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Skywolf

FMC not calculating altitude - VNAV disconnect - KMSP to KSFO

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Happy Holidays everyone,

I am enjoying my holiday today as I bought 2 new airports for my sim.  I am traveling a real world route with FSCaptain from KMSP to KSFO.  I can not figure out why FMC is not calculating altitude so that I can engage it.

My Airac is 1712

Here is route

KMSP/30L SCHEP9 ONL DCT NUXRO DCT VOAXA Q136 OAL DCT INYOE DYAMD3 KSFO/10L (or try 28L)

I am reading the FCOM2 11.30.X-11.42.X (going up and down the pdf, Just can't figure out on what is happening). 

Any suggestions on what is happening (I have searched the avsim forums for this but can not find an answer that I am looking for).  Can someone point me in a direction on how to solve this.

Thanks

Update:

Around DYAMD - FMC calculates T/D and right about here I am able to activate VNAV for descent. 

Quite confused why it isn't working before and then it works

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PEBKAC, usually. ;)   Probably didn't have something executed on the PERF INIT.

Previously when it wasn't working, were you able to activate VNAV? 

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11 minutes ago, Spin737 said:

PEBKAC, usually. ;)   Probably didn't have something executed on the PERF INIT.

Previously when it wasn't working, were you able to activate VNAV? 

PEBKAC??

I had everything in Perf Init.  I was even able to put the V-speeds in etc (just like in Tutorial 1 and Tutorial 2...and already done few other flights since doing those tutorials).  In all other flights VNAV worked.  But this time VNAV only worked right near the T/D.  T/D didn't even show up till I got to location in flight.

I hope this info is in FCom somewhere as it will provide answers.

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11 minutes ago, Skywolf said:

In all other flights VNAV worked.  But this time VNAV only worked right near the T/D.

I do not understand this, maybe I don't know what you mean when you say "VNAV worked."  Please describe in more detail, your use of VNAV could have many different meanings.  Does the VNAV button light when you press it?  What does the FMA indicate?  If TOD didn't show up until you got to the location of the TOD, then what predicted altitudes were shown in the FMS on the LEG pages?  If VNAV only worked near the TOD, what modes were you flying up to that point? Yeah, unable to decipher what you are doing or not doing.

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Hmmm. That sounds odd. The T/D should have been calculated long ago. The flight attendants should call you about an hour in and ask, "Are we there yet? How long until we start down?" etc. That's your cue to look at the Prog page and see how long until T/D. The T/D shouldn't just appear - unless you made some changes in your profile. If you change the descent (change speeds, alts, add a STAR, etc) that'll cause the T/D to recalculate. It should be there before that, though.

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44 minutes ago, downscc said:

I do not understand this, maybe I don't know what you mean when you say "VNAV worked."  Please describe in more detail, your use of VNAV could have many different meanings.  Does the VNAV button light when you press it?  What does the FMA indicate?  If TOD didn't show up until you got to the location of the TOD, then what predicted altitudes were shown in the FMS on the LEG pages?  If VNAV only worked near the TOD, what modes were you flying up to that point? Yeah, unable to decipher what you are doing or not doing.

As soon as I engage Autopilot, I can then activate LNAV but VNAV doesn't light up.  As soon I as I click on it, it lights up for a sec and disconnects and FMC points to VNAV Disconnect.  There were no predicated values.  See pictures attached.

43 minutes ago, Spin737 said:

Hmmm. That sounds odd. The T/D should have been calculated long ago. The flight attendants should call you about an hour in and ask, "Are we there yet? How long until we start down?" etc. That's your cue to look at the Prog page and see how long until T/D. The T/D shouldn't just appear - unless you made some changes in your profile. If you change the descent (change speeds, alts, add a STAR, etc) that'll cause the T/D to recalculate. It should be there before that, though.

Yes, it is very odd.  I wish FCOM had scenarios written in it. 
 

The FMC does not at all calculate the Altitude as soon as I press Activate.  The waypoint ARREX with 3100A turns purple.

 

It will be awesome once this issue is solved.

U13lvnc.png

 

 

Ez3teHT.png

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54 minutes ago, Ephedrin said:

Did you execute your perf init page?

I sure did.  I know it doesn't show up in the picture as the screenshot was taken before hand.

 

Can anyone try to put this in the FMC

KMSP/30L SCHEP9 ONL DCT NUXRO DCT VOAXA Q136 OAL DCT INYOE DYAMD3 KSFO/10L (or try 28L)

and execute it and see what happens on your FMC.

My Airac is 1712 (try something older and newer 1713).  I want to narrow it down.

I read the SID chart SCHEP9 for KMSP and I could not see weird in it (again, I am learning on how to read these charts).

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5 hours ago, Skywolf said:

As soon as I engage Autopilot, I can then activate LNAV but VNAV doesn't light up.  As soon I as I click on it, it lights up for a sec and disconnects and FMC points to VNAV Disconnect.  There were no predicated values.  See pictures attached.

Yes, it is very odd.  I wish FCOM had scenarios written in it. 
 

The FMC does not at all calculate the Altitude as soon as I press Activate.  The waypoint ARREX with 3100A turns purple.

 

It will be awesome once this issue is solved.

U13lvnc.png

 

 

Ez3teHT.png

you  fmc  is  telling  you  to  activate  the  route

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7 minutes ago, pete_auau said:

you  fmc  is  telling  you  to  activate  the  route

 I mentioned that before as stated above - that these screenshots were taken before activating.  I have activated the route when I started the flights etc. 

I will have to post new pictures with activated route

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34 minutes ago, Skywolf said:

 I mentioned that before as stated above - that these screenshots were taken before activating.  I have activated the route when I started the flights etc. 

I will have to post new pictures with activated route

ooops  sorry  about  that   didnt  read  all of  posts,  anyways  the issue  is  that  you have  entered  a much  too higher  alt,  try  setting  a  alt of  around  270  which  should  solve  your  issues

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2 hours ago, Skywolf said:

Can anyone try to put this in the FMC

KMSP/30L SCHEP9 ONL DCT NUXRO DCT VOAXA Q136 OAL DCT INYOE DYAMD3 KSFO/10L (or try 28L)

and execute it and see what happens on your FMC.

My Airac is 1712 (try something older and newer 1713).  I want to narrow it down.

I read the SID chart SCHEP9 for KMSP and I could not see weird in it (again, I am learning on how to read these charts).

Hi Skywolf,

I tried your route with the NGX in P3D 4.1 and I had predicted altitude for all waypoints as soon as I activated the route with the departure runway and SID selected. I was able to arm VNAV on the ground. After take-off, I activated AP at around 800ft above airport elevation with VNAV + LNAV working. VNAV stayed ON all the way to FL380, which was my final cruising altitude.

Once level, the PROG page of the CDU displayed that the TD point was 1203 nm ahead, but I did not have any TD circle displayed on the DU, which is normal since at that time, the TD would be some 80nm past the last waypoint of the route (INYOE) and I would still be at FL380 at that point. After entering the STAR and approach (DYAM3 with transition at INYOE for ILS28L) the TD circle was visible on the DU when looking at the far end of the route (using the PLN mode with STEP).

Note: I selected STAR and approach once I was level at FL380, but it should not make any difference if I had entered it while still on the ground before departure. It is just the way I do things.

So in short, I had no problem with VNAV on that route and I have no idea why you did. My AIRAC cycle is 1713.

Best regards and good luck !

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1 hour ago, NBouc said:

Hi Skywolf,

I tried your route with the NGX in P3D 4.1 and I had predicted altitude for all waypoints as soon as I activated the route with the departure runway and SID selected. I was able to arm VNAV on the ground. After take-off, I activated AP at around 800ft above airport elevation with VNAV + LNAV working. VNAV stayed ON all the way to FL380, which was my final cruising altitude.

Once level, the PROG page of the CDU displayed that the TD point was 1203 nm ahead, but I did not have any TD circle displayed on the DU, which is normal since at that time, the TD would be some 80nm past the last waypoint of the route (INYOE) and I would still be at FL380 at that point. After entering the STAR and approach (DYAM3 with transition at INYOE for ILS28L) the TD circle was visible on the DU when looking at the far end of the route (using the PLN mode with STEP).

Note: I selected STAR and approach once I was level at FL380, but it should not make any difference if I had entered it while still on the ground before departure. It is just the way I do things.

So in short, I had no problem with VNAV on that route and I have no idea why you did. My AIRAC cycle is 1713.

Best regards and good luck !

Thank You for trying this route.  I am going to exactly what you did.  My gut feeling is that it could be AIRAC 1712...lets see.  I will post results.  I Had tried my flight 5 times, and each time VNAV was unable to activate. 

Stay tuned for further results

Thanks @NBouc for your results and very grateful for your help on this (same goes out to everyone who has been helping me on this thread @pete_auau, @Spin737, @downscc, @Ephedrin thank you again)

 

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Looks like this problem is solved.  I deleted the navdata and reinstalled the Airac 1712 and now it is working.  I have the altitude predicted and the VNAV and LNAV are both enabled even on the ground as a test.

Thank You for everyone for helping me. 

I don't know how these gremlins show up in FSX-SE

But very grateful to everyone who has been helping me on this issue. 

 

This fmc issue is absolutely the most bizarre problem I have encountered in all my years in this hobby.

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a corrupted download or installation can do a lot of funny stuff it seems... glad it's working now for you. 

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