Mailing List lml@lancaironline.net Message #8834
From: Scott Krueger <sky2high@hotmail.com>
Subject: Experimental Amateur Built Aircraft and GPS approach certified receivers
Date: Fri, 09 Mar 2001 08:17:47 -0600
To: <lancair.list@olsusa.com>
Cc: <Sky2high@aol.com>
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Jeff wrote:

<...Where does it state that if you install a GPS approach receiver that it has to be signed off by the FAA?...>

If you want an airworthy airplane (experimental or otherwise) using GPS for IFR enroute, terminal and approach operations, including autopilot guidance, read all of Paragraph 1-1-21 of the 2001 AIM, Advisory Circular AC20-138 or AC20-130A (installation), and especially the recent addition to the AIM, paragraph 1-1-21.b.1(a).

GPS is different!  Even if a TC or STC exist, follow on installations must have a 337 signed off by FSDO.

In general, certain GPS equipment, such as the Garmin 430, must be installed by an "authorized" shop.  Their sign-off of the installation also requires that the FAA (FSDO) sign the 337.  This is certainly true here in the North Central Region.  In addition, the FAA would not accept my Rocky Mountain Instrument's Micro-encoder pressure altitude output to the GPS even though it "meets" TSO specs.  I had to install a "certified" encoder in order to get their sign-off even though they couldn't explain the difference.  BTW, the Micro-encoder does provide heading and air-data to the GPS.

You also said:

<I was under the understanding that under the regs that the only the MIN equipment spelled out for IFR flight is REQUIRED. (aka AI DG TurnCoord, nav equipment applicable to the flight)...>

If you are using GPS, it is applicable, but also still considered supplemental and it must be backed up by ground based "primary" nav equipment(VOR, etc).  Remember that the 430 contains COM1, VOR/LOC, Glide Slope, IFR GPS (with current database) and implied DME.  The 430 contains all of my navigation equipment except for the marker beacon and that 12th century technology gem, the compass.  I do have a COM2.


Scott Krueger
N92EX

Note: read Appendix 1, paragraph 2 of AC 20-138.  You can find these ACs by doing a Google search for them.

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