Jump to content

Sign in to follow this  
kmanning

Very High Vertical Speed When Using VNAV

Recommended Posts

Please keep in mind with all these comparisons that the temps and winds may be very different, which would all cause perf differences. If my memory serves correctly, that vid was made in the summertime. It's winter now. Assuming Virgin uses the same exact engines as those modeled, it is possible that Virgin may have derated the engines as a maintenance function, in this case, the pilots cannot override the derate.What I'm trying to say is, you cannot base an argument as strong as you'd like to make on only one video. Maybe you'd like to buy the World Air Routes 747F video. It's a mix of 200 and 400 series airplanes doing about 6 or 8 sectors.Paul

Share this post


Link to post

I have watched this VA ITVV video numerous times. Nowhere you can see any appreciable difference in performance with the PMDG craft. This of course assumes you know what you are watching - you must be very precise in watching this video not to miss things like weights or current speed-thrust setting and vertical speed - and there are only very short periods of times due to editing and camera action where you have access to stable numbers - unless you freeze your picture you are going to miss it. The data comes at you with such a rate, the editing misses some scenes that it takes some detective work to actually put 2 and 2 together to have any faith in numbers you can see in a fraction of a second. I hate when folks go to great extent to mis-represent what they actully see to fit they preconceived ideas. There was someone else on this forum before who based on this video concocted an argument that PMDG's startup sequence was incorrect. 100 posts later he finally admitted he was not watching this video carefully, at least he was honest.Michael J.http://www.precisionmanuals.com/images/forum/pmdg_744F.jpghttp://www.hifisim.com/images/asv_beta_member.jpg


Michael J.

Share this post


Link to post

>What I'm trying to say is, you cannot base an argument as>strong as you'd like to make on only one video. I`ve flown G-VXLG from the video and other Virgin 747- 400s for about nine years,including EVEN some flights with Alan Carter and Alan Rattigan,but there`s no way I`d be able to make an argument that strong! Truth is I havn`t got a clue what my rate of climb is going to be on any flight until I look down at the VSI and read it.But the fact is the PMDG 400 certainly doesn`t seem to be out of character.regardsJon(PS Paul,our engines are a slightly underpowered version of those in PMDG)

Share this post


Link to post

>If my memory serves correctly, that vid was made in the summertime. It's winter now.Hi Paul, The video was made on Octorber 19, 2000.> Assuming Virgin uses the same exact engines as those modeled, it is possible that Virgin may have derated the engines as a maintenance function, in this case, the pilots cannot override the derate.You may have something there. That would explain some of the differences.> temps and winds may be very different, which would all cause perf differences. Yes, you're correct.> Maybe you'd like to buy the World Air Routes 747F video. It's a mix of 200 and 400 series airplanes doing about 6 or 8 sectors.Where do I get the videos? I might like to check them out. Ken.

Share this post


Link to post

>but there`s no way I`d be able to make an argument that strong!I'm not making any arguments here. I'm only stating the facts from the video.> PS Paul,our engines are a slightly underpowered version of those in PMDG.This could explain some of the differences. If I had known this in the first place, I would have understood what was taking place. Why did someone stated this in the first place? Thanks for letting us know. Ken.

Share this post


Link to post

>This of course assumes you know what you are watching - you must be very precise in watching this video not to miss things like weights or current speed-thrust setting and vertical speedYes, you're correct. I had to set the airplane's gross weight, fuel weight, freight, number of passengers on board, temperature and pressure at the time of departure, and make sure the thrust limit page was set exactly as in the video. I've mentioned that the PMDG did performed close to the Virgin video, except for a slight increase in the V/S at higher altitudes when I changed altitudes. >and there are only very short periods of times due to editing and camera action where you have access to stable numbers - unless you freeze your picture you are going to miss it.Yes, you got that right. That's what I had to do. A couple of times, I had to go a frame or two to clear up the images, because the camera was moving. >The data comes at you with such a rate, the editing misses some scenes that it takes some detective work to actually put 2 and 2 together to have any faith in numbers you can see in a fraction of a second.That's why we have to freeze the action or go one frame at a time. It's only miliseconds.>I hate when folks go to great extent to mis-represent what they actully see to fit they preconceived ideas.I would not do that. >There was someone else on this forum before who based on this video concocted an argument that PMDG's startup sequence was incorrect. 100 posts later he finally admitted he was not watching this video carefully, at least he was honest.It was me. But I never said that the startup sequence was incorrect in the PMDG. I think I said that I thought or was there a bug when using the autostart but I didn't know for sure and wondered if anyone had the same problem I described. I did not bring it up just to make an argument about it. I also was confusing the Cathay Pacific video with the Virgin Atlantic video. I was thinking at the time that a manual start was performed in the Virgin video. But it was the Cathay pacific. Ken.

Share this post


Link to post

>I'm not making any arguments here. I'm only stating the facts>from the video.Nobody is doubting that, (at least I'm not). What I'm talking about is you are trying to use that exact video as evidence that the PMDG 747 doesn't perform correctly. There are WAY to many variables that you don't get from that video, that would cause the planes to react differently.There is NO way you can say because it happens in the video, and not in FS9 with the PMDG that the PMDG performs incorrectly. That is what I interpet your posts as. Which as I think has been shown, is incorrect. What would you like someone to do or show you so that you can see the PMDG performs correctly? Jon has already stated many times now that the PMDG performs correctly, what else do you need? You said you take a real world 747 pilots word, well there it is.Edit: BTW, don't take this or any of my posts personally. It seemed like you were there for a bit, and I don't want you to. I mean nothing by it, I was just trying to understand where you were coming from, and explain things. Of which, I know I did a bad job. I'm glad others came in and helped me out.


Mike Roth

Share this post


Link to post

>There are WAY to many variables that you don't get from that video, that would cause the planes to react differently.What other variables have you thought about that I could not get from the video? >What would you like someone to do or show you so that you can see the PMDG performs correctly?If it's possble, real charts and flight performance datas from the real thing and whatever information I need to show this, but that may not be possible and I understand. If it is possible, I sure would appreciate it. I really would like to know how one determines that it perfomrs like the real thing. But don't get me wrong. It's not that I don't trust the team and I hope they'll understand how motivated I am to learn a lot more about this. Since you explained that they have real 747-400 pilots on the team, then I believe it should perform like the real thing. But I would like to find out how it's determined that it performs like the real thing.> Jon has already stated many times now that the PMDG performs correctlyOkay. I assume by this that Jon is a real 747-400 pilot. At least I know who this person is because I never knew. Okay, I have several questions I would like Jon to answere. I thought about posting them in another post but I guess it would be better to just post it here. If I should make another post, someone let me know:To Jon:1. When setting the trim for take-off, are the trim settings set differently for each 747-400 fleet, considering they all have the exact same weight, center of gravity, fuel, passengers, freight, and all flight performances, temperature and pressure being the same? In the Vigin video, 7.6 units was set. The FMC in the PMDG has never went over 6.0 units, no matter how I load the airplane? Why is there a difference? I loaded the airplane exactly, or at least, very close to the one in the Virgin video but I did not get 7.6 units from the FMC. I did get enough information from the video to load the airplane correcly. 2. In the PMDG manual, when setting the V2 speed, it says to enter V2+10 into MCP IAS/MACH window. In the Virgin video, Allen only entered the V2 speed, which was 174 knots. He did not enter V2+10. Why is this different? Is this based on the airline company's operations manual?3. I'm not sure how to explain this but I'll explain it the best way I can. I've posted here before about how differntly the cockpit sounds are between the PMDG and the cockpit sounds I hear in the Virgin video. I've listened to many other video sounds of the cockpit and they all sound the same. When watching a video of a 747-400 taking off, I can actually hear the low frequency rumbling sounds of the tires rolling or vibrating the cabin, but I don't hear that in the PMDG. Of course the sound levels are set correctly in the flight simulator. During the landing phase of a video, I can actually hear, probably the sound of the struts, or the vibrations of the cabin, when the 747-400 settles onto the runway. I hear this sound in every video I listen to of a 747 but I don't hear that in the PMDG. I was wondering if that could be modeled in the PMDG. I hope I explained it so that you understand what I'm talking about. I would appreciate your assistance.4. Is it true that when the flaps are set to 5 or 10 degrees, the nose is up from about 5 to 10 degrees? I know they actually fly with the nose slightly above horizon and the airspeed has an effect on this, but I lower them when the PFD airpseed tape commands it. I would appreciate your assistance.Ken.

Share this post


Link to post

Virgin Atlantic has CF6-80C2-B1F engines which are rated at 57,900 pounds thrust, I just quoted that off the top of my head without any reference to any manuals,you understand;-) PMDG has simulated CF6-80C2-BF1F engines rated at 58,000 pounds thrust,again I`ve got that figure in my head ;-) .The 400lbs difference (4x100lb) won`t make much of a difference to your rate of climbregardsJon

Share this post


Link to post

KenJust briefly (as I`am off to bed but I`am sure you`re keen for feedback) 1)Not all planes weigh the same or have the same CofG they all differ slightly even with the same fit in the same airline.Also the FMC will calculate a different stab setting to those of a manual or computerised loadsheet used by airlines.the FMC for example will take into account any power derate entered into the machine. I`ve not compared the PMDG stab settings thus far to any real flights I`ve done as it would be impossible to recreate the exact weight and CofG conditions2)Not sure where the PMDG manual gets this from,maybe a procedure from another airline but the Virgin SOP is to set V23)There was a thread about sounds I got into a few weeks ago on this forum.Basically the sounds you hear on a recording,a dvdv for example are very different from those you would hear with your own ears if you were there. I once took a tape recorder on a flight and recorded the radar vectoring from BNN to the ILS at LHR so I could recreate the approach in real time using PS1 for practice of constant descent aproaches.The sound that was replayed through my tape recorder sounded nothing like the real flight deck.The PMDG sounds IMHO are very good and capture the atmosphere of the flight deck.4)As the speed comes back the nose rises,the flaps lower the nose a bit,but yes level flight at 180kts flaps 5 would give a nose up pitch.Again the PMDG pitch power settings are quite near the real thing.regardsJon

Share this post


Link to post

>2. In the PMDG manual, when setting the V2 speed, it says to>enter V2+10 into MCP IAS/MACH window. There are probably tens of pages worth of discussion on this (and old) forum on this very topic. It has been stated number of times that V2 (not V2+10) is what you need.Michael J.http://www.precisionmanuals.com/images/forum/pmdg_744F.jpghttp://www.hifisim.com/images/asv_beta_member.jpg


Michael J.

Share this post


Link to post
Guest D17S

Ken, hang in there. Your curiosity and energy is just the right stuff. But I'm gonna make you pay! . . . Time to dig in. About your #2 question. . . .Initial climb airspeed (V2) is one of my favorite bones to chew on. There's so much going on in such a short amount of time. It's just fascinating (to those of us that want to understand . . . and not just 'believe'). I recognize that V2(+0) is the MCP

Share this post


Link to post

>The 400lbs difference (4x100lb) won`t make much of a difference to your rate of climbYes, I agree with you. Thanks for the information.Ken.

Share this post


Link to post

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  
  • Tom Allensworth,
    Founder of AVSIM Online


  • Flight Simulation's Premier Resource!

    AVSIM is a free service to the flight simulation community. AVSIM is staffed completely by volunteers and all funds donated to AVSIM go directly back to supporting the community. Your donation here helps to pay our bandwidth costs, emergency funding, and other general costs that crop up from time to time. Thank you for your support!

    Click here for more information and to see all donations year to date.
  • Donation Goals

    AVSIM's 2020 Fundraising Goal

    Donate to our annual general fundraising goal. This donation keeps our doors open and providing you service 24 x 7 x 365. Your donation here helps to pay our bandwidth costs, emergency funding, and other general costs that crop up from time to time. We reset this goal every new year for the following year's goal.


    5%
    $1,450.00 of $25,000.00 Donate Now
×
×
  • Create New...