I’m not a pilot, so I don’t know how this should work IRL. Do you happen to have anything to confirm it?
I’m participating in a course taught by a 737 pilot. I’m also a retired pilot but didn’t fly the “big iron”.
Im having problems with Lnav/Vnav rnp approaches…
Is there some sort of algorithm or triggers to make this more consistent…
I did the same approach into Queenstown twice, first time I had everything set up, dialed down to the mda alt and when below the final fix altitude before decent, dialed up the alt to the go around… the plane kinda followed then it kicked into go around and climbed…
The second time… everything went smoothly as it should and all but ILS approach smoothly down…
But now…
Im in the 737-700 now and its just dose not seem to work…
Is it a bug or a simple thing im not doing…
Like mentioned…
I decend to the final approach alt, for example 2000ft then just before I reach it or when I’m on the RNP, I dial it down to the mda i.e 300 ft, when like 200ft below the final approach alt i.e 2000ft. I dial it up to the missed approach alt… Just like a330 driver shows on yt… but man, It just wants to climb as soon as I dial up the altitude…
There is a minimum amount below the final fix altitude you have to be before dialing back up to go-around altitude. If you dial it up too soon, it will mess up your approach.
I’m pretty sure it’s discussed in either this thread or the original thread (note this is “Part 2”). I’m also sure I’ve seen it discussed on the PMDG forums before. I believe it’s also discussed in the FCOM if you can search yourself up a copy of it from some corner of the internet.
In lieu of the above, perhaps @Stearmandriver2 or another of the actual IRL 737 folks can chime in with guidance.
Mate thanks for that…
As you sent that, I was on approach into Regas and decided to try the rnp one more time and I did wait till 300ft under the final fix and it held the rnp glideslope…
It must be winding up the go around alt too soon… as in, not way before the final fix alt is reached but even being 300ft above the final fix…
I don’t believe it’s related to final approach fix altitude, but rather your present altitude. If you set the MCP to an altitude below your current altitude (or within a few hundred feet above it) then that will be captured and you’ll level off there. So, the trick is to wait until you’re a few hundred feet below missed approach altitude, and then rapidly spin through your current altitude to set the missed. Do it fast though, or present altitude will get captured.
I’m not certain of the exact altitude buffer you need because we don’t actually do it this way. Our procedure is, once cleared for the approach and in LNAV/VNAV, with all altitudes and path verified in the FMC, we set field elevation in the MCP (round down to the nearest 100ft). This eliminates the threat of present altitude being captured and the approach destabilized on the spin-through, but introduces the need to set the missed approach altitude on the missed. We capture that by making “gear up, set/verify missed approach altitude” a standard call on every go around.
Both methods have pros and cons, there’s no “right” answer. Either works fine as long as you’re aware of the potential gotcha.
4 Likes
I have recently noticed on the 737-600 variant, that when I have the map open on the EFB, I get a severe FPS drop. This happens in VR, I do not fly in 2D so not sure if it happens in 2D.
Has anyome else noticed this.
Thanks.
Last year, after SU15 or so, I stopped using the maps in the UFTs for that reason. The problem mostly went away after that.
I recently flew the -700 for the first time in a while and specifically checked to see if the table map affected performance. In my quick tests, it made zero difference whether the map was displayed or not, nor how far I zoomed in or out. Of course, everyone’s system is different and results may vary.
Thanks for these details!
After I tagged you above, I let my fingers do a little googling and found a Boeing NG Flight Crew Training Manual. The FCTM indicates that during a VNAV or Vspeed descent, once you are at least 300’ below missed approach altitude and descending on the approach, you should set the missed approach altitude on the MCP. So I guess the “official” buffer range is 300’.
I’m sure it is company specific, but I’ve also seen an SOP for non-precision approaches stating that the missed approach altitude should be set when 1000’ above the airport elevation (top of white bar on the altimeter) on the approach.
Yes it happens on 2D also. Even if you disable the EFB from the FMC but it was left in the map it will cause performance issues.
Once you press the home button in the EFB it goes away.
I kinda like this. If you’re going to use the spin-through method at all vs setting field elevation until the missed, I like tying it to a set gate on the profile vs a moving target of “300ft below the missed.”. You could train to set missed on a precision approach at the same point and have more commonality between profiles.
The main things that bug me about the “spin through” method are the potential to A. Screw it up and destabilize yourself; and B. forget to set the missed at all. If you don’t have a common procedural backstop like we do to ensure the missed is set or verified at the same point on every go around, you run the risk of it not happening, especially with a crew that’s distracted and doesn’t do many non-precisions.
2 Likes
Yes. The map view is causing a lot of issues with frame rates. The zoom function is too severe as well.
Navigraph charts crash every so often.
And lots of features are missing from the EFB generally, forcing you to use the cdu. It’s a primitive solution that probably needs a redesign. FBW and Fenix are miles ahead.
I really like flying it though. But I just prefer the Boeing way I guess.