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drag required and some other things

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1)what I quite don't understand is that many often I get a message from the FMC that drag is required from as high as above 20000 ft.Is this common ?2)most of the times I get VNAV disconnect and end up to high to capture ILS.I thougt that the FMC would calculate the apropriate descend profile to get things right?right?3)when downwind and turning base -final (with LNAV) most always ,the plane makes some kind of a shortcut and never flies above the fix(es), so again ...to high...this happens using the SIDS&STARS as provided.I don't know , but I have the impression that it,s wurse since the service update (might be subjective, though)hope that someone can help,Patten

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I'm having the same problem. I insert the STAR before descent and always loose the VNAV sometime during approach. I've setup the wind on the forcast page and I'm not overspeeding. Then when I revert to LVLCH I always endup high on the GS.Dave FisherCYYZP4 2.8 GB 478P 533 MHZ CPUP4P800S Asus Motherboard512 DDRGeforce Ti 4200/128Maxtor 80 Gig ATA 133 HDhttp://www.precisionmanuals.com/images/forum/ng_driver.jpg

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All those problems can be from not entering the decent wings. Enter the destination's wings into the DES FORECAST page. Since you can only enter 3 layers, make on every 10,000 feet or soNick B.Continental Airlines Virtual 737NG Pilothttp://www.precisionmanuals.com/images/forum/800driver.jpg--AMD Athlon XP 3200+ @ 2.2 Ghz (Equal to 2.8 ghz)400W Power supply3x 80 mm Case FansSoyo VIA KT600 Dragon PlusnVidia GeForce FX 5200 128 mb2 x 512 PC400100 GB Western DigitalMicrosoft Sidewinder Precision 2

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It seems to help if you go to the descent page and click "Desc Now" at 20nm before the calculated TOD. If "Drag Req" comes up, then deploy spoilers. This way, the profile is retained, though it does seem a bit unusual.

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the problem is : although the descend path seems to be flown correctly, that at some point (say about 6000 ft or less) VNAV disconects,without warning. By no way (but a very uncomfortable for passengers)you can correct it (steep descend).So it's too late to anticipate.In adverse , you never get too low, always too high, wathever the winddirection.So , in real , with a sophisticated FMC , could this happen, or is this PMDG "virtual FMC" not as real, or is it something else ?Patten

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Adding my experience to this discussion:the fact that spoilers are called for too often is true, or at least is true for me.It happens very many times.Then i too have to point a finger at the vertical path following precision of the FMC.It is not that precise as advertised.It becomes all the more un-precise if you setup precise altitude and speed constraints.I mean that if you plan a route and do not enter any manual speed or altitude constraint for any point, the vertical path is unprecise but acceptable.If you ever happen to enter any constraint, say adios to your vnav path.It goes nowhere near where you expect it to be.For example, i often land at Rome Ciampino (LIRA), the ILS passes over Urbe civilian airport (LIRU) and before that there are minimum altitude constraints due to hills and radar.So if you plan it the way it is intended to be flown, you have very many constraints:CMP 6000ftURB 200/3000 which means you HAVE TO BE at 3000 at URB because it is the ILS intercept point.Whenever i use such a setup, manually entering the contraints, the plane always fails to fly such a path: a DECEL point is created, and the plane refuses to maintain the necessary vertical speed prior to that point; when it reaches that point, it further levels up to reduce speed then dives in, but the vertical path has already gone to hell long before and you end up well above the glideslope and all the more above the altitude you should have been.

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You must not be setting up the FMC right. Keep in mind that the FMC is designed to help you, not do it for you. You have to use your skills to determine to use spoilers (even if you get no message), descent faster, etc.You should also make sure you enter a descent target speed speed about 10 kts below your cruising KIAS (ex: if you cruise at FL350 and your cruising speed is 280 KIAS, make your descent target speed about 270 KIAS). The reason I say this is because the default descent speed is 315, which at FL350 is almost 600 kts and way to fast and can cause overspeed disconnect.Nick B.Continental Airlines Virtual 737NG Pilothttp://www.precisionmanuals.com/images/forum/800driver.jpg--AMD Athlon XP 3200+ @ 2.2 Ghz (Equal to 2.8 ghz)400W Power supply3x 80 mm Case FansSoyo VIA KT600 Dragon PlusnVidia GeForce FX 5200 128 mb2 x 512 PC400100 GB Western DigitalMicrosoft Sidewinder Precision 2

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Your example is just what I wanted to say, you 're quite right...so after all, the PMDG FMC does not what it should do; does it ?Could someone of the PMDG team answer this ?

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Nick, I think you're right if you have to use your skills, and it works (most of the times); but what's the point then having such a sophisticated system, if you can't realy relie on it ?

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Yes it does happen to me too, if I let it. ONE problems bugs me in the fmc though: whenever VNAV is disconected,at X nm from a waypoint or an airport, an I fly the rest of the flight in basic autopilot ( hdg, vs, spd..) the distance to airport or whatever in the progess page of the FMC increases as the flight progesses in the right direction. So it's useless to aid calculating the 3:1 rule of the descent, since it doesn't provide acurate distance to waypoints/airport.

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To the orginal poster, you are required to sign your real name while posting on this forum, please take a moment and read the rules here, thank you. http://forums.avsim.net/dcboard.php?az=show_topic&forum=136&topic_id=2402&mesg_id=2402&page= I think a very important issue is missing from this conversation, namely, that the default VNAV does not keep speed just like the real bird. Descent is not set it and forget it. We as the PIC must monitor and plan our descent, this is one of the greatest challenges to flying this type of aircraft. Let me answer some questions from the orginal post."1)what I quite don't understand is that many often I get a message from the FMC that drag is required from as high as above 20000 ft.Is this common ?" Anytime you are 10 knots or more over target you will receive this message, it does not matter what altitude you are at. It is the pilot's responsibility to control the aircraft speed, the AFDS will not make any attempt to keep the target when in VNAV PATH. If you become too slow the FMS will add some thrust."2)most of the times I get VNAV disconnect and end up to high to capture ILS.I thougt that the FMC would calculate the apropriate descend profile to get things right?right?" You actually have two questions here so will answer both. First, you will only get a VNAV disconnect ifa: Are not controlling speed which has reached 15 knots over the target which happens to be 240 knts under 10000', over 10000' you can reach the barber poll before reversion to another pitch mode.b: You have some constraint that is out of the ability of the FMS achieve.You have a speed constraint without having an altitude constraint on the same wpt. You have a discontinuity. c: You have touched the controls with the A/P engaged causing reversion to another pitch mode such as LVL CH or CWS P. Second, the FMC calculates a proper descent profile based upon what you have entered. You have a VNAV path deviation scale on the navigation display to monitor your profile. I have followed this in V/S on the dime to the RWY. "3)when downwind and turning base -final (with LNAV) most always ,the plane makes some kind of a shortcut and never flies above the fix(es), so again ...to high...this happens using the SIDS&STARS as provided." You are confusing what is displayed on the ND and how the 737 actually follows such tight turning paths. I will state this with some backing from others who know the NG in and out that this is a very complex add-on and it takes some time to master flying correctly, what it boils down to is the PIC's technique. I know Mr. Brad Marsh has talked about this very issue we are discussing and has said some of the same things. He takes folks on a flight that he published in his Geezer Guide and does not suffer from what we see here. This is because he knows exactly what to expect and how to handle the situation and plan ahead. I cannot stress enough the importance of taking some time learning the systems on this aircraft and what to expect. 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 |

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I have frequently flown in real life in a 738 and I cannot recall a single flight where spoilers were not used at some point during descent.Spoilers are made for a very specific job and they do it very well both during descent to slow the slippery sucker down and upon landing to kill lift.Imagine aircraft from the Kangeroo airline (Qantas) without spoilers - they would imitate the image on the tail and Boeing would have to rebadge themselves dropping the 'e' from their name 'Boing'. :D Andy b

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The PMDG created the FMC as close to the real thing as possible. You must remember the FMC is there to help you, not do the work for you. If it was to do the work for you, you wouldn't even be on the plane, just the FMC and passengers. It's your discretion on when not to rely on the FMC.Nick B.Continental Airlines Virtual 737NG Pilothttp://www.precisionmanuals.com/images/forum/800driver.jpg--AMD Athlon XP 3200+ @ 2.2 Ghz (Equal to 2.8 ghz)400W Power supply3x 80 mm Case FansSoyo VIA KT600 Dragon PlusnVidia GeForce FX 5200 128 mb2 x 512 PC400100 GB Western DigitalMicrosoft Sidewinder Precision 2

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I use FSNAV for flightplanning and sometimes I'll use a STAR from their database. I wonder if their descent paths are unachievable?BTW, where can I find Brad Marsh's "Geezer Guide", I've searched the library but no luck.Dave FisherCYYZP4 2.8 GB 478P 533 MHZ CPUP4P800S Asus Motherboard512 DDRGeforce Ti 4200/128Maxtor 80 Gig ATA 133 HDhttp://www.precisionmanuals.com/images/forum/ng_driver.jpg

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It was removed from it's sticky position, well here is a link to Brad's home page http://homepage.powerup.com.au/~speedyBest 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 |

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Hello,There are two things that havent yet been mentioned on this topic:1) You have to remember that real pilots use every single chart that they should use. These charts give them what heights to be at by what waypoints on their descent/STAR. 2) In the real world, apart from flying over he Atlantic and over Africa (and other places of course) real pilots would have non-stop ATC coverage. Of course not to rely on, but they do give instructions to pilots as to what heights they should be at at different waypoints on the STAR. 3) The STAR (Standard Terminal Arrival Route) is a set route that takes you from an airway to your arrival airport. I say arrival airport, but it is in fact a route that takes you from the airway to a VOR/INTERSECTION/NDB (or whatever) that the airport use for holding. It does NOT include the remainder of the route you get on your ND that the FMC has set out, that lines you up on the RWY. Lets take London's Heathrow (EGLL) for example. It has four arrival VORs which are the end of all of it's STARS where the aircraft take up the hold if nessarcerry. (sp-sorry) BNN, LAM, OCK and BIG. If the pilot of the arriving aircraft comes to the end of one of his STARS and has not heard from the approach controller he should automatically take up the hold. This way, all the approach controller has to worry about is taking aircraft off the hold and directing them to the ILS. This would be mayhem if all of the aircraft just left the holds by themselves and intercepted the LOC without ATC's permission. This is why STAR charts always end at VORs or NDBs. So when instructed to leave the hold by ATC, the pilot will be given a heading altitude and speed. He will not normally keep it on an LNAV path to intercept the LOC, but will have the a/c on heading select following the heading that ATC has given him/her to intercept the localiser. So when arriving into your airport, if you are using online ATC on VATSIM or IVAO or another server, or even if you are flying online, and you do not have charts, the best thing todo is use your discretion and choose some headings to fly to help you intercept the LOC. The best thing I find to do is fly a nice downwind leg, then turn a base leg (of about 4 miles) then turn to intercept. I was a proud owner of the DF 734, and on the arrival page, it had an option where you could extend the RWY centerline. I havent yet found this on the PMDG. Maybe the NG does not have this option. Hope this helpsRoss

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I'm the poster of this topic and my name is Patrick Dochy (MFS since FS 98).1)to resume: what I want to know is how does this PMDG-FMC is in comparaison with the real thing.I still believe (correct me if wrong) that the real FMC is able to fly the plane from A to B without the pilot and does it better and more acurately.The pilot is still the ultimate master and looks if everything 's ok.(or puts in new info if needed for example according instructions by ATC ).In other words : the FMC does the job for you, and not otherwise that the PIC does everything in order to keep the FMC going.2)I flew with Dreamfleet 737 and its FMC was better calculating des-path in VNAV mode,I believe.(although it had other "bugs").Also the descend-arc was steady and you could rely on it in V/S mode to get you at the proper altitude . The PMDG-one isn't at all ...wobbling up and down.Don't get me wrong, I love this plane and I fly this without FMC or even without AP (every pilot has to be able to fly without help of the internal computer in real), but still...this FMC seems to be a bit off a toy.Am I asking too much ?patten

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RE: drag required and some other things I'm the poster of this topic and my name is Patrick Dochy (MFS since FS 98).1)to resume: what I want to know is how does this PMDG-FMC is in comparaison with the real thing.I still believe (correct me if wrong) that the real FMC is able to fly the plane from A to B without the pilot and does it better and more acurately.The pilot is still the ultimate master and looks if everything 's ok.(or puts in new info if needed for example according instructions by ATC ).In other words : the FMC does the job for you, and not otherwise that the PIC does everything in order to keep the FMC going.2)I flew with Dreamfleet 737 and its FMC was better calculating des-path in VNAV mode,I believe.(although it had other "bugs").Also the descend-arc was steady and you could rely on it in V/S mode to get you at the proper altitude . The PMDG-one isn't at all ...wobbling up and down.Don't get me wrong, I love this plane and I fly this without FMC or even without AP (every pilot has to be able to fly without help of the internal computer in real), but still...this FMC seems to be a bit off a toy.Am I asking too much ?patten

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Well Patrick Dochy, thanks for sharing now make sure to include this name in each and every post ;-)"1)to resume: what I want to know is how does this PMDG-FMC is in comparaison with the real thing.I still believe (correct me if wrong) that the real FMC is able to fly the plane from A to B without the pilot and does it better and more acurately.The pilot is still the ultimate master and looks if everything 's ok.(or puts in new info if needed for example according instructions by ATC ).In other words : the FMC does the job for you, and not otherwise that the PIC does everything in order to keep the FMC going."Sorry but that is incorrect. Maybe you should re-read my post about descents and proper use of VNAV. This FMC (up to the newest updates) is the most advanced 737 FMC ever made for flight simulator bar none. Sure there are some folks who claim otherwise but one can simply ask the real pilots who come here what they think or get hold of some training material or FMC books and judge it yourself. I believe you should look at how complex this simulation is in regards to it's real world counterpart before making such assumptions regarding it's modelling. Do you believe one can simply jump into a rocketship and assume anything on how they think it should behave? RL pilots spend many months just learning these systems and what we have here is a very close replication of that rw aircraft. What you and I think means little compared to what is. If you believe something is incorrectly modelled then provide detailed information and facts to back up your conculsions. I know because I have spent many hours helping (Beta testing etc) make sure what we have on this FMC is as close to the rl FMC as possible. For sheer complexity try a HOLD and watch the FMC target speed automatically engage during the hold only. Can you tell me another that does that? What about route offsetting? What about detailed ILS A/P modelling so that the secend A/P while being armed prior to G/S will not engage until passing 1500 RA? The list of things modelled here is incredible. Mr. Brad Marsh who happens to fly the 800 NG for Virgin Blue airlines believes this sim to be the most accuate ever to date, good enough to train rw pilots on. Now if that does not speak a world of information to a non pilot than maybe nothing will."2)I flew with Dreamfleet 737 and its FMC was better calculating des-path in VNAV mode,I believe.(although it had other "bugs").Also the descend-arc was steady and you could rely on it in V/S mode to get you at the proper altitude . The PMDG-one isn't at all ...wobbling up and down." This is really just an opinion which you are certainly welcome to have. Are you saying this because you believe it is more simple and you do not encounter the issues I already clearly explained to you in my previous post? I will just stand behind what the RW pilots have stated in regards to ALL the systems on this aircraft without giving you my personal opinion since they fly it and I do not although I believe my study on the RW FMC is pretty good."Don't get me wrong, I love this plane and I fly this without FMC or even without AP (every pilot has to be able to fly without help of the internal computer in real), but still...this FMC seems to be a bit off a toy.Am I asking too much ?[/b}" Maybe you should ask "Am I not spending enough time learning what a rw NG + FMC is like ot make such a judgement"? Please do not go by the classic FMC because they are not alike for a proper comparison unless that particular FMC has a U10.4 and up software upgrade. In conclusion, write a post with what you are seeing that you believe is incorrect in regards to VNAV and the FMC and we can look up real world performance manuals, operation manuals from the NG to compare it's function and what we should expect here. This way we have a reliable means of judging. 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 |

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VNAV disconects,without warning. This is incorrect, it always has a reason and if you have the FMC open you will notice messages to you the pilot on the CDU stracthpad. VNAV does not just disconnect, there is always a reason and is very simple to find out way. The next time this happens PAUSE the sim and take a screenshot of the main panel with the FMC showing and post it here. Take a look at the FMA on the PFD, this will tell you what MODE the AFDS has reverted too and also tell us what is going.... 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 |

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Randy,I have read this thread with some interest as I have suffered some VNAV disco. problems myself.I fully agree with you that it is ultimately the pilot's resposiblity to monitor airspeed in descent. But quite often I found that the FMC has disconnected the VNAV for (as far as I can see) no reason.I usually suffer this when entering the approach stage of the descent. For example, flying the 738. I am approaching a waypoint where I am required to slow to from 240 to 210 (this is programmed in the FMC). Quite often I need to approach this point with spoilers at the flight detent in order to maintain 240. As soon as I reach the decel point the VNAV disconnects. Then I use hdg and vs to slow her down to 210 manually. Once on the correct path and speed the VNAV refuses to re-engage. This isn't any particular STAR but it has happened at more than one airport.Judging from your response it seems you haven't suffered this problem, but at the same time I doubt that I am doing anything wrong. Next time I see this occur I will post a screenshot for you to give me your expert opinion.Thanks,AhmedP.S. I usually fly pretty heavy, at or near max ZFW. Could this be the difference? Come to think of it I have only really experienced this when the a/c is heavily loaded.

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** double postNick B.Continental Airlines Virtual 737NG Pilothttp://www.precisionmanuals.com/images/forum/800driver.jpg--AMD Athlon XP 3200+ @ 2.2 Ghz (Equal to 2.8 ghz)400W Power supply3x 80 mm Case FansSoyo VIA KT600 Dragon PlusnVidia GeForce FX 5200 128 mb2 x 512 PC400100 GB Western DigitalMicrosoft Sidewinder Precision 2

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Because of that drastic speed change, I think VNAV will disconnect you if you are above 15 kts of your target speed. If you must slow to 210, you should be 225 kts instead of 240 when entering that restriction and VNAV shouldn't disconnect you. Also, on the LEGS page, us AT OR ABOVE/BELOW by placing an A (for at or above) or B (for at or below) after the height (ex: 250/10000A) to help control the descent profile. If you just have the altitude, it will only be a prediction.Nick B.Continental Airlines Virtual 737NG Pilothttp://www.precisionmanuals.com/images/forum/800driver.jpg--AMD Athlon XP 3200+ @ 2.2 Ghz (Equal to 2.8 ghz)400W Power supply3x 80 mm Case FansSoyo VIA KT600 Dragon PlusnVidia GeForce FX 5200 128 mb2 x 512 PC400100 GB Western DigitalMicrosoft Sidewinder Precision 2

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Like I said in this thread, learning to fly this type of aircraft in descents is quite often the most challenging thing to accomplish. In the RW, a 800 NG at idle and level flight will take about 5 miles to slow from 250 to 210 knots. Now think what happens when you are taking this same aircraft down hill and impose a restriction that is impossible for VNAV to perform. The FMC does not have use of speed brakes only we do. These planes do not come down hill and slow down at the same time very good. Some things to take into account is your planned descent speeds. Don't you believe it is a good idea to program another speed/altitude restriction say like 220 OR let the aircraft level off for a minute to help slow? If you want to use VNAV all the way to glide slope then you must program it in accordance with your route making judgements such as this. Of course in some places in the RW the 250/10000 is not even needed which certainly helps the FMC ;-). You know what the real issue I believe here? It goes for all others too, it's simply a dependence upon the FMC without making use of all availible AFDS functions in these situations. Sometimes one has to go LVL CH or V/S. Another thing to keep in mind regarding VNAV and under 10000', you cannot program a restriction that places the aircraft beyond 6 degrees because it is impossible for the aircraft to perform and keep the speed. This is even true above 10000' but it is limited to no more than 7 degrees so be careful where you want a restriction. If you do not need a restriction do not put one in your route! I have seen guys with restrictions in amazing places and altitudes simply because they thought they could. Anytime you can clear one by all means do it. In fact even RW will have to simply because it will not be possible for them to make it. And one last thing, VNAV disconnects in the RW too. It's certainly got better with U10.4 and above and I have been told by many pilots that VNAV in descent is much improved. Plan plan plan and then plan some more. We as flight simmers do not look at this sim like the rl pilots yet we somehow expect it to work the way it does for them. If you were actually flying a 737 would you be looking at bit more at the instruments and paying much more attention to things like SPEED? I know I would be glued to this! Of course this does not really fly so we are comfortable and *slack* a bit, if we do not do a descent checklist oh well it's not like a simulated boss will fire us or the sim pax will care if we do some 90 degree turns ;-). 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 |

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Indeed Randy I do quite often use the LVL CHG and VS on the AFDS for when required.But what would you say the is reason for the VNAV refusing to reconnect once I establish the a/c back on the correct descent path? Is it possible to reconnect following a VNAV disconnect?Lastly just to clarify the 240kts decel to 210kts was just a case of me picking random numbers, I've had disco at smaller speed changes.Thanks for your responsesAhmed

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