Pilot stress has been cited as the probable reason for the crash of a Fishtail Air helicopter in Nuwakot last August, an investigation report submitted to the Tourism Ministry on Sunday said.

Captain Ranjan Limbu’s social and professional obligation to evacuate a post-maternity sick woman and her infant to hospital in Kathmandu from Gorkha resulted in his losing situational awareness and control of the chopper after it entered cloud over Kakani.

Seven persons including the pilot, newborn child and passengers were killed in the mishap.

While navigating around the terrain, the helicopter stuck a high vertical cliff at Chuchebhir hill, first impacting on the front side of the aircraft at high speed, and then chopping trees with the main rotor.

The helicopter with callsign 9N-AKA had taken off from Philim in Gorkha and had been chartered to fly the newborn infant to Kathmandu for medical treatment.

The aircraft had no mechanical failure and the pilot had not violated standard operating procedure. But he lacked experience and was not familiar with the specific low-level weather pattern of hilly narrow valleys, the report said.

“He was anxious to complete the rescue mission of the post-maternity sick woman and her infant as soon as possible,” the report said. “And he became overconfident in such unsafe conditions,” said Hari Bhakta Shrestha, chairman of the investigation committee. But pilot stress was not the sole reason behind the crash. Trouble started when the aircraft approached Kakani pass to enter the Kathmandu Valley.

It was flying at an elevation of 5,500 feet. Due to fast building clouds on the flight path over Kakani, the pilot planned to take the eastern ridge, another track leading to Kathmandu. So the chopper circled the sky waiting for instructions from the air traffic control tower in Kathmandu.

“Unfortunately, the tower was so busy that it failed to make a timely response to the pilot,” said Shrestha. “Had the tower responded in time, the situation could have been different,” he said.

Shrestha added that strained capacity at Tribhuvan International Airport, from air traffic controllers to infrastructure, had become a serious issue.

Not getting any response from the tower, the pilot flew back to the western ridge to enter the valley which was blanketed with clouds, and inadvertently entered Instrument Meteorological Conditions (IMC), under which pilots fly primarily by reference to instruments and subsequently flew into terrain at 6,824 feet.

While navigating, the helicopter slammed into a cliff, the report said. The report said that the pilot was familiar with the Kakani route as he had conducted more than 90 percent of his flights from there.

The aircraft investigation commission has made 21 safety recommendations to the concerned agencies to enhance safety and prevent such accidents in the future. The commission has recommended introducing terrain specific training for pilots.

The probe panel said that Fishtail had a high rate of accidents and incidents in past years, but still it had not launched any accident prevention programme. The commission has asked the regulator to monitor operators strictly and assess the capacity of the airport in Kathmandu.