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Replacing GNS530/430W to take advantage of VNAV in my Jetprop

Thailand has been recently introducing RNP LNAV/VNAV approaches nationally, and particularly at regional airports with no existing ILS approach. There is no SBAS coverage in Thailand, nor do I foresee there being any in my flying lifetime. ;-)

I currently have a GNS530/430 WAAS combo with Flightsream210 installed in my Jetprop. This has and continues to serve me well, especially when used in combination with Garmin Pilot and FS210. FS210 really has given the GNS boxes a new lease of life and had it not been for the adoption of LNAV/VNAV at local airports with no ILS, I was not considering changing them anytime soon.

My existing GNS WAAS boxes are unable to provide the VNAV component outside of SBAS coverage due to :- (quote from Garmin technical support)

The GNS 430/530W Models which are operated outside of SBAS Coverage does not have the ability to navigate the VNAV component associated with a coded approach/procedure included in a Navigation Database. To allow for the LPV functionality of the GNS 430/530W Models, the units are required to be operated in an area where the SBAS is approved for operation in the GNS 430/530W Software. There are no SBAS Coverage for Thailand which will allow for an LPV to be selected.

May I mention that the later revision GTN 650/750 (sw 6.41 and later) and GTN 650/750 Xi Models which superseded the discontinued GNS 430/530W models, offers the ability to provide Advisory Vertical Guidance (LNAV+V) outside of SBAS Coverage for an Approach/Procedure coded with the Vertical Approach Component. The reason for the differences is due to the MOPS DO-229 C/D which added optional implementation of Advisory VNAV in TSO-c145/146 Equipment operated in a non-SBAS environment

This raises the question of whether an avionics upgrade would be worth pursuing to gain the +V element at least.
I am hoping the learned wisdom of the forum could guide me on the following questions/ assumptions?

Do I understand Garmin’s last paragraph correctly that outside of an SBAS environment a current GTN or IFD box would automatically generate a +V advisory glideslope for a published LNAV/VNAV approach?
If so, would the box generate an emulated ILS glideslope signal my KFC225 autopilot would couple and follow, in the same way my current GNS box deals with an LPV approach in an SBAS environment? (I have flown LPV approaches in the US with my existing set up, so I know it works).
I understand that +V would essentially downgrade the LNAV/VNAV to LNAV minima, so on me to monitor MDA and MAP etc.

Due to my remoteness from any meaningful support or good local avionics resource, I am currently attracted to the IFD5xx/440 offering as in theory at least those boxes should pretty much be plug and play, and not require an expensive new panel install.

Thanks in advance for any help.
Cheers – E

Last Edited by eal at 20 Jul 10:48
eal
Lovin' it
VTCY VTCC VTBD

Hi E

I have just signed a contract to purchase a Jetprop. It has the avidyne suite with twin 430s.

A leading German avionics company has quoted me approx $14,500 to install twin GTN 650s, if that is of any use. I believe it is pretty much a slide out, slide in solution.

Can I as you a question please. I notice that you fly your Jetprop off grass and unimproved runways a lot. I want to operate off a good quality grass strip. The prop clearance on the Jetprop I am buying (with 4 blade MT prop) is only about 20 cm/8 inches. I have flown my PA46 Mirage off this same strip for the last 7 years, but I had the nose gear strut “pumped up” about another 3 inches to provide better prop clearance. Do you do anything like that with your Jetprop? What kind of prop clearance fo you operate with.

Last Edited by Buckerfan at 20 Jul 11:08
Upper Harford, United Kingdom

Congratulations on the Jetprop purchase, you are going to love it!

I have also pumped up the nose strut an additional 2-3” as you mention. It does make a big difference to the prop clearance with my 4 blade metal Hartzell prop.

Why do want to upgrade from Avidyne IFD440’s to GTN 650? From what l am researching the IFD’s have as much if not more functionality than the GTN’s

Cheers. E

eal
Lovin' it
VTCY VTCC VTBD

G1000W will not provide the advisory +V nor fly LNAV/VNAV without SBAS (it falls back on Baro VNAV source when it has no SBAS signal), no idea about GTN but I think it’s easy to test if one disables EGNOS/WAAS? but I don’t see why GTN can give +V and GNS can’t when both don’t have SBAS…

In non-SBAS env, I can bet GTN will always annunciate “LNAV only”, no Glide Path unless you feed in your altimeter pressure

eal wrote:

Why do want to upgrade from Avidyne IFD440’s to GTN 650? From what l am researching the IFD’s have as much if not more functionality than the GTN’s

Does IFD440 offer a “Visual Approach” feature? GTN comes handy for IFR back to home base in UK (usually private grass strips)

Last Edited by Ibra at 20 Jul 11:47
Paris/Essex, United Kingdom

Buckerfan wrote:

It has the avidyne suite with twin 430s.

I read it as Avidyne 5000 + 2×GNS430…

EGTR
G1000W will not provide the advisory +V nor fly LNAV/VNAV without SBAS (it falls back on Baro VNAV source when it has no SBAS signal), no idea about GTN but I think it’s easy to test if one disables EGNOS/WAAS? but I don’t see why GTN can give +V and GNS can’t when both don’t have SBAS…

In non-SBAS env, I can bet GTN will always annunciate “LNAV only”, no Glide Path unless you feed in your altimeter pressure

Currently using my GNS on the LNAV/VNAV approaches out here l get a downgraded LNAV as you describe, but reading the response from Garmin, it appears the newer software on the GTN does provide the +V in a non SBAS environment. Or at least that is how l am reading it. So presumably this is a feature they have enabled recently on GTN’s only?

I am currently hoping/ assuming the IFD’s behave the same way as the GTN.

Cheers. E

eal
Lovin' it
VTCY VTCC VTBD

eal wrote:

Currently using my GNS on the LNAV/VNAV approaches out here l get a downgraded LNAV as you describe, but reading the response from Garmin, it appears the newer software on the GTN does provide the +V in a non SBAS environment. Or at least that is how l am reading it. So presumably this is a feature they have enabled recently on GTN’s only?

Yes, GNS-W & G1000-W are very close to each other just different screen sizes !

GTN in the other hand is different, maybe worth asking local GA pilots in Oz or Nz?

I just asked this question to a friend who flies in Singapore, he mentioned he has +V advisory glide paths on his Garmin Perspective (just G1000W with extra software addons of GTN features like “Visual Approach”), so I would not be surprised if you have the “LNAV with advisory VNAV” (LNAV+V) in your GTN as well as “Visual Approach” without SBAS coverage if you have recent software but I doubt you will ever get the “LNAV/VNAV” (L/VNAV), this will surely need barometric inputs when SBAS is not around…

PS: if it makes you happy, GTN650/750 trainers shows advisory VNAV (LNAV+V) to VTBS with SBAS OFF


Last Edited by Ibra at 20 Jul 13:01
Paris/Essex, United Kingdom

Thanks for checking that. Very encouraging.
Presumably the LNAV+V would allow the autopilot to couple with the vertical glide slope, although l would manually have to disconnect at MDA?

Now l need to establish if the current IFD offering behaves the same way…

Last Edited by eal at 20 Jul 13:10
eal
Lovin' it
VTCY VTCC VTBD

@ncyankee is the expert AFAIK and latest firmware versions in GTNs (and possibly IFDs?) do not need the SBAS signal to deliver +V functionality.

However, AIUI, +V functionality requires an IAP (GPS or conventional navaid) to be published on that runway, so if you want to fly to your “farm strip” you need the “next hack” which is a synthetic glideslope to a given user waypoint, and while that does not need SBAS I don’t know whether IFD boxes have this.

This may be relevant.

@steveavidyne ought to know more too.

EDIT: corrected “GPS or conventional navaid”

Administrator
Shoreham EGKA, United Kingdom

As I understand it, Garmin added the LNAV+V capability to the GTN series regardless if it is in an SBAS service volume. It is not available in the GNS series. Avidyne supports +V as well outside of SBAS service volume. Both the RTCA DO—229C and D versions have this statement:

Note: LNAV equipment may provide advisory vertical guidance. Advisory vertical
guidance is defined as supplemental guidance where the barometric altimeter
remains the pilot’s primary altitude reference. This advisory guidance should
use the vertical path and deviations defined in Section 2.2.4. This advisory
guidance may be provided even when SBAS corrections or integrity information
is not available. This advisory guidance cannot be used to descend below the
LNAV MDA or step-down altitudes.

Also with the latest version of the GTN Xi, the GPS derived +V Advisory Vertical guidance is provided on conventional straight in VOR/NDB approaches as well as for RNP approaches.

KUZA, United States
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