What is the optmum climb/ decend and the other setting in the Airbus?

Question

On the Airbus' push/ pull feature, what's the difference between pushing to select and pushing to select - what do both modes do?

Also what does 'OP CLB/ DEC' do and what is the other mode?

Answer 1

Pushing the k**b will make it managed by the aircraft, pulling makes it go to your selection.

For example, if you are at the top of descent, you can either push the altitude k**b, the FMA will announce DES, and you will follow the optimum descent and speed. If you pull the k**b, the FMA will announce OP DES, and the throttles will be retarded to idle, then the plane will descend to maintain the speed selected.

CLB/DES are managed modes- the computer decides the most economic flight plath- speeds and rates of descent are controlled.

OP CLB/DES is the "open" mode. In this mode, the throttles are either fully idle for descent, or fully open to climb power for climbs. The aircraft then climbs/descends to try and maintain the speed selected.