--- title: "AWO.B.CATIII.121 CS AWO.B.CATIII.121 General — CS-AWO · Avioverse" description: "(See CS 25.1309 and its AMC, and AMC1 AWO.B.CATIII.121 and AMC2 AWO.B.CATIII.121) (a) The effects of failures of the flight guidance system including the…" url: "https://avioverse.aero/regulations/easa/cs-awo/subpart-b/awo-b-catiii-121" --- # AWO.B.CATIII.121 CS AWO.B.CATIII.121 General All Weather Operations (CS-AWO) · CS-AWO · EAR revision 14 Aug 2026 Official sources: [EASA Easy Access Rules (opens in a new tab)](https://www.easa.europa.eu/en/document-library/easy-access-rules/easy-access-rules-all-weather-operations-cs-awo) IR Implementing rule ## AWO.B.CATIII.121 CS AWO.B.CATIII.121 General (See CS 25.1309 and its AMC, and AMC1 AWO.B.CATIII.121 and AMC2 AWO.B.CATIII.121) (a) The effects of failures of the flight guidance system including the navigation means (facilities external to the aircraft) shall be considered in accordance with CS 25.1309 and CS 25.1329. (b) The radio altimeter (or other device capable of providing equivalent performance and integrity level), and excess-deviation alerts shall comply with CS AWO.B.CATII.120 and CS AWO.B.CATII.121 respectively. \[Issue: CS-AWO/2] IR · AWO.B.CATIII.121 — CS-AWO · ED Decision 2022/007/R · CS-AWO Easy Access Rules · EAR revision 14 Aug 2026 AMC Acceptable means of compliance ## AMC1 AWO.B.CATIII.121 Flight demonstrations of failure conditions 1 Failures 1.1 Indications and alerts Failure indications and alerts should be demonstrated. (See AMC 25.1309) 1.2 Effects For compliance with CS 25.1309, the effects of failure conditions will need to be demonstrated including not only failures of the landing system but also failures in other aeroplane equipment which could affect the landing (e.g. engines, reverse thrust, nose-wheel steering) and failures in the xLS ground facility. Although this demonstration may be done primarily by using a ground simulation, some cases should also be demonstrated in flight to confirm the conclusions of the simulation. (See AMC 25.1309) 2 Crew errors Individual landings additional to those of AMC AWO.A.ALS.106 paragraph 2.1 should be carried out to demonstrate that errors, which can reasonably be expected to occur, are not hazardous (e.g. asymmetric braking or reverse thrust, incorrect approach speed). (See AMC AWO.A.ALS.106 paragraph 2.2) \[Issue: CS-AWO/2] AMC — CS-AWO · ED Decision 2022/007/R · CS-AWO Easy Access Rules · EAR revision 14 Aug 2026 AMC Acceptable means of compliance ## AMC2 AWO.B.CATIII.121 Flight crew and maintenance checks When exposure times relevant to failure probability calculations are dependent on flight crew and maintenance checks (i.e. preflight, first flight of the day, pre-land, etc.) and/or inspection intervals for dormant (latent) failures, these tasks, time intervals and the recommended component monitoring programme should be specified in the AFM or maintenance manual as appropriate. \[Issue: CS-AWO/2] FAILURE CONDITIONS AMC — CS-AWO · ED Decision 2022/007/R · CS-AWO Easy Access Rules · EAR revision 14 Aug 2026 [All rules in SUBPART B – APPROACH AND LANDING](https://avioverse.aero/regulations/easa/cs-awo/subpart-b) Consolidated from the EASA Easy Access Rules (revision 14 Aug 2026, extracted 2 Nov 2026) for convenience. Not the official publication — verify against the Official Journal of the European Union and the EASA publications before operational use.