500-1000 FPM Variation in Descent Profile

[falk781 0]

Here's one... As the aircraft passes the top of descent and is descending along the descent path, I noticed that the nose constantly bobs as if it's hunting for the proper descent angle. The variation is about 500 to 1000 feet per minute. If I use verticle speed descent, this doesn't happen. Either way it makes the altitiude requirements, but I don't quite understand why this is happening.Running ASX, but I don't notice this with other planes.Anybody else?

[falk781 0]

Nobody else sees this?

[ExternalUse 0]

Hi,I'm still a newbie, but as far as the documentation goes, the plane will follow the VNAV path programmed in the FMC, trying to do an economic idle descent. The better your decent forecast (wind direction and speed) the less adjustments should be necessary by the plane. In addition, on your ND screen you should see a path deviation indicator which will show you an explanation for the adjustments. You will find more information in the autopilot and FMC manual.Kind regards,Stefan

[Shmiffy 0]

Hi There:I've been flying the 744 for years, and yes i do see this a lot. The PMDG 744 is a little sensitive to temperature and wind shifts (moreso than the real one) and so it does occasionally have issues. The best thing to do is jump into FLChg or V/S Mode and help the Aircraft intercept the path. Once that's done, you can re-enable VNav. I know a couple of real world 777 pilots that do a similar thing on the T7 more to make sure the Pax are comfortable than any deficiency of the aircraft. Basically they start the descent early, and use V/S to intercept the path giving a shallower angle of descent (initially) and reducing rapid pressure changes.The trick is to use the tools available to you. You are the PIC. You have HDG, SPD, THR, VNAV, LNAV, VS, FLCHG - All of those are tools that will acheive similar outcomes, and when used properly, the aircraft is a beauty to fly. There are things that she does a little incorrectly, but on the whole, sometimes the real ones screw up some times...CheersPaul

[falk781 0]

Hi There:I've been flying the 744 for years, and yes i do see this a lot. The PMDG 744 is a little sensitive to temperature and wind shifts (moreso than the real one) and so it does occasionally have issues. The best thing to do is jump into FLChg or V/S Mode and help the Aircraft intercept the path. Once that's done, you can re-enable VNav. I know a couple of real world 777 pilots that do a similar thing on the T7 more to make sure the Pax are comfortable than any deficiency of the aircraft. Basically they start the descent early, and use V/S to intercept the path giving a shallower angle of descent (initially) and reducing rapid pressure changes.The trick is to use the tools available to you. You are the PIC. You have HDG, SPD, THR, VNAV, LNAV, VS, FLCHG - All of those are tools that will acheive similar outcomes, and when used properly, the aircraft is a beauty to fly. There are things that she does a little incorrectly, but on the whole, sometimes the real ones screw up some times...CheersPaul

Thanks alot for your comments. Glad to have heard from someone who really knows some of the systems. From a flight dynamics perspective, since you are a 744 pilot, how close is the sim to the real experience?

[Shmiffy 0]

since you are a 744 pilot

hehehe. I wish, i should have been clearer, i've been flying the PMDG 744 for years. I would love to have been flying the real ones.As for the real 744. I believe more than one 744 Captain has described her as a big Cessna. Very docile....CheersPaul

[michal 44]

since you are a 744 pilot, how close is the sim to the real experience?

There were quite a few 747 real-life pilots on these forums soon after the product was released. They had many comments (mostly very positive). Two user-names that come to my mind are 'jon b' and 'cowpatz', you may want to use advanced search and dig out many of their older posts.

[Guest Totalbeginner]

I agree with previous posts about changes during a VNAV descent in the real 744. But, these do not compare to the rollercoaster VNAV descent that is apparent in the PMDG 744 and it is definitely a bug! This problem doesn't occur in the FS9 version. The aircraft continously pitches up and down oscillating quite quickly. If you look at the flight controls on the EICAS page you can see the elevator moving up then down etc... This problem goes away if you select FLCH.The aircraft also does this in level flight at cruise altitude. It's not as pronounced, but still very irritating. For these reasons, I ditched this aircraft shortly after purchasing it.Regards,Martin Neep

[falcon999 24]

Hi There:I've been flying the 744 for years, and yes i do see this a lot. The PMDG 744 is a little sensitive to temperature and wind shifts (moreso than the real one) and so it does occasionally have issues. CheersPaul

Another perspective would be... :( I am not seeing this issue. PMDG has labored to model the flight characteristics, engines, fuel systems, etc. to be as close to reality as possible. So the model is realistically responding to the virtual world it is operating in. For me, this problem was caused by the significant and sometimes radical (unrealistic) changes in wind, temp and barometric pressure the default FSX weather and other weather add-ons can induce. Once I turned on FSUIPC weather smoothing and made sure all of the weather smoothing functions were turned on within my weather add ons, the 744 is working fine in all phases of flight.

[Guest cit1991]

Another perspective would be... :( I am not seeing this issue. PMDG has labored to model the flight characteristics, engines, fuel systems, etc. to be as close to reality as possible. So the model is realistically responding to the virtual world it is operating in. For me, this problem was caused by the significant and sometimes radical (unrealistic) changes in wind, temp and barometric pressure the default FSX weather and other weather add-ons can induce. Once I turned on FSUIPC weather smoothing and made sure all of the weather smoothing functions were turned on within my weather add ons, the 744 is working fine in all phases of flight.

Mine does this too.Weather, no weather, smoothed weather, makes no difference. If there's a wind shift, some hunting afterward is expected, but this is periodic all the time, and goes away in VS mode, which tells me it's not 100% weather related.Everything else about the place is so great, it makes this bug very irritating.me loescher IAH