing visibility and causing the pilot to lose ground contact.
- The pilot failed to execute a necessary turn, resulting in the aircraft striking a hill at approximately 6,000 feet.
- A lack of familiarity with the local topography, compounded by the absence of detailed route maps and charts, contributed to the error.
- Organizational deficiencies, including inadequate flight follow-up and a lack of operational supervision, were identified as contributing factors.