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minimum requirements for the ETOS application under all conditions. The
OPA is found in Appendix B. For this application, the performance
requirements are invariant of the prevailing natural visibility (weather
The OSA derives safety requirements by considering potential hazards to
which the flight crew and/or aircraft might be exposed during the ETOS
application, and derives requirements in order to control the likelihood of the
hazards and their effects. In this application, multiple OSAs are defined in
Annex C. These OSAs vary as a function of the prevailing natural visibility,
the airport infrastructure (e.g., lighting), and installed vision system
technologies performance. EFVS takeoff minima are achieved through the use
of vision systems technologies, treated as subsystems, which together with
other subsystems including navigational aids and airport lighting and
markings, are used to accomplish the OPA and achieve levels of reliability,
availability, and integrity appropriate to the intended function and phase of
flight, as defined in the OSA.
Note: For a more detailed description of the methodologies used for these assessments,
please refer to Section 3.1 and the Appendices themselves.
Interoperability Requirements (Interop)
The objective of the interoperability assessment is to identify the minimum requirements
needed, to ensure that the elements of the aircraft equipped and approved for EFVS takeoff
can operate effectively and efficiently within the airport and airspace environment.
Recommendations are also proposed so that systems are designed in a robust fashion to
accommodate growth and other EFVS capabilities.
The following subsections define four key terms used throughout this document; these are:
assumptions, mitigation means, requirements, and recommendations.
Assumptions and mitigation means are important aspects of the operational definition of
the ETOS application, and have profound impact on the associated requirements.
While the primary objective of this document is to present minimum requirements needed
for the operations defined for the application, recommendations are also proposed—found
primarily in the Interoperability Specification—which identify highly desirable options or
performance above the absolute minimum specified.
Use of Requirements and Recommendations and Key Words
The SPR and INTEROP chapters contain "shall", "should", and “will” statements with the
"Shall" statements ensure safe, compatible and interoperable systems of sufficient
performance for the ETOS application. The use of the word "shall" in bold type
indicates a requirement for the application.
The use of the word "should" in bold type indicates a recommendation that would
typically improve the application but does not constitute a requirement.
The use of the word "will" describes expected system behavior when the system
complies with the reference requirements, and/or this section's requirements.
The INTEROP (Section 4) also contains recommendations (enumerated) that are included
as guidance material to implementers of ETOS.
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