After a bird collided with the right engine of the Sita Air’s Dornier aircraft, a small particle or fiber spread out from the engine blowing out the “vertical tail fin” that disabled the flight control, according to aviation experts.
As the crew was unable to control the aircraft, it nose-dived on the banks of the Manohara River in Bhaktapur district on Friday morning, killing all 19 on board.
Experts from the Civil Aviation Authority of Nepal ( CAAN) and the Airlines Operators Association of Nepal (AOAN) assume that the break-off of the vertical stabilizer made the aircraft uncontrolled immediately after it took off.
The vertical tail fin of an aircraft points upwards. This is also known as the vertical stabiliser, which allows the pilot to control the plane.
The tail fin helps the plane take direction. Air presses against both its surfaces with equal force when the plane is moving straight ahead. But if the aircraft turns right or left, air pressure increases on one side of the stabilizer and decreases on the other. This imbalance in pressure pushes the tail back to line.
“Although the probe committee will come up with the details, preliminary finding shows that the aircraft was first ‘bird-hit’ that triggered the break-off of the tail fin,” said AOAN President Rameshwore Thapa, after a meeting between air operators, government officials and ( CAAN) representatives.
The aircraft was at around 4,440 ft, some 50 ft up from the runway, when the bird hit it.
Aviation experts said the panic-stricken pilot made a steep turn to the left to land the plane at the Tribhuvan International Airport (TIA) from the north without
maintaining a required radius.
After the right engine and subsequently the tail fin were damaged, the plane lost its balance and failed to take direction, added experts, seeking anonymity. “This could have resulted in the stalled condition of the plane.” According to a press statement issued by the ( CAAN) on Friday, traffic controllers noticed the aircraft making unusual maneuvers right after its take-off. The “unusual turbulence” of the plane was noticed from the ground. The aircraft was cleared for Lukla, 136-km east of Kathmandu, at 6:17 am by the Air Traffic Controller (ATC).
The aircraft made its last contact with the ATC at 6:18 am, reporting a ‘bird-hit.’ The plane crashed 30 seconds later.
The pilot was not even able to inform the ATC on his plan to divert the aircraft back to TIA for an emergency landing when he faced the two problems simultaneously, the experts presumed. Meanwhile, Minister for Culture, Tourism and Civil Aviation, Post Bahadur Bogati directed the air operators to take up quality assurance and safety measures seriously. He also directed the ( CAAN) to update technical documents and make effective monitoring and supervision. He directed it to appoint safety inspectors in Kathmandu, Pokhara and Nepalgunj immediately.
A post-casualty meeting held on Saturday under the chairmanship of Minister Bogati decided to recommend the government provide discounts in aeronautical parts to the air operators by amending the existing aviation policy in a bid to make the industry more sophisticated. The meeting decided to activate National Birds Control Committee.