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“WAAS” Upgrades

400/500 Series WAAS  Upgrades

(Note: As of May 2020, WAAS Upgrades are no longer available)
 – Use of this content is for reference only –

As we all know, Garmin has been selling new 400W/500W series systems and has been upgrading existing 400/500 series systems for a little while now. The focus of this text is to inform you of what to expect and to address a few issues we have encountered thus far.

The “Basic” WAAS Upgrade

The basic WAAS upgrade consists of the following steps:

  • Pre-upgrade documentation of all current configurations and interfaces for the purpose of:
         – Making the installation of your upgrade                    400W/500W series system easier.
  • Allowing us to confirm all interfaces are in          compliance with the STC.
         – NOTE: Any interface not found to be in                      compliance with the STC will require an FAA         ‘Field-Approval’.                                                                  Additional contingencies may be required as          part of the ‘Field-Approval’ compliance. Your          local Avionics Shop should be contacted to             discuss local FSDO requirements.    
  • Ship 400/500 Series unit to Garmin for an upgrade – This option is no longer available. Your only option is to purchase a used WAAS unit on the open market and try to sell your non-WAAS unit. Another option is to purchase a new or used Avidyne IFD unit which will slide into the GNS tray as a ‘plug & play’ option with a few notable caveats.
  • Measure GPS antenna coax length and determine the type of coax – RG400 or RG142B/U coax is the minimum requirement and must be between 6.5ft and 35ft. If the coax type is not in compliance, the coax MUST be changed. If the coax type is in compliance but the length is too short, an additional length can be added to achieve the minimum 6.5ft requirement.
  • Change the GPS Antenna – Garmin will provide a new GA35 GPS WAAS Antenna as part of the $3,395 WAAS upgrade charge. The GA35 antenna ‘footprint’ is identical to the existing GA56 GPS antenna on your aircraft. Therefore, most antenna changes should be relatively straight forward barring any complications resulting from unforgiving aircraft headliners/ panels, etc.
  • Change Antenna Connector – The new GA35 antenna requires a TNC type connector. The old GA56 used a BNC type connector. As of the writing of this text, there currently is not a 90° Adapter commercially available to expedite this process, therefore, the antenna connector must be changed.
  • Confirm 400W/500W series unit is physically within the “ACCEPTABLE VIEWING” area – The “Acceptable Viewing” area is clearly defined in the appropriate installation/upgrade manual. Because aircraft differ in configuration, final determination for compliance is the responsibility of your Garmin Dealer, however, the following should provide a basic understanding of this requirement:
          – Note: The following is assuming the 400/500 series unit is located to the right of the pilot and the 400/500 series unit is on the same vertical plane as the pilot’s instrument panel. For those aircraft (example: Cirrus SR20/22) with the units located below this vertical plain, see “Non-Basic WAAS upgrade”.
  1. Determine the “Centerline” of the Pilot’s scan – Draw an imaginary line thru the center of the pilot’s seat, thru the center of the pilot’s yoke, and up the panel. (This line will typically fall in line with the center of the DG/HSI and Attitude Gyro/Flight Director on most aircraft).
  2. Measure from this point to the left bezel edge of the 400/500 series unit.
  3. If this measurement is 11.8 inches or less, no annunciation should be required and hence should remain a “Basic WAAS Upgrade”.
  4. If this measurement is greater than 11.8 inches, your upgrade MAY become a “Non-Basic WAAS Upgrade”.
  • Install used Garmin 400W/500W series unit   Installation of the upgraded unit requires the following steps:
  1. Configure the upgraded unit using pre-upgrade settings and make any changes necessary as appropriate.
  2. Complete “Post Installation” forms as required by Garmin.
  3. Perform a complete ‘check-out’ or upgraded system and interfaces.
  4. Complete all applicable FAA legal paperwork as related to the upgrade.

This should complete the “Basic WAAS Upgrade” process. $750-$800 typically covers our labor as described above & miscellaneous parts. REMINDER: Any item found during the upgrade process that changes the upgrade status to “Non-Basic” most likely will result in additional labor and parts charges. 

The “Non-Basic” WAAS Upgrade

The “Non-Basic” WAAS Upgrade is defined very simply whereas any portion of the upgrade that falls outside of the realm as previously written. These areas can include but are not limited to any of the following:

  • 400/500 series unit is outside the “Acceptable Viewing Area”.
         – If this measurement exceeds 11.8 inches but is less than 13.41, VLOC/GPS annunciation is required. This can be accomplished via a GI106A indicator, an EHSI (as applicable), a PFD (as applicable), or another form of independent annunciation.
          – If this measurement exceeds 13.4 inches, VLOC/GPS, MSG, WPT, APR, TERM, INTEG annunciation is required. The VLOC/GPS can be accomplished via a GI106A indicator, an EHSI (as applicable), a PFD (as applicable), or another form of independent annunciation. The MSG, WPT, APR, TERM, INTEG annunciation can be accomplished via an EHSI (as applicable), a PFD (as applicable), or another form of independent annunciation.
           – Assuming a worse case scenario, if you need all stated annunciators, expect approximately $1500 in parts and labor to install the required annunciators.

  • Antenna coax needs to be changed – The installer who performed the original installation used the minimum allowable grade coax for your install (RG58). This type of coax is not in compliance with the STC therefore needs to be changed to RG142 or RG400 with a length between 6.5ft and 35ft.
  • If changing the Antenna and/or Antenna coax connector requires more than 1.5 hours to perform the work due to accessibility problems or lack of coax ‘service-loop’.
  • Any system interfaced to the 400W/500W series unit that is NOT an APPROVED interface. Only items/systems listed in the 400W/500W series installation/upgrade manuals ARE APPROVED. These items will most likely require an FAA ‘Field-Approval’.
  • If your aircraft is equipped with a Sandel SN3308 EHSI.
  • If your aircraft is equipped with an STEC GPSS Roll Steering Adapter.
  • If your aircraft has a GPS400, GNC420(A), GPS500, or GPS500-TAWS.

Upgrading with New Equipment

Garmin now offers the new GTN Series of units, most popular being the GTN650Xi and GTN750Xi and Avidyne offers the IFD Series. If you currently have a non-WAAS GNS unit and would like to obtain WAAS thru purchase of new equipment, the above text and procedures related to antenna change and annunciator requires are applicable to the process. In addition, given the differences in devices (GNS vs. GTN), these units are not tray and connector compatible therefore additional work is required whereas the Avidyne IFD Series are tray and connector compatible (with a few notable exceptions). Consult your Garmin or Avidyne Dealer for details.

The bottom line regarding the “Non-Basic” upgrade is that exact costs must be determined on a case-by-case basis. Your Avionics Shop can help you with this given enough details regarding your installation.