I correct myself. The plane isn't flying what it should at all! Just made the same approach again and look at that shot:http://www.paulifamily.ch/martin/wrong_altitude.jpgIf you beliefe the FMC the flightpath is 1000 ft above you but the next waypoint is only 2.5 miles away and there you should be 4000ft not 6000ft!And another thing: The plane is in VNAV mode. It should descend now at least with 1500 ft/min but it remains at 5000ft, why?As from de exemple in my last post you can see that it worked this morning. what is different now?Thnaks Martin

Hi GeorgeLook at the two series of shots I posted and tell me what's wrong in the second one (only one image) please? I did the same things and the plane is doing something completely different!"I think" I know how VNAV is supposed to work. And it doesn't work as it should.Fly the approach in Zurich yourself. You will see what I mean.Good luckMartin

Hi Randy1.) MCP altitude was set to decision altitude with VNAV on. Once you see the runway, AP is turned of and plane flown manually.2.) I use SPD INTV all the time. When on final approach course I'll need it to reduce speed to set flaps. My problem is not about speed but about PATH (see your (my) third point).3.)I know VNAV is a PATH mode. Therefore all the points on the final approach are programmed WITH ALTITUDE CONSTRAINTS. It doesn't matter what speed you have. The FPA should stay the same if the points are programmed correctly (see example approach below).If you look at the chart from www.swissfir.org for Zurich RW28 you'll see that the procedure I use is correct. (BTW: All the MD11 and Airbus crews I know are doing it the same way. The modes of there A/P have other names but work almost similar to those in a B737NG)Tell me what you think about my shots, please.ThanksMartin

Ok Martin let's see if we can sort this out.First, I am not questioning your understanding of VNAV, I am questioning how and when you use it. I am not familiar with Zurich, but I researched the KSEA example, so let's use that (and there are screenies above).There are 3 approaches to RWY34L at KSEA. There is an ILS34L (no CATII or CATIII), VOR34L and RNAV34L.As has been mentioned in this post, VNAV is only appropriate for non precision approaches (except for the new airline procedures mentioned below which I am not sure whether or not the current PMDG approach procedure file has the appropriate data for precision approaches). In the KSEA screenies above it looks like you are using VNAV to fly the ILS34L approach. This is not correct. You need to be using APP mode to appropriately capture the LOC and GS and fly the approach.For the VOR34L and RNAV34L VNAV can be used (if the FMC is programmed properly) to fly the approach down to DH and MAP (Decision Height and Missed Approach Point). Which for the VOR34L straight in approach would be DH: 840ft MSL and the MAP: Crossing the SEA VOR or 4.3DME from the DONDO NDB. So VNAV can be used to take you down to 840FT until you have the runway environment in sight or you reach the MAP. If you get the runway, obviously you need to hand fly the aircraft down to landing. Also, you will need to enter in the appropriate speed at the FAF into the FMC to ensure that you can make the runway once you see it. Finally, why use VNAV for this approach??? Why not just use LNAV and LVL CHG or LNAV, VS and Speed modes. It is a heck of lot easier and you don't have to worry about the FMC.Ok? :-)

Martin, I do not understand why you are having so many problems. While I am not a professional pilot or have ever flown a 737 I do study what is available on the internet to help me to learn the systems and my PMDG 737's seem to act in a manner that coincides with what the real world "manuals" tell me. I will look over your various posts in this and other threads and see if I can't find something to help you out. One thing that I have always done, and maybe you should too, is not compare what the PMDG FMC does compared to releases by other companies. I am not putting anyone down here but sometimes "cheats" are used to get around MSFS programming or maybe the company does not have enough of the real world info. to make it work as in real life. Just because something works a certain way in another product does not mean that is the way it works in real life. According to what I have been able (in my limited ways) to learn about the 737 NG FMC, PMDG has modelled the most accurate one ever for FS, for me it works as I think the real world one does, at least according to what I have read. Just like real life pilots do, you have to learn the way that these systems work and use them as they are intended, slow down, read and learn the systems and do not assume that you know better than the FMC how it is supposed to work as that is a fatal error to make. Real world pilots have the luxury of training by people that know the systems, we have to learn it on our own, a big disadvantage! Don't get me wrong, you may be on to something here, but I am just saying that things seem to work just fine for me but I will check out what you say. Take a deep breath and keep an open mind, there are only two things that can be wrong here, either the PMDG FMC or your perception of how it should work, we will find out which with a little work. Tonight I'll have some time to check out what you and others have said and I'll put the plane through it's paces. I'll post here when I have something. Best Regards,Philip Olsonhttp://www.precisionmanuals.com/images/forum/supporter.jpg

First off sir you are NOT in STRICT VNAV PATH operation, you are in fact in SPD INTV which DOES NOT FOLLOW ANY PATH. It is on a speed profile, look at the FMC, it clearly shows 170/MCP. Don't expect much out of this mode! It is a simple mode and does not follow anything other than your speed input. It is very much like VNAV SPD but without guidence for restrictions etc other than MCP altitude level offs. See, what I gather here is that your approach style is at odds with establised flying regulations and where you have to use SPD INTV around the terminal area whereas following an airline SOP you would never be caught up in this. It's your work around and how you want to fly it but if I were you I would fly it like the rw or don't worry about impossibilities with your own procedures. Now if you really want to learn and I believe you do then please spend some more time reading on the proper operations of the AFDS. This post is a perfect example of not understanding SPD INTV and that it does not follow path, I know you want to be able to fully understand this bird but confidence does not imply knowledge and if you were on a real training that image would be very different wouldnt it? Why you would be fying this way in the first place is well different than the way I see RL pilots doing approaches. You can send me an email is you want at crvm%iwon.com. I replaced the @ with % to avoid SPAM BOTS ugh...Best Wishes,[h4]Randy J. Smith[/h4][h3]P M D G's 747-400[/h3][h4]coming to a runway near you[/h4][/font color]Caution! Not a real pilot, but do play one on TV ;-)AMD 64 3200+ | ASUS KV8 DELUXE | GFORCE 5700 ULTRA @535/1000 | Maxtor 6Y080M0 SATA 80 GIG | 512 DDR 400 | Windows Xp Pro | Windows Xp Pro 64 |

RandyI just sent you a mail. Thanks...CheersMartin

Hello PhilipIf you could look at it that would be great! I'm always looking for other sources of information...All the bestMartin

Martin, I got stuck working all night so I have not had the chance to check anything out yet. I am going to try and get some sleep and probably later I'll have some info. for you. Oh the joys of owning your own business! LOL!Best Regards,Philip Olsonhttp://www.precisionmanuals.com/images/forum/supporter.jpg

The problem is clear. VOR LOC will not decend him in any situation. Switch to APP then you'll be able to fly right down the glideslope.Hope that helps in a nutshell. :-)

Sleep well PhilipNo need to hurry I won't run away! ;)Regards,Martin

Hi Bj

VOR LOC is the roll mode. He should be able to descend in that mode using V/S, LVL CHG, VNAV, or CWS P.

It doesn't look like he's doing that. I think he thinks that it will do that for him. Just a hunch.

Hi again Martin.Quote;" And it doesn't work as it should.Fly the approach in Zurich yourself. You will see what I mean."Well, I have done a couple of flights from LSGG to LSZH. Took off from rwy 05, MOLUS1N departure. Arrival at LSZH VORDME28 approach via EKRIT transition, assigned FL200. The path down to thr showed 3.7 deg as for you.I don't say this is the correct procedure for this approach, but for the sake of this test of VNAV I stayed in strict VNAV path down to MDA at LSZH. For both flight it stayed on the numbers all the way. I took shots at every wp, but I post just a few here:At EKRIT:http://forums.avsim.net/user_files/88527.jpgAt KLO8:http://forums.avsim.net/user_files/88528.jpgAt KLO6:http://forums.avsim.net/user_files/88529.jpgAt MDA:http://forums.avsim.net/user_files/88530.jpgI really don't know what's happening for you, but it works ok for me. About PAPI lights: In the sim they may not always show the correct path. This is hardcoded into the bgl files, and can(at some places) differ from what updated real world procedure tells you.A little OT maybe but: As far as I know this particular approach is now replaced(at least my charts tells so), it's now called VORD.DME.28(STOL) and only available on request. This was changed due to the already mentioned accident. It now also has different constrainst and have a steeper descend, a path at 5.7 degrees(which may be tricky is VNAV)