SRS

Arming

Engagement

Disengagement

Guidance

Speed Reference System (SRS)

The Speed Reference System (SRS) guides the aircraft in the vertical plane at a speed defined by the SRS control law.

The Speed Reference System (SRS) is armed when :

The Speed Reference System (SRS) engages automatically ( so long as it is armed) when the thrust levers are placed into the the TOGA or FLX/MCT detents on the ground.

V speeds have been entered into the MCDU on the Performance Take off page.

Slats are extended

Aircraft has been on the ground for longer than 30 seconds.

The SRS mode disengages when

At the acceleration altitude.

Whenever another vertical mode engages, ( usually ALT* or ALT CST *

The flight crew select a new speed on the FCU. SRS then reverts to OP CLB

The SRS mode guides the aircraft in the vertical plane at a speed of V2+10 knots for both engines running and for the highest of V2 or current air speed (limited to V2+15) when an engine failure is detected.

The SRS mode guides has the following guidance constraints:

Attitude limiting to protect excessive attitudes during takeoff

Speed limit of V2 + 15

Minimum climb rate of 120 ft/min

SRS mode engaged, aircraft accelerating along the runway about to pass V1

SRS speed is 155 knots, guidance will be to V2+10 = 165 knots

There is no annunciation of the armed state on the FMA.