What happened
On 27 May 2022, Etihad Airways flight ETD-72K, a B787-900 with registration A6-BLF, was operating a scheduled passenger service from Abu Dhabi to Allama Iqbal International Airport (AIIAP) in Lahore. While descending through FL 200, the flight crew attempted to deviate 20 NM to the east to avoid an active weather cell identified on radar.
Upon turning onto a heading of 060 degrees, the aircraft entered clouds and immediately encountered a powerful updraft lasting approximately seven seconds, followed by severe turbulence that persisted for three to four minutes. The sudden vertical acceleration caused the aircraft to experience loads of +1.8 and -0.75 Gs. During the event, the flight crew applied a sharp left control input, which resulted in the autopilot disconnecting due to override force.
Following the encounter, the crew discovered that several individuals had been injured. Upon arrival at Lahore, it was confirmed that eight cabin crew and three passengers had sustained injuries. One cabin crew member suffered a fractured pelvis and required hospitalization, while others received first aid for various ailments including neck, shoulder, and limb pain.
The investigation
The Bureau of Aircraft Safety Investigation Pakistan (BASIP) examined the meteorological conditions and flight data. The investigation reviewed satellite imagery and weather radar to determine the source of the turbulence. Investigators also looked into the communication between Air Traffic Control (ATC) and the flight crew regarding recent weather updates.
Findings
- The primary cause of the event was an in-flight turbulence encounter resulting from a dissipating thunderstorm.
- A stable atmospheric layer above the area prevented vertical dissipation of the storm, causing the effects of the dissipating cell to propagate horizontally as far as 40 NM from the active center.
- Because the turbulence originated from a dissipating cell rather than an active one, it was not visible on the aircraft's weather radar and could not be avoided.
- The investigation noted that while ATIS provided weather warnings for dust and thunderstorms, specific recent updates were not communicated to the crew by ATC.
- At the time of the turbulence, although the seatbelt sign had been activated, cabin crew members were still performing duties in the cabin.