The FMC calculates a descent path based on altitude and speed constraints at the End of Descent point. If you increase the descent speed it will not necessarily change the TOD as the geo path limitations lower down may be the restriction. Now back to basics, what happens when you increase the descent speed to a figure higher than the CRZ? what will happen at Mach Transition? how about the effect of TAI in the DES Forecast page on the N2 and profile? what happens if the speed is outside the cost index limits? Before you mess around with the "advanced factors" I would enjoy the course, stick to the procedures and don't become a "child of the magenta" When you suddenly get a series of green decel dots and msg "unable next altitude" or "drag required" this is when you know you forgot to check the route DATA and you are asking the aircraft to do things it can't. The biggest change to TOD will come with changes in the STAR or removal of restrictions lower down, not speed, this just temporarily displaces the magenta deviation while it tries to figure out what you are trying to do! as a rule of thumb for every 10 kts above Econ descent you should be 300 feet below the path, so in your scenario if you change from 270 to 350 to be "on path" you would actually need to show approx 2400 below the path on the magenta deviation. Of course you could mess around in the DES page and put 350 Kts, but is that really much use? your display will be scattered in green dots and eventually the VS will go to zero while it slows to where it needs to be.
Last edited by Avenger; 5th Jun 2018 at 08:16.