autopilot nav and approach modes

[pollito]

hey all
whats the difference between autopilot nav and autopilot approach modes...do they use the same frequency?
thank you

[lnuss]

The NAV and APP modes are modes, or methods of operations, not frequencies. Among other things, they are sensitivity settings, so that APP mode is four times as sensitive as the NAV mode -- after all, you're generally closer and tolerances of being on course are tighter -- so basically NAV is used for enroute (VORs) and APP is used for instrument approaches, especially the localizer approaches and ILS approaches.

Localizer signals are on 40 odd-numbered* navigation frequencies between 108.10 MHz and 111.95 MHz, while VORs are on the even-numbered frequencies# in that range AND ALSO on all the other frequencies up through 117.95 MHz. Above that (118.0 to 136.95 MHz) is for radio communications with ATC, Unicom, air-to-air and more.

You can get a tremendous amount of information about this and other subjects from the FAA web site: faa.gov but there are instrument flying lessons built in to the sim and Wikipedia is also a wonderful resource, whether you are looking up NDB or aileron or stringer.

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* Actually it's the first digit AFTER the decimal point that must be odd.

#Actually it's the first digit AFTER the decimal point that must be even.

[mrzippy]

Good info, as always, Larry! You're a walking encyclopedia of aviation! Special thanks to the "original" Mickey Mouse Club for the spelling of encyclopedia!

https://youtu.be/cy2jWJtO3lE

[lnuss]

That's cute, Charlie. That was in the good old days when life was often much simpler -- fond memories. Thanks.

[pollito]

hmm... a bit to much to chew,,,a simpler answer will be appreciated.
dont think I dont thank your help tho.

[il88pp]

Nav Mode
is opposite of
GPS Mode.

Gps Mode:
AutoPilot flys the plane as the GPS plan says.

Nav-Mode:
Autopilot follows HDG, Alt, VS, that you set in the AP Windows.
Or follows to a selected mode like:
Approach-Mode during ILS
or
VOR-LOC when enroute.

[pollito]

still not clear...please read the question
thank you

[Nels_Anderson]

Nav mode - used for en-route navigation

Approach mode - used for instrument landing approach

That's the simple answer, but the original answer you got is a better one.

[mrzippy]

Actually the 2 things that you mentioned in post #1 do, indeed, use the same Nav1 frequency. Does that answer your question?

[lnuss]

I guess that's one way to put it, Charlie, but those modes don't actually use any frequencies- the NAV radio receivers DO use frequencies, but the modes are part of the auto-pilot, not of the radios.