Pitch oscillation at curise altitude with 747

[downscc 1,327]

Nothing obviousely wrong jumps out at me.. the first two CLB shots appear normal. In the second one you are below 10,000 climbing at 257KIAS and the first one you have climbed above 10000 and are accelerating to climb speed. I notice you lost a 20kt tail wind so if that happened quickly then adjustments to pitch to control speed are necessary in msfs. It is normal for the green arc to vary during climbs. The descent looks like it is staying on the VNAV profile fairly well, but it is hard to see any difference in pitch that you are complaining about. Again, it is normal for the green banana to vary in VNAV. I notice you are descending to 2900 ft at ULUBA, about 15 nm ahead and the FMS speed but is 242 instead of 240 because of the min clean maneuvering speed at your current weight... I'd recommend first notch of flaps pretty soon to let the speed drop below 240 as you approach the terminal area.Let me ask this: What is the magnitude of the pitch oscillation (degrees) that concerns you? Ignore the green banana, how much is the nose going up and down on the PFD?

[sbclark 55]

Dan,It is very difficult to communicate this issue via static images when the issue is relative motion.The swings in altitude vary from -2100 to -1500 during the descent phase. The "Green Banana" swings are excessive, in my opinion, given the flight is being carried out in calm weather. For example it swings beyond the targeted way point and then comes way back ahead of it. The climb phase swings are similar to the descent phase in terms of the magnitude of the elevation swings. I still fly the LevelD 767 in FS9 on occasion, and it doesn't exhibit this characteristic, but I'm in the process of migrating to FSX, and I love this rendition of the 747-400X.The best way to communicate this is to send you a video, so maybe I could create a video and mail it to you, or post it on the server of my ISP if I have sufficient space to store a video there? Would FRAPS be the best tool to use? Please let me know what I should do next?Bill Clark

[FLEX1978 373]

Dan,It is very difficult to communicate this issue via static images when the issue is relative motion.The swings in altitude vary from -2100 to -1500 during the descent phase. The "Green Banana" swings are excessive, in my opinion, given the flight is being carried out in calm weather. For example it swings beyond the targeted way point and then comes way back ahead of it. The climb phase swings are similar to the descent phase in terms of the magnitude of the elevation swings. I still fly the LevelD 767 in FS9 on occasion, and it doesn't exhibit this characteristic, but I'm in the process of migrating to FSX, and I love this rendition of the 747-400X.The best way to communicate this is to send you a video, so maybe I could create a video and mail it to you, or post it on the server of my ISP if I have sufficient space to store a video there? Would FRAPS be the best tool to use? Please let me know what I should do next?Bill Clark

If the file is less then 100mb try http://drop.io/ Rob

[downscc 1,327]

The swings in altitude vary from -2100 to -1500 during the descent phase. The "Green Banana" swings are excessive, in my opinion, given the flight is being carried out in calm weather. For example it swings beyond the targeted way point and then comes way back ahead of it.

I think you mean the verticle speed varies from -2100 to -1800? That is not a problem, I asked how much the pitch changes. For example in your pics the nose is up about 4-5 deg in both pics in descent where you said there is much variance in pitch... is it only varying one degree or many more? This is how I would define a pitch oscillation.

[sbclark 55]

Dan,The pitching of the A/C is excessive in my opinion. The numbers I gave you (-2100 to -1800) are the only means I have to quantify this for you in terms of the pitching action.The ADI doesn't show any pitch change at all, but when looking outside the plane, or observing the "Green Banana," it is very evident that plane is pitching up and down continuously at a cyclic rate. I'll see if I can create a video in the next week or so as I'm not very good at articulating this issue.Bill Clark

[rsrandazzo 6,353]

Bill-A couple of things come to focus when looking at your images and reading your post.While you do not appear to have downloaded or set any WIND per se, you do have temperature variances taking place in your sim-world. Take a look at the temperature readout on the upper EICAS. You are flying through some extremely odd temperature ranges- and some rather extraordinary temperature inversions. I would expect to see a temperature SIGNIFICANTLY colder than the one you saw at FL200, and the temperature relationship between your climb and descent images is equally odd... So the environment you are flying in is not following even close to the standard adiabatic lapse rate...The result? As the air surrounding the wing changes in temperature, you are going to get different lift results- so the airplane is behaving correctly in this instance by adjusting the rate of descent to meet the VNAV PATH targets as needed. This is why you are using VNAV PATH after all- it is constantly monitoring your descent path and making adjustments to keep the airplane on a geometric PATH so that you arrive at the proper location in space, rather than simply flying you at a set vertical speed and accepting the results.Watching your green altitude intercept ring move around isn't really going to tell you much because it is (correctly) influenced by factoring Even a subtle change in '50/min will rill result in a large position change if you are still high in the descent. In the airplane, you use it to get a general idea that you are "in the neighborhood of your requirements" and for very fine tuning when in close if you are using V/S to manage the vertical component of, say, an NDB approach.One other item to point out- in your climb pics- the reason you might have seen some oscillation is that the airplane was in the acceleration/cleanup phase of flight. This is normal- and you want the airplane adjusting pitch to capture and maintain the target speed. In your images above- the airplane is doing precisely what I'd expect it to do....

[sbclark 55]

Bill-A couple of things come to focus when looking at your images and reading your post.While you do not appear to have downloaded or set any WIND per se, you do have temperature variances taking place in your sim-world. Take a look at the temperature readout on the upper EICAS. You are flying through some extremely odd temperature ranges- and some rather extraordinary temperature inversions. I would expect to see a temperature SIGNIFICANTLY colder than the one you saw at FL200, and the temperature relationship between your climb and descent images is equally odd... So the environment you are flying in is not following even close to the standard adiabatic lapse rate...The result? As the air surrounding the wing changes in temperature, you are going to get different lift results- so the airplane is behaving correctly in this instance by adjusting the rate of descent to meet the VNAV PATH targets as needed. This is why you are using VNAV PATH after all- it is constantly monitoring your descent path and making adjustments to keep the airplane on a geometric PATH so that you arrive at the proper location in space, rather than simply flying you at a set vertical speed and accepting the results.Watching your green altitude intercept ring move around isn't really going to tell you much because it is (correctly) influenced by factoring Even a subtle change in '50/min will rill result in a large position change if you are still high in the descent. In the airplane, you use it to get a general idea that you are "in the neighborhood of your requirements" and for very fine tuning when in close if you are using V/S to manage the vertical component of, say, an NDB approach.One other item to point out- in your climb pics- the reason you might have seen some oscillation is that the airplane was in the acceleration/cleanup phase of flight. This is normal- and you want the airplane adjusting pitch to capture and maintain the target speed. In your images above- the airplane is doing precisely what I'd expect it to do....

Rob and Dan,Thanks for your quick responses.Now that you mention the "temperature" discrepancies, I did think that they were rather low at cruise altitude, but didn't give much thought to it at the time. So you make an excellent point. Since I have made a concerted effort to move from FS9 to FSX, I'm beginning to notice a lot of funny quirks about FSX not seen before.Given this temperature anomaly is potentially the cause of the 747-400 oscillation behavior, I have some questions:1) Is there anything I can do to the FSX settings to bring these temperatures back into line?2) Has anyone experienced this temperature issue besides me?3) Should I purchase FSUIPC and change some parameters to mitigate this issue.....I have it installed in FS9? 4) I suppose I could try activating real weather in FSX to see what happens?5) I do have one more question, why does the 747 EICAS show the plane in CRZ when it is actually in descent phase?Thanks again,Bill Clark

[rsrandazzo 6,353]

Bill-1) Is there anything I can do to the FSX settings to bring these temperatures back into line?I find that the temperature variances are present in both FSX and FS9. They appear in slightly different ways, however. To mitigate them, I generally set weather to "real world static" unless using a 3rd party application such as ActiveSky. Even with a good product like ActiveSky- you'll still see some fluctuations- it's a part of the lifestyle of a sim pilot...2) Has anyone experienced this temperature issue besides me?Plenty of people. You'll find that if you are flying in areas where there are very few weather reporting stations (airports) you can get some very large fluctuations. These changes in the real world would cause the airplane to cease flying or disintegrate due to stress loads- but fortunately nature has some laws that it follows for temperature/pressure changes in a fluid...3) Should I purchase FSUIPC and change some parameters to mitigate this issue.....I have it installed in FS9? Others are probably in a bettter position to answer this question...4) I suppose I could try activating real weather in FSX to see what happens?See my answer to #1 above...5) I do have one more question, why does the 747 EICAS show the plane in CRZ when it is actually in descent phase?The EICAS isn't showing the airplane in CRZ... it is showing your THRUST LIMIT MODE in cruise. This can happen for a multitude of reasons, all of them pilot actions. :-) Without knowing how you managed your FMS, it would be hard to predict- but you can also force the thrust mode in most cases. (Some airlines don't even use CRZ thrust, for example- they force the FMS to remain in CLB thrust because you get better responsiveness and a higher maximum thrust limit, for example...)Hope we could help, Bill- Welcome to advanced simming. :-)

[sbclark 55]

Bill-1) Is there anything I can do to the FSX settings to bring these temperatures back into line?I find that the temperature variances are present in both FSX and FS9. They appear in slightly different ways, however. To mitigate them, I generally set weather to "real world static" unless using a 3rd party application such as ActiveSky. Even with a good product like ActiveSky- you'll still see some fluctuations- it's a part of the lifestyle of a sim pilot...2) Has anyone experienced this temperature issue besides me?Plenty of people. You'll find that if you are flying in areas where there are very few weather reporting stations (airports) you can get some very large fluctuations. These changes in the real world would cause the airplane to cease flying or disintegrate due to stress loads- but fortunately nature has some laws that it follows for temperature/pressure changes in a fluid...3) Should I purchase FSUIPC and change some parameters to mitigate this issue.....I have it installed in FS9? Others are probably in a bettter position to answer this question...4) I suppose I could try activating real weather in FSX to see what happens?See my answer to #1 above...5) I do have one more question, why does the 747 EICAS show the plane in CRZ when it is actually in descent phase?The EICAS isn't showing the airplane in CRZ... it is showing your THRUST LIMIT MODE in cruise. This can happen for a multitude of reasons, all of them pilot actions. :-) Without knowing how you managed your FMS, it would be hard to predict- but you can also force the thrust mode in most cases. (Some airlines don't even use CRZ thrust, for example- they force the FMS to remain in CLB thrust because you get better responsiveness and a higher maximum thrust limit, for example...)Hope we could help, Bill- Welcome to advanced simming. :-)

Rob,Thanks much!I have a follow-up to my question number 5) as I'm a little confused:If you look at the last two images I posted (Ignore the image at the very bottom - sorry about that as I didn't know how to delete it), I was in the descent phase of flight. However the following information appears appears in the image just above the bottom image: ADI - SPD / LNAV / VNAV PTH EICAS - CRZNote - the only descent image you should be looking at is screenshot number 5 from the top. I started my descent from FL210 and as you can see the altitude is around 7,720 and the descent rate is 2100 ft/min when I took the screenshot, but the EICAS still says CRZ.So my take is that you are referring to the very last image when you mention "Thrust Limit," not the screenshot image above bottom one that actually reflects descent. I just want to clarify that we are looking at the same image? I apologize since I didn't do a great job of labeling my images.Thanks again for your assistance,Bill Clark

[downscc 1,327]

Time to refer to the AOM, see Aircraft Systems pg 11-29 you'll find thrust mode annuciation. Note there is no descent thrust limit. The CRZ limit will apply during descent until a go-around is active.

[sbclark 55]

Time to refer to the AOM, see Aircraft Systems pg 11-29 you'll find thrust mode annuciation. Note there is no descent thrust limit. The CRZ limit will apply during descent until a go-around is active.

Dan,Thanks, I had already printed out the entire manual and have read most of it, including the section you mentioned. There is a lot to digest in the manual, and this is an item that is not intuitive to grasp when you first read page 11-29 by itself, or even remember it 30 pages later. But now that you have pointed it out..............In my mind, I assumed there would be an indication for CLB, CRZ, and DES.......heh, heh......it seemed logical to me.This hobby is always full for surprises......I wonder what the next one will be?Thanks again, all of you,Bill Clark

[Guest cit1991]

FWIW, I have this problem too...registered FSUIPC, 747-400X, XP64, REX (textures only not wx engine).+/- 100ish VS swing in VNAV PTH cruise (no weather). and +/- 400 ish swings during VNAV PTH descents.If I put it into VS hold descent...no swings at all. 100% stable, so it's not weather or temperature related. In cruise, if I hold altitude by VS set 0000, no swings.Also I noticed: If I accel the sim to 4x, no swings in cruise or VNAV PTH descent. They will actually damp out to nothing at 4X, and then resume if I put it back into 1x.I wouldn't think the sim rate should make any difference in anything...or if any, make it worse, not better.No swings once on glideslope.I'm pretty sure there's a bug in there somewhere.If I have to, I'll upload a youtube video.LoescherKemah

[Guest Totalbeginner]

I have the same problem with the 744X. The aircraft oscillates in cruise at all speeds, irrespective of weather, temperature etc etc...The oscillations are most pronounced during a VNAV PTH descent, where quite frankly, it's like a rollercoaster ride!Changing from VNAV ALT to ALT HOLD makes no difference, but changing from VNAV PTH to FLCH during the descent, causes the oscillations to stop! As others have mentioned, the oscillations are fairly small, but enough to be noticeable and rather irritating. No oscillations whatsoever in FS9!Regards,Martin Neep