scope:

PURPOSE AND SCOPE

Introduction

This document contains minimum operational performance standards (MOPS) for GNSS integrated with inertial reference systems (IRS) or attitude heading reference systems (AHRS). It is not meant to be a replacement or substitute for RTCA DO-334 (MOPS for Strapdown Attitude and Heading Reference Systems). A key assumption is that any AHRS used for compliance with the performance requirements in this MOPS first meets the performance standard described in RTCA DO-334. That is, RTCA DO-334 is the starting point for any AHRS used to comply with requirements in this MOPS.

RTCA DO-334 provides standards for strap-down AHRS equipment intended to output attitude (pitch, roll), heading, turn and slip information along with presenting this information to the pilot (see Figure 1-1) but does not provide detailed requirements for GNSS aiding. The 14 code of federal regulations (CFR) Part 121 Appendix G provides requirements for INS/IRS, but an AHRS (including those with air data computer inputs) is not presently accepted for navigation.

The 14 CFR 121 Appendix G requirements were developed in the 1970's primarily for self-contained oceanic long-range area navigation (RNAV) capability and pre-dates performance-based navigation concepts as well as GNSS. RTCA DO-229() (MOPS for GPS/SBAS Airborne Equipment) and RTCA DO-316 (MOPS for GPS/Aircraft Based Augmentation System Airborne Equipment) both include an Appendix R that describes tightly-coupled GPS/inertial requirements and tests intended for integrations with inertial sensors satisfying the 14 CFR Part 121 Appendix G requirements. This MOPS is intended to replace Appendix R in RTCA DO-316 (RTCA DO-229) and expand beyond tightlycoupled, 14 CFR Part 121 Appendix G compliant inertial integrations.

In this document, the term "shall" is used to indicate requirements. An approved design will comply with every requirement, which can be assured by inspection, test, analysis, or demonstration. The term "must" is used to identify items that are important but are either duplicated somewhere else in the document as a "shall", or are considered to be outside the scope of this document. The term "should" is used to denote a recommendation that would improve the equipment, but does not constitute a requirement. The term "may" is used to denote an optional implementation at the manufacturer's discretion.

The requirements in this document define minimum performance, functions and features for both GNSS-aided inertial references systems and enhanced attitude heading reference systems. Due to the wide range of possible capabilities, it is important for manufacturers using this MOPS to characterize the equipment's intended function and expected performance. There are three performance categories and three associated Sub-categories within this MOPS. The word "equipment", as used in this document, includes all components or units necessary (as determined by the equipment manufacturer) to properly perform the intended function.

Compliance with these standards by manufacturers, installers and users is recommended as one means of assuring that the equipment will satisfactorily perform its intended functions under conditions encountered in routine aeronautical operations. The regulatory application of these standards is the responsibility of appropriate government agencies. In the United States, the Federal Aviation Administration (FAA) plans to publish a Technical Standard Order (TSO) to reference the requirements and test procedures for each equipment category.

Section 1 of this document provides information and assumptions needed to understand the rationale for equipment characteristics and requirements stated in the remaining sections. It describes typical equipment applications and operational goals and forms the basis for the standards stated in Section 2.

Section 2 contains the performance and testing requirements. These standards define required performance under standard operating conditions and stressed physical environmental conditions. It also details the recommended test procedures necessary to demonstrate compliance.

Section 3 provides references to guidance material for installed equipment performance.

Section 4 provides references to guidance material describing equipment operational characteristics.

Appendices A through P provide guidance material in support of requirements interpretation and testing. Appendix Q proposes methods to document performance of the GNSS aided inertial system to detect erroneous GNSS input based on the alternate trajectory concept.