I reviewed the Canadian IFR equipment requirements again, and have concluded that I really need to add a completely independent second IFR approach capability. Canadian Aviation Regulations (CAR) 605.18(j) says:

Power-driven Aircraft - IFR605.18 No person shall conduct a take-off in a power-driven aircraft for the purpose of IFR flight unless it is equipped with...  (j) sufficient radio navigation equipment to permit the pilot,   in the event of the failure at any stage of the flight of any   item of that equipment, including any associated flight   instrument display,    (i) to proceed to the destination aerodrome or proceed to     another aerodrome that is suitable for landing, and    (ii) where the aircraft is operated in IMC, to complete an     instrument approach and, if necessary, conduct a missed     approach procedure.

My original plan was perhaps affected by my experience in type certification of aircraft designs. The regulations that govern type certifications have a concept of Equivalent Safety (see CAR 511.07(1)(b)). A manufacturer may argue that although his design does not meet the literal wording of the requirements, it has special features, or will have Flight Manual Limitations, that make the design equivalently safe to one that met the requirements. This allows us to sometimes focus on the intent of the requirement, rather than the literal wording.

I viewed the intent of CAR 605.18(j) as being to ensure that the aircraft can safely get on the ground after any single failure of any item of the navigation equipment, including displays. I have a Garmin GNS430, which has independent NAV and GPS, but they are both managed by the GNS430's display. If that display fails, it is not possible to change the NAV frequency, or manage the GPS. So, I planned to put a Limitation in my POH, requiring that either the destination or alternate airports have weather that allowed a VFR descent and landing. If the GNS430 failed on an IFR flight, I would pull out my handheld GPS and use it for enroute navigation, and then count on the VFR weather at either my destination or alternate.

But, these equipment requirements are not aircraft certification requirements, they are what we refer to as Operational requirements. And the concept of Equivalent Safety does not exist in operational requirements. You either have to meet the literal wording of the requirement, or you need an official Exemption from the requirements. Exemptions are difficult to obtain, and they are only valid for one or two years - they are intended as a solution to a temporary problem, they are not supposed to be a permanent "let" to the requirements.

So, I really need to add a second independent IFR navigation and approach aid, if I want to eventually obtain an IFR approval. I had originally considered a Narco 122D, which is a VOR/ILS receiver contained in the same box as its indicator. It fits in a standard sized instrument hole - you provide power and hook up the antennae, and you have a self-contained second IFR navigation capability. I decided to purchase a Narco 122D, and all the other miscellaneous items that I will need to install it. It will fit right below the CDI. It will be easier to install it now than later, so I will order it on Monday, and move on to other things while I wait for it to arrive. I'll probably start the engine baffle plenum cover.