AWO.A.EFVS.108 CS AWO.A.EFVS.108 Enhanced flight vision system (EFVS) level of safety

During the development and design of an EFVS, the safety design goals for airworthiness approval should be established. The safety criteria for each phase of flight, including approach and landing systems, should be defined in terms of accuracy, continuity, availability, and integrity. Appropriate design guidance should be used to determine the overall required level of safety for the aircraft, in any mode of flight, and for any combination of failures which can cause an unsafe condition in order for them to be fully assessed and categorised. This should include the ability of the flight crew to cope with these failures. The hazard level for any aircraft system will depend on the ability of the flight crew to cope with failures. For failures where the SSA assumes a particular pilot intervention to limit the hazard effects (for example, from catastrophic or hazardous to major or minor), it should be shown that the pilot can be relied on to perform that intervention. For example, the pilot might be assumed to detect a system error because of other displays or out-the-window view.

It should be demonstrated that flight crew can detect the error in a timely fashion and not be hazardously misled. The demonstration must validate the hazard classification contained in either CS 23.2510 or CS 25.1309, as appropriate.

The applicant should demonstrate a satisfactory safety (failure and performance) level which should not be lower than the safety level required for precision and NPAs with decision altitudes (DAs) of 200 ft or above without the use of an EFVS. In showing compliance, probabilities cannot be factored by the fraction of approaches which are performed using EFVS. Consideration, however, can be given to the EFVS critical flight time, such as from the highest DH that can be expected for an approach to 100 ft above the TDZE using an EFVS-A.

The selected DALs are directly linked to the specific intended use and to the specific EFVS installation as an integrated part of the flight deck flight information system.

In showing compliance with these safety criteria, the probabilities of failure conditions of an EFVS-L should not be factored by the fraction of approaches which require an EFVS-L. The probabilities of failure conditions of an EFVS-L should also not be factored by a statistical distribution of visibility conditions. The exposure time used for failure calculations of an EFVS-L should be the elapsed time from descent below the highest expected DA/H for the approach using an EFVS-L to completion of roll-out to a safe taxi speed.

Any malfunction, fault detection and annunciation schemes should satisfy the required levels of safety and should perform their intended functions.

[Issue: CS-AWO/2]

Easy Access Rules for All-Weather Operations (CS-AWO)