Dutch noted steep authority gradient in ill-fated A330

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Dutch investigators pointed out possible cockpit authority problems on board the ill-fated Afriqiyah Airways Airbus A330 in their formal comments to the draft crash inquiry report.

The Dutch Safety Board also expressed concern that the tasks of the crew needed to be described in greater detail, pointing out that there were three pilots in the cockpit, none of which was monitoring the aircraft's flightpath.

But it also commends the Libyan Civil Aviation Authority for managing to compile the report "in view of the current difficult situation" in the country. The accident occurred in May 2010, nine months before the uprising and armed conflict in Libya which ousted the government of Muammar Gaddafi.

While the Dutch investigators acknowledged that the draft report offered a "plausible reconstruction" of the Tripoli accident, it sought greater detail on the pilots' actions which allowed the A330 to descend prematurely before a mishandled go-around resulted in the crash.

The captain was distracted at the moment the first officer, flying, started the final descent. Both failed to monitor the flightpath and no-one in the cockpit noticed the aircraft was passing a crucial marker point at a lower altitude than required.

Noting that the relief pilot was in a position to observe the inadvertent descent, given his limited responsibility at the time, the Dutch pointed out that his role had been "insufficiently addressed" by the inquiry.

Between them the three pilots had logged over 23,000h but each had only 516h on type.

In its comments the Dutch Safety Board also identifies evidence of a "steep authority gradient", highlighting the first officer's hesitation in proceeding with a go-around without the captain's explicit approval. It also points out that the investigation revealed instances, during the go-around, in which both the captain and first officer were making sidestick inputs.

Afriqiyah Airways "accepted" this practice, says the Dutch Safety Board, but the fact that the dual inputs were "tolerated" at the airline indicated that the carrier did not sufficiently enforce compliance with the standards set out in its operating manuals.

Dutch investigators have been co-operating closely with the A330 probe because a large number of passengers on board the aircraft were nationals of the Netherlands.