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Guest glenb

RNAV Approach FMC MCP setup

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Just basic question. Is it even 'legal' to fly such RNAV approach as the one discussed above in Phoenix in 737-NG?. GPS is required for this approach and 737-NG has probably GPS as part of its FMS but GPS itself may not be enough. In the unit like Garmin 430/530 such approach would be treated correctly by switching to the approach mode and providing correct sensitivity for the CDI deflection. Unless I am wrong 737's FMS has no clue this is a GPS approach and therefore will not provide correct lateral sensitivity treating those waypoints like part of enroute portion. Does anyone follow my point?Michael J.WinXP-Home SP2,AMD64 3500+,Abit AV8,Radeon X800Pro,36GB Raptor,1GB PC3200,Audigy 2

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Guest glenb

Frank,Those are old plates! I don't know when Phoenix built the 8/26 but I believe it is the newest. I wonder if they just named it the way they did to avoid a center "C" runway.I have the version 3 from Jeppson but now I get all the Terminal Proccedures fromhttp://avn.faa.gov/digital_tpp.asp?ver=050...5&end=2-17-2005Glen

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Guest glenb

Michael,Interesting point. The RNAV approaches are in the SIDSTAR file and I think I read somewhere that the company (airline) can include them if approved equipment etc.BTY When the approach goes well it's a hands off approach from cruise altitude to the DH, except for flaps, gear and very little drag. Very clean. And lots of fun to watch.Reality check. This is a simulator on a PC at home right? A side note I think PMDG along with MSFS have done a fantastic job and for under $200. What does a Boeing 737NG cost?A personal note. Many years ago I worked as an instrument instructor and the first few times I made an approach to mins with PMDG I got that same feeling in my gut just before breaking out of the overcast.I could not believe the realism.Glen

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Glenn,I agree with you. VNAV in works better by inserting hard altitude constraints for some reason.Don't know if your aware of this but if you ever see a magenta bug on the IVSI on the PFD during a VNAV PTH descent, you need to cycle the VNAV button OFF then back ON to get rid of the magenta bug. The IVSI should only have a magenta bug when in VS mode. If you don't cycle the VNAV button then VNAV PTH will only try to maintain a shallow descent and not make any more altitude constrains.Floyd

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Guest frankathl

Yep, I should get some new plates, Glen!It could well be your suggestion regarding renaming of runways is correct!Thanks for the link. Very good site.BR,Frank

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Guest frankathl

Thank you, George. Your post is very helpful!My only comment is that I believe RNAV also covers the flight route itself, not just the approach. The idea is to fly a more direct route than VOR to VOR by flying offset from the navaids with the help of LNAV.BR,Frank

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Guest hlm65

Hi Frank,RNAV is mainly created to supply non precision approaches to airports/runway that don't have other IAP, or to supplement existing ones. Certain RNAV are truly "precisionlike", because they provide a "certified" glideslope (check on 737 Manual regarding RNP).A FNAV approach is much less costly in terms of installation and maintenance than any other instrument approach.Best regards.

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Guest tmetzinger

>Just basic question. Is it even 'legal' to fly such RNAV>approach as the one discussed above in Phoenix in 737-NG?. GPS>is required for this approach and 737-NG has probably GPS as>part of its FMS but GPS itself may not be enough. In the unit>like Garmin 430/530 such approach would be treated correctly>by switching to the approach mode and providing correct>sensitivity for the CDI deflection. Unless I am wrong>737's FMS has no clue this is a GPS approach and therefore>will not provide correct lateral sensitivity treating those>waypoints like part of enroute portion. Does anyone follow my>point?The GPS is just one more sensor to the 737 Autoflight system. The FMC autoflight system does in fact adjust sensitivity to the required level of performance (RNP 0.3) in this case. However, in LNAV mode the GPS is usually providing this level of precision at all times. .The reason for the difference in CDI sensitivity on the GA avionics like the 430/530 is that the GPS is usually driving a protein-based autopilot (the human) and not a silicon based one. The airplanes I fly that have GPS roll steering on the autopilot always maintain the selected course within .1 NM, even in cruise.

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Guest hlm65

Hi,it seems strange indeed, but the real world correct procedure to fly a RNAV (LNAV+VNAV) approach (authorized when a descent gradient is published) is to set the MCP ALT at zero (737 manual, section 3)."using VNAV for descent on the gradient path from the FAF to minimums requires the setting of "zero" on the MCP altitude window".

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Guest hlm65

Hi,you can set any DA you wish, even down to a single foot, using the MINIMUMS rotary knob located on the left glareshield. If you for any reason must round a DA, it must be rounded upwards (1600 instead of 1560).

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>The FMC autoflight system does in fact adjust sensitivity to>the required level of performance (RNP 0.3) in this case. >However, in LNAV mode the GPS is usually providing this level>of precision at all times. .Interesting. I wonder if it also holds true for something like 747-400 which may not have GPS built in.Michael J.WinXP-Home SP2,AMD64 3500+,Abit AV8,Radeon X800Pro,36GB Raptor,1GB PC3200,Audigy 2

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Guest glenb

EnricoThanks for the info. You answered the question of how to set the MCP altitude. In all my confusion I forgot the min setting.

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Guest glenb

OK, I am on a mission now.Sometimes the RNAV approaches are smooth with near ILS precision. Other times I get to the final approach fix and the descent reduces, the vertical path is very high and I end up too high to make a safe landing. I will find out why this is happening.RNAV is the future for aviation navigation including approaches. I am having a lot of fun with all the trial and error and am going to stick with it.

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