Zimmerbz

Navigation question

Recommended Posts

Quick question.  In the sim, when would I shy away from using the navigation in the fmc and fly by tuning in the nav radios and flying a specific track?  Coming from the Airbus where everything auto tuned, I never much worried outside of a spot check here and there what my radios are tuned to.  It is my understanding that the 737 doesn't auto tune yet I have never had issues following the flight plan from point a to b when simply flying the route I entered into the fmc and using lnav and vnav. So when / why should I be tuning these in?  Is it just for redundancy if something fails?  Please enlighten me because I'm not sure!  Thanks

Share this post


Link to post
Share on other sites
Help AVSIM continue to serve you!
Please donate today!

Quick question.  In the sim, when would I shy away from using the navigation in the fmc and fly by tuning in the nav radios and flying a specific track?  Coming from the Airbus where everything auto tuned, I never much worried outside of a spot check here and there what my radios are tuned to.  It is my understanding that the 737 doesn't auto tune yet I have never had issues following the flight plan from point a to b when simply flying the route I entered into the fmc and using lnav and vnav. So when / why should I be tuning these in?  Is it just for redundancy if something fails?  Please enlighten me because I'm not sure!  Thanks

Share this post


Link to post
Share on other sites

The 737 will follow the flight plan in the fmc but you manually have to tune the ILS frequency. The 747 and 777 do it automatically once you select your rwy and approach on the fmc.

Share this post


Link to post
Share on other sites

The NAV radios are used not only for contingency purposes but also to provide raw data cross-checks of position when either airmanship or regulation demands it. 

If you are flying a conventional nav SID/STAR/IAP then in most cases you are required to have the relevant navaids tuned and identified and the needles displayed, even if you are using the FMC to fly the procedure (I say in most cases because some airlines have obtained dispensation to do away with this requirement, but even if you don't have to it doesn't mean you shouldn't).

How do you know that the magenta line is in the right place? Less of an issue with GPS these days, but a raw-data cross check of position (especially prior to descent or entering/leaving an area of sparse radio coverage) will confirm that you are where you (and the FMC) think you are.

I believe the 737 FMC automatically tunes DMEs in the background (separate from the NAV radios and transparent to the pilot) to aid in its internal position updating but I stand to be corrected.

  • Upvote 1

Share this post


Link to post
Share on other sites
5 hours ago, skelsey said:

The NAV radios are used not only for contingency purposes but also to provide raw data cross-checks of position when either airmanship or regulation demands it. 

If you are flying a conventional nav SID/STAR/IAP then in most cases you are required to have the relevant navaids tuned and identified and the needles displayed, even if you are using the FMC to fly the procedure (I say in most cases because some airlines have obtained dispensation to do away with this requirement, but even if you don't have to it doesn't mean you shouldn't).

How do you know that the magenta line is in the right place? Less of an issue with GPS these days, but a raw-data cross check of position (especially prior to descent or entering/leaving an area of sparse radio coverage) will confirm that you are where you (and the FMC) think you are.

I believe the 737 FMC automatically tunes DMEs in the background (separate from the NAV radios and transparent to the pilot) to aid in its internal position updating but I stand to be corrected.

Thanks Simon!  Good to hear from you again while I wait for the Bus to get ready for V4!

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now