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Guest l_bowes

Managing vertical speed in the B737-600

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Guest l_bowes

Hi,When flying the PMDG B737-600, to start my descent I usually select the altitude given to me by ATC in the MCP altitude indicator and set a target speed in the MCP for descent. This works OK for flights below FL250. However, when starting descents above FL250, sometimes this method tends to result in the AP descending at a rate of -6000ft/m until the target speed has been reached! Is there any way to set a vertical speed for the a/p to follow as well as maintaining the target speed during descent?Thanks,Luke

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Guest Robin.B

Are you aware and able to use the VNAV function in the NG? If not, then check out the manual and try to learn to use it. It's VERY useful and IMO almost essential in speed/altitude management.

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Guest l_bowes

Hi Robin,Thanks for your reply. I have used the VNAV in the past when flying offline, however is it practical for use with online ATC? For example, using VNAV, how would I manually tell the FMC to descend to and maintain FL210 from FL300 until I specify a further altitude to descend to?Thanks,Luke

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Are you using mach or knots for your target soeed above FL250? I know for the VA I fly, the flight releases specify a mach and a speed for the decent and climb (you fly one until reaching the other), most of my decents in the 737 have been 0.74/300. So the VNAV will decend .74mach until it exceeds 300knots, then it'll just maintain 300. When mach .74 exceeds 300knots so far has generally been somewhere between FL250 and FL290 dependant on the temperature and pressure.----------------------------------------------------------------John MorganReal World: KGEG, UND Aerospace Spokane Satillite, Private ASEL 141.2 hrs, 314 landings, 46 inst. apprs.Virtual: MSFS 2004"There is a feeling about an airport that no other piece of ground can have. No matter what the name of the country on whose land it lies, an airport is a place you can see and touch that leads to a reality that can only be thought and felt." - The Bridge Across Forever: A Love Story by Richard Bach


John Morgan

 

"There is a feeling about an airport that no other piece of ground can have. No matter what the name of the country on whose land it lies, an airport is a place you can see and touch that leads to a reality that can only be thought and felt." - The Bridge Across Forever: A Love Story by Richard Bach

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>Hi Robin,>>Thanks for your reply. I have used the VNAV in the past when>flying offline, however is it practical for use with online>ATC? For example, using VNAV, how would I manually tell the>FMC to descend to and maintain FL210 from FL300 until I>specify a further altitude to descend to?>>Thanks,>>Luke This depends but if you are farther than 50 NM of TOD then simply reset the MCP alt dial to FL210 and enter this into the CRZ ALT line and hit EXECU. This will perform a "CRZ DESCENT" and hold at the new altitude. Be aware that VNAV will NOT keep the SPD but the PATH, for SPD simply LS SPD on the Descent page. If you are not in a hurry you can also use DES NOW which will descend more slowly than VNAV. Remember that the AFDS does not take pax comfort into account for modes. Also, since you are above FL1000 simply use FLCH by setting the restrictive altitude clearance into the MCP. If it were me and ATC ask me for a lower altitude while early in cra I would perform a crz descent, if on the other hand ATC desired me to start my descent I would choose FLCH.[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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Guest tmetzinger

>Hi,>>When flying the PMDG B737-600, to start my descent I usually>select the altitude given to me by ATC in the MCP altitude>indicator and set a target speed in the MCP for descent. This>works OK for flights below FL250. >>However, when starting descents above FL250, sometimes this>method tends to result in the AP descending at a rate of>-6000ft/m until the target speed has been reached! Is there>any way to set a vertical speed for the a/p to follow as well>as maintaining the target speed during descent?>>Thanks,>>LukeSure. Set ALT HOLD mode, then select your new target altitude. Then set your preferred VS in the VS window, and your target speed in the speed window. Your airplane will descend at the chosen VS, and the autothrottle will attempt to maintain the chosen speed. Note, however, that if you set too fast a rate of descent, your airplane may overspeed even with the throttles at idle.Another alternative discussed is to use LVL CHG and set the appropriate speed (in mach or knots).ATC will eventually tell you if you need to adjust anything.Best wishes,

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Guest jeffg

Tim, Whats the story on your book,any update? JeffG

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Guest l_bowes

Hi Randy and Tim,Thanks very much for your replies, you've answered my question perfectly :)Thanks,Luke

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