Copyright D.P. Browne 2011

Climb

Descent

Automatic Speed protection in V/S or FPA

The V/S or FPA guidance has priority over the aircraft’s speed control. If too much V/S or FPA is targeted, then the Auto thrust may not have sufficient authority to control the aircraft’s speed.

Only when the aircraft’s speed reaches the upper or lower limits, does the V/S or FPA target automatically change to maintain that limit. When this happens the FMA V/S or FPA annunciation is boxed and the target value pulses. An Aural triple click is initiated if the A/P is engaged.

The V/S target is bleed off to stop the speed from dropping below VLS.

The V/S FMA is boxed with a flashing amber box and the V/S value pulses

An Aural warning triple click is initiated

On some aircraft, when flying F/D only, the V/S or FPA target value is reduced to maintain VLS but no aural warning or FMA change occurs.

The V/S target is bleed off to stop the speed from dropping below VLS.

The V/S FMA is boxed with a flashing amber box and the V/S value pulses

An Aural warning triple click is initiated

On some aircraft, when flying F/D only, the V/S or FPA target value is reduced to maintain VLS but no aural warning or FMA change occurs.