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ESzczesniak

PMDG 737-800 Poor Early Climb/Nose Down Attitude

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I'm having a strange issue/response with the 737-800 in P3D v4.  I say strange, because I've used this aircraft extensively in P3D v3 and it has not behaved this way.  What I'm seeing is the aircraft has very poor acceleration from V2+20 to 250 kts after acceleration height.  During this time, the aircraft also takes a nose down attitude.  It seems the nose down attitude comes as I accelerate through 160-180 kts going to flaps 1.  The aircraft then often has no acceleration for seconds at a time, or is very slow.  Additionally, VS can be zero or descending, and rarely >500-1,000 fpm.   

I have ensured that I am trimmed appropriately for takeoff, have removed the derate from the FMC N1 limit page, and am relatively light (TOW 125-130,000 lbs).  Below is a picture of the PFD during this behavior...

7RftyQd.jpg

FMC vertical mode had been LVL CHG prior to ALT HLD/capture in this picture.  Remaining modes where in place for the entire climb.  As you can see, even though mode is ALT HLD, with flaps 1 and full CRZ thrust (was doing pattern work), there is almost no acceleration and a nose down attitude.

Any suggestions, ideas, or comments?  I no longer have P3D v3 installed on my system, so I can't test this again there.  However, she was always a solid performing in 3rd segment climb after AH in v3. 

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2 minutes ago, ESzczesniak said:

Any suggestions, ideas, or comments?

Bad flaps axis in FSUIPC. Remove the FSUIPC.ini file from your modules folder of your sim directory to verify. If it goes away, delete the file to let it rebuild (or put it back and troubleshoot). If it remains, put the file back.

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I imagine this won't surprise you, but that was it exactly.

For most aircraft, I have a Saitek yoke and quadrant.  However, I'm in the early stages of a 737NG home cockpit and have a motorized TQ.  I'm still using the yoke though and unknowingly when I assigned the yoke in FSUIPC, it kept the flap/spoiler settings from the Saitek quadrants as well, even though they weren't connected.

I should have guessed, as the spoiler lever was going crazy when I first got the bird in V4 and I realized it was this FSUIPC axis calibration interfering (removed that calibration it all was well).  I just didn't realize the flaps were also an issue, as they were being set just fine...but unbeknownst, messing up the flight dynamics. 

In case it helps any one else, I just deleted all the lines in FSUIPC.ini pertaining to flaps under my 737 profile, so everything else was able to stay the way it was for other aircraft. 

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Curious - the picture shows flaps 1 -
Am I mis-understanding that although the plane indicates flaps 1, the plane is somehow flying as if it is in a different flap setting? 

As in - the indicator says flaps 1, but the plane's flight dynamics are acting as if it is flying in flaps 10 or something.... is that whats going on?

I had a random flight in the past month where on approach the thing was dragging as if the flaps were down at 30... but clearly instrumentation showed flaps 1. It was obvious, the engines were up near 80-85% just to maintain speed on a descent path. I dropped the flaps and pulled them back up and it went back to normal. It happened once, never again.

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9 minutes ago, Nick Dobda said:

Curious - the picture shows flaps 1 -
Am I mis-understanding that although the plane indicates flaps 1, the plane is somehow flying as if it is in a different flap setting? 

As in - the indicator says flaps 1, but the plane's flight dynamics are acting as if it is flying in flaps 10 or something.... is that whats going on?

I had a random flight in the past month where on approach the thing was dragging as if the flaps were down at 30... but clearly instrumentation showed flaps 1. It was obvious, the engines were up near 80-85% just to maintain speed on a descent path. I dropped the flaps and pulled them back up and it went back to normal. It happened once, never again.

The answer to the issue was posted above by Kyle. Mapping the flaps axis to FSUIPC can cause this unusual behavior in flight physics. Following what he said will clear the issue. 

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11 minutes ago, Angelo Cosma said:

The answer to the issue was posted above by Kyle. Mapping the flaps axis to FSUIPC can cause this unusual behavior in flight physics. Following what he said will clear the issue. 

yeah I followed what Kyle said - which was FSUIPC's axis calibration caused the problem.

Eric's second post tied the flap axis to flight dynamics. 

I am confused in that I thought what the plane showed is what the flight dynamics governed. 

I thought that if you have an axis problem, your hardware might not match what is shown in the cabin - for example you might have your hardware throttle 50% up, but the VC would show the throttle full up (and the engines would be throttled up, there would be thrust... the flight dynamics would match what you are seeing in the VC and not necessarily what your hardware shows). To me thats what an axis problem would look like. 

My question is - can you have a disconnect between what you are seeing in the VC and the flight dynamics. Using the last example, can you see flaps 1 indicated in the VC and have the plane running the flight dynamics for flaps 30? In my head thats not an axis problem, thats some sort of programming problem. Maybe its just semantics that are confusing me.

I'm just clarifying what was discussed, I am not disagreeing with what was discussed, just trying to understand. 
 

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This FSUIPC problem appears here about once every week or so, wasn't hard to stab a guess at the problem give the unique circumstances.

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2 hours ago, Nick Dobda said:

yeah I followed what Kyle said - which was FSUIPC's axis calibration caused the problem.

Eric's second post tied the flap axis to flight dynamics. 

I am confused in that I thought what the plane showed is what the flight dynamics governed. 

I thought that if you have an axis problem, your hardware might not match what is shown in the cabin - for example you might have your hardware throttle 50% up, but the VC would show the throttle full up (and the engines would be throttled up, there would be thrust... the flight dynamics would match what you are seeing in the VC and not necessarily what your hardware shows). To me thats what an axis problem would look like. 

My question is - can you have a disconnect between what you are seeing in the VC and the flight dynamics. Using the last example, can you see flaps 1 indicated in the VC and have the plane running the flight dynamics for flaps 30? In my head thats not an axis problem, thats some sort of programming problem. Maybe its just semantics that are confusing me.

I'm just clarifying what was discussed, I am not disagreeing with what was discussed, just trying to understand. 
 

Simple warning hear, I have no real idea.  But it seemed like a lot more than a "different" flap setting.  The plane seemed to have helluva drag and slugish acceleration.  Even down the runway from 0-80 kts.  It messed with something with the flight model, but I have no idea what.  I would expect if it was simple acting as flaps 30 or whatever, then it would be similar to go-around performance.  It was not...just very odd. 

It was sneaky too, as I didn't think FSUIPC had any spoiler or flaps settings for the NGX.  Turns out it applied axis calibrations for controllers not even connected.  I know the PMDG birds have been built to work without FSUIPC, and in fact odd things can happen using FSUIPC.  So I thought I was keeping it to a minimal just using it for elevator/ailerons, but little did I know more came with that. 

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