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VNAV PMDG 747

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There is a wealth of info in this forum and it has been helpful. However at this point in time I am confused. I have never been able to get the 747 to follow the VNAV path. It works on another Boeing aircraft in my inventory but not the PMDG. In my opinion the 747 is truly a good product but after reading this forum closely and investigating and testing various options I am not sure what my plane is supposed to do and what it is not. My goal is become proficient and then fly on Vatsim.Thanks to all those who have posted POSITIVE meassages.RegardsRickP.S. I am retired and my wife says PMDG is keeping me off the streets. "It's A GOOD THING as Martha would say."

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Rick,Good thing you are keeping busy. We don't want you on the streets... :-)VNAv is a pretty complicated matter and without any more information than given above it is very hard to troubleshoot. What exactlly is your problem? What flightplan are you using? What does the FMA tell you? During which stage do you have problems?If you could elaborate on these above questions I'm sure we will sort you out!Yo man,


Mats Johansson
PMDG Flight Test Dept
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As Matts said, Vnav is one tough dog to get to hunt. Actually, it's one of the most interesting aspects of the APFD/FMS. Back in the early 80s, I remember reading about the early 757 days where Vnav was installed as part of this 'new fangled' FMS, but not certified for actual use. Pilots could play with it, but they could not officially use it. I expect the problem might NOT have been totally with the system. There might have been another factor. It's the same thing you just ran into. It just took a while for even experienced pilots to get comfortable with this new concept. It's not as intuitive as Lnav. It's easy to think in terms of Lnav. Just like a map. Town to town with roads in between. It's called track or course or heading or whatever. We can argue endlessly about the terms, but basically, we get it. But think vertically? Ugh. Welcome to Vnav. Actually it's same idea. It's just tells the airplane to go up (this 'path") or go down (that 'path'). But how to you make it do dat? First as a quick overview how Vnav thinks. There are just 3 Vnav modes (thank goodness). Vnav uses it

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Hello Rick, VNAV is pretty simple at it's base, it controls the vertical profile pre programmed into the flight management system, it's complexities are directly related to criteria and or rules of operation that, of course, are also related to aircraft performance, weather etc. Lets take an example here. Say we are departing XXXX rwy 07L. We can load a SID, fly it manually or build or load a comanpy rte. If we build the rte ourselves, we must make sure that the restrictions/Wpts are not impossible for the aircraft to achieve. Can one place a wpt at 10,000' 3 miles from the departure rwy? Certainly not. So, like knowing our cars and how it performs, we must also know what is and is not possible to program into the FMC, again based upon many operational factors and considerations. This is the real challenge. Operation/performance limits now become the goal for each pilot on it's type. You must also know the deparure airfield well so you know what to expect on top of knowing your airplane. It's easy to fall into the snare of complacently when using the FMC. Why did it do that? Why did it not do that? What is it doing now? We are descending and see a wpt that we must be at a certain speed and altitude. Is the aircraft going to slow and descend and nail the restriction on it's own simply because VNAV and LNAV is engaged? At times this will not be the case. The plane can be too fast so the pilot who is busy monitoring performance will use the speedbrakes to help the plane slow. Other times you might find the plane slowing past target speed and so the pilot adds thrust. Or, the plane simply cannot lose enough altitude in a given time frame. I have learned that the FMC is a "help", not a pilot in command even though it is controlling the airplane at a certain phase of flight. If the FMC is not performing in a way the pilot believes it should he simply flips the switch and says "I got the aircraft". So how does one learn how to use VNAV? Tutorials. I believe there is no better way for one to become efficent. After you follow a certain tutorial you will find that you can modify things the way you see it. You also see quickly what works and what does not. Other things come with time. One airline might do something because they have their own standards and operations that have been learned over the years (SWA without the use of autothrottles is one example. Another area that is often over looked in flying glass is the use of other AFDS modes in conjunction with VNAV. At times, it just makes for a safer flight by utilizing these others modes and is not unrealistic to do so. So grab a tutorial and start your journey :( [h4]Randy J. Smith[/h4]AMD 64 4000+|ASUS K8V DELUXE|SAPPHIRE ATI X800XT PE|MUNCHKIN 3200|80 gig SATA|DELL 1905FP 19" LCD|TRACKir PRO|PFC JEPPESEN MOONEY YOKE|CH PRO PEDALS|


Randy J Smith

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Thanks for all the replies that were sent.I tried keying in a flight and also flew one canned flight (laxord001). I used a SID and then specified altitudes and speeds that I thought the plane could handle. I am sure it is something that I missed. I will continue trying to learn this. The detail is great and does keep me occupied.RegardsRick

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Thanks again for the help.I flew sucessfully with VNAV from LAX to JFK. Everthing went well except for an OVERSPEED situation for short interval. Selecting and lowering the speed corrected this and then back to VNAV speed and path.I realize there are lots of canned flights that come with the software but I wonder if anyone would be interested in sharing any interesting flight plans. I am Canadian but prefer to fly in the USA. I am not willing to use 'flight planning' programs because my setup is working well and at this time my computer resources are pretty well maxed out. I have read where some add-ons were suspect in the problems with service updates and even original setups. A pic of my touchdown on 22L is attached if anyone wants to view it.RegardsRick ( Happy at FLxxxxx )

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