New Delhi: IndiGo flight 6E2142 that flew through a severe hailstorm on its way to Srinagar from New Delhi on Wednesday plummeted at a speed of 8,500 feet per minute at one point of time, the Directorate General of Civil Aviation (DGCA) has said.
The DGCA has, meanwhile, grounded the two pilots of the aircraft that suffered severe damage. Officials have said that this is routine procedure when an inquiry is underway.
Even civil aviation minister Ram Mohan Naidu has appreciated the role of the pilots.
“We are looking into the incident, but in the meantime from the information that I have, I would like to appreciate the efforts of the pilots and the crew who have been very composed in the way they have handled even in that weather that the flight has gone through,” Naidu said.
“We are very thankful that no incident has happened and everyone is safe, but we are going to thoroughly investigate what has exactly happened,” he added.
The DGCA has, meanwhile, revealed that the Airbus A321 Neo, carrying 227 passengers, plummeted at 8,500 feet per minute at one point of time, even as the pilots fought to regain control of the aircraft while trapped inside the storm. The normal rate of descent is 1,500-2,000 feet per minute.
Officials revealed that the pilots received simultaneous warnings of stall (a condition in which an aircraft begins to lose altitude) and overspeed conditions.
Details have also emerged of how the pilots initiated contact with air traffic control in Pakistan after Indian controllers, bound by reciprocal airspace restrictions following recent military tensions, advised against deviating westwards but provided contact frequencies to coordinate directly with Lahore ATC, which denied the request despite the emergency.
The crisis began when the aircraft “entered a hailstorm and severe turbulence near Pathankot” whilst “cruising at 36,000 feet. Recognising the danger ahead, the pilots requested northern control (under the Indian Air Force) for deviation towards left (the International Border) due to weather on the route. However, this was not approved.
The IAF control’s denial was an advisory based on the Pakistani NOTAM, in place since the cross-border military operations earlier this month.
Growing increasingly desperate as the storm approached, the crew contacted Lahore to enter into their airspace to avoid the weather but this too was turned down.
“Northern area control advised the Indigo crew within the frame of the NOTAM… and immediately assisted in coordinating their route diversion by contacting Delhi area and passing the requisite contact frequencies of Lahore control for an overflight weather diversion request,” this person explained.
However, Lahore control, according to the DGCA, did not allow overflight permission, leaving the crew with no viable escape route.
The crew initially attempted to return back but as they were close to the thunderstorm cloud, they decided to penetrate the weather, the DGCA said.
What followed was a cacophony of alarms and alerts for the pilots. “While in thunder storm cloud, warnings of angle of attack fault, alternate law protection lost, backup speed scale unreliable were triggered. Due to updraft and down draft encountered by the aircraft the autopilot tripped and aircraft speed had wide variations,” Hindustan Times has quoted the DGCA as saying.
In other words, several of the aircraft’s computerised systems failed one by one, forcing the pilots to fly manually through violent turbulence without reliable instruments or the normal protections that prevent a modern aircraft from stalling or exceeding its structural limits.
After regaining control, the crew declared emergency. “After carrying out all check list actions, crew declared PAN PAN to Srinagar ATC and requested for radar vectors and made a safe landing with auto thrust operating normally,” the report stated.
PAN PAN is an international urgency signal indicating serious difficulty requiring assistance, one level below a MAYDAY distress call.
