You can put an RTA in seconds as well.
personally this is my process.
insert time marker
1. CI=0 (MRc)
2. Lower descent speed towards green dot.
Note: only go the Green Dot + 20 to allow for a slower descent speed to be selected on descent if winds are not as forecast unless you have an up to date wind link on ACARS.
if no luck
3. Set RTA to the assigned time minus 15 sec
( -30 sec/+0 requirement average)
if it targets green dot pull green dot +10 when above 25000’ (G loading on Alpha prot settles around this altitude and below)
4. Look at the extra track miles required to make the time (distance between RTA and time market) and how long I have to do it.
5. Descend to a new cruise altitude, allowing average 5 Kt TAS plus 1 knot green dot reduction reduction per 1000, approx.
Eg.
Nil wind, Required crossing time of 2130
difference between waypoint and RTA is 8 nm after points 1-3.
present time is 2100. 30min to lose 8 nm, or 16nm over 60 min, therefore 16 kts.
16/6 kts per 1000’ is about a 3000’ reduction in altitude.
hemispherical = descend 4000’
insert new cruise alt if required on the PROG page
Check/reinsert descent speed. RTA should do the rest.