Hi everyone, I've had this problem for a while with my NGX. When I take off and then engage autopilot with VNAV and LNAV engaged my plane gets really violent and shoots up into the sky, sometimes at 8,000 fpm it pitch's up as high as 20 degrees, clearly this can't be normal. During decent it's not as bad but it will pitch down to 10 degrees and go for a 6,500 fpm dive to achieve its decent path! I've tried every route, double checked my sids and stars to make sure everything is programed into the FMC properly but the same thing happens. I Just wish it would start my decent sooner instead of shooting me into the earth. I wonder if cost index could have something to do with this? Although I've tried everything from 80 to 99. Wonder if anyone else if having this issue or if it's just me. I've included some pictures taken with my phone to shot you what I'm talking about.

CI on th 737 is normally in a range of 15-40 (or even only 35). Try if that helps!

Did you read through this thread:http://forum.avsim.net/topic/353013-revived-passengers-vomiting-in-vnav-mode-thread/page__view__findpost__p__2179295

No I didn'tThanks

With that CI you'll get hi descent speeds and therefore high V/S. Try a lower CIor set a lower descent speed manually in the cdu des page. That will give you an earlier T/D.

First pic not normal, second pic is if you're very light.. ATC tells you when to descend anyway, so start your descent sooner.. A typical vertical speed on initial descent should be around 2000-2500 fpm and around 1000 fpm below 10,000..

First on your descents are you helping the FMC out with entering winds aloft in the Forecast Page. This will help the plane think ahead and not just take conditions as they come.Also as Ryan explains in thread posted above by Chris this really should be expected with light loads and using such pitch/thrust mode and high CI entries. If that's your style on climb to cruse then you might want to just set a lower N1 manually (or Climb-2) or just set a comfortable V/S. But you must have a lack of understand how VNAV works, it's not thinking about PAX comfort but rather just getting the job done.On short routes/loads I use CI of 0-5 and normal loads 20 MAX.Also fulls names are required here on PMDG side of the AVSIM forum for support or your thread might be deleted. Just a heads up.

First on your descents are you helping the FMC out with entering winds aloft in the Forecast Page. This will help the plane think ahead and not just take conditions as they come.Also as Ryan explains in thread posted above by Chris this really should be expected with light loads and using such pitch/thrust mode and high CI entries. If that's your style on climb to cruse then you might want to just set a lower N1 manually (or Climb-2) or just set a comfortable V/S. But you must have a lack of understand how VNAV works, it's not thinking about PAX comfort but rather just getting the job done.On short routes/loads I use CI of 0-5 and normal loads 20 MAX.Also fulls names are required here on PMDG side of the AVSIM forum for support or your thread might be deleted. Just a heads up.

I am skeptic here, maybe I am wrong but I am skeptic.Assuming CI in the reality goes from 10 to 30 more or less, do you mean that if a real 737 flies with CI of 90 she takes off at 6000 fpm and she descends at 6000 fpm ?A real pilot should chime in to comment.

... do you mean that if a real 737 flies with CI of 90 she takes off at 6000 fpm and she descends at 6000 fpm ?

On a positioning flight with no passengers and a light fuel load, yes. Try the 'vomit comet' mission if you want a laugh.

I am skeptic here, maybe I am wrong but I am skeptic.Assuming CI in the reality goes from 10 to 30 more or less, do you mean that if a real 737 flies with CI of 90 she takes off at 6000 fpm and she descends at 6000 fpm ?A real pilot should chime in to comment.

Yeah, with a lightly loaded plane. You act like weight and thrust don't have a relationship together in this! Like I said VNAV isn't thinking about the pax comfort. So if you have high CI (90) and light load your going to see some sky rocketing climbs. It give the thrust needed (say 99.2% N1) and from witch a pitch in climb is flown and in this case it's 6000fpm.As for decent the Forecast Page within the Descend page is your friend

Pax don't care about V/S unless you're changing it rapidly or flying unpressurized. Pax can't tell the difference between 6000 fpm and 2000 fpm. Your fuel tanks do though: climb and descend at optimum rates, not 1-2000 fpm ( unless it's little altitude changes, then be smooth).

Pax don't care about V/S unless you're changing it rapidly or flying unpressurized. Pax can't tell the difference between 6000 fpm and 2000 fpm. Your fuel tanks do though: climb and descend at optimum rates, not 1-2000 fpm ( unless it's little altitude changes, then be smooth).

I'm sure the Pax will notice when the beverage cart slams into the flight deck door descending at 6000 fpm with 10 degrees nose down pitch..

I'm sure the Pax will notice when the beverage cart slams into the flight deck door descending at 6000 fpm with 10 degrees nose down pitch..

Surely it depends on the force and not the rate of descent or climb. If its a pitch for speed scenario you wouldn't really notice as you are at a constant speed.

Surely it depends on the force and not the rate of descent or climb. If its a pitch for speed scenario you wouldn't really notice as you are at a constant speed.

It's more dependent on the flight attendants applying the brake to the cart

gman1986, on 12 December 2011 - 08:24 AM, said:Surely it depends on the force and not the rate of descent or climb. If its a pitch for speed scenario you wouldn't really notice as you are at a constant speed.It's more dependent on the flight attendants applying the brake to the cart Please, don't call me Shirley.. haha.. No seriously, it's just not a real situation to have such a nose down pitch on descent.. ATC knows your aircraft type, and will call your descents accordingly so you don't have to nose dive.. There have been situations where descent was started 70 miles before T/D.. It depends on the sequencing, speeds, winds etc.. Rarely do you fly a full star into an airport and get vectored off your flight plan to intercept the loc or visual approach, then it's heading select, v/s mode or take it over manually.. I know some companies are different, but when I got into flying, I wanted to fly, not be a computer programmer .. I spoken to many pilots who agree with me that too much automation can cause more problems.. That's why Boeing designs their aircraft where the pilots always have the final say.. Cheers, happy holidays and all that good stuff..