History of the Flight
On 20 May 2019, SP-LWA, a Boeing 737-89P, was operating a commercial passenger flight from London Heathrow to Warsaw Chopin Airport. The load sheet was produced by a dispatcher using the operator's load management computer system. The commander initially noted that the stabiliser trim was close to limits on a provisional load sheet and requested a check. After adjustments, the final load sheet was signed and used for takeoff performance calculations. The aircraft pushed back at 0552 hrs and the takeoff was reported as normal.
At 0630 hrs, during cruise at FL350, the crew received a corrected load sheet via ACARS indicating an increase in zero fuel weight of 953 kg and a forward shift in centre of gravity of 3%. The flight crew updated the flight management computer and the remainder of the flight was uneventful.
Weight and Balance
Investigation revealed that 953 kg of mail loaded into hold 2 had been omitted from the final load sheet. The mail consignment had initially been recorded twice in the load management system. The dispatcher deleted one duplicate entry and produced a correct Loading Instruction Report (LIR). However, shortly after, an electronic message from the cargo company resulted in the removal of both entries, effectively deleting the mail from the system. When the dispatcher printed the load sheet, a system message indicated an external input had been accepted, but the dispatcher was unfamiliar with the message and did not notice the omission.
Reports
The handling agent reported that the dispatcher had deleted one duplicate entry but later accepted an external input that removed the mail entirely. The operator's system logs showed that at 0534 hrs, the cargo company sent a message deleting 981 kg of cargo and adding 28 kg of mail, netting a removal of 953 kg. The cause of the original duplicate entry was not determined.
Analysis
The consignment of mail was initially duplicated in the system, a situation the handling agent noted was not uncommon but usually resolved by the dispatcher. On this flight, the dispatcher corrected the duplication but was then unaware that a subsequent electronic update had removed the mail entirely. When generating the load sheet, a system message alerted the dispatcher to an external change, but the dispatcher did not recognize its significance and failed to verify that the load sheet matched the actual loading. The error was only discovered after departure.
Safety Action
The handling agent took safety action to remind dispatchers of the importance of verifying that the load sheet reflects actual loading. They also changed dispatcher work patterns to ensure familiarity with all IT systems they service across different operators. The operator requested that all future occurrences of duplicate cargo entries be reported to them so that the root cause can be investigated and resolved.