Climb predictions on ND vs MCDU page (A320)
Hello guys,
Once again, I'm getting confused and frustated not to clearly undestand: Imagine you are in NAV mode, speed managed in managed climb to FL320. You must reach your cruising altitude before waypoint Bravo. But you won't make it with a managed speed of 300kt. The TOC arrow is like 15 miles ahead of the waypoint on your ND. You decided to use Vertical speed ( eg VS+2000) instead of selecting a slower speed. Now the aircraft flies rougly at 260/270kt to maintain the vertical speed. My question is: I noticed the TOC arrow on the ND was not really accurate. Like I reached FL 320 way before the actual prediction on the ND. and also the prediction on the ND (TOC arrow) and the TOC predictions on the FMS are not always exactly the same... Can someone explains please? Does the FMS predictions assume selected or managed speed only? Looks like it gets confused when using vertical speed and the actual IAS is away from for the target speed... please bring some lights on this case. Aircraft was a brand new A320 with Thales FMS.
Thank you.