Pitch problems

[Christopher Low 5,352]

Since I updated to the latest P3D v4 version of the 747, I have noticed that the plane "pitches down quite suddenly" when the thrust reduces at the top of a climb. I would not expect such a heavy aircraft to do this, and I do not see it in either the 737 NGX or 777. I guess at this point it is also worth mentioning the "bounce" when thrust is reduced to idle at the start of the descent. Can I ask if these two "issues" (since I consider them to be so) will be addressed by the upcoming patch?

EDIT: I have just noticed that the update has been released!

Edited January 13, 2019 by Christopher Low

[downscc 1,327]

1 hour ago, Christopher Low said:

I have noticed that the plane "pitches down quite suddenly" when the thrust reduces at the top of a climb

Are you handflying when reaching top of climb?  Using A/T with A/P disconnected?  I don't understand how pitch/power coupling would be a thing if you were using the AFCS so gotta ask.

[Christopher Low 5,352]

When I say "top of climb", in this case it is a quick take off/circuit/landing, so TOC is only 4000 feet. Autopilot and autothrottle engaged. LNAV and VNAV engaged.

Edited January 13, 2019 by Christopher Low

[downscc 1,327]

Chris, the aircraft is going to have challenges to level off at 4000 if light, and I'm not surprised you are seeing some pitch excursions.  Even with derated takeoff and climb thrust settings it is sometimes better to hand fly with manual throttle in these cases, or load the tanks so you have some weight.

[Sekkha 15]

3 hours ago, Christopher Low said:

 the plane "pitches down quite suddenly" when the thrust reduces at the top of a climb. I would not expect such a heavy aircraft to do this,

meanwhile leveling of at 4000 ft with low weights is really a special situation as Dan pointed out,   I must say that I have always found the autopilot quite jerky and unsmooth in the pitch axis on the speed by pitch modes. This is absolutely  the only thing which I really reall dislike about this aircraft. Especially on climbout and in combination with sharp  turns many times the plane is rocking up and down in a way which feels very "unorganic" for such a heavy aircraft and is for me quite immersion killing.............:(

(probaby many wont agree, but immersion is highly subjective.....)

 

best regards

[Christopher Low 5,352]

I do not recall the "sudden pitch drop" after thrust reduction when flying the plane in P3D v3.4, and it does look rather strange for such a large aircraft. I am not convinced that it should react like that, even when it is light. For the record, I also have the fuel set to MEDIUM range, so a lot more than is actually necessary (although there are no passengers on board).

Edited January 14, 2019 by Christopher Low

[VHOJT 172]

13 hours ago, Sekkha said:

meanwhile leveling of at 4000 ft with low weights is really a special situation as Dan pointed out,   I must say that I have always found the autopilot quite jerky and unsmooth in the pitch axis on the speed by pitch modes. This is absolutely  the only thing which I really reall dislike about this aircraft. Especially on climbout and in combination with sharp  turns many times the plane is rocking up and down in a way which feels very "unorganic" for such a heavy aircraft and is for me quite immersion killing.............:(

(probaby many wont agree, but immersion is highly subjective.....)

 

best regards

The whole pitch instability during turns, and turns tracking, has been mentioned before, affecting all PMDG aircraft.  I think I recall correctly in that it was going to take an enormous amount of work to resolve this issue.  @downscc might be able to clarify.  It is certainly something that is on my wish-list to be resolved.

Here is a post related to this issue:

I agree the aircraft seem to pitch up and down a lot when in VNAV SPD or FLCH modes - whether or not this is realistic, I don't know, I am not a B744 pilot and haven't tried such a thing in a Level D sim.  I suspect it isn't.

Edited January 14, 2019 by VHOJT

[Sekkha 15]

4 hours ago, Christopher Low said:

I do not recall the "sudden pitch drop" after thrust reduction when flying the plane in P3D v3.4, 

I also find it more pronounced recently, but I suppose that in my case it is just because after over time having learned a bit to live with it  I only recently learned how smooth the MaddogX is doing this......and I just wanted to cry when I came back to the queen and got this rocking climbout and turns...  I dont think that actually anything changed from P3D V3 to V4 in this regard, but  of course I dont know.....

[Christopher Low 5,352]

I assume that nothing has changed in this regard after the latest update? I only just noticed last night that the "big Christmas update" was released on January 6, so I have not had a chance to test the updated version yet.

[Christopher Low 5,352]

The 777 is not affected by either this "pitch down suddenly on reduction of thrust" problem, or the "bounce" just after TOD. It is super smooth on both occasions.

[VHOJT 172]

7 hours ago, Sekkha said:

I also find it more pronounced recently, but I suppose that in my case it is just because after over time having learned a bit to live with it  I only recently learned how smooth the MaddogX is doing this......and I just wanted to cry when I came back to the queen and got this rocking climbout and turns...  I dont think that actually anything changed from P3D V3 to V4 in this regard, but  of course I dont know.....

Yeah, it is a little disappointing from one of the top developers to be honest.  It does take away from the immersion quite pronounced pitching up and down chasing one knot of speed with the autopllot, as well as everyhing else discussed.  Very noticeable when coming back from the FSL A320 etc.

[berts 97]

10 hours ago, VHOJT said:

I agree the aircraft seem to pitch up and down a lot when in VNAV SPD or FLCH modes - whether or not this is realistic, I don't know, I am not a B744 pilot and haven't tried such a thing in a Level D sim.  I suspect it isn't.

This is disappointing and not realistic if it is happening to you, because the actual aircraft is very stable in flight due to its large inertia - provided it is kept in trim of course.  Whenever I have seen this sort of pitching effect in the QOTS II, I have usually found it to be either an out of trim or hardware calibration issue - although this is not always the case.

Dan said in a recent B777 Forum Post "The QOTSII does a better job than the 777 but they (i.e. PMDG) still need to elevate it above the underlying code and do it their way in my opinion."   I tend to agree.

Edited January 14, 2019 by berts
Additional quote

[Sekkha 15]

10 hours ago, berts said:

because the actual aircraft is very stable in flight due to its large inertia 

thanks for your  info, I am of course not a RW 744 pilot but  I imagined that because it is a really heavy bird...

10 hours ago, berts said:

 Whenever I have seen this sort of pitching effect in the QOTS II, I have usually found it to be either an out of trim or hardware calibration issue - although this is not always the case.

But we are talking about the autopilot here. So trimming should be done automatically then , shouldnt it?

As by options my hardware controller should not interfere when the autopilot is switched on, so this is also not likely to be the cause for this behaviour..

 

best regards

 

P.S.  I cant say anything about any other PMDG aircraft, I only have the 744

Edited January 15, 2019 by Sekkha

[berts 97]

3 hours ago, Sekkha said:

But we are talking about the autopilot here. So trimming should be done automatically then , shouldnt it?

As by options my hardware controller should not interfere when the autopilot is switched on, so this is also not likely to be the cause for this behaviour..

In the real world, yes.  But we are talking about a PC simulation, aren't we? 

As I said, I did have a problem with the PMDG B744 autopilot pitching in the past and managed to fix it by recalibrating my hardware.  I accept this fix might not work for everyone, but it is certainly worth checking.  However, only PMDG and other addon developers will know what causes these sorts of issues to their software and what additional coding, if any, may be necessary within their own aircraft or scenery to fix them and to hopefully overcome the inherent shortfalls in the basic simulator programs and/or hardware drivers; especially in a simulator program as old as FSX with its limited memory issues.

[VHOJT 172]

9 hours ago, berts said:

In the real world, yes.  But we are talking about a PC simulation, aren't we? 

As I said, I did have a problem with the PMDG B744 autopilot pitching in the past and managed to fix it by recalibrating my hardware.  I accept this fix might not work for everyone, but it is certainly worth checking.  However, only PMDG and other addon developers will know what causes these sorts of issues to their software and what additional coding, if any, may be necessary within their own aircraft or scenery to fix them and to hopefully overcome the inherent shortfalls in the basic simulator programs and/or hardware drivers; especially in a simulator program as old as FSX with its limited memory issues.

I'm fairly sure it's not my controls - but you're right, it is worth checking.  I'll unplug them next time and see.

Cheers,
Rudy