Dutch investigators have determined that an ASL Airlines Ireland Boeing 737-400 freighter had been incorrectly loaded during a tight turnaround, before its crew experienced difficulty in rotation during the take-off roll.

The aircraft had arrived at Amsterdam from Dublin on 19 December 2023, carrying five empty cargo containers plus a 1.46t ballast block which had been placed in the aft position on the main freight deck.

This ballast block was supposed to remain in the aft location, and only the containers unloaded, because the aircraft was due to fly a connecting service to Brussels without cargo.

But the Dutch Safety Board states that the containers and the block were unloaded. When the block was returned to the aircraft it was placed in the cargo-door position.

“This misunderstanding could not be explained,” says the safety board. But it says loading was carried out with the support of electronic scanners and, since only two scanners were available, some of the six ground-handling staff might not have been familiar with the loading plan.

The turnaround time at Amsterdam was just 30min and there was pressure to meet the departure schedule.

According to the inquiry the cargo company’s supervisor handed the loading paperwork to the crew to sign, and signed it themselves, even though neither the supervisor nor the ground-handling staff had checked whether the jet was correctly loaded.

Under the carrier’s procedures, the crew did not have to check the loading, and only the captain was required to sign off the documents.

The first officer had been standing next to the ballast block at the time the cargo door was closed, but “didn’t realise it was in the wrong place”.

With the block located at the door, the aircraft’s centre-of-gravity shifted “significantly” further forward than the crew had expected.

The crew set the trim for a centre-of-gravity position of 10.6% mean aerodynamic chord, when the actual figure was -8.9%, substantially different from the forward limit of 7%. This shift equated to seven trim units prior to take-off.

Although the take-off roll from intersection E4 of runway 18L began normally, the first officer found the aircraft did not rotate as expected – despite near-maximum elevator input – when it reached the calculated rotation speed of 118kt.

The aircraft continued to accelerate until it started to rotate at 134kt, finally lifting off at 150kt.

Investigators point out that, while the available runway was reduced by the intersection departure, the jet was light from being nearly empty and only carrying fuel sufficient for the short flight to Brussels.

The safety board states that the first officer subsequently retrimmed the aircraft after which no further elevator control problems were encountered.

As a result of the incident, the freight company instructed employees to send loading and unloading plans to ground-handlers by email to prevent miscommunication. The carrier also reminded crews that the captain is ultimately responsible for ensuring correct loading, and stressed the need for checks on ballast block positions when flying lightly-loaded aircraft.