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alex98

LNAV STAR issue

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Hi everybody,

 

I am experiencing LNAV issue since a few days.

I was using a Flightsim yoke with autocoordination ON and read that the PMDG 777 was not designed to be flown with autocoordination ON so I decided to switch to a joystick with rudder controlled by rotating the stick. I have to say that I rediscover my 777 and enjoy it a lot. But I also experience an over-anticipation of LNAV turns when following STARs.

 

For example, I recently flew from KJFK to SBGR and followed the ANSUG1B arrival for ILS09R. At some point, the STAR commands you to turn right almost 90° to downwind track. 5 NM before the turn, the plane starts turning and very soon I find myself way inside the turn by more than 1 NM. The plane levels off, turn left to join the magenta line, then turn right again and overshoots the flightpath. (Am I clear? Hope so... :pardon: ).

I must precise that:

- I have the latest version installed

- this problem happened AFTER I changed my flight controller.

- I have FSUIPC not registered

 

Thank you for any insight! :drinks:

 

Cheers,

Alex

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- this problem happened AFTER I changed my flight controller.

 

Not quite understanding the 'problem' here. Can you be more specific?

 

Also, keep in mind that the plane is going to behave more like the real one, which means that it must be flown realistically to behave realistically.

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Not quite understanding the 'problem' here. Can you be more specific?

 

Also, keep in mind that the plane is going to behave more like the real one, which means that it must be flown realistically to behave realistically.

 

Hi Kyle,

 

Let me try to be more specific.

During climb and cruise, the plane behaves perfectly. But I noticed on some occasions while flying STARs with some tight turns, the plane tends to anticipate way much that what I would have expected it to do. Something I do not experience with the NGX.

And as far as I remember I never experienced this "issue" before with the 777. So I asked myself - and the community - if maybe it could be related to the change of game controller (yoke to joystick).

 

Should I reinstall the 777?

 

Thanks for any help,

 

Alex

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Should I reinstall the 777?

 

That usually doesn't help anything, honestly. If anything, try installing/updating the driver on your hardware.

 

 

 

One thing you haven't addressed here is if you're on AP, or flying by hand. If you're on AP, I highly doubt the hardware change would cause what you're seeing. Sounds a little more like an awkward procedure. Are you flying into an airport that doesn't usually see 777s? Are you flying the STAR at 400 knots? 250? ...or a more realistic 220 or less for a downwind leg like that?

 

If it's by hand, then sure, your hardware is probably more of the issue, but the issue is more likely caused by you not being used to the new hardware.

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Hi Kyle,

 

I was on A/P around 270-250 KIAS.

In my example, we are flying from A to C with a right turn at B. Let say the AB leg is track 180° and the BC leg is track 270° (maybe more, maybe less). I would normally expect the plane to anticipate the turn 2 or 3 NM before B. Instead, the plane starts the right turn more than 5 miles before B at 25° bank angle and ends up right off track by 1 or 2 miles without reducing the bank angle. Then it corrects left and right again.

Maybe I was too fast for the turn? Possible. What is even more puzzling me is that nothing like this happens during SIDs where you could also deal with tight turns...

I guess it is one of those quirks I have to get used to.

 

By the way how do you deal with speed during STARS especially with tricky turns? I guess in RW ops crew is being given vectors most of the time anyway...

 

Thanks for your insight

 

Edit: Right after this episode, I experienced an OOM. Do you think it could be related to some memory issue? Seems strange.

I must say I almost never experience OOM. In some very rare occasions.

Edited by alex98

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I was on A/P around 270-250 KIAS.

 

And this was on the "downwind" per your original post? There's your issue.

 

By the way how do you deal with speed during STARS especially with tricky turns? I guess in RW ops crew is being given vectors most of the time anyway...

 

You slow down to a reasonable speed in the terminal area. Vectors aren't as common in places outside of the US. Other places use them, but they're not as common, from what I understand.

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Hi Kyle,

 

I was on A/P around 270-250 KIAS.

In my example, we are flying from A to C with a right turn at B. Let say the AB leg is track 180° and the BC leg is track 270° (maybe more, maybe less). I would normally expect the plane to anticipate the turn 2 or 3 NM before B. Instead, the plane starts the right turn more than 5 miles before B at 25° bank angle and ends up right off track by 1 or 2 miles without reducing the bank angle. Then it corrects left and right again.

Maybe I was too fast for the turn? Possible. What is even more puzzling me is that nothing like this happens during SIDs where you could also deal with tight turns...

I guess it is one of those quirks I have to get used to.

 

By the way how do you deal with speed during STARS especially with tricky turns? I guess in RW ops crew is being given vectors most of the time anyway...

 

Thanks for your insight

 

Edit: Right after this episode, I experienced an OOM. Do you think it could be related to some memory issue? Seems strange.

I must say I almost never experience OOM. In some very rare occasions.

Three different topics, I'll try to help.

 

I just flew to/from SBGR the other night simulating the AA flights and know exactly what you mean.  Those arrivals at Sao Paulo are usually ATC vectors on the base and intercept to final, so I usually start using the imaginary ATC in my head and MCP HDG in these cases. However, it is possible to continue with LNAV if you wish using a little trick:  As the aircraft is approaching the heading or track for the next segment, you can cancel the track error by pressing the LSB next to the next waypoint twice and EXEC. This recalculates the path from current position and eliminates the overcorrection that the simulation is prone to do with changes in heading over 30 deg.

 

Lacking any speed constraints in the arrival procedure, I keep it at or below 240 KIAS within 40 nm which is usually below 10000 so no big change but then I slow to Flap 5 on the intercept final segment. If there are tight turns like SBGR or even EGLL the speeds are going to be 220 KIAS or lower.

 

OOM errors are something that you need to be proactive with, follow the recommendations in the Introduction, use FSUIPC or Process Explorer as recommended in the Introduction to watch your VAS. I will normally save, quit, restart and load the flight if my VAS remaining is less than 1 GB at TOD... about 40 nm before TOD is a good time to do this and it usually restores over 0.800 GB of VAS.

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I am experiencing LNAV issue

If you are going to fast in a terminal area, what you are seeing is normal. If you have the ND range set at 10 or 20 miles you will think the A/C is sloppy in turns. You will see the same thing in the NGX if you are too fast and have your ND range set low.

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Thanks Kyle, downscc, pcubine for your help!

 

Problem solved -> shame on me. Did a quick GRU-GRU this morning to make sure it was not a overspeeding issue... and it was. Elevated airfield height plus going too fast on arrival and voila! Reduced to a more realistic 220kias before downwind and the Triple behaved like expected! I just need to anticipate way more than what I do with the NGX. This is how deep PMDG goes! :hi:

 

I guess you learn everyday. :wink:

 

Have a great day!

 

Alex

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