What happened
On 26 April 2024, a Boeing 737-4K5, registration G-JMCZ, was performing a commercial cargo flight from London Stansted to Edinburgh. As the crew initiated the descent into Edinburgh, they heard a loud, double-impact noise accompanied by a momentary increase in vibration on the right engine. While the crew initially considered an engine surge, they also suspected a potential cargo shift within the main deck.
The aircraft landed safely at Edinburgh without any further issues. Upon arrival, during the unloading process, ground personnel discovered that a unit load device (ULD) originally positioned in Bay B had moved into Bay A. This movement caused minor damage to the paint and liner tape on the forward bulkhead.
The investigation
The investigation examined the aircraft' and the loading procedures. The Boeing 737-4K5 had been configured for cargo, featuring a bulkhead between the large cargo door and the forward aircraft door. At the time of the incident, the aircraft was loaded with 8,944 kg of cargo, with Bay A left as a void space.
Investigators found that the aircraft's centre of gravity remained within safe manufacturer limits despite the shift, and no handling difficulties were experienced by the crew. Because the cargo was unloaded before the crew could inspect the locks, it could not be determined if the movement was due to a mechanical failure of the locks or human error during the securing process. The investigation noted that the physical layout of the cargo deck makes it difficult for crew to visually verify the security of all locks once the main deck is loaded.
Findings
- The ULD in Bay B moved forward into the empty Bay A during the descent phase.
- The ULD locks in Bay B were likely not properly secured, allowing the unit to slide forward when the aircraft pitched down.
- The shift resulted in no injuries and only minor damage to the forward bulkhead's interior surface.
- The operator's procedures for managing void bays were reviewed to mitigate the risk of similar occurrences.