737NG Violently and Sporadically Pitching Up On Climbout

[Guest Longhornmaniac8]

Hello All,First off, love the PMDG products. I've had the 747-400 for a while, but just recently got the 737NG series. It took a little getting used to, but for the most part, I'm used to it. However, I have this one problem that is really keeping me from using it and enjoying it. After takeoff, when I activate LNAV and VNAV, the plane continues trimming up and pitching up very violently until it stalls. The initial altitude restriction on my next waypoint is not so high and close such that the plane would have to do this to "normally" reach it. I've tried the derated takeoff and climb, as well. I've read the manual (though quite possibly missed something important), and I can't for the life of me figure out what's going on. It does seem as though once I get a ways up (like 25,000 feet or higher), the VNAV will do the job correctly.Another problem I'm having is on descent, the VNAV doesn't correctly find the correct descent profile. It doesn't start far enough out (like less than 100nm out at a 39,000 feet cruising altitude.Can anyone help me out?!?!I'm using FS9, FWIW.Cheers,Cameron

[Tabs 2,790]

Cameron,Could you post some screenshots of what the panel and the FMC LEGS page look like when you're seeing this happen?

[Guest Longhornmaniac8]

Hello Ryan,I made another test flight from AUS-IAH, in a 737-800 with winglets. I'll let you guess the airline. ;)Basically, I had encountered this problem with several flights, although not all of them were immediately after takeoff (that being said, it did happen on two of the four). Here is my legs page (just page one, it's all that's relevant).I taxied to the runway, and here's what the overhead/main panels looked like:OverheadMain PanelI took off, activated the autopilot and VNAV, then shortly after LNAV. Nothing strange happened. Plane made a left turn on course, and a reasonable climb (albeit fairly fast ~3500 FPM). If you look back to the Legs page, you'll see my first waypoint, HOOKK, is estimated to be reached at ~13,500 feet. Although this fluctuated as I ascended a little bit, it did not change more than 1,000 feet in either direction. As I approached HOOKK, both altitude and distance wise, for some reason the FMC changed the target altitude to my cruising altitude, FL210. When it did this, I must've been at about 12,000 feet, and about 8 miles away from the waypoint. That would require about a 9,000 fpm vertical speed, something which my plane tried to accomplish. The result is a dramatic, and herky-jerky pitch up until stall.Pitch UpI have experienced this at some point during all of my flights. I do not know why my plane "decides" to do this, but it's really detracting from what would otherwise be an incredible add-on.Can you help me out?Cheers,CameronP.S. I'm not sure exactly why my plane on my last flight (from AUS-CUN on an Aeromexico 73G) had such an erratic/awful descent from FL390, but no such thing happened this flight (although it did have one >4000 fpm section for a second). Also, during descent, my VNAV disconnects a lot, as though it isn't properly calculating the descent path, and once it determines it can't fly the planned path, it disconnects. This leaves me manually entering altitudes a lot. Very frustrating.

[downscc 1,327]

I don't recommend using LVL CHG during a normal climb, I use it only for specific reasons... how does this same scenario work if you use VNAV?Note your MCP speed setting is A310.. that A in front of the number means that the speed is unattainable, you've got so much pitch that you're getting into deep stall zone. After that, you are totally out of control. Gotta fly the airplane, this airplane is flying itself.

[basa 0]

Cameron, At the present time I can't figure what is causing your problem, but let me tell you that there are some wrong things (in my humble amateur opinion) in your panels configuration.In the overhead you have not armed the emergency lights.You have not switched on the passenger signs and not set the pressurization altitudes.You should also set continuous ignition for takeoff.In the main panel before takeoff, you have some cautions lights on (you should check all of them).The speed window should show V2, not 250 (the under 10.000" speed), and wheter you fly by hand or with the AP you should change the value in the window according tho the flap retraction sequence (yes, it's a hard work for a crew of only one pilot).The heading window should show the rwy heading or your first leg heading....But still don't know what is cusing your problem...I'm not an expert as I said before.Best regards.

[Guest Longhornmaniac8]

>I don't recommend using LVL CHG during a normal climb, I use>it only for specific reasons... how does this same scenario>work if you use VNAV?>>Note your MCP speed setting is A310.. that A in front of the>number means that the speed is unattainable, you've got so>much pitch that you're getting into deep stall zone. After>that, you are totally out of control. Gotta fly the airplane,>this airplane is flying itself.>Dan,That is part of my problem. I did not set the LVL CHG. After takeoff, my LNAV and VNAV were the only two Autopilot functions enabled. It was only after my plane started pitching sporadically did the LVL CHG and SPD become selected.Thanks all for the replies!Cheers,Cameron

[downscc 1,327]

Let's look at your weather a moment... MSFS WX engine is terrible, and will give you wind shifts that will knock your nose cone off, or at least lead to the kind of problem you're having.Notice any wind, pressure or temperature shifts (MSFS messes with all of 'em)?What WX are you using?Do you have a registered version of FSUIPC?

[Guest Longhornmaniac8]

Hey Dan,I don't think it would've been the weather, as I do use Active Sky. I do have an unregistered copy of FSUIPC, though.Thanks for the continued help!Cheers,Cameron

[Tabs 2,790]

Active Sky, as good as it is, doesn't protect you from everything as far as potential stuff like this.It's very hard to say what could be going on here - a couple ideas:1. Weather shifts - this is definitely possible to see this sort of thing if you're getting sudden unrealistic wind, temperature and pressure shifts. I'd try to generate one of these situations while having the shift+Z messages open and watch the wind and TAT closely when the problem occurs.2. Joystick spiking - this seems unlikely because you're not getting an AP disconnect, but it could be possible.Can you tell me the exact route you're using and I'll try it myself?

[downscc 1,327]

In FS9, Active Sky works thru FSUIPC where it takes care of the weather smoothing. I recommend getting a registered version. The default aircraft do well enough with default WX but the PMDG planes are much more sensitive to the WX shifts. It's essential that you tame those.

[Guest Longhornmaniac8]

Hey Ryan and Dan,Thanks for the suggestions, thus far. I will definitely get a registered version on FSUIPC, and see where that leads me. I suppose it does make sense that a change in wind would result in such a dramatic change, but my question is, would it make the FMC change an altitude restriction so drastically as it did on this one?Ryan, my route was KAUS CWK3.ILEXY RIICE2 KIAH, if my memory serves me correctly.Thanks for the awesome suggestions!Cheers,Cameron

[Mats_J 2]

Gents,Before we get too deep into WX-related issues... Cameron, care to try your regular flight without ANY weather and see if you get the same issue?Hope it helps,