I have been working solely on the PMDG 737-600 recently as I was treated to a full size simulator flight with a real 737 pilot recently.

I have been making progress but the question I have not been able to resolve is the reason why I cannot engage VNAV. The are copious amounts of YouTube videos on the subject but many are quite a few years old so it's difficult to decide if they are still relevant. 

I have tried to replicate the flights in the videos but this isn't always easy as the tutorials often start in mid-air and it needs good eyesight to see where the flight originated from and destination.

The other issue that is repeated is the fact that the first waypoint has to be within 5 degrees from the departure course. I did find a YouTube tutorial on this but can't find it now. 

So far I have only found one tutorial where VNAV has worked "out of the box"

but I haven't been able to apply this to other flights. I greatly appreciate all the time and effort people put into creating the videos they are a source of endless information but it has to be said some are better than others and it's easy to get taken down a rabbit hole.

So the point of this post is a request what steps do I need to cover in order to be able to engage VNAV in simple terms including how to ensure the 5 degree rule for the first waypoint is covered.

Thanks

 

 

Edited October 7, 20241 yr by ivatt

A bit difficult to answer as we don’t know what you’ve done, or importantly, haven’t done. 

1. Have you programmed the FMC? 
2. Have you set the departure runway and SID? 

 

Sounds like Pilot error, Vnav works fine in that aircraft. 

1 hour ago, ivatt said:

 

So far I have only found one tutorial where VNAV has worked "out of the box"

So the point of this post is a request what steps do I need to cover in order to be able to engage VNAV in simple terms including how to ensure the 5 degree rule for the first waypoint is covered.

 

 

Unless I have just woken up extremely confused 5 Degree rule is for LNAV not VNAV - you can take off with VNAV engaged every flight, even taking off in heading mode I have never taken off without VNAV engaged.

Steps I follow (from memory):

Position Init / Load FlightPlan / Complete Performance Page / Legs (check and Load Winds) / Check & Set CLB, CRZ & DES Forecast / Set Departure (Recheck legs) / Set N1 Limit / Set TakeOff Performance / Set AP Init Altitude, Speed to V2, Runway heading / FDs ON / AutoThrottle On / Engage LNAV or Heading & VNAV.

Works every time......

G

Edited October 7, 20241 yr by Gazzareth

23 minutes ago, Gazzareth said:

 

Unless I have just woken up extremely confused 5 Degree rule is for LNAV not VNAV - you can take off with VNAV engaged every flight, even taking off in heading mode I have never taken off without VNAV engaged.

Steps I follow (from memory):

Position Init / Load FlightPlan / Complete Performance Page / Legs (check and Load Winds) / Check & Set CLB, CRZ & DES Forecast / Set Departure (Recheck legs) / Set N1 Limit / Set TakeOff Performance / Set AP Init Altitude, Speed to V2, Runway heading / FDs ON / AutoThrottle On / Engage LNAV or Heading & VNAV.

Works every time......

G

Or watch a tutorial video or two. There are many of them. 

VNAV is complex and takes a while to learn.

In case you haven't found them, A330 driver's videos are really helpful, he does a 15 part series on how to fly the 737 here:

And a VNAV video here:

 

A lot of times VNAV failing to engage comes down to controllers...  If there is a lot of noise in your throttle hardware in a lot of cases it can prevent VNAV from engaging.  No idea what this 5 degree thing is.  Never had any issues with VNAV here although I have the setting in the CDU to ignore my throttles when AT is active I believe.... 

The 5 degree thing is for LNAV. Not VNAV. 
 

Nevertheless, have you completely filled out your PERF INIT page? 
 

in order to arm VNAV on the ground…

a valid flight plan must be entered

performance data has been entered and executed 

both flight director switches must be ON

VNAV guidance becomes active at 400 AGL.

If you have done all these things correctly? Take it up with PMDG, you might have a specific issue regarding your specific set up and hardware.

Just a quickie, make sure both FD's are UP and A/T is armed?

If so then turn both off and reset A/T as real plane sometime needs this especially if another vertical mode/flight plan was engaged or deleted.

I'm going from reading the FCOMs regular not an IRL 737 pilot.

Also flight plan DEPARTURE must be complete. Missing runway is easy to miss, SID not enough must have RWY. 

Check or recycle IRS. 

Also load up a ready to fly panel state. Can't remember exact name as I never use it. Then enter same airport DEP/ARR set take off rway and do a quick INIT.

As others have said the basic PMDG tutorial should have you covered. 

The PMDG 736 is my most used simtube of all time.

10 hours ago, ivatt said:

 

I have been making progress but the question I have not been able to resolve is the reason why I cannot engage VNAV. The are copious amounts of YouTube videos on the subject but many are quite a few years old so it's difficult to decide if they are still relevant. 

 

OK, some statements need to be corrected here.

 

You need to have a departure (DEP) and arrival (ARR) airport, and in our specific case, a runway (RWY), standard instrument departure (SID), or a waypoint (WPT) connecting to a route to the destination.

 

PERF INIT must be completed. We need more details about that, or we can create a short flight between two airports.

 

You actually don't need a Flight Director (FD) or even an Autothrottle (A/T); they can be deferred (on MEL) and VNAV and LNAV will work just fine. 

 

I can create a short flight between KJFK and KEWR with all the data for you. You should be able to enter it in the Flight Management Computer (FMC), and it will work with FD on/off or A/T on/off. I strongly suggest following some tutorials first, and if you still have problems, we can try to find the issue.

6 hours ago, LRBS said:

 

 

I can create a short flight between KJFK and KEWR with all the data for you. You should be able to enter it in the Flight Management Computer (FMC), and it will work with FD on/off or A/T on/off. I strongly suggest following some tutorials first, and if you still have problems, we can try to find the issue.

 

Thanks that would be quite useful.

 

I appreciate all the comments and will endeavour to check and implement as and when I can. I am going to try the PMDG flight again just in case I missed something. It is most likely something I am missing to do.

 

9 hours ago, LRBS said:

...

 

PERF INIT must be completed. We need more details about that, or we can create a short flight between two airports.

 

...

If VNAV cannot be armed, the probable cause is: the PERF INIT page has not been filled in as written above but also validated by pressing the EXEC key

 

@ivatt, it's nothing to worry about. After a while, learning the preflight sequence will make it easy. Please keep us informed and ask for help. We all make mistakes for whatever reason and constantly learn. There is no stupid question, and nobody knows it all.

I would recommend closely following the PMDG 737 tutorial found in the documentation that comes with the PMDG 737.   Hi-lighting the essential steps can lead to building a check list that covers every essential step.  Using the tablet properly is also helpful in setting up a successful flight.

 

Jim Driskell