Go around after being vectored

[Hadi]

Hello,

I wanted to try a GA at the end of my last flight, and noticed I was unable to engage LNAV after the GA procedure (TOGA, flaps 15, set GA trust, positive climb gear up).

I think the reason is because I used HDG mode in order to get established on the localizer, so the FMC still had a previous waypoint at the top of the legs page, and also in the top right corner of the ND. So I got a discontinuity and was unable to engage LNAV.

Here is an example at KLAS, rwy 26l, we have a vector at the end of the COKTL2 arrival, so I used HDG mode to get on localizer course. On the screenshots you can see the next waypoint is (VECTOR), so after going around I can't engage LNAV to follow the missed approach.

The solution I found is, when on final course to the rwy, to put RWY26L at the top of the legs page. By doing that I am able to engage LNAV at 400ft ABGL and follow the missed approach procedure.

Edit: you can also see I'm low on profile, by making a direct to rw in the legs page I get back on profile.

Of course I don't get that issue when I stay in LNAV all along.

Is this the normal behavior? So every time I am being vectored I need to put RWxx on top in case of GA?

Thanks, I hope it's clear enough.

[Captain Kevin]

Hadi, any time you have a vector, that means air traffic control would tell you where to go. If you don't have air traffic control available, you could just drop the next fix, in this case, BERBN, into the line where the vector is. LNAV won't work if vector is the active waypoint because, by definition, air traffic control would vector you, so LNAV wouldn't know where you want to go.

[Hadi]

Hadi, any time you have a vector, that means air traffic control would tell you where to go. If you don't have air traffic control available, you could just drop the next fix, in this case, BERBN, into the line where the vector is. LNAV won't work if vector is the active waypoint because, by definition, air traffic control would vector you, so LNAV wouldn't know where you want to go.

Hi!

I think I was unclear.

My question is : when doing a go around, is it normal that the missed approach doesn't become active in the FMC? After doing the GA I can't engage LNAV because the active waypoint is behind me, in this example it's the vector which doesn't go away by itself.

He asked the same thing more clearly

https://www.pprune.org/tech-log/537105-737ng-go-around-waypoint-sequencing.html

[Nathan7378]

Hi!

I think I was unclear.

My question is : when doing a go around, is it normal that the missed approach doesn't become active in the FMC? After doing the GA I can't engage LNAV because the active waypoint is behind me, in this example it's the vector which doesn't go away by itself.

He asked the same thing more clearly
https://www.pprune.org/tech-log/5371...equencing.html

This is accurate behaviour. The FMC will only sequence the missed approach sequence when you pass the last waypoint on the IAP, but in order to do that you must delete the VECTOR beforehand. When you move off the STAR onto the IAP, the correct practice is to remove the VECTOR at the end of the STAR and allow the FMC to begin sequencing the next set of waypoints on the approach procedure, as you described. If you do not do that, the FMC will remain on the VECTOR for the STAR and will not cycle to the next legs (including the missed approach sequence).

If you are flying with ATC, you can remove the VECTOR the moment you begin receiving ATC vectors off the STAR and are cleared for the approach. If not flying with ATC, you would do the same when you begin vectoring yourself off the STAR.

-Nathan Chetram

[Captain Kevin]

Hi!

I think I was unclear.

My question is : when doing a go around, is it normal that the missed approach doesn't become active in the FMC? After doing the GA I can't engage LNAV because the active waypoint is behind me, in this example it's the vector which doesn't go away by itself.

He asked the same thing more clearly
https://www.pprune.org/tech-log/5371...equencing.html

No, I understood what you were saying quite clearly, and my response doesn't change. VECTOR on the FMC is the point in which air traffic control would typically guide you towards the runway. LNAV won't work when VECTOR is the active waypoint because it doesn't know what the air traffic controller wants, so can't guide you. Prior to starting your approach, if you take BERBN and drop it where VECTOR is to make it the active waypoint, LNAV would be able to follow the FMC route. Otherwise, as long as VECTOR is active, LNAV will never work.

[Hadi]

No, I understood what you were saying quite clearly, and my response doesn't change. VECTOR on the FMC is the point in which air traffic control would typically guide you towards the runway. LNAV won't work when VECTOR is the active waypoint because it doesn't know what the air traffic controller wants, so can't guide you. Prior to starting your approach, if you take BERBN and drop it where VECTOR is to make it the active waypoint, LNAV would be able to follow the FMC route. Otherwise, as long as VECTOR is active, LNAV will never work.

I know that Captain, that’s not what I asked.

I was asking if it was normal that the vector stayed active in the FMC even after going around. I thought the FMC would automatically sequence the missed approach in order to be able to engage LNAV. I don’t remember but I think the bus does that, need to to try again.

Nathan perfectly answered my question.

I rarely go around except for training so I had never noticed before that the FMC would not sequence the missed approach after a vector, or even after skipping the end of the star when being vectored, without updating the FMC.

[Captain Kevin]

I know that Captain, that’s not what I asked.

I was asking if it was normal that the vector stayed active in the FMC even after going around. I thought the FMC would automatically sequence the missed approach in order to be able to engage LNAV. I don’t remember but I think the bus does that, need to to try again.

Nathan perfectly answered my question.

I rarely go around except for training so I had never noticed before that the FMC would not sequence the missed approach after a vector, or even after skipping the end of the star when being vectored, without updating the FMC.

I don't know anything about Airbus, but as far as the Boeing jets, from what I can tell, it follows the sequence as depicted in the FMC, so if you have it on a vector, it just stays there, even after a missed approach.

[N347DT]

If you go missed, you are obligated to execute the procedure. After the miss, you should see Hold in the FMC. Press the appropriate lsk/rks to place on the clipboard and then the vector key. This will take you to the hold. Catch a breath, Then, reload your approach and activate by Leaving the hold, as cleared by ATC.
home

Hope that helps.

[Captain Kevin]

If you go missed, you are obligated to execute the procedure. After the miss, you should see Hold in the FMC. Press the appropriate lsk/rks to place on the clipboard and then the vector key. This will take you to the hold. Catch a breath, Then, reload your approach and activate by Leaving the hold, as cleared by ATC.
home

His issue is even trying to execute the procedure in the first place since the STAR took him to a vector and he never set it up to execute the initial approach to the runway, let alone make it to the missed approach procedure. As far as being obligated to execute the procedure, that could go either way. If air traffic control gives you something different, then you'd follow that instead.

[Hadi]

His issue is even trying to execute the procedure in the first place since the STAR took him to a vector and he never set it up to execute the initial approach to the runway, let alone make it to the missed approach procedure. As far as being obligated to execute the procedure, that could go either way. If air traffic control gives you something different, then you'd follow that instead.

Please don’t make up wrong statements.

I know what a vector means, and I did the approach after vectoring myself, it was absolutely not what I asked (and I’m used to being vectored on VATSIM). It seems that you really have not understood my point. My point was the fact that the Vector remained the active waypoint even after doing the approach and the go-around.

I never asked what a vector is, I don’t know why you insist on that.

Anyway, no need to debate further, Nathan gave the perfect answer to this topic.

[Captain Kevin]

Please don’t make up wrong statements.

I know what a vector means, and I did the approach after vectoring myself, it was absolutely not what I asked (and I’m used to being vectored on VATSIM). It seems that you really have not understood my point. My point was the fact that the Vector remained the active waypoint even after doing the approach and the go-around.

I never asked what a vector is, I don’t know why you insist on that.

I'm not sure what was wrong with what I said. The STAR took you to a point where you would get vectored, that point is true based on your screenshots. You never set the FMC up to execute the initial approach to the runway, that point is true based on your screenshots. Because of that point, you weren't able to use LNAV to execute the missed approach procedure because the FMC wasn't set up to do so, nor would it automatically do so. Therefore, Gregory's advice wasn't really going to help solve your issue, which was what I was responding to. At no point did I ever question whether you knew what a vector was, there must be a misunderstanding somewhere.

[AngelofAttack]

It's realistic behavior for FMC, and not only (VECTOR), but it could also happen if you have a non-disconnect STAR inputed but ATC have vectored you from a very far away route and you fly it via HDGSEL without modify LEGS page.
While not SOP, the recommended procedure for us is once clear for approach, bring IF/FACF (eg. CI26, CD26 etc..) to the first and input runway or final approach course in R6 then EXEC.