Alitalia A321 brakes failure @ Naples

[Sinbad1]

Serious incident in Napoli

to wings1011

There are four braking modes on the airbus, their availability depends on other factors such as the hydraulic system availability, the position of the anti skid switch next to the auto brake selection and the parking brake position on the centre consul.

Before landing,

• Auto braking already selected by the skipper before touch down regulated and controlled by the BSCU the brake sys cont unit which control the anti skid operation as well.Green hydraulic sys must be available

Manual braking uses Green hydraulic ,

• When the crew apply the brakes via the pedal of course, the electrical signals sent to the BSCU as well. Anti skid is available and the Green hydraulic sys must be available.

Parking brake,

• Uses Yellow hydraulic and accumulator pressure.(when Parking brake is used all other brakes become inop elect and hydraulically) and it can be used as an ultimate emergency braking (the A340 500/600 is the same)

Alternate brakes with anti skid it uses Yellow sys,

• comes on when the green hydraulic lost or failure on the normal braking system but anti skid is available.when pressure is applied it can be seen on the gauge.

Alternate brakes with out anti skid uses Accumulator yellow pressure ,

• When anti skid/nose wheel steer switch is OFF or power is failed
• Or Accumulator yellow pressure available only.Pilot have to do the brake balancing pressure to prevent wheel locking.this can be observed on the brake pressure gauge.

So you see, there are many factors as to why the brakes has failed i.e selector valve, wheel rotation signal and air data inertia reference unit inputs are all supplied to the BSCU to compute the braking and the anti skid operation, they are all factor to the cause of failure.

The Master Minimum Equipment List presented by the factory to the operator as the minimum requirement to dispatch the aircraft safely with some systems equipment being INOP, as for the Minimum Equipment List is set by the Airline and usually their requirements are more restrictor to the MMEL.

More info can be found on the FCOM.

I hope the above is helpful and very glad to hear no one was hurt.

Safe flying to all