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Noel

Two questions on 737NG

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I know this is covered in other posts, but in reading them I am still confused . . .Two things: after inputting the perf data and climb rates, when I use VNAV and change altitudes, the climb rate falls back to 250 knots despite being over FL10, even though climb rate is set well above that, like at 293 knots. Any ideas on what I have done wrong on VNAV?My 737NG as I am flying it is not holding the glideslope even after locking on to it. APR light goes off, then the sucker will tend to go nose up at about 2K feet and I have to manually land the bird. Any thoughts?If there are not quick solutions you can offer on this, I will go back and read the manuals etc and see. But alas, I am one who, right or wrong, tends to not read these guys unless it's to solve a discrete problem.Thanks in advance . . .Noel


Noel

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>>My 737NG as I am flying it is not holding the glideslope even>after locking on to it. APR light goes off, then the sucker>will tend to go nose up at about 2K feet and I have to>manually land the bird. Any thoughts?>Excessive pitch up when flying the glideslope generally causes to loose it. Extend more flap, this will help in bringing the nose down (the flaps will generate enough lift as to not need greater angles of attack). >If there are not quick solutions you can offer on this, I will>go back and read the manuals etc and see. But alas, I am one>who, right or wrong, tends to not read these guys unless it's>to solve a discrete problem.>Bad thing !! read the manuals, read the manuals and read the manuals !!!jose Luis.


signed: José Luis

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Noel, if you not into reading the manuals then I would recommend flying the FS default aircraft. PMDG and a few others make very accurate, hence complex, flight simulations which require some education before you can expect to have all the systems working properly. For me a good portion of the fun and challenge is getting to know these complex birds! :-)


George Morris

 

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>Excessive pitch up when flying the glideslope generally causes>to loose it. Extend more flap, this will help in bringing the>nose down (the flaps will generate enough lift as to not need>greater angles of attack).Thank you kindly jose for noting the kind of information I was seeking here in this post. Most helpful and I will play with that concept, though I pretty much always come in exactly as the FMC suggests for speeds and flap settings on approach.>Bad thing !! read the manuals, read the manuals and read the>manuals !!!>>jose Luis.Yes, as I say, right or wrong, I am disinclined to read the manuals in detail.


Noel

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>Noel, if you not into reading the manuals then I would>recommend flying the FS default aircraft. PMDG and a few>others make very accurate, hence complex, flight simulations>which require some education before you can expect to have all>the systems working properly. >>For me a good portion of the fun and challenge is getting to>know these complex birds! :-)>>>George, I guess I should thank you for taking the time to respond, but holy cow I should fly the default aircraft because I don't learn every detail enought to be rated on this simulation? Your assumption that I know nothing is just invalid. I fly them all, with their FMC's, land in the worst of conditions, but I had two questions I needed some suggestions with. If you can't explain why VNAV results in limited climb speed, I have to assume you don't know much about it. I read manuals but I am in no way interested in learning every aspect there is to learn, and I'm sure there is a happy place between total fanatic and "should fly default aircraft only."


Noel

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"But alas, I am one who, right or wrong, tends to not read these guys unless it's to solve a discrete problem."No criticism meant Noel, sorry it came across that way. The above comment leads me to believe you hadn't read the manuals at all. "...but I read manuals..."No way to know that until now. :-)To your question on VNAV, does your route have any airspeed constraints? Concerning the ILS, ensure you are following the flap schedule. The APR light going off is normal operating for the A/P. What's your airspeed look like after the FAF? The manual has a good section on how to fly the approach, but I would recommend nothing greater than VREF+10-15 on final and VREF+5 over the threshold. Others may also have some suggestions. I believe techniques for flying a good approach have been discussed a few times, so you may want to also try a forum search.A screen shot or two would also go a long way in assisting you with the problem. I have not seen the VNAV or APPR behavior you have described. I have a few hours in the NG. ;-)


George Morris

 

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Thanks George.Despite setting TGT SPD in the CLB interface in the FMC to 293/0.78 (or MAX RATE or any other setting), when I engage VNAV speed drops down to 250 knots even after exceeding FL10 with the default SPD REST of 250/10000. I have reviewed the manual, and this is the quote:"TGT SPD: The Airspeed / Mach numberdisplayed at 2L represents that target climbspeed/mach number for the climb phase offlight. This is the target climb speed towhich the airplane will accelerate if operatedunder VNAV once the airplane is clear ofother, more restrictive speed constraints forflaps or regulated airspace."Of note, I am able to select VNAV, and it will control speed down to 250 knots no matter what I set the TGT SPD to. I am getting no error messages, the plane just slows down to 250 even after exceeding FL10. The plane will stay at an IAS of 250 until reaching the ALT set in the MCP. In the past I have always just set a speed and altitude cleared to, then used the LVL CHG control to get there. Perhaps I just don't understand what VNAV is used for though it seems pretty obvious. What prompted this question was that recently I tried hitting the VNAV button, and it does light up with no FMC error messages, but then the speed will drop down to 250 and stay there. The same thing happens with the CRZ speed setting as well. The routes I set up are just direct routes from one airport to another with no other waypoints.Could be there is just so much more to input I am missing most of what's required to use the VNAV feature as it is intended.I did review sections on the FMC, and again can't see why I'm not able to reach the speeds set in the FMC--I thought this was used instead of setting speeds in the MCP for using VNAV for this aspect of flight control. From the comment from the manual, perhaps it has to do with flap speed restriction, though when all this is happening I have flaps retracted.Noel


Noel

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NoelWith the greatest respect, you are going to have to read the manual. If you haven't entered any route data into the FMC then VNAV will simply not work it has no data reference to input into the autopilot in respect of speed or altitude. Setting the autopilot alone will not progam the FMC.If you really want to get the best out of this product then you need to forget how you auto controlled the default aircraft in FS9 and sorry there's no short cut to reading and understanding the manual.Martin Plain

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As mentioned, if you haven't set up the FMC with a target alt and a flight plan then VNAV won't work. Could you give some specifics on how you have set up the FMC?


George Morris

 

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1. I will input my depart/arrival airports, input a crz altitude, select the runway ATC tells me to . . .2. I will arm the autothrottle, set speed to about 210, altitude to where I was cleared to by ATC, flaps to 5, heading inline with the runway, and when ready to take off, I will hit the TO/GA button and voila, she roars up and off we go. So far, no one's died!3. I will manually fly until I choose to engage the autopilot, at which point I will hit the LVL CHG button, and the aircraft will fly at whatever speed I have set in the MCP speed setting. It levels off as the plane reaches the altitude setting. This all works great of course, and thusfar, my virtual airlines has killed no passenger before his time!4. I will use LNAV or manually input headings as the spirit moves me . . .5. For descent, it's the same issue in reverse. I use the LVL CHG control most of the time, and all is well.So, I do have a route, and have set in CRZ ALT. The VNAV button does light up (IE, I'm getting no error messages) and will take the plane to the ALT set up in the MFD, but climb speed drops down to 250 despite going past the SPD REST setting of 250/10000. Same same for CRZ speed, it always stays at 250 even though I have input another speed into the FMC, or gone with it's default suggested CRZ speed for the PERF INI data that I put in.I do have one concrete question perhaps you can answer George: when using VNAV and ATC has cleared you to the next FL, what action do you perform to get the plane up to this next FL? I just chang the ALT setting in the MFD, hit VNAV again, and off she goes up to the next level--at 250knots the whole way.My guess is that I am only missing a small bit of information to determine why VNAV does this and therefore to make it work as it is intended. If anyone has insight into what piece I'm missing I would greatly appreciate it. Certainly I have elements of the FMC doing what they are supposed to, but obviously I am missing a critical piece. I have skimmed the FMC manual, and it still evades me.


Noel

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Martin, I have entered route data, but I'm sure I'm missing one or two critical pieces. I do have an active route, crz alt, target speed, etc. The only aberrancy with how this thing performs is the issue of the target speeds not being attained thru the FMC. as it must be pretty dang straightforward to cause this behavior.I understand your position on reading manuals, but alas I have read the FMC section and can't figure out why the thing does this. Kinda surprising someone here has not figured out exactly what is missing in my FMC programming for the thing to behave as it is. It has to be something very simple that I am missing, since most elements work as they should.I am not interested in complete understanding, flying SIDS/STARS and all the rest, but do wish to solve this little mystery. I enjoy the heck out of the sim and know I am flying it with a minimal level of understanding, but I do enjoy it :()


Noel

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Have you set a performance index usually between 80 and 100? This affects speed in VNAV since it establishes the fuel burn limits for your weight based on economy. This index can even limit your optimum and maximum altitude.What does your VSI read in climb? For the fuel burn restriction the lower your VSI (fpm) the lower the aircraft pitch and your speed will increase.In addition check out your takeoff weight to insure it is within limits.Your N1 page should be at default (no de-rate).While it may seem a dumb question, make sure your flaps and gear are retracted.Just random thoughts here.


Ron Ginsberg
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I agree with Bill, this would help you understand VNAV better. Simply put, I don't believe VNAV will work correctly if you don't have waypoints, other than DEP and ARR airports, within your route.


George Morris

 

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