Auto flight Navigation and Auto Flight.

[Oskar Speer 22]

Hi! I have a problem when I planing a flight from LFMN. I create a rout in FMC as usual, get a aktive rout, T/O and press A/P on. Then the aircraft will not follow the aktive rout, she try to returns to the ORIGIN. As you can see at the picture neater time "Z" or distans "NM" are displayed.  The issue only occurs at LFMN. What do I do wrong?

//Oscar Speer

 

 

 

 

 

[Samany69 41]

Hello Oscar.

Can you show me a Picture of your PFD as well ? I want to make sure you have LNAV Armed ( that is what lets AFDS to command the A/P to follow the Required Lateral Navigation Path entered and activated in FMCS ). Do not forget to have Flight Director and LNAV Armed. 

Edit:

Assuming your picture is just a sample not what you are really trying to do, I hope you understand that the Airplane will not move and taxi around with Engines off magically and will not follow the active route without being Airborne and 250ft AGL at least.

Regards.

 

-S.

Edited May 20, 2018 by Samany69
extra edit.

[Johannvr 3]

Oskar, I don't think you're doing anything wrong here. This looks like the RNAV SID off rwy 04L/R at LFMN with the first "arbitrary" waypoint on hdg 043 deg. when at 420 ft. then turning right to track radial 138 outbound from NIZ VOR till 8 dme, etc. Seeing you are still stationary, no distance or time to this first waypoint can thus be calculated and so none displayed. Have you tried manual flying the SID till the second point and then select A/P? It works for me. It's actually fun to fly the whole departure manually.🙂

 

Edited May 20, 2018 by Johannvr

[Oskar Speer 22]

Hi, Johann and Saman! Yes I have fly the sid with manually input to A/P (HDG, Speed, Altitud). It works:-) The problem occurs at 4000 ft AGL or higher. Yes, LNAV, VNAV and FD are on. I have this issue only at LFMN. 

[downscc 1,327]

The departure  procedure looks like it is missing something.  This is the BADOD6E (this is not a RNAV procedure Johann).  It is normal for the distance and time to not be display until after you takeoff, first the time is unknown until you start flying and second the distance is unknow because it is a conditional waypoint (043 until 420... how far is that?  You don't know until have a rate of climb to predict the distance).

6 hours ago, Oskar Speer said:

Then the aircraft will not follow the aktive rout, she try to returns to the ORIGIN.

This is what I don't understand.  The aircraft should fly to the ndb and not the airport after passing NIZ d11.  You haven't provided enough information to figure out why this happens.

[Oskar Speer 22]

    The picture from my flight LFMN-ESGG. If I engage LNAV the aircraft turns back to ORIGIN. Disconnect LNAV and input data to A/P manually and it works fine again.  In the ND, you can see that "Z" and "NM" data is missing. This issue only occurs when T/O from LFMN. In addition, tonight during the flight, the left CDU just get a Black Out (=the display goes black) when I press "FMC". I guesses that I have done several wrong commands. Dan, I do not know what kind of info you need from me about the flight but maybe you can tell what you need from me. The CDU FMC do not "EAT" way points and airways in the Legs page as it use to do. I can see them all in the display even if I left them behind during my route.

 

[berts 97]

10 hours ago, Oskar Speer said:

Hi! I have a problem when I planing a flight from LFMN. I create a rout in FMC as usual, get a aktive rout, T/O and press A/P on. Then the aircraft will not follow the aktive rout, she try to returns to the ORIGIN. As you can see at the picture neater time "Z" or distans "NM" are displayed.  The issue only occurs at LFMN. What do I do wrong?

//Oscar Speer

The first three entries on your LEGS page (   420); (NIZ-8) and (NIZ-11) are all conditional waypoints.  They are NOT in a fixed geographical position and only indicate when an event will occur.  Because these three conditional waypoints are relatively close in to the airfield it is perhaps hardly surpising you are having problems trying to reconcile your initial LNAV tracking.  Every flight is different on the day, but it can sometimes be easier to look through the Flight Director and fly the aircraft manually using VNAV and LNAV in these situations, possibly until you are cleared direct to NCNB or AMIRO; then you can engage the autopilot.  Incidentally, LFMN is not the only airfield where conditional waypoints are generated automatically when entering a SID or STAR and you will find you cannot enter conditional waypoints manually.

To get rid of the waypoints behind you all you need do is activate a direct intercept to the next waypoint.

Bertie G

Edited May 20, 2018 by berts
additional info

[downscc 1,327]

I've seen problems with the NGX/777 and cascaded conditional waypoints in other cases.  For example, selecting the OCK transition for an EGLL ILS will lock up the PMDG FMS.  This was fixed in the 747 QOTSII.  I think the NGX should fly these three cascaded conditionals but it seems not to want to... and in other cases I've seen the ND rendering a wrong direction turn only to have the FMS/AP follow through on the correct course.  Having said all that (it should but has a bug) in RW were I piloting the departure I'd either be selecting one of the many RNAV based procedures or handflying this one until I was direct AMIRO and hand it off to otto at that time.

By the way, glad you posted this. I used to visit Nimes for a couple of days every year when stationed in Germany and taking my summer vacation in Spain. Nimes was a great place to stop overnight. Such a beautiful and historic city.  I feel in love with it and used to dream I'd retire to the South of France.. haha. Well, South of Texas will have to do and my visits to Nimes will be a simulator.

EDIT:  I've been looking at your picture and I cannot make out the LEGS page on the CDU.  Is the FMS advancing through each of the conditional waypoints as you pass them?  You should be getting a time an distance to waypoint once you are enroute to that waypoint.  Also, climbing through FL290 on the departure looks very odd..not sure what you got going on there.

Edited May 20, 2018 by downscc

[Christopher Low 5,332]

EDIT

Edited May 21, 2018 by Christopher Low

[Copper. 78]

I will try the departure for myself. Whilst I do, can you provide me with:

zero fuel weight, fuel load, the flight planned route you are following, cruise altitude, cost index.

[Copper. 78]

My attempt at it. At 12 mins is the takeoff roll. Please don’t rate my crap performance. It was an experiment flight (definitely has nothing to do with my crap piloting skills lol). This was second shot at the SID. First attempt had same fmc/lnav behaviour.

At 12 minutes mark is start takeoff roll (no atc, no traffic, nadp1). As you can see, not sure if normal or not, fmc/lnav path rendering a bit off... not sure what to expect from real world fmc or what manuals say. Dan seems to know a fair bit. Anyone else care to chime in? Lnav tried somewhere in the climb, but as expected, would not track properly as op originally reports.

For all I know, this could be normal behaviour....... I don’t know.

 

 

Edited May 22, 2018 by Copper.

[Oskar Speer 22]

On 5/20/2018 at 11:08 PM, berts said:

The first three entries on your LEGS page (   420); (NIZ-8) and (NIZ-11) are all conditional waypoints.  They are NOT in a fixed geographical position and only indicate when an event will occur.  Because these three conditional waypoints are relatively close in to the airfield it is perhaps hardly surpising you are having problems trying to reconcile your initial LNAV tracking.  Every flight is different on the day, but it can sometimes be easier to look through the Flight Director and fly the aircraft manually using VNAV and LNAV in these situations, possibly until you are cleared direct to NCNB or AMIRO; then you can engage the autopilot.  Incidentally, LFMN is not the only airfield where conditional waypoints are generated automatically when entering a SID or STAR and you will find you cannot enter conditional waypoints manually.

To get rid of the waypoints behind you all you need do is activate a direct intercept to the next waypoint.

Bertie G

Yes, you are right. I going to create a flight from LFMN to morrow when I get time for the simulator and activate a direct intercept to the next waypoint. I believe that the PMDG B744 is not a very advance simulator but still, I do not know how to "activate a direct" in this case. 

[Oskar Speer 22]

On 5/20/2018 at 11:27 PM, downscc said:

I've seen problems with the NGX/777 and cascaded conditional waypoints in other cases.  For example, selecting the OCK transition for an EGLL ILS will lock up the PMDG FMS.  This was fixed in the 747 QOTSII.  I think the NGX should fly these three cascaded conditionals but it seems not to want to... and in other cases I've seen the ND rendering a wrong direction turn only to have the FMS/AP follow through on the correct course.  Having said all that (it should but has a bug) in RW were I piloting the departure I'd either be selecting one of the many RNAV based procedures or handflying this one until I was direct AMIRO and hand it off to otto at that time.

By the way, glad you posted this. I used to visit Nimes for a couple of days every year when stationed in Germany and taking my summer vacation in Spain. Nimes was a great place to stop overnight. Such a beautiful and historic city.  I feel in love with it and used to dream I'd retire to the South of France.. haha. Well, South of Texas will have to do and my visits to Nimes will be a simulator.

EDIT:  I've been looking at your picture and I cannot make out the LEGS page on the CDU.  Is the FMS advancing through each of the conditional waypoints as you pass them?  You should be getting a time an distance to waypoint once you are enroute to that waypoint.  Also, climbing through FL290 on the departure looks very odd..not sure what you got going on there.

Strange thing happens. When I climb out from NIZ. The T/C in ND is marked much to early all ready at FL100 can I see the marker. In this case was T/C=350 (odd or not odd).

[Oskar Speer 22]

15 hours ago, Copper. said:

My attempt at it. At 12 mins is the takeoff roll. Please don’t rate my crap performance. It was an experiment flight (definitely has nothing to do with my crap piloting skills lol). This was second shot at the SID. First attempt had same fmc/lnav behaviour.

At 12 minutes mark is start takeoff roll (no atc, no traffic, nadp1). As you can see, not sure if normal or not, fmc/lnav path rendering a bit off... not sure what to expect from real world fmc or what manuals say. Dan seems to know a fair bit. Anyone else care to chime in? Lnav tried somewhere in the climb, but as expected, would not track properly as op originally reports.

For all I know, this could be normal behaviour....... I don’t know.

 

 

?

[Copper. 78]

16 hours ago, Oskar Speer said:

?

clearly the lnav path is not drawn properly. I inserted a few fix range rings and radial lines from which a mental picture of the early stage of the SID can be imagined and flown. fmc lnav path and charted sid do not reconcile.

 Additionally, the 2nd cond wpt in the sequence becomes active but never transitions to the 3rd cond wpt or to the nice ndb wpt, which is why when you engage a/p with lnav active, the plane turns back to the 2nd cond wpt spatially located near the 04r der.

In this example, I modify the fmc programmes sid and replace the 2nd and 3rd cond wpt's. The lnav path is drawn mostly correct. The intent was to test if it would work, and it did.

There is a problem with the sid nav data coding, or fmc, or both. I think the nav data cannot be coded properly because the fmc is not capable.

For those playing at home, the sid in concern is LFMN, BADOD6E - an ndb sid and below is the navigraph  nav data code string for the departure.

SID BADO6E RNW 04R RNW 04L TRK 043 UNTIL 420 TRK 138 UNTIL 8.0 FROM FIX NIZ TRK 158 UNTIL 11.0 FROM FIX NIZ TURN RIGHT DIRECT FIX NCNB AT OR ABOVE 6000 FIX AMIRO FIX BADOD