I have a question about calculating my altitude in FPL (in order to have acceptable vertical speed while descending) through waypoints in STAR’s and approach procedures when they are blank/need input.
I have a rough idea of what should be correct and what isn’t but a rough idea could result in a rough flight if you know what I mean.
I’ve attached a screenshot of my current flight into KSJC using the ROBIE5 STAR and I30L APP. I’m flying a 737–700.
Do you think the altitudes I’ve set in the STAR would be appropriate? They were blank, except for the I30L APP altitudes they were obviously pre-filled - and I don’t think it’s appropriate to rely on VNAV to descent from 36,000ft to the first waypoint in the approach (KLIDE @ 4,000ft) - unless this is proper? Meaning, just let VNAV handle the STAR and watch speed?
I just leave it to descend direct to the lower approach altitudes, it works well for me. Trying to add higher altitudes might result in a steep descent and not to mention a lot more work.
What I typically do in situations like yours where there is not much help from the approach plate in terms of what flight level to be at for each waypoint it this…
As a good rule of thumb, to keep a reasonable descent rate between waypoints is to allow at least three miles for every 1,000 feet you are going to be descending.
In your case, you are wanting to descend a total of 10,000 feet between ROBIE (30,000 ft) and GOALI (20,000 ft) meaning if you want three miles for every 1,000 feet, you would need at least 30 miles between the waypoints. You have 35 so you are perfectly fine! Same process repeats for the rest of your STAR waypoints, and from what I can see the altitudes you put in will all work great for a smooth descent!
Feel free to hit me up with any other questions you may have. I am happy to help!
To be honest I would just leave VNAV away when flying such an approach profile. You can adapt your descend rate (pitch) based on the speed and descend rate you want to fly, which can have you flying an idle descent (engine to idle for the whole descend till the glideslope).
So just use a proper TOD and have fun ;)
(There are many tutorials here on the community on the TOD, so feel free to have a look regarding this!)
