4.2.2. AIRCRAFT PERFORMANCE UNDER FAILURE CONDITIONS
With the A330, the following RNP levels have been determined from aircraft and aircrew performance in abnormal conditions including engine failure, latent system failures, Flight Guidance orders runaway, etc.) and are considered as envelope RNP levels following EASA requirements for demanding RNP AR operations. Aircrew performance is assuming ad-hoc training. For the operator, the use of the hereunder table suppresses the requirement to perform a Flight Operational Safety Assessment (FOSA).
RNP with AR (SAAAR or equivalent) A330  Departure NAV mode  Approach  Missed approach NAV mode 
APP NAV mode  FINAL APP mode 
AP ON  0.3  0.3  0.3  0.3 
AP OFF / FD ON  0.3  0.3  0.3  0.3 

Alternatively, lower RNP levels may be approved on a case by case basis, based on a FOSA performed by the airline and under  responsibility of the national authorities. The aircraft performance under failure conditions documented here below can be used as guidelines, for the national authorities, to determine a RNP level suitable for the considered operations, and ultimately approve it. The tables below give demonstrated maximum TSE values for different failure conditions. The effects of engine failure and system failures have been assessed in flight and in the simulator.
. Engine failure and OEI operations
RNP AR  AP ON 
Engine failure  NAV mode  FINAL APP mode 
TSE max in RF* SA aircraft  0.24  N/A 
TSE max in TF* SA aircraft  0.18  N/A 
TSE max in RF* A330  0.15  0.07 
TSE max in TF* A330  0.09  0.07 

(*) TF: Track to Fix FMS leg; RF: Radius to FIX FMS leg
4. Certified RNP capability

-19 -
Upon Engine Failure, Airbus recommends the use of AP, except in approach for SA with FMGC standard requiring to disconnect AP. 
Besides engine failure, the effect of other system failures must be taken into consideration. As an example, an extract of the ACD for the A330 is given below.
.  Demonstrated TSE in Probable System Failures conditions
Probable failures are considered when the probability of occurrence is more than 10-5 per
operation (based on a 15min exposure time).
Sizing probable failure considered is: loss of FMS guidance.

Probable Failures  Departure  Approach  Missed Approach
APP NAV mode  F.APP mode 
TSEmax in TF (straight) leg  0.10 NM  0.10 NM  0.10 NM  0.10 NM 
TSEmax in RF (turning) leg  0.15 NM  0.15  0.15 NM  0.15 NM 

.  Demonstrated TSE in Remote System Failures conditions
Remote failures are considered when the probability of occurrence is from  10-5 to 10-7 per operation (based on a 15min exposure time). Sizing Remote failures considered are: Loss of NAV mode, AP roll runaway.
　
中國航空網 www.k6050.com
航空翻譯 www.aviation.cn
本文鏈接地址：getting to grips with RNP AR Required Navigation Performance(13)