Aircraft Flight Operation Regulations Article 136

The navigation equipment installation shall be such that the failure of any single unit required for either communications or navigation purposes or both will not result in the other unit required for communications or navigation purposes.The airplane shall be sufficiently provided with navigation equipment to ensure that, in the event of the failure of one item of equipment at any stage of the flight, the remaining equipment will enable the airplane to navigate in accordance with Article 132. For flights in defined portions of airspace where Performance-based navigation (PBN), MNPS or RVSM is applied, Article 133, 134 or 135 shall be adopted as applicable.