scope:

PURPOSE AND SCOPE

Introduction

This document sets forth minimum operational performance standards for Mode Select (Mode S)¹ airborne equipment. Incorporated within these standards are system characteristics that will be useful to users of the system as well as designers, manufacturers and installers.

Compliance with these standards is recommended as a means of assuring that the equipment will perform its intended function(s) satisfactorily under all conditions normally encountered in routine operations.

It is recognized that any regulatory application of these standards is the responsibility of appropriate government agencies.

Because the measured values of equipment performance characteristics may be a function of the measurement method, standard test conditions and methods of test are included in this document.

This document considers an equipment configuration consisting of: transponder, control panel, antenna and interconnecting cables. It should not be inferred that all Mode S airborne equipment will necessarily include all of the foregoing components as separate units; this will depend on the design configuration chosen by the manufacturer. Additional functions and components that may refer to expanded equipment capabilities are identified as additional capabilities. Equipment features that are beyond the scope of this document may be developed in future RTCA activities.

If the equipment implementation includes a computer software package, the guidelines contained in the most current issue of RTCA DO-178, Software Considerations in Airborne Systems and Equipment Certification, should be considered. If the equipment implementation includes design considerations for use in conjunction with TCAS functionality, the guidelines contained in the most current issue of RTCA DO-185, Minimum Operational Performance Standards for Traffic Alert and Collision Avoidance System (TCAS) Airborne Equipment, should be considered. If the equipment implementation includes design considerations for use in conjunction with ACAS Xa functionality, the guidelines contained in the most current issue of RTCA DO-385, Minimum Operational Performance Standards for Airborne Collision Avoidance System X (ACAS X) (ACAS Xa and ACAS Xo), should be considered. If the equipment implementation includes design considerations for use in conjunction with ACAS-Xu functionality, the guidelines contained in the most current issue of RTCA DO-386, Minimum Operational Performance Standards for Airborne Collision Avoidance System Xu (ACAS Xu), should be considered.

Throughout this document, the term CAS is used to mean a generic collision avoidance system, applicable to any of the existing airborne collision avoidance implementations. The specific terms TCAS, ACAS Xa (or RTCA DO-385) and ACAS Xu (or RTCA DO-386) are used when the associated text applies only to a particular implementation. The full descriptor ACAS Xa/Xo is shortened to ACAS Xa, and TCAS II is shortened to TCAS. Specific versions of TCAS (6.04A, 7.0, and 7.1) are identified where necessary by the terms FAA TSO-C119a, RTCA DO-185A, and RTCA DO-185B respectively. In this document, the term ACAS X is used when text applies equally to ACAS Xa and ACAS Xu. Original RF message names, e.g., TCAS Resolution Message, are retained. Note that TCAS 7.1 and ACAS Xa/Xo are the two CAS recognized as ACAS II, i.e., compliant with the ACAS II SARPs as documented in ICAO Annex 10 Volume IV.

¹ For the purpose of this document, the term "Mode S" implies a combined ATCRBS/Mode S capability.