7. RNP AR Operations and Training
Getting to grips with RNP AR
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30° on SA and 25° on LR at IAS > Vman – 3 kt
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15° at IAS < Vman - 10 kt
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An intermediate bank angle at IAS between above values
In some cases a specific airspeed constraint may need to be defined to ensure sufficient bank angle margin so that the AP will always be able to steer the aircraft on the define flight path.
During departure or missed approach, the AP performance with OEI during acceleration and configuration changes needs to be assessed. On some Airbus aircraft types, acceleration during turns will produce lateral flight path deviations that may not be compatible with the expected AP performance to remain within the RNP lateral limit. In that case, adapted flight crew procedures will have to be developed to define an acceleration point (instead of an acceleration altitude) where engine out acceleration has to take place.
7.1.2.2 AIRCRAFT OEI CLIMB PERFORMANCE
For departure, missed approach and balked landing, the aircraft climb performance needs to be assessed taking into account the obstacles within the 2xRNP limit. The Airbus performance software tools can be used for takeoff analysis. The calculated performance must be in adequacy with the defined flight crew procedures to cope with the AP performance for lateral navigation.
7.1.2.3 AIRCRAFT SYSTEM FAILURES
In the context of each RNP AR procedures, the airline should address the effect of aircraft system failures and validate the adequacy of the associated abnormal procedures. The failure cases to be addressed are listed in the ACD and SCOC document with indication of major procedure steps. They include mainly:
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Loss of GPS PRIMARY or NAV ACCUR DOWNGRAD
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Navigation alerts
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Failures of the FMS
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Failures of AP and AP/FD modes
The objective of this evaluation is to establish mitigations means to demonstrate an appropriate level of safety.
The airline may have to develop a Flight Operational Safety Assessment (FOSA), to comply with AC 120-29A requirements of § 4.3.1.1 quoted below:
Note: For AC 120-29A, RNP approaches are included in the CAT I approach category!
4.3.1.1. Operational Safety Evaluation. For any instrument approach using either Category I or Category II minima, the operator must adequately consider and provide for safe operations considering at least the following:
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The possibility of a failure of any one of the pertinent navigation systems, flight guidance system, flight instrument system, or annunciation system elements used for the approach or missed approach (e.g., ILS receiver failure, Autopilot disconnect, etc.).
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