Alliance Air Flight 7412 was a regularly scheduled flight between Calcutta-Netaji Subhas Chandra Airport (CCU) and Indira Gandhi International Airport (DEL), with stops in Patna Airport (PAT) and Chaudhary Charan Singh International Airport (LKO) in Lucknow.
The aircraft operating the flight was a 29-year-old Boeing 737-200 with the registration number VT-EGD. At the time of the flight, the plane had completed 51,278 cycles and was to be retired at the end of the year to comply with Indian government rules not allowing aircraft over 20 years old to operate in Indian airspace.
The plane was carrying 52 passengers and six crew
The pilot flying the plane was 31-year-old Captain Arvind Singh Bagga, who had 4,085 flying hours, 3,605 of which were on the Boeing 737. The pilot not flying was 35-year-old Captain Manjit Singh Sohanpal. of 4,361 hours, of which 1,778 were on the Boeing 737. Both were described as being very experienced pilots.
Alliance Air Flight 7412 route map. Image: GCmaps
The plane took off from Calcutta at 06:51 local time carrying 52 passengers and six crew for the first leg of the journey, a short 293-mile flight to Patna. At 07:17, Patna Air Traffic Control (ATC) asked the plane to report its descent and check descent traffic with Calcutta Area Control. The aircraft was cleared to descend to 7,500 feet and then to 4,000 feet for an approach to runway 25.
Captain Bagga turned towards Patna and, three minutes later, reported coming upon the localizer. ATC then asked the plane to descend to 1,700 feet, saying they were clear to land on runway 25. The crew thought their altitude was too high for the landing and requested they circle the airport for a second approach. Patna said yes and told the crew to report back again when they were on the final approach, which the crew acknowledged.
The aircraft began to stall
This was the last transmission between the plane and ATC. While banking left while turning, the shaker stick activated, warning of an impending stall. As the aircraft continued to bank, it lost altitude and eventually clipped the top of some trees and a house before crashing. Patna ATC immediately raised the alarm, but the emergency services did not reach the crash site until 15 to 20 minutes after the accident.
With chaos all around and locals and onlookers trying to see what was happening, the situation was not under control until a large detachment of police arrived. All six crew members died, along with 49 passengers and five people on the ground. the crash were all sitting at the back of the plane.
An investigation was launched with Air Marshall Philip Rajkumar from Bangalore’s Aeronautical Development Agency in charge. The United States sent representatives from the FAA and NTSB along with experts from the plane’s manufacturer Boeing.
The flight voice recorder indicated that Captain Bragga was flying the plane from the left seat while Captain Sohanpal handled radio communications.When the aircraft reached Patna and was on final approach, it was at an altitude of 1,280 feet when it should have been no higher than Now, rather than discuss what they were going to do, Captain Sohanpal requested a 360-degree orbit which Patna ATC granted.
This could have been confused Captain Bagga as it was not in line with the Alliance Air Standard Operating Manual (SOP).
Following the plane’s clearance to orbit, Captain Bragga initiated a steep left turn, a right turn, and another zigzag motion as he looked to lose altitude. Also, pitching the nose, the aircraft had gone from flying at 130 knots to flying at 122 knots. The lower speed caused the shaker stick to activate, and the rate decreased to 119 knots.
Within two seconds of the shaker stick activation, the thrust was increased, and the aircraft started to climb. The landing gear was retracted, and the flaps moved back to 15 degrees. While this was the correct procedure for a go-around, it was not what you should have done to recover from a stall. Captain Bragga should have instead applied full thrust and reduced the pitch of the plane’s noise. He should also not have retracted the flaps as this caused a simultaneous loss of lift. pointing upwards and a loss of lift, the plane stalled despite the increased thrust and crashed.
The crash was caused by human error as the crew had not followed the correct procedure, leading to the plane being too high while on the final approach. When the shaker stick activated, rather than execute a stall recovery, they initiated a go-around that resulted in a stall and the subsequent crash.