This varies by company. Starting a descent with VNAV isn’t the problem, it’s the ATC vectoring and constraints that can cause issues with the calculated VNAV path later in the descent. There’s nothing wrong switching over to LVL CHG as you get closer to the airport.
1 Like
Adding to @ncbartschi 's point, since ATC will very often vector you off a STAR in order to streamline their incoming traffic, VNAV PTH becomes redundant.
Furthermore, in the climb & (in particular) step-climb phases, VNAV couldn’t care less about passenger comfort. You’ll see it referenced in a couple of MentourPilot’s videos for example, that pilots often use v/s mode near ToC to make it an overall smoother transition.
Yes for sure, But I am trying to help the poster, get to grips with the Plane.. SOP’s just confuse matters. If they at least get to the point where they are comfortably flying the plane and not arriving high on their approach then they can get into the details.
If you watch FlightDecktoSim for example who is also a real 737 Pilot he never uses VS at all in the climb, I am not saying he does not IRL I dont know that, but I would imagine he fly’s as he does IRL, but the point is getting into Airline SOP’s only confuse things when you are learning.
It also important to take what Real World Pilots say in the specific context.
In Fact I came here to post a link to his latest live stream where he is on VATSIM and I have time stamped it where is setting up the VNAV. I was thinking it may help @SBarker12:
I would say dont worry about the Fix points he is adding for now, you can get to that
Yes. obviously if you are taken off the STAR then VNAV Path becomes redundant, but I have no info on how he is flying I just know he said he has found that he is always too high or too fast, that’s not a great and must be frustrating.
I really wish people would look at what people are trying to explain to others and stop measuring with obvious facts. I am aware of all the flaws, but as I have said, I am trying to help them have a successful flight, I doubt he is on VATSIM where he would get clear directions, and it is so much more easy, you are usually talked down, and vectored really well not always, but I rarely if ever have to refer to a chart on VATSIM, plus if you say you are new or struggling most VATSIM ATC are more than helpful! I was talked down once in the MD80 in X-Plane as I had totally messed up the approach.
I am not an airline pilot and I have stated I maybe wrong, but I just trying to help the guy, coming in stating the obvious or specific airline SOP’s is not going to help. Once they are comfortable with the plane flying it more or less as it should be or without much change to what it wants to do, then they can get into other stuff, so please either help out too or word stuff better, because right now I feel like you have not and it just puts people off helping.
Ultimately I have stated there are a few real world 737 pilots in this thread and I hope they can chime in and help @SBarker12: and maybe teach us non pilots something.
@ncbartschi: Point taken but as I said above, I have no idea how the person is flying the plane, I am trying help them get down, and land using the VANV, again I am aware of the fact that if ATC take you off, then VANV becomes a problem, but MS ATC is garbage, and I doubt and do not know if he is flowing any ATC! So the best action would be to use VNAV down and get comfortable with that, maybe get those charts etc.
If I am using Pilot2ATC for example, actually in my last flight to EDDP prime air, I was cleared for the STAR started going down, but at about FL70 I started getting vectors for whatever reason it wanted me at FL30 a lot quicker than the charts and even though I was fine on the STAR it decided that I should be vectored, so yeah Level Change or VS was the choice at that point, But let’s get the easiest path first, then they can get into it, is my feelings. I can’t understand why we need all the If’s and but’s at this stage, it just confuses matters IMHO.
3 Likes
Wow, I’m surprised the company that started the hyper-realistic would skip a detail such as this. Then again, their failures engine doesn’t appear to be even close to what Fenix has brought to the table. Even the circuit breakers, which I would think would be a fairly common source of minor, transient glitches, doesn’t work, so that might create an issue.
But secondary flight plans? Your plane doesn’t have to break to need that, just have bad enough weather.
3 Likes
Available where?
Mochas gracias!
It’s amazing to me just how difficult it is becoming to tell if videos like this are from real life or the sim. You still can, especially the colorization just doesn’t compare that well to reality, but I imagine in just a short amount of time…
What a weirdly unhinged and aggressive response.
@SBarker12 is already doing the correct thing by having good knowledge of all 3 vertical control modes and using them respectively to manage energy sufficiently through descent. And as he/she already mentioned, they had better success doing it that way. In this regard, I have nothing more to suggest to them other than to keep practicing and to be meticulous in their descent planning. The further input from myself and several others in this thread have been to further deter them from relying solely on VNAV, so it is indeed very relevant (contrary to the dictatorship that you seem to think you have over this thread)
EDIT: I see the swear words and some of the aggressive tone has since been edited out from your post. Nice save. 
Looks like one of the mods made the edit. I don’t think it’s worth continuing this topic regarding the VNAV descent pitfalls, as I think another user and myself have made our point clear. I’m not sure why VNAV has become such a controversial topic, but it’s really very simple.
1 Like
Generally using V/S near TOC is an absolute no no, and completely unnecessary. Why? Because it’s very easy to set a V/S that is beyond the performance characteristics of the aircraft. For example, some people think setting a V/S of 1000fpm is the thing to do as you approach your level off, notwithstanding the fact that VNAV or LVL CHG / FLCH have very complex altitude acquire logic built in. So you set 1000 fpm but the aircraft performance can only give you ~500fpm. What will happen to the speed? You got it…it will decrease. Then something comes along that distracts you and as still sadly happens, one pilot doesn’t focus on flying the aircraft. Before you know it you have a completely avoidable slow speed event. That would never happen using more capable autopilot modes.
To then justify this on the basis of passenger comfort is also pretty daft. People wouldn’t have the slightest clue what you were doing up front, except for perhaps during an emergency descent. The 737’s VNAV isn’t as capable as more modern aircraft but it is still very good and there’s no reason not to use it to it’s full capabilities, and that includes off a STAR. As long as there is a pink string for it to follow it will work just fine.
1 Like
As much as ingame ATC is frustrating at times, the stepped descents do really mess with VNAV path. I’m constantly finding myself above the required path. Last night into KLAS RNAV 08R and ATC late to descend me. I was kind of prepared for their late instructions, but VNAV path suddenly got away from me (happens in a blink of an eye it would seem). I had to switch to V/S mode to descend faster, before switching into APPR mode for G/S path descent.
I think it would work great without having to factor ATC in. Are real ATC this much of a pain to deal with IRL?
Always wondered how flight level requests are done and caried out. In FS you are restritced ATC wise to max altitude change of 10000 ft (or less) at a time, what is more common procedure wise IRL? I suspect VNAV would probably work great if at FL360 you could request FL30 and leave it to do its thing.
Absolutely they are! 
Generally by necessity though, the guys and girls controlling the London TMA and the airfields in and around it have a hellishly complicated job to do and they do it very well.
I could sit and write a 5000 word essay on descent profiles, autopilot modes and energy management but I have a life so won’t be doing that 
However, in a nutshell on the 737;
- I’d still use VNAV wherever I can but it’s generally personal preference. Properly programmed it’s a great tool
- If you get an intermediate level off and start to get high on the profile either speed intervene or use ALT HLD to open the speed window. Store energy by reducing your speed.
- Once you get cleared for further descent get that going and wind the speed back up to at, or beyond, your target. You’ll get a sporty ROD, if you need more use the speedbrake.
- I generally only use V/S on the latter stages of the approach to achieve a constant descent on to the glide or if I need to take immediate control of the aircraft’s climb or descent rate, for example a TA warning.
4 Likes
I was a little confused by this remark. I think you mean reduce speed to create some room for more (kinetic) energy later?
Wouldn’t ATC be surprised if you suddenly reduce speed?
Thanks for your insights, and I hope that you can find the time to write that essay. I would certainly be interested to read it!
1 Like
Whichever terminology you use it achieve’s the same thing. I’m trying to put it in laymans terms and clearly failing, but yes, you reduce speed to store kinetic energy allowing you a significantly higher rate of descent to regain the profile. I’ve seen 5,000fpm at times which is totally fine.
Unless ATC assign you a speed it’s yours to do with as you see fit. As a pilot descent management is always a trade off between you flying the aircraft and the demands of ATC. In many parts of the world ATC ask impossible things of you, flying the aircraft safely is always our first priority. Make of that what you will 
2 Likes
Thanks for this very useful insight. I will try to slow down more when levelled off, seems like I need to contemplate energy more. I take it you just do a manual override on speed as opposed to change the target speeds in FMS VNAV profile?
I think the bits in ATC in game that annoy me the most are the step downs where you level off for maybe <1min due to ATC delays or ATC passing control over to a new ATC area, which interrupts a nice VNAV descent profile. If you say request FL260 from FL360 and they then say descend to FL290 and expect FL260, but are late calling the FL260 part it’s very annoying.
I regularly dial in FL260, and sometimes it works as they quickly give you clearance. Other times they just shout at you for being below your cleared level.
Is this just an in game quirk/anomaly? Or reflective of the real world?
In reality, the ATC would do their utmost to keep you descending on a constant glide (traffic allowing) and/or even tell you to cross a waypoint at a certain altitude. They are also happy to tell other aircraft to “standby” if they have a more time-constrained message to deliver to another aircraft first (such as a vector onto final approach or further descent clearance).
1 Like
I think this is not what the 737driver is saying in his tutorials with the 3 2 1 rule..
1 Like
Yes, Which is why one the famous pilots saying is:
“I can go down or slow down, but I can’t do both”
1 Like
It totally depends on which airport.
Busier bigger airport overstacked with traffics (plus hellish weather)? Forget VNAV, listen to ATC if you don’t want to bump the queue. You’ll get instructions to slow down way more than what is required in the path.
Smaller airports with sparse traffic? Just follow the VNAV.
1 Like
Truth is it’s both. It’s very very rare to be given a single descent clearance from cruise to platform, particularly in Europe.
1 Like
Are you saying that you are trying to follow the commands of the in-game ATC? Maybe it’s just me but I gave that up as impossible ages ago. I got sick of being told to maintain FL 290, when in reality, according to the STAR I’m on, I should be at 6,000’. Once I’m at cruising altitude, I simply ignore ATC for the rest of the flight.
Or are you using VATSIM or some ATC program that actually uses a bit of logic?
1 Like