Investigators are probing an apparent ballast shift on board a Bluebird Nordic Boeing 737-400SF during its descent towards Paris Charles de Gaulle.
The incident involving the Icelandic-registered freighter occurred on 10 February, according to French investigation authority BEA, which is citing preliminary information from its Icelandic counterpart.
BEA says the aircraft was undertaking a ferry flight with payload ballast in one of the aft container positions – designated position 10 – on the main deck.
As it descended towards Paris there was a “huge bang” which “shook the entire aircraft”, it states.
This resulted in a “strong” yaw which destabilised the aircraft’s flight trajectory, says BEA.
It adds that the crew investigated the situation and found the payload ballast had shifted from its aft position towards the 9g bulkhead wall in the forward cargo hold.
BEA says the loose ballast moved again, hitting the wall, during both flap extension and deployment of the landing-gear.
The aircraft had departed Brescia’s Montichiari airport. None of those on board was injured.
BEA identifies the airframe involved as TF-BBL, which was originally delivered as a passenger aircraft to Alaska Airlines in 1997 before being converted to a freighter in 2018 and introduced to the Bluebird fleet.