Originally Posted by
FlightDetent
a. Estimate track miles to FAP, using any method you could find
b. [NM x 3] + FAP ALT = 3° profile, check where you are compared to that
c. use Ground-Speed / 20 to find out, what V/S will give you 3 deg trajectory and check what descent rate is being achieved
E.g
Track miles to FAP 26
FAF ALT 6000'
your FL150
IAS 290 kt, GS 370
actual V/S 2200 fpm
What do you think? My answer after yours.
Firstly the great thing is that from whatever position this distance is correct, by using the THR depending on the position (fe downwind expected vs long final) my result could be from very low to very high, so a correction would be needed.
In the above example to be on profile I should be approximately 13800’ so around 1200’ high without accounting for deceleration from 290. Accounting for deceleration I’d consider myself around 2200/2500’ high (if the FAF alt had been lower I’d accounted for more deceleration).
Looking at the VS I’m descending slightly steeper than 3° (required approx 1900). In this scenario if cleared to maintain 290kt I’d probably continue without using S/brakes and reassess the profile at around FL120/FL100 and every 1000s below FL100.
Then about 2000’ above FAF alt I’d start decelerating from 290kt and from there see If I need a bit of S/brakes or not. All of this provided ATC allows 290kt below FL100 otherwise I’d used some S/brakes above FL100 before deceleration to 250 (and maybe during) to go back on a 3° profile.