Patna, June 22: A Patna-Delhi Air India flight sharply tilted left and then right and lost thousands of feet in seconds, giving passengers a sensation of “free fall”, apparently because two planes had been allowed to come closer than stipulated.
It all happened as air traffic control (ATC) allowed Flight AI-410, carrying 119 passengers, to try and climb to 33,000ft from its assigned height of 32,000ft.
An aviation expert said the A319 probably got caught in the wake turbulence — the turbulence that forms behind a flying aircraft — of a bigger plane that had possibly flown above it a little earlier breaching the critical separation limit of 1,000ft between flights.
No Air India official at Patna airport would confirm the incident but an airline source said it was not a safety threat.
Among the passengers was Union agriculture minister Radha Mohan Singh, former director-general of police D.N. Gautam and an aviation expert, Atul Singh.
“The flight first tilted 40 degrees to the left and began losing altitude. Then it tilted 80 degrees the other way and continued to lose height,” said Singh, executive director of the Delhi-based company, Centre for Aviation Policy, Safety and Research.
“It lost around 5,000ft from its assigned height of 32,000ft within 10 to 12 seconds.”
He said the aircraft almost seemed out of control and was on the verge of entering into a stall — a situation where a plane can fall vertically because of lack of speed.
Gautam said from Delhi that the passengers “had to hold the meals kept on the tray as they were falling”.
Retired IAS officer Phool Singh said: “Suddenly, there was a thud and a feeling of free fall. The flight stabilised in a few seconds. A similar turbulence was felt a few moments later for 2-3 seconds. There wasn’t much panic among the passengers.”
Captain Amitesh Ahuja, the pilot, announced the situation was under control.
Singh, the aviation expert, said he spoke to Ahuja in the cockpit. “He said he had requested the Varanasi ATC to grant permission to ascend to 38,000ft but was directed to go up to 33,000ft only,” Singh said.
“Ahuja said probably a Boeing 747 or Boeing 777 had passed through the same altitude a little earlier. He said he had never experienced such wake turbulence in his career. As I am certain there was a human error, I shall file an official complaint with the (aviation regulator) DGCA.”
Another aviation expert, Mirza Faisan, who was not on the plane, said a “bank (flying with one wing above another) of 40 degrees is quite sharp for an A319, as the maximum permissible banking according to its design is 45 to 60 degrees”.