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How long can I run LNAV and VNAV

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How long can I run LNAV and VNAV for...for example right after takeoff I usually put them both on....is this alright or should I wait a little longer....also when coming in for a landing I ussually bring it in pretty close til doing an ILS approach...should I do this diffrent...?Thank youChad Moore

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Hi Chad,Simple answer is you can use as needed. For the climb-out after takeoff, in my IFR experience (flying GA), typically ATC will vector me to my first waypoint and then I assume own NAV so I typically use "HDG SEL" mode until I get a "direct to" from ATC to my first waypoint. I then use LNAV. Concerning VNAV, again it is dependent on ATC. I typically use "VNAV" or "LVL CHG" depending on climb instructions (mostly VNAV). Landing is a different story. I typically use VNAV and LNAV through a STAR, but then I use "CHG LVL" and "HDG SEL" modes for vectors to the approach. If you are setup for a precision approach such as an "ILS", then LNAV and VNAV are not appropriate. You should be using "APP" mode from the time ATC gives you a heading to intercept the "LOC" or clears you for the approach. For a non-precision "VOR" approach, I will typically use "VOR LOC", "CHG LVL" and the clock. Maybe a RW NG pilot could chime in for further info.Again, these examples are for a "Typical" flight. What mode to use when depends signficantly on the specific situation. This is why the autopilot has many different modes!

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Thanks George ....I have one other question.....What does CHG LVL do for me...ThanksChad Moore

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Hi Chad,Quoting from the manual:"The LVL CHG mode coordinates pitch and thrust commands to make automatic climbs and descents to preselected altitudes at selected airspeeds."Take a look in the PMDG documentation directory under FS at the "Aircraft Operating Manual". It explains the autopilot modes in detail.

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