Originally Posted by
321XLR
Hello Everyone
Quick question
Some may be aware of the "trick" where you can "override" Cost Index managed speed and force the plane to do best forward speed to the destination, while in managed mode. This involves putting an RTA at the destination. With that said, my question is this: We recently had a ATC directed speed restriction, for example "Cross ABC at 280 knots and 15,000". We entered that but the plane had no intention of slowing to this user-inputted constraint. So we were wondering if the RTA had something to do with it.
Thank you
RTA stands for Required Time of Arrival, it is not a "trick" and should be used for what it is meant to, i.e. cross a specific waypoint (or destination) at a specific time. I suggest You don't fall in those bad habits of some smart Captains you get to fly with, because the day you end up in overspeed and will have to file a report explaining that you were cruising at 0.81 without a valid reason there will be lots of tea and biscuits waiting for you at the safety office.
With that being said, I do not have the FCOM handy right now but most likely the speed restriction you inserted was disregarded because of the RTA.