Intercept Course To: INTC CRS TO VNAV switches to HDG/TRK ?

[downscc 1,327]

1 minute ago, sloppysmusic said:

It does not matter WHY I want to do this, the FCOM clearly states you CAN do it and does NOT state "entering a heading not on intercept will immediately cancel VNAV and put you on a TRK/HDG hold before you even press EXEC or ERASE"

You mean cancel LNAV?

I'm not agreeing that the FCOM is clear on this.  I don't think you can be in LNAV and then remain on or create a track to intercept a course inbound to a waypoint and remain in LNAV.  Change to HDG.  Then set up the intercept to course.

By all means you should write this up on a support ticket if you think the behavior of the PMDG product is incorrect.

[sloppysmusic 194]

17 minutes ago, downscc said:

You mean cancel LNAV?

I'm not agreeing that the FCOM is clear on this.  I don't think you can be in LNAV and then remain on or create a track to intercept a course inbound to a waypoint and remain in LNAV

Yes cancel VNAV without EXEC confirmation is the issue. YOu definitely CAN be in LNAV and change course however you wish and still remain in LNAV. Last night for example I used a short cut to intersect a waypoint (by skipping a leg) after a right turn that was just before T/D. As I pressed EXEC the waypoints disappeared until the intercept line 20 miles away and no TD displayed on ND. FMC still followed VNAV and LNAV by starting descent at correct spot (we talking no magenta lines/legs nothing here until the intercept line ahead - ND appears as if plane is floating in space with no legs or routes). Then when I reached the line plane turns right and we are back on course VNAV/LNAV remaining active the whole time. This is how FCOM alterations are supposed to work. VNAV/LNAV should always be active UNLESS you EXEC an invalid action (incompatible within the constraints of LNAV behavior).

Yes I will probably send a ticket I just wanted someone else to agree this was not normal behavior. Will make sure I wont use the word VNAV anywhere this time it confused the whole issue sorry again!

 

Edited February 11, 2019 by sloppysmusic

[sloppysmusic 194]

For the record here is my PMDG ticket request text, as my initial first post was wildly confusing with reference to VNAV instead of LNAV:

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Hi, the video shown below displays the behavior I am talking about. Following FCOM 2 11.42.9 Flight Management/Navigation/FMC Cruise.

https://www.youtube.com/watch?v=-Pe9IzQQUrA

In every other CDU route change procedure on this and every other plane of yours I have used no action is taken by the autopilot after leg page changes are made UNLESS EXEC to confirm the change or ERASE to delete the change is selected. There are 2 circumstances in this video when VNAV immediately and silently deactivates in the background without warning BEFORE either of these 2 buttons are pressed. The first time I noticed this was after I had flown of course for 10 miles and realized pane had put me in TRK HLD (therefore disconnecting AP roll mode I believe?).
This behavior happens every time
1) An intercept course NOT on current intercept heading is entered into RK6
or
2) ABEAM PTS (RK4) is selected
Would be very interested to know if this is intended behavior as it conflicts with the logic shown during every other FMC LEGS change procedure.
Usually the PROPOSED route change is shown on the ND where it stays until EXEC is pressed or ERASE is pressed. VNAV/LNAV always stay activated until a change is EXECUTED/ACTIVATED. 
Look forward to hearing what you pros make of this!
Regards
Russ
PS Love your planes more than ever once I dissect the FCOMS!

 

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I have total confidence in the pros at PMDG giving us a clear answer when they get a chance. These planes are wonders of engineering and the FCOMS reveal so many useful tip and tricks explaining how to take complete control of the planes whatever flight stage you are at.

[thibodba57 462]

@sloppysmusic I understand what you are saying.  You are correct.  PRIOR to any execute no mode changes shoulr happen.  Doesn't matter if you are or are not on an intercept heading.  After you hit EXEC then a mode change can be expected.

The protection is there in case you fat finger in a heading intercept or any other of a hundred reasons. Not that I've accidently ever fudged a number before.....

Edited February 12, 2019 by thibodba57