Spirit A320
 

Recently jumpseated in the cockpit (getting to be a regular thing - crews have been great - kudos). The crew was given a descent from cruise to hit an altitude by a specific fix on the STAR. They programmed the altitude at the appropriate fix in the FMS and set the FCP altitude to the lower. However, they had to initiate the descent when the time came because the autopilot would not start down on its own. I think they were in PROF but couldn't say for sure.

Is that due to the options the operator chooses to buy? In a previous life, I thought I remember being able have the jet start down on its own using PROF) as long as we were within a specific distance from top of descent (200 NM or something similar). Just trying to figure out if my memory is getting that bad (and curious, too). Any 320 operators from other airlines have some perspective?

On the A-320 series I have flown (at Spirit and United), you had to start the descent manually, unlike on B-75/67 where you have VNAV that starts down at TOD.
Never heard of "PROF". Might be an A-300 thing?

I guess I am losing my mind. I was at UAL too. I could have sworn the "vnav" mode on the 320 was called "prof" or profile mode. That's what it is on the MD-11 and I thought I remembered them being similar. Too many jets in too few years back then, I guess.

The aircraft won't intercept at tod on it's own via traditional vnav. When the descent is managed, the plane enters 1000 fpm descent until it captures the calculated geometric
descent path. I much prefer vnav compared to the managed airbus descent, but it works well as long as the descent winds are entered.

There is a vertical deviation indicator on the prog page. Maybe that is what you remember.

In order to start descent in A-320 you have to pre-select lower altitude AND PUSH or PULL alt knob. Airbus won't do anything if it reaches TOD, but you don't push or pull ALT with pre-selected lower number. It's one thing of the so called "Airbus philosophy" as french instructor told me...