The only time it occurs is on approach with the control tower.I have to reset the radio

to the approach freq.Great time for that,when flying the approach,no time to

be messing with that,right?

Thanks.

Are we talking Nav radio or Com?

I'd usually set up the ILS or VOR frequency I'm using for the approach during the decent/approach brief. I usually put it in NAV1 and the NAV2 standby. At this time also check the CRS - you may need to switch out of LNAV mode momentarily for this.

 

On approaching the IAP, switch out of LNAV into NAV mode to pick up the localizer or radial.

 

Com radio management is different - Setting up Tower frequency in the standby com1 when you get handed to Approach control is a good idea (so that it's just 1 button press away).

 

But this is on all aircraft types from B747 to C172.

 

The JS4100 does not have an autotune for ILS (neither do most turboprops or GA aircraft). If it's swapping on it's own it might be other software doing that like FScopilot or that kind of thing. The JS4100 should only change it's com and nav frequencies when you do it yourself.

 

At this time also check the CRS - you may need to switch out of LNAV mode momentarily for this.

 

There is really no need...

Simply tune NAV1, hit V/L once (twice for NAV2), set the appropriate track within 5 sec and arm NAV on autopilot. As the LNAV active and NAV armed, autopilot will capture the selected ground based station track.

The JS4100 should only change it's com and nav frequencies when you do it yourself.

 

This is correct and how it should be working.

 

It seems you have some other software running in the background that's messing with your frequencies.