cobravila
When you start your descent in managed mode the Auto thrust goes to idle mode but FADEC gives you Modulated Idle till flaps lever is out of zero position. In this mode N1 is regulated by bleed system demand. So if you select Anti Ice the N1 will increase to maintain minimum N1.Also if cabin descent time is longer than a/cdescent time a repressurisation segment is necessary during which the a/cvertical speed is limited to permit cabin pressurization. If you consult Descent table in QRH you will see the required N1from TOD. Since in Open descent you are commencing descent later FAEDEC gives you the minimum idle N1. On ground It is possible to modify idle setting which is done by maintenance.
Last edited by vilas; 16th May 2013 at 05:48.