As a PPL in the 70's, getting to know the modern avionics systems such as Garmin and other FMS glass cockpits has been a real eye-opener for me.  Their capabilities are astounding.  I am surprised by one thing, however...

The Garmin iterations and some of the other systems auto-tune the navaids in the approach segment of the flight plan.

Now, I'm not complaining about auto-tuning Nav1.  Having the system pre-tune the approach localizer or primary VOR is a nice touch and reduces the work-load (which is what you want under IFR conditions).  However, these systems are pre-tuning both NAV1 and NAV2 to the same frequency.  Now, we have a problem - is this how they operate in the real world?  I've been very impressed with the work of WT in their continuing development of the Garmins and other systems but have they missed the boat on this or is it a real-world procedure by the avionics?

I was a VFR pilot in my flying days, but I did start training in IFR procedures and have some RW IFR (dual) approaches under my belt.  We were taught to always be ahead of the airplane, especially when doing IFR procedures.  Pre-tuning all navaids was  part of this (VOR/ILS1, VOR2, ADF, etc).  This was especially important as many approaches used a secondary navaid for intersections, DME ARCS, DME, etc.  Even with many of the modern approaches using RNAV waypoints, a secondary VOR or ADF is still important for some approaches.

Unless I'm flying a DME ARC, I really don't want both navaids receivers tuned to the same transmitter.  I want the second navaid tuned to a reference VOR, reference DME, etc.  What's happening is I preset NAV2 in many situations only to have the Garmin and other systems knock it out during the approach sequence by tuning both navaids to the same station.  Now the system is causing extra workload - I have to re-tune the second NAV back to the appropriate frequency when I'm in the middle of the approach.

I have trouble believing that this is the RW behavior of these systems, as they would take away what the pilot needs to be ahead of their game.  Now, maybe procedures are different than when I was in training, but this seems to be one thing that would be a nuisance and may, under a heavy approach workload, create a dangerous situation?

9 minutes ago, RandallR said:

 

I was a VFR pilot in my flying days, but I did start training in IFR procedures and have some RW IFR (dual) approaches under my belt.  We were taught to always be ahead of the airplane, especially when doing IFR procedures.  Pre-tuning all navaids was  part of this (VOR/ILS1, VOR2, ADF, etc).  This was especially important as many approaches used a secondary navaid for intersections, DME ARCS, DME, etc.  Even with many of the modern approaches using RNAV waypoints, a secondary VOR or ADF is still important for some approaches.

 

A lot of thing changed since 70th that include IFR approaches. When I was getting my IR ticker there were a lot of ILS approaches with marker beacons. However, one by one marker beacon got replaced with GPS fixes! You no longer needed to have cross radial and dial another VOR to identify you approach fix - all you have to have is current GPS NAV database. 

As far as dual ILS frequency for NAV1/NAV2 is also technique coming form the past. If NAV1 fails during approach you can always switch to NAV2 and continue . I can't remember how real G1000 handles it, but most airplane I fly have independent sources for NAV1 and NAV2. When I shoot ILS I always put ILS frequency active for both NAV1/NAV2 and miss approach frequency on standby. 

The G1000 does auto-tune, but the behavior you describe doesn't appear to be accurate. From the G1000 manual (page 120):

Quote

When loading or activating a VOR or ILS/LOC approach, the approach frequency is automatically transferred
to a NAV frequency field as follows:
• If the current CDI navigation source is GPS, the approach frequency is transferred to the NAV1 active
frequency field. The frequency that was previously in the NAV1 active frequency field is transferred to
standby.
• If the current CDI navigation source is GPS, and if the approach frequency is already loaded into the NAV1
standby frequency field, the standby frequency is transferred to active.
• If the current CDI navigation source is NAV1 or NAV2, the approach frequency is transferred to the standby
frequency fields of the selected CDI NAV radio.

 

2 hours ago, sd_flyer said:

You no longer needed to have cross radial and dial another VOR to identify you approach fix - all you have to have is current GPS NAV database.

True, but there are still approaches that use DME separate from the localizer.

2 hours ago, sd_flyer said:

. I can't remember how real G1000 handles it, but most airplane I fly have independent sources for NAV1 and NAV2. When I shoot ILS I always put ILS frequency active for both NAV1/NAV2 and miss approach frequency on standby. 

I do the same as you. loading the missed approach VOR (if that is the MAP source) into NAV2, but the Garmin units replace that with the approach navaid frequency when the approach is initiated.

When loading or activating a VOR or ILS/LOC approach, the approach frequency is automatically transferred
to a NAV frequency field as follows:
• If the current CDI navigation source is GPS, the approach frequency is transferred to the NAV1 active

frequency field. The frequency that was previously in the NAV1 active frequency field is transferred to
standby.
This is replicated.

• If the current CDI navigation source is GPS, and if the approach frequency is already loaded into the NAV1
standby frequency field, the standby frequency is transferred to active.
This is replicated.

• If the current CDI navigation source is NAV1 or NAV2, the approach frequency is transferred to the standby
frequency fields of the selected CDI NAV radio.

I believe this is also replicated. The problem is that it also resets the NAV2 frequency to the approach frequency.

• In the case of the Garmin units, the frequency I set is now in NAV2's standby.  I therefore need to transfer my selected frequency back to active.  This is certainly not a difficult thing but they have now added a step I shouldn't have had to do.
• In the case of the FMS in the CJ4, for instance, the NAV frequency entries have no Standby (that I can locate).  Therefore my pre-entered frequency in NAV2 is erased.  I now have to go to Tuning and re-enter the frequency while busy in the approach.

The ONLY gps system I've found to behave remotely like the real world unit in msfs is the TDS gtn 750xi which performs brilliantly. Nothing else comes close. 

From what I can tell the G1000 as represented by the work of WT is pretty accurate to the real world.  I'm trying to find out if they erred while assigning auto tune to both NAVs,

As far as the TDS is concerned, do they auto-tune both NAVs or just NAV1?

On 8/16/2024 at 9:15 AM, RandallR said:

From what I can tell the G1000 as represented by the work of WT is pretty accurate to the real world.  I'm trying to find out if they erred while assigning auto tune to both NAVs,

As far as the TDS is concerned, do they auto-tune both NAVs or just NAV1?

Why not ask WT in their Discord forum?  They are usually pretty good about responding..

@MattNischan ?

Yep - that's the next step.  I'll update this thread once I get a response.