The crash of an Air Kasthamandap plane at Chilkhaya in Kalikot last February was caused by engine failure, a probe report has revealed. Both pilots were killed while the nine passengers on the charter flight survived.

According to the findings, the crew tried to force land the aircraft on a barley field after losing power, and the right landing gear struck a pile of firewood, causing it to pitch forward onto its nose. The cockpit was destroyed by the impact.

Captain Dinesh Neupane died on the spot while Copilot Santosh Rana died one and a half hours later. There were nine passengers on board including an infant. The single-engine P750 XL, manufactured by Pacific Aerospace of New Zealand, was on its way to Jumla from Nepalgunj.

The investigation report submitted to Tourism Minister Jeevan Bahadur Shahi on Sunday concluded that the crash happened because the engine lost useful power due to deterioration of one of the six bearings in the engine.

“The breakdown of surface layers on the number one bearing resulted in axial movement of the compressor into gross mechanical damage,” said Ramesh Kumar Singh, a senior engineer of Goma Air and a member of the government’s fact-finding commission.

“The engine had a defect in its rolling-element bearing. The bearing assembly was improper or faulty,” he said, presenting the details of the mechanical aspect of the crashed aircraft.

The engine of the 10-seater aircraft was manufactured in 1991. Initially, it was used on a multi-engine aircraft of Fiji Airways. Air Kasthamandap had leased the engine in December 2015, according to the report.

The engine had been overhauled at Airforce Turbine Service in the US in 2012. When Air Kasthamandap leased the engine from Tasman Aviation Enterprises of Australia, it was disassembled appropriately for a single-engine plane. “However, the engine’s bearing assembly was improper,” said Singh.

“There was a foreign object or debris between the bearing and the body of the engine that was regularly building up friction, and ultimately led to the breakdown of the layers of the bearing,” he said. “There are no records about how the engine was preserved between 2012 and 2015.”

The crew had tried several times to restart the engine after it stopped abruptly when the aircraft was at a height of 11,000 feet and at a distance of 75 km north of Nepalgunj airport.

The aircraft with the registration number 9N-AJB had taken off from Nepalgunj at 12:16 pm, the third flight for the crew on that day. The aircraft had last established contact with Nepalgunj airport at 12:33 pm.

The authorities concerned were informed about the crash at 12:50 pm. However, a rescue operation was mounted a full four hours after the accident.

The report said that engine failure was not the sole reason behind the crash. “Although single-engine aircraft can glide a fair distance after losing power to execute a safe force landing, the route lacks proper landing spots,” said Hari Bahadur Khadka, member-secretary of the commission.

The crew had flown for nearly 15 km searching for a suitable landing spot after the engine shut down. “There should be a force landing spot for every three minutes of flying distance, but no such spots were designated,” said Khadka, adding that the civil aviation regulator had also not followed up on this issue.  

The report said that the accident "could also be the result of the financial health of the airline”. Khadka said, “Due to the deteriorating financial condition of the company, it was unable to conduct proper monitoring of the operation. It had not been able to retain technical manpower due to financial stress.”

Meanwhile, the investigation committee has concluded that the Civil Aviation Authority of Nepal has not been able to oversee the use of different types of aircraft due to capacity constraints. This has affected efficient monitoring of the Nepali skies, it added.