Home' RTCA Documents for Review : DO-253D_Change1_FRAC Contents Appendix J
DO-253D Change 1
© 2019, RTCA, Inc.
APPENDIX J: RELATIONSHIP BETWEEN AIRBORNE RECEIVER GEOMETRY
SCREENING AND AIRWORTHINESS ANALYSES
The purpose of this appendix is to describe an example means for deriving the GAST D
aircraft tailored geometry screening parameters to support demonstration of conformance
with existing and future potential airworthiness requirements that may be applied to GBAS.
Airborne satellite geometry screening parameters may be derived as a function of airplane
performance in terms of total system error and GBAS ground and airborne error monitoring
This introduction provides a brief overview of three key airworthiness requirements used
in the derivation of the ground monitor requirements, the resulting ranging source fault
monitoring requirements for the ground subsystem and the airborne satellite geometry
screening requirements. Section J.2 assumes that each requirement used in the ground
monitor performance derivation corresponds to an airworthiness requirement to be applied
for GBAS. Section J.2 provides an example method for deriving the required geometry
screening parameters that is based on the ground subsystem’s ranging source fault monitor
performance and airplane performance in terms of probability of exceeding each such
Three airworthiness requirements have been selected and adapted for use in the derivation
of the ICAO Annex 10 ground subsystem’s ranging source fault monitoring requirements.
These requirements were located in the following documents:
1. AC 120-28D, Appendix 3, Section 6.3.1 (Nominal Performance)
2. AC 120-28D, Appendix 3, Section 6.4.1 (Performance with Malfunction)
3. JAR AWO Subpart 1 (Performance Demonstration Limit Case Conditions)
Item (1) is applicable to GBAS as written. Items (2) and (3) have been adapted by the
GBAS community and are expected to result in new airworthiness requirements for GBAS
in an FAA 20 series advisory circular. The requirements have been given monikers
(Nominal Condition, Malfunction Condition, and Limit Condition respectively) that relate
to their original purpose within the airworthiness documents; these names are not intended
to be indicative of the role they play in the proposed ICAO Annex 10 material. For
example, the malfunction condition does not address ground or airborne subsystem
malfunctions and the limit condition does not address performance at a single extreme
value. The limit condition, as applied here, addresses the compatibility of the satellite fault
monitoring in the pseudorange domain with the aircraft specific constraints on the
projection of these errors to the position domain. The malfunction condition, as applied
here, addresses all undetected transient errors more probable than 10-9
anomalous space weather induced errors.
The resulting three conditional requirements include a group of performance parameters,
each with an associated maximum probability that the parameter may exceed a specified
limit for that condition. The performance parameters include longitudinal and lateral gear
touchdown locations, structural load, and airplane attitude at touchdown.
These requirements and their treatment based on GBAS requirements and airplane
performance are described in more detail in the following sections.
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