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Leif9619

VNAV-problem

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Hello guys,

 

I just completed my flight and don't know if it's an issue or not.

 

I started my descent from FL360 by pushing the altitude intervention knob. I was still some miles away from T/D.

So I was descending with approx. 1200fpm until I intercepted the glidepath. Then I was descending with 2500fpm, but the problem was that

the A/T didn't go to IDLE. The engines were running at ~70% N1 and the airplane got faster and faster. I manually pushed the speed intervention knob and the engine's N1 decreased to IDLE and then HOLD (which should be normal). I thought that the engines also should decrease to IDLE when VNAV glidepath is intercepted without speed intervention.

I also had a slight tailwind, but that shouldn't really matter.

 

Btw. I don't have FSUIPC and my hardware doesn't manually override A/T.

 

Although I know there are some issues with the default PMDG cold and dark state, I just want to mention that I don't get all the 'failures' like "HYD PRESS SYS L-C-R" or "ENG SHUTDOWN" when I turn on the batteries and the GPU. When I load another state I downloaded,all these information are shown in the upper EICAS.

 

Thanks fo your answers and well done PMDG!  :rolleyes:

 

Greetings

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I believe Ryan stated that this was a quirk of the actual 777 Flight Management System, so I think you're experiencing normal behavior!

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I thought that the engines also should decrease to IDLE when VNAV glidepath is intercepted without speed intervention.

 

Go to your PMDG Setup > Simulation settings and check to make sure your setting is not "IN HOLD/ARM MODE ONLY."  If it is, when the plane is in descent it will enter HOLD mode and allow you to override the throttle with your hardware,  If your hardware is still where you left it when you took off, when the plane hits HOLD mode, the throttles will sync to your hardware and you'll have an issue.  Either turn this mode to a setting where your hardware never overrides the AT, or get in the habit of setting your hardware on the idle stops before descent.

 

...also, have a gander at the into manual.  It describes all of the settings, and quirks of the plane.

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...also, have a gander at the into manual. It describes all of the settings, and quirks of the plane.

 

Hi Kyle -

 

Flying a real world route from KDEN - KORD last night and VNAV's ANP was way off. I was on the BULLZ5 arrival from MYRRS and the decent ended up being way to high once I got to the 14L approach. I hit all of the altitude restrictions within limits but when VNAV should've had me at 2500 to intercept the LOC I was actually at 7000 and had to go around. I did read the tutorial and manual completely. Any ideas on what went wrong? Thanks!

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That star requirs vectors, so my guess is that once you leave the arrival VNAV no longer has a path for you to follow. You may need to revert to MCP control and use SPD INTV and V/S to get to where you want to be.

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Flying a real world route from KDEN - KORD last night and VNAV's ANP was way off. I was on the BULLZ5 arrival from MYRRS and the decent ended up being way to high once I got to the 14L approach.

 

Careful there:

ANP is not how well the aircraft is tracking the horizontal/vertical track.  ANP is how well the aircraft can calculate where it is accurately, given all sources of information (in the case of the 777: the IRSs, GPS inputs, and VOR/DME).  What you're thinking of is path error (VERT DEV for vertical, and XTRK [ERROR] for horizontal).

 

If you hit all of the altitude restrictions, it points more towards some procedural error somewhere.  Looking at the STAR, it requires vectors, so a controller would be doing some vectoring to help you kill altitude.

 

EDIT: Dan beat me to the latter part  :wink:

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Hi Kyle -

 

Flying a real world route from KDEN - KORD last night and VNAV's ANP was way off. I was on the BULLZ5 arrival from MYRRS and the decent ended up being way to high once I got to the 14L approach. I hit all of the altitude restrictions within limits but when VNAV should've had me at 2500 to intercept the LOC I was actually at 7000 and had to go around. I did read the tutorial and manual completely. Any ideas on what went wrong? Thanks!

 

 

+1: Had the option 'never override' enabled and my descents ended up with speed higher than magenta and above descent path while engines were still running at some 60%.

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That star requirs vectors, so my guess is that once you leave the arrival VNAV no longer has a path for you to follow. You may need to revert to MCP control and use SPD INTV and V/S to get to where you want to be.

 


If you hit all of the altitude restrictions, it points more towards some procedural error somewhere. Looking at the STAR, it requires vectors, so a controller would be doing some vectoring to help you kill altitude.

Thanks Dan & Kyle! I do believe that is the reason. I wasn't flying with any ATC so I fully admit that I moved the first fix of the approach over the vector from the arrival. Chalk that one up in the "my bad" category. Thanks guys!

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Go to your PMDG Setup > Simulation settings and check to make sure your setting is not "IN HOLD/ARM MODE ONLY."  If it is, when the plane is in descent it will enter HOLD mode and allow you to override the throttle with your hardware,  If your hardware is still where you left it when you took off, when the plane hits HOLD mode, the throttles will sync to your hardware and you'll have an issue.  Either turn this mode to a setting where your hardware never overrides the AT, or get in the habit of setting your hardware on the idle stops before descent.

 

...also, have a gander at the into manual.  It describes all of the settings, and quirks of the plane.

 

 

I've experienced this problem with the override set to never as well. With the override set to never, moving my throttle hardware changes the thrust lever position in the sim in HOLD mode.  Is this considered normal for the programming as well?

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