Help with VNAV on 777

[sideburn 0]

Hey guys,

 

I am having some issues learning how to get the VNAV to work with the FMC and the flight director/autopilot.

Everything is working perfectly except it is not auto controlling the vertical altitude even though I can see all of the flight levels in the FMC. The only way I can get the plane to climb or defend to the right altitude is to manually set it on the altitude control of the autopilot.

 

I have attached a screenshot so you can see all of my settings. You can see that VNAV, LNAV, and A/T are all enabled on the autopilot and you can see that the speeds/altitudes are set for each leg.. I can't figure out what I am missing...Can someone help me sort out my confusion?

 

 

Edited December 7, 2013 by firehawk44
Image removed. Exceeds 1600W and 400KB weight limit (yours 1.54MB). Please repost with proper size.

[Mike777 163]

 

 

I am having some issues learning how to get the VNAV to work with the FMC and the flight director/autopilot.

Everything is working perfectly except it is not auto controlling the vertical altitude even though I can see all of the flight levels in the FMC. The only way I can get the plane to climb or defend to the right altitude is to manually set it on the altitude control of the autopilot.

 

Hi, Sideburn,

 

I don't have the X-Plane version of the 777, but I'm familiar with several others.  In a climb, the aircraft should never climb above the altitude set in the MCP (autopilot) altitude window, no matter what altitude the FMC is set for at the next waypoint.  This is so that if ATC restricts you to a certain altitude, the aircraft won't go above that altitude.  Your altitude is set at 20,000, and the aircraft is holding at  that altitude, so it is behaving normally.  To climb further, you need to increase the altitude and possibly do something else, such as click on the center of the altitude setting dial. You need to check the manual.   When you get it right, you will see the engines spool up to max climb power and the leftmost  entry on the PFD change from speed to thrust, I believe. 

 

The same thing is true during descent.  It should not go below the altitude set in the MCP altitude window, no matter what altitude is set in the FMC.

 

Mike

[sideburn 0]

Hi, Sideburn,

 

I don't have the X-Plane version of the 777, but I'm familiar with several others.  In a climb, the aircraft should never climb above the altitude set in the MCP (autopilot) altitude window, no matter what altitude the FMC is set for at the next waypoint.  This is so that if ATC restricts you to a certain altitude, the aircraft won't go above that altitude.  Your altitude is set at 20,000, and the aircraft is holding at  that altitude, so it is behaving normally.  To climb further, you need to increase the altitude and possibly do something else, such as click on the center of the altitude setting dial. You need to check the manual.   When you get it right, you will see the engines spool up to max climb power and the leftmost  entry on the PFD change from speed to thrust, I believe. 

 

The same thing is true during descent.  It should not go below the altitude set in the MCP altitude window, no matter what altitude is set in the FMC.

 

Mike

But if one of my waypoints in my route has an altitude set of say 20,000 and I set my autopilot to 30,000 shouldn't it only climb to 20,000 while it is on that waypoint?

 

Right now my current leg is MZB and the altitude in the MCP is 14,000 feet.. my autopilot setting is 30000 feet and the plane is holding at 30,000. I am in the final approach and I am supposed to be descending.. I thought the MCP/FMS was supposed to descend for me?

Heres a better screen shot.. I am in the final legs of the route.. Should't the plane be descending to 14,149 feet?

 

 

 

Edited December 7, 2013 by firehawk44
Image removed. Exceeds 1600W and 400KB weight limit (yours 1.33MB). Please repost with proper size.

[Swe_Richard 1,172]

But if one of my waypoints in my route has an altitude set of say 20,000 and I set my autopilot to 30,000 shouldn't it only climb to 20,000 while it is on that waypoint?

 

Right now my current leg is MZB and the altitude in the MCP is 14,000 feet.. my autopilot setting is 30000 feet and the plane is holding at 30,000. I am in the final approach and I am supposed to be descending.. I thought the MCP/FMS was supposed to descend for me?

Heres a better screen shot.. I am in the final legs of the route.. Should't the plane be descending to 14,149 feet?

 

nav2.PNG

 

It won't descend as long as you haven't reset the altitude on the MCP. Try setting the altitude lower and it will descend on its own. Notice the FMC message. 

[sideburn 0]

It won't descend as long as you haven't reset the altitude on the MCP. Try setting the altitude lower and it will descend on its own. Notice the FMC message. 

Yeah I just noticed that and have been playing with it.. So you always have to manually get your altitude "in the ballpark" for the FMC to do its thing then basically?

Yeah I just noticed that and have been playing with it.. So you always have to manually get your altitude "in the ballpark" for the FMC to do its thing then basically?

In the beginning of my flight if I set the manual altitude to 40,000 feet and the FMC is set to 30,000 feet for a particular leg will it climb to 30,000 or will my manual setting override that and the plane will climb to 40,000? In other words does the FMC ONLY descend and ONLY if your current altitude is in range?

[Swe_Richard 1,172]

Yeah I just noticed that and have been playing with it.. So you always have to manually get your altitude "in the ballpark" for the FMC to do its thing then basically?

 

Well.. I usually set my cruising altitude before t/o. Then I don't really bother before the T/D point. I then reset to, say 2000 feet (depending on airport). It will then follow the altutude profile of the plan you have entered.

[sideburn 0]

OK Starting to clear things up.. Not sure what t/o is... still a newb with this stuff..

Another issue I have is that I am using simroutes.com to calculate out my waypoints to enter into the FMC but they hardly ever end up aligned with the runway. Am I better off just creating my own route using the x-plane map and finding VORs , waypoints etc myself so I can align with the runway better?

[Mike777 163]

 

 

In the beginning of my flight if I set the manual altitude to 40,000 feet and the FMC is set to 30,000 feet for a particular leg will it climb to 30,000 or will my manual setting override that and the plane will climb to 40,000? In other words does the FMC ONLY descend and ONLY if your current altitude is in range?

 

Hi, Sideburn,

 

We need to distinguish between climb, cruise and descent.  In the first part of your question, you are talking about climb.  If the FMC is showing a cruise altitude of 30,000 ft, and the MCP altitude is set to 40,000, the plane should climb until 30,000 and then level off.  In the cruise phase, you should see a Top of Descent (TOD or T/D) point (on the navigation screen and in the "progress" window of the FMC), which marks the beginning of the Descent phase.  The FMC should show the "reset MCP" message, which it is showing in your screen shot. At that point the FMC is expecting a lower altitude to begin the descent phase.  When you set a lower altitude in the MCP altitude window, it should start to descend, but to either a) the first fixed altitude of a later waypoint (in larger than normal numbers) or the altitude you have set in the MCP altitude window, whichever is higher. 

 

I am not familiar with the particular version of the 777 you have, since I don't have X-Plane.  But I am guessing that your 777 came with a detailed manual and possibly a tutorial flight or two.  I suggest you do the tutorial flights or read the manual section on VNAV.

 

 

 

Am I better off just creating my own route using the x-plane map and finding VORs , waypoints etc myself so I can align with the runway better?

 

If your T7 implements STARs and Runway approaches (often called IAPs), you need to add a runway approach.  See if clicking on the "DEP/ARR" button brings up a list of runways and choose one.  Again, this should be covered in your manual -- learning all the details of flight planning and FMC operation is best done by reading the manual and doing tutorial flights, if you have some that came with the aircraft.  This is a complex aircraft and you will learn it better that way.

 

Mike

[sideburn 0]

I don't know what's going on... I tried again KSFO to KSAN. I am in the final legs of the flight.. I am near the airport and the plane is still at 28,000 feet and cruising at 315kts.

 

According to the FMC, I should be at 295kts and descending to 7,000 feet right now. No matter what I try I cannot get the plane to descend. I have even changed my autopilot altitude to 7,000 feet and clicked the button in the center of the dial. I have tried reseting autopilot on and off, vnav and lnav on and off... no luck.

 

Screenshot attached of current situation:

 

 

Edited December 7, 2013 by firehawk44
Image removed. Exceeds 1600W and 400KB weight limit (yours 1.43MB). Please repost with proper size.

[Mike777 163]

 

 

According to the FMC, I should be at 295kts and descending to 7,000 feet right now. No matter what I try I cannot get the plane to descend. I have even changed my autopilot altitude to 7,000 feet and clicked the button in the center of the dial. I have tried reseting autopilot on and off, vnav and lnav on and off... no luck.

 

It's difficult to tell what is going on, as you have the navigation display in Plan mode instead of Map mode.  Plan mode is to be used for stepping through your flight plan to make sure the waypoints are entered correctly.  It is not meant for navigation.  Another thing I've noticed in several of your screen shots is that your altimeter is not properly set to standard (yellow "29.92" on PFD).  That's not why it isn't descending, but it leads me to believe that you have to go through the manual and/or tutorial flights.

 

Who is the author of the 777 you have?  Did it come with an instruction manual or tutorial flight? 

 

Mike

[sideburn 0]

It's difficult to tell what is going on, as you have the navigation display in Plan mode instead of Map mode.  Plan mode is to be used for stepping through your flight plan to make sure the waypoints are entered correctly.  It is not meant for navigation.  Another thing I've noticed in several of your screen shots is that your altimeter is not properly set to standard (yellow "29.92" on PFD).  That's not why it isn't descending, but it leads me to believe that you have to go through the manual and/or tutorial flights.

 

Who is the author of the 777 you have?  Did it come with an instruction manual or tutorial flight? 

 

Mike

It came with a manual. It is the official boeing manual. I've been reading it. There are some basic tutorials I have found and I have watched several on how to setup the MCP and VNAV but they work for them of course and not for me (yet) there must be some little thing I am missing..

I've been going through the manual and videos I can find on youtube but no luck yet. That is why I have resorted to this forum..

 

It is the 777 by Ramzzess & Philipp for x-plane. It is really impressive. High quality graphics and I thing 95% accurate to the real thing.

The manual, like I mentioned is the actual boeing manual with side notes on what is not simulated or different than the real 777 (and there are not many).

 

I toggled back and forth between standard and the othersetting on the PFD to see if it changed anything so that's not it but yeah, I have been kindof hacking my way through the learning process..

[Mike777 163]

 

 

I toggled back and forth between standard and the othersetting on the PFD to see if it changed anything so that's not it but yeah, I have been kindof hacking my way through the learning process..

 

Here are some resources:

 

This is Smartcockpit.com:

http://www.smartcockpit.com/plane/BOEING/B777.html

 

The pdf called "normal procedures" is more or less a step-by-step description of aircraft operation, and there are several other manuals that may be of help.

 

The JB panel by Greg Wilson, which is for FSX is free on Avsim.  It comes with a good manual which you can read without having FSX.However it is not realistic in that it uses FS only flight plans and doesn't have its own waypoint database.  I'm pretty sure your aircraft does.  So the manual will tell you to enter a flight plan in a way that won't make sense to you.

 

http://library.avsim.net/download.php?DLID=167467

 

The manuals are in the Docs folder inside the zip folder.  If the above link doesn't work search "777 jb panel wilson" in FSX>panels.  You want version 1.032.  This panel is not as good as most payware aircraft but it does have a working FMC and working VNAV.

 

Level-D simulations makes an excellent 767-300 for FS9 and FSX.  They have a very good manual that describes FMC operation among other things, and the manual is free:

http://www.leveldsim.com/sevensix_downloads.asp

Choose "download the operations manual".

The 767 is not identical with the T7, but the Boeing FMCs are all quite similar.

 

None of these is going to be perfect -- perhaps in your aircraft there is some way to activate a VNAV climb or descent that is different from what I am used to, which is clicking on the center of the altitude nob after setting the altitude.  That will be specific to the Ramzzees, and a generic manual may not cover it.  Nevertheless, most of the procedures are pretty standard, and you really need to go through a step-by-step tutorial.  Try the step-by-step from SmartCockpit first.

 

Mike

[Tabs 2,790]

I don't know what's going on... I tried again KSFO to KSAN. I am in the final legs of the flight.. I am near the airport and the plane is still at 28,000 feet and cruising at 315kts.

 

According to the FMC, I should be at 295kts and descending to 7,000 feet right now. No matter what I try I cannot get the plane to descend. I have even changed my autopilot altitude to 7,000 feet and clicked the button in the center of the dial. I have tried reseting autopilot on and off, vnav and lnav on and off... no luck.

 

Screenshot attached of current situation:

 

vnav3.PNG

 

I'm not with the developer of this particular package, but I know a thing or two about 777s...   

 

Notice your current pitch mode at the top of the PFD - VNAV ALT. What this means is that the altitude set in the MCP window conflicted with what VNAV wanted to do. My guess based on experience is that you didn't roll the MCP altitude knob down to 7000 until *after* you'd passed the top of descent (T/D) waypoint. That will most definitely lead to VNAV ALT and the plane will stay level. The only way the airplane will descend automatically at T/D is if you've lowered the MCP altitude *before* reaching T/D.  You'll notice (assuming this addon is modeled correctly) that the RESET MCP ALT message comes up in the scratchpad 2 minutes before T/D, not after it. To get out of the situation, you need to put the plane back into VNAV SPD or VNAV PTH mode by pressing the altitude selector knob after you've rolled it down to 7000 like this. That commands it to begin the descent. You will now be above the normal path though so you'll likely need drag and/or increased airspeed to get back onto the path from above. The normal mode for this is VNAV SPD and then once you're back onto the path it'll switch back to VNAV PTH.

 

Basically you should think of the MCP altitude window as a limiter on the FMC and VNAV making changes to your vertical flight path without your positive authorization. This is a safety feature in real life - you do not want the encoded altitudes of waypoints on a SID or STAR for instance causing the airplane to climb or descend beyond what ATC may have restricted you to. In real life deviations from what are on the chart are extremely common - ATC will have you do all kinds of things that aren't written there based on the current traffic situation, weather etc.

 

Now in a simming environment where you may not have ATC or traffic to worry about, what I usually do before T/D is roll it down to the restriction altitude for my first approach waypoint. This lets it fly the whole STAR hands off and it'll hit all the restrictions on the way down to the approach. Once you're at the approach you transition out of VNAV into G/S for the pitch mode anyway so it works out.

[sideburn 0]

I'm not with the developer of this particular package, but I know a thing or two about 777s...   

 

Notice your current pitch mode at the top of the PFD - VNAV ALT. What this means is that the altitude set in the MCP window conflicted with what VNAV wanted to do. My guess based on experience is that you didn't roll the MCP altitude knob down to 7000 until *after* you'd passed the top of descent (T/D) waypoint. That will most definitely lead to VNAV ALT and the plane will stay level. The only way the airplane will descend automatically at T/D is if you've lowered the MCP altitude *before* reaching T/D.  You'll notice (assuming this addon is modeled correctly) that the RESET MCP ALT message comes up in the scratchpad 2 minutes before T/D, not after it. To get out of the situation, you need to put the plane back into VNAV SPD or VNAV PTH mode by pressing the altitude selector knob after you've rolled it down to 7000 like this. That commands it to begin the descent. You will now be above the normal path though so you'll likely need drag and/or increased airspeed to get back onto the path from above. The normal mode for this is VNAV SPD and then once you're back onto the path it'll switch back to VNAV PTH.

 

Basically you should think of the MCP altitude window as a limiter on the FMC and VNAV making changes to your vertical flight path without your positive authorization. This is a safety feature in real life - you do not want the encoded altitudes of waypoints on a SID or STAR for instance causing the airplane to climb or descend beyond what ATC may have restricted you to. In real life deviations from what are on the chart are extremely common - ATC will have you do all kinds of things that aren't written there based on the current traffic situation, weather etc.

 

Now in a simming environment where you may not have ATC or traffic to worry about, what I usually do before T/D is roll it down to the restriction altitude for my first approach waypoint. This lets it fly the whole STAR hands off and it'll hit all the restrictions on the way down to the approach. Once you're at the approach you transition out of VNAV into G/S for the pitch mode anyway so it works out.

 

 

Thank you this is useful info and looks promising... I will try again tomorrow.

 

So is this the correct procedure:

 

1) Prior to take off set the altitude on the MCP to the same cruise altitude that is set in the FMC (in my case FL350, so set the MCP altitude to 35000). -- in my experience so far, doing this was causing the plane to climb straight to 35000 feet ignoring the altitude levels assigned to each leg/waypoint in the FMC's route --

 

2) When getting near the end of the route prior to the FMC's route leg/waypoint's descending altitudes, set the MCP altitude near a final approach altitude (say 2500 feet or so). -- the plane should not descend until we reach one of the leg/waypoints that has a lower altitude assigned to it.

 

Am I getting warmer ?

 

Thanks for the help everyone...

 

-Tavis

[Mike777 163]

 

 

So is this the correct procedure:



1) Prior to take off set the altitude on the MCP to the same cruise altitude that is set in the FMC (in my case FL350, so set the MCP altitude to 35000). -- in my experience so far, doing this was causing the plane to climb straight to 35000 feet ignoring the altitude levels assigned to each leg/waypoint in the FMC's route --

 

Altitudes that appear in waypoint entries in small print, 16500 are just predictive; VNAV will not treat them as restrictions. If the aircraft gets to the predicted altitude before that waypoint, it will still keep climbing.  But if the altitude is in large print, 15000 it is a restriction and VNAV should not go past that altitude until it passes that waypoint, whether climbing or descending.

 

ATC might restrict you to a lower altitude than your cruise altitude (or you might know there are other aircraft above you); in that case you set the MCP altitude window to the lower altitude, and VNAV should not allow the aircraft to climb above it.

 

 

 

2) When getting near the end of the route prior to the FMC's route leg/waypoint's descending altitudes, set the MCP altitude near a final approach altitude (say 2500 feet or so). -- the plane should not descend until we reach one of the leg/waypoints that has a lower altitude assigned to it.

 

Strictly speaking, you should set the altitude lower than cruise just before top of descent (TOD).  You should see TOD on the Progress page of the FMC and also on the magenta line on the Navigation map display.  Also, as already pointed out, you should see an FMC message "reset MCP altitude" or something similar.   The descent will start well before you reach a waypoint with a lower altitude set -- it is aiming to already BE at that altitude when it gets to that waypoint.

 

Again, on the way down ATC might tell you not to descend below a certain altitude.  If you set that in the MCP, the aircraft should not descend below that altitude until you change it.

 

 

 

Am I getting warmer ?

 

Yes!

 

Mike