Hello,

One thing that I never understood is why the GTN750/G60 has a limited number of approaches compared to what's available in the real world. As far as I know the Nav data isn't that old so I don't know why some approaches are missing.  For example at KRNO I have the charts for the ILS X, Y and Z Rwy 16R, but in the GTN I only see the ILS X and Y. Is there any particular reason for this? Is there a way to fix this?

Kayden

 

Hi,

There could be a number of reasons. Some of these have been discussed here:

 

Hi Kayden,

What you're seeing is real world.  The ILS Z Runway 16R uses RF legs from the HOBDA and KLOCK transitions.  RF legs require specific capabilities from the auto flight system, for example a roll steering autopilot.  Not all aircraft with the Garmin GTN have this equipment.  Even if so equipped, the type certificate (TC) or supplemental type certificate (STC) holder may not have accomplished all of the certification requirements in AC 20-138D Change 2 to demonstrate the capability to fly RF legs.  The Lear 75 that I fly has been "capable" of RF legs since its original certification in 2014, just Bombardier never bothered to do the certification on it.  However, with the release of  Garmin Phase IIIA just last month that RF legs were finally approved in the type certificate and in the AFM.  We're actually still waiting to complete the SBs upgrading to Phase IIIA <sigh>.   Now I fly RF legs in the real airplane instead of just in flight simulators. 

The Garmin systems (all of them) handles RF legs at the box level.  There is a switch/pin setting that enables RF legs.  The Garmin nav-database, the same one that is in the Garmin trainer that drives the RXP simulation, has all the procedures, including those with RF legs, in the database EXCEPT RNP AR APCH (i.e., RNAV (RNP) AR) procedures. If the switch/pin in the avionics is set to enable RF legs, then the Garmin system will display procedures RF legs.  In the RXP set up program, the one you set from within the flight simulator, there is an option to enable RF legs.  If you set that setting to show RF legs, then you see procedures with non-RNP AR APCH procedures with RF legs.  How to do this is in the RXP manual.  After you set this to include procedures with RF legs, you will see the KRNO ILS Z 16R, the KCRQ RNAV (GPS Z 24, STAAY RNAV SID at KSNA, and ZEFFR RNAV SID at ATL. These are all procedures in the US that use RF legs. 

RNP AR APCH procedures are specials.  They require special aircraft and aircrew qualification.  Further, the nav-database requires special validation. Each RNP AR APCH must be evaluated for the aircraft that will fly it for accuracy and flyability.  It is what we in the industry refer to as the "Golden Database" because any slight errors in coding the database can result in unexpected aircraft response.  For example, when Alaska began flying the RNP AR APCHs in the early 2000's at PAJN, they found that a slight error in coding of the bearing in and out of fix could result in the B737 doing a 360 degree turn over the fix.  Not good when you're trying to fly down the Gastineau Channel to runway 26 at PAJN. 

Because of the aircraft certification, crew training, and operational procedures required to fly these approaches, the RNP AR APCH nav-database is tightly controlled, in fact it's the most tightly controlled of all databases.  FAA says you will not have it in your airplane unless the operator holds the FAA-issued authorization.  Garmin and Jeppesen will not furnish the database with the RNP AR APCH procedures unless you show them that you hold OpSpec/MSpec/LOA C384.  Also, because of the extra database validation required, RNP AR APCH nav-database costs a lot more than the standard nav-database. 

Beyond the RNP AR APCH and RF leg restrictions, there will always be certain procedures that will not be coded in the nav-database.  For example, the Ft. Lauderdale Eight SID cannot be coded because it has no runway transitions and no common route for the SID.   There are multiple routes from different VORs around the KFLL airport that can be assigned, but there is no way to code these using the ARINC 424 specification.  Therefore, Jeppesen does not code this departure and similar ones at KMIA and KLAS.  Garmin will code them in their database, and you can access that database in the actual GTN trainer application on the Settings page.  On this page, you change between the Jeppesen and Garmin database.  The Garmin only provide the North American database. 

There may also be approaches that are not coded, and that's usually because they are not codable per the ARINC 424 specs. These procedures are usually conventional navigation procedures, e.g., ILS, LOC, SDF (particularly SDF for Garmin - I don't believe they code these type of approaches period), VOR and NDB.  Don't throw away your green needle, conventional navigation flying skills.  You still need those in the US NAS and elsewhere in the world. 

I hope this helped!

Rich Boll

Wichita KS

 

 

Thanks for your detailed response rich! Greatly appreciated and helps me better understand the systems, thanks!

Kayden