ok, it’s just that I don’t remember this happening for me on previous versions. VNAV PATH was usually followed right until APPR engaged. It is following the path prior to suddenly drops it on the approach leg though.
You may be onto something with shortening path though as the latest incident was heading for EGCC 23R last night and the initial route was via MCT transition and I shortened it to vectors to final, so this would make sense. Will keep an eye out for that and monitor it the future. Thanks.
I find it very touch and go depending on the approach/STAR I’m on whether or not it’ll switch from VNAV PTH to VNAV SPD. When it switches I usually just deploy spoilers until VNAV PTH is back on.
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You have to intervene or VNAV PATH gets away from you quite fast. I find that nothing responds fast enough so resort to V/S (which does), but realise now that this is not SOP. Maybe I’ll try some spoilers instead. Or try entering a different speed in DES page.
Well that’s what we were asking from PMDG for a very long time, a correct simulation of what VNAV does in real life. As always, you’re flying the airplane. If you’re on VNAV PTH and suddenly the airplane recalculates and turns out that it’s high, it will not stay in VNAV PTH and dive for it. It’ll revert to VNAV SPD and the pilot is who has to regain path. Just do it in VNAV SPD at a higher speed and not in V/S. V/S is an undesirable mode.
If I’m descending at 260kts or so (econ speed based on CI) and suddenly ATC gives me a huge shortcut and now I have 20nm less to descend, I may be suddenly some 5000ft high. If I’m not speed restricted what I’ll usually do is use VNAV SPD and roll up the speed so that the airplane dives while still in a VNAV protected mode. Then I’ll type a faster speed in the DES page, something like .79/310. That should be enough to regain the path. Only if this isn’t enough I’ll use Speedbrake.
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Spoilers shouldn’t be the first course of action unless you’re speed restricted. First option is usually to increase descent speed. Just use VNAV SPD and dial in a faster speed and update the speed in the DES page. The airplane will recalculate a steeper path that it will most likely be already on or close to regaining.
Spoilers are usually used only during the last portion of descent when speeding up isn’t desirable or when we’re speed restricted by ATC or speed transition level.
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So are spoilers the best option in VNAV SPD? to descend faster or editing DES page ?
I often find that editing a page when you find a certain condition on approach is far from efficient process! It’s more like how do I get this bird down now when you are 10 miles out and high on path.
From what I have seen, when they choose a higher SPD, they don’t seem to update the descent page with that speed. The only major change I have seen has either been changing the 240/10000 to 250/10000 or adjusting the CI descent speed if there is a required speed higher than it, usually if it requires 290 which most CI are below that, least the one I fly with.
It’s always a good idea to update the speed in the FMC. Oldschool pilots may not update it, get slighly lower and then let the airplane decelerate and catch from below. Nothing wrong with that but it’s a higher workload for sure. Always keep your workload as low as possible as you don’t know what may distract you later on.
If you update the speed in the FMC, the deceleration points will be recalculated.
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I’ve never had a problem with just using spoilers to kick down the descent like I said. The more realistic way seems to be just increase the SPD and then enter that into the DES page. But then there’s the issue of if you dial up to 300 to get down but then you have a 250 restriction, would you then use spoilers to bleed that off?
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+1 on the decel points. Had not thought about that actually. Having simmed in my ways for so long I actually, as you stated, rarely if ever use the spoilers. I do have access to an old SOP but never looked into or researched procedures to follow VNAV profiles (not sure where it would be).
There’s nothing technically wrong in using the spoilers. It’s just something that new student pilots do coming from flightsim into the real airplane that captains will quickly correct and go “why spoilers?”. It’s just not elegant.
If you’re high and already flying the maximum speed you’re allowed to fly, say 250kts, then yes, spoilers or asking for more track miles are your only options. But if you’re descending through FL260 and have a lot of spare speed to use, why use spoilers? Spoilers are something you can forget and leave on if you have a sudden workload increase or get startled by something. Spoilers may become problematic in case you enter an upset. Just use them when they’re absolutely necessary and there are no other options. The best thing to do is to glide faster and to update the speed in the FMC. That’s the safest course of action and the most effective use of automation.
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Will give it a go on my next flight. The part I need more brush up and knowledge on would be properly slowing up from 250 to the SPD UP and not having to scramble to get the speed down and dropping flaps early or the gear which sometimes leaves me high.
Thanks. I am pretty sure that they were ILS and selected and tuned. It annunciated “GS” in the vertical mode and actually flew the ils properly down to minimums. If it happens again I will report the actual approach. I don’t remember which ones it happened.
It is flat-out awesome to read through your comments and really absorb just how much every decision on what to do with the airplane is made with a thorough consideration as to what is the safest option no matter the present circumstances. Your words speak volumes as to just how much work goes into making air travel what it is today. Thank you for taking the time to share your knowledge and thought process in a way that allows us to learn and enjoy the sim that much more.
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I’ve had about 5% of my approaches go awry when the aircraft doesn’t capture the GS. I’m on speed, localizer captured, at the correct altitude, with APP engaged and the aircraft just keeps flying at fixed altitude. By the time I note it, there is no chance to catch the GS and around I go. It’s quite annoying.
I concur. Thinking this latest update might be a step backwards.
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I have never had a situation where the PMDG 737 wouldn’t capture an ILS. It always works as expected. The same with Fenix A320.
Here’s a question for our real-world pilots (maybe @FormerSnail5736 ? 
) regarding the use of A/T during initial climb - I know that during approach the A/T should be disengaged as soon as you switch off the autopilot.
Now, what about AT without autopilot during initial climb? I usually like to hand-fly the whole SID (just more fun) and follow lateral/vertical guidance from the FD with VNAV/LNAV armed but I do not engage the autopilot for quite some time. Leaving A/T on reduces the workload but I’m wondering if I’m taking a flight-simming shortcut here and don’t follow real procedures…
So is this also a big no-no, similar to leaving A/T on during approach when disengaging the AP, or something that is done in real-world piloting too?
I’m pretty sure the issue is with me but I just haven’t been able to figure out what I’m doing wrong. It seems like in these cases, I’ve done everything by the book.
Really appreciate your insight. As a non-aviator, I’ve had multiple occurrences where I put the speedbrakes out and then start working on final approach, checking instruments and then notice 5 minutes later that I neglected to retract them (usually when I hear the engines spool up to a higher level than they should be at for that phase of the approach). It’s quite easy (for me at least) to lose situational awareness and forget about them. Based on your response, it sounds like this may have happened once or twice to the pros?