On 19 April 2018, a Boeing 787-8 (VT-ANI) being operated by Air India on a scheduled domestic passenger flight from Amritsar to Delhi as AI462 encountered severe turbulence as it climbed from FL160 to FL190 in day IMC and exceeded its assigned level by 600 feet before flight path control was regained. Three passengers sustained minor injuries as a result but the remainder of the flight was subsequently completed without further event and on arrival, the injured passengers were taken to an airport medical facility for treatment. Minor damage to cabin furnishings occurred but there was no other aircraft damage.
An Investigation was carried out by the Indian DGCA in accordance with the Aircraft Accident Investigation of Accidents and Incidents Rules 2017. Data from the CVR and FDR were successfully downloaded and used to support a reconstruction of the sequence of events.
It was noted that the 43 year-old Captain had a total of 5,646 hours flying experience which included 3,393 hours on type. The 36 year-old First Officer, who had been PF for the flight, had a total of 4,976 hours flying experience which included 3,126 hours on type. The same crew had operated an earlier Delhi to Amritsar flight in the aircraft.
Prior to takeoff, no special instructions were given to the cabin crew in respect of the expected weather conditions after departure. Takeoff performance was based on the wet runway condition which was due to the prevalent light rain / drizzle. The available Met Briefing folder was not downloaded and the crew did not seek weather updates from ATC. The latest available Amritsar METAR at this time was found to have given the current weather as ‘Thunderstorm’ with the surface wind as variable at 2 knots and a TREND of TEMPO (temporary) for the surface wind 310° 20-32 knots. However, the bigger picture in the vicinity of Amritsar apparent from satellite images showed that there had been a steady build up of Cumulonimbus (Cb) clouds during the 90 minutes prior to departure and Doppler Weather Radar returns during the half hour prior to takeoff showed that the airport was “covered by large-scale CB with tops at up to 49,000 feet”.
As the aircraft turned on track at FL 060 after takeoff from runway 34, the crew reported having observed rapid build ups ahead and left of their intended track and decided to deviate 10 nm to the right towards the airport overhead where their weather radar returns indicated that significant turbulence was least likely. The seat belts were kept on as “light to moderate” turbulence was experienced above FL 080. This then suddenly became severe at the aircraft climbed through FL 160 with a clearance to FL 190 six minutes after takeoff. FDR data showed that, with the speed averaging 270 KIAS, vertical acceleration during this period had varied rapidly within the range +1.778 to -1.307 over a period of 30 seconds with an uncommanded disconnection of the AP as the aircraft passed FL180. Without making any standard call to take over control, the Captain did so and, after “a couple of attempts”, was able to re-engage the AP. However during this time, the aircraft exceeded its cleared level by “almost 600 feet” before he was able to return to it.
ATC were informed of the bust and a report from the passenger cabin was obtained. This established that three passengers had been injured, one suffering a cut to his head when he hit the ceiling. It was also reported that “one seatbelt had come off”, that one PSU had been damaged and several others had dropped and that an interior window panel had separated. ATC was then advised that the flight would continue to destination but that a priority landing there would be needed due to passengers requiring medical attention.
The Probable Cause of the event was determined as “the flight crew did not appropriately assess the weather conditions before departure from Amritsar and encountered severe turbulence during climb which resulted in passenger injuries and damage to the cabin furnishings”.
One Safety Recommendation was made as follows:
- that Air India should re-emphasise instructions that flight crews shall use all resources to analyse the prevailing weather situation prior to flight operations in inclement weather conditions.
The Final Report of the Investigation was completed on 28 May 2019 and subsequently published.