747 FSX - Power setting surging in cruise w/autothrottle

[Guest David Ketchum]

Hi,With the latest update to the FSX 747, I'm noticing that with autothrottle engaged that engine power setting constantly surges up and down during cruise. I had orginally attributed this to FSX's goofy interal real-world weather logic (or lack thereof), but then tried it in calm/clear conditions. The problem does not seem to be related to wind. Also, I disconnected my USB throttle quadrant to make sure it was not the source of the problem and it still happens without it being attached.Specifically, the autothrottle does not seem to be able to find a power setting that results in constant mach number at alitude, and seems to spend the entire cruise portion of the flight searching for a power setting it can never find. Up and down, etc, never staying the same.I do get a stable Mach number cruise, it's just that the autothrottle has to yo-yo up and down constantly to maintain it. Has anyone else noticed this on their installation?I have the latest 2.10 update installed and I have also run the Flight1 registry repair toolThanks!-David Ketchum

[ccaughie 0]

David,I notice you replied to my post from a while back about this. I was hoping the service pack would fix the issue but it doesn't seem to have.It seems like the autothrottle logic is slightly flawed -- when the plane is going too slow the throttle increases to speed it up, but it doesn't pull back until the speed has already reached the target speed. But because it takes a few seconds for the thrust to drop in response, the plane keeps accelerating to a few knots over target speed, which means that the throttle then has to pull back to slow down again, and so the cycle continues.The LevelD 767 (the only other payware airliner I have to compare this with) doesn't seem to have this problem; it finds a stable thrust setting pretty quickly after reaching cruise.Colin

[Guest David Ketchum]

Hi Colin,I concur 100 percent with your observations, and as I mentioned in the other post experience the exact same thing. You are not alone. :)I wonder if anyone else will chime in with the same problem? This would help identify a problem with the software itself and make it more visible to PMDG hopefully.I will make a video of this phenomenon and post on Youtube later today to illustrate what's happening in hopes that perhaps PMDG can take a look at it. -David

[Vic1 3]

i too have noticed this but what with the other problems regarding heading select i am experiencing i have not mentioned it for fear of overloeding the forum with issueskav

[Vic1 3]

i may add that i see the exact symptoms you have deicribed here but also there is a slight porpoising effect too as the surging has an affect on vert speedthe surging is not always present but the other day the autopilot was not capable of correcting it i had to disconnect and hand fly the aircraft to correct the bouncing by thinking ahead insted of the deleyed auto throt reaction you have described. only then did it smooth outkav

[FOD 23]

Just to add my two penny {cents} worth. I have seen exactly the same problem since I installed the FSX update.John Rooum

[Beener 0]

I've seen this issue happening as well since the update.Norm Guindon.

[Guest grim_marmazet]

Im getting a similar problem, with the throttle constantly twitching up and down during flight.

[sddjd 117]

Add me to the list for the surging; it's not extreme, but noticeable.However, last night I did experience a strange behavior while cruising at fl325 in a loaded F. Suddenly engine 3 indicated an overspeed warning (not sure of the exact title, thrust on all four reduced, and the FMC popped up stating a max FL of 155....? After reducing alt and babying #3 back in line I was able to climb back to 325 and continue. However, the FMC continued to complain about max of 155.Note- this was with failures disabled in fsx.

[Jackie 0]

Yea add me to the list as well. Is there a fix for this problem

[usmc3073 3]

Add me to the list for the surging; it's not extreme, but noticeable. However, last night I did experience a strange behavior while cruising at fl325 in a loaded F. Suddenly engine 3 indicated an overspeed warning (not sure of the exact title, thrust on all four reduced, and the FMC popped up stating a max FL of 155....? After reducing alt and babying #3 back in line I was able to climb back to 325 and continue. However, the FMC continued to complain about max of 155. Note- this was with failures disabled in fsx.

I have the same problem as wellGuthrie Zuehlke

[achriste 0]

Hi, On the max alt warning, just press VNAV twice. And I also experience the surges in thrust @ cruise. Andrew Christe

[Guest Mower]

Still happens...is there a fix besides buying FSUIPC @$60 when I do not need it otherwise?It must be stressed that this problem does not happen, ever, with my LDS 763.IMHO that is a dangerous situation in need of immediate attention.Because, obviously, which product am I more liable to fly?Not trying to be snarky but just because this product has been out a while does it mean support for it is abandoned?Thanks.

[Sartanius 399]

I have this problem as well. It's really the only troubling issue I have with the PMDG 744. This behavior only occurs when VNAV Mode is enabled, both during cruise and descents. Oddly it doesn't happen during the climb phase. I recently got back into flight simming and am using the PMDG 744X in FSX SP2 on a Dell XPS 720 H2C running Windows 7 x64 RTM. If this one issue with the Queen could be resolved it would make this combination nearly unbeatable. Suggestions welcome...Doug

[downscc 1,327]

Doug, this old thread actually hints at several different symptoms.Is your indicated airspeed changing rapidly? Does it happen with no weather selected (clear all weather)?Or, are the throttles constantly moving back and forth? This is just an animation, doesn't affect flying.