If you observe too fast descents and you have often to use the speedbrakes - it may be caused by this "SP1 IDLE BUG". The conditions are:- CH yoke- FSUIPC- and you assigned one button "Gear UP"In this case the N1 suddenly increases at 15500ft from 34.9% to 40%. And that leads to an increase of speed forcing the considerable use of the speedbrakes or you will overshoot.BTW. there is no problem with assigning the axises and it doesn't matter which button is used. Assigning one button to "Gear Up" and using this button after takeoff leads much later during the descent to the N1 jump! So, don't do that until the bug is repaired. Use the "G"!I hope that the images will illustrate what I mean.