GM1 SERA.11013(b) Degraded aircraft performance
CAA ORS9 Decision No. 1
DEGRADATION OR FAILURE OF THE RNAV SYSTEM
(a) If an aircraft cannot meet the requirements due to a failure or degradation of the RNAV system that is detected before departure from an aerodrome where it is not practicable to effect a repair, the aircraft concerned should be permitted to proceed to the nearest suitable aerodrome where the repair can be made. When granting clearance to such aircraft, ATC should
take into consideration the existing or anticipated traffic situation and may have to modify the time of departure, flight level or route of the intended flight. Subsequent adjustments may become necessary during the course of the flight.
With respect to the degradation/failure in flight of an RNAV system, while the aircraft is operating on an ATS route requiring the use of RNAV 5:
(1) aircraft should be routed via VOR/DME-defined ATS routes; or
(2) if no such routes are available, aircraft should be routed via conventional navigation aids,
i.e. VOR/DME; or
When the above procedures are not feasible, the ATC unit should, where practicable, provide the aircraft with radar vectors until the aircraft is capable of resuming its own navigation.
With respect to the degradation/failure in flight of an RNAV system, while the aircraft is operating on an arrival or departure procedure requiring the use of RNAV:
(1) the aircraft should be provided with radar vectors until the aircraft is capable of resuming its own navigation; or
(2) the aircraft should be routed by conventional navigation aids, i.e. VOR/DME.
Subsequent ATC action in respect of an aircraft that cannot meet the specified requirements due to a failure or degradation of the RNAV system, will be dependent upon the nature of the reported failure and the overall traffic situation. Continued operation in accordance with the current ATC clearance may be possible in many situations. When this cannot be achieved, a revised clearance may be required to revert to VOR/DME navigation.