European safety regulators are advising operators to use a simplified procedure for operating Boeing 737s in cold-soaked fuel frost environments.

The simplified procedure was proposed by Boeing to avoid the need for cockpit crews to determine frost thickness, which could prove difficult.

Cold-soaked fuel frost can form on the ground when aircraft tanked fuel has been cooled by exposure to high altitude temperatures or when cold fuel is uplifted during preparation for flight.

European authorities sought clarification in 2012 over a discrepancy centred on permitting take-off with current-generation 737s – from the -600 upwards – in such conditions.

The European Aviation Safety Agency says US regulations prohibited departures despite their being allowed by the aircraft’s flight manual.

EASA subsequently recommended that take-off with cold-soaked fuel frost should be conducted in accordance with the flight manual, but acknowledged the problems with gauging frost thickness.

Last year the authority reviewed a new simplified procedure, proposed by Boeing, which did not rely on measuring frost thickness.

This review concentrated on demonstrating that – in a normal turnaround – the fuel frost would not build up beyond limits once the crew had verified compliance after the previous landing.

EASA subsequently approved a new aircraft flight manual containing the simplified revised procedure.

It has issued a safety bulletin to draw operators’ attention to this revision, formally recommending that operators use this procedure to set out cold-soaked fuel frost operations, pointing out that the required conditions are “easier to confirm by the pilot”.

Source: Cirium Dashboard