Home' RTCA Documents for Review : ACAS X MOPS DRAFT Vol.1 Contents 2
ACAS X MOPS
procedures necessary to demonstrate compliance, including specific bench tests for the
collision avoidance logic performance.
Section 3 of Volume I describes the performance required of the installed equipment.
Tests for the installed equipment are included when performance cannot be adequately
determined through bench testing.
Volume II contains the Algorithm Description Document (ADD), which includes the
required collision avoidance algorithms for ACAS X. The algorithms are presented in
the Julia programming language with informational commentary text.
Both Volumes I and II contain certain standards and performance requirements that are
intended to ensure that ACAS X is fully interoperable (see §1.6.5) with other airspace
elements and equipment. It is mandatory that all interoperability provisions be met
without exception or deviation. Other technical and performance requirements s tated
herein that were derived from the particular implementation approach that formed the
basis for the development of this MOPS may be waived if the manufacturer or installer
provides evidence of equivalent system performance for an alternative method of
implementation and if the alternative implementation does not violate interoperability
Since the measured values of equipment performance characteristics may be functions of
the methods of measurement, standard test conditions and methods of test are
recommended in this document.
The general operational goals of ACAS X are described in the following subparagraphs.
The detailed requirements for the equipment are provided in Sections 2.0 and 3.0 of this
document. Implementation of new ATC system elements under development will
improve communication, surveillance, and data management. This will increase the
effectiveness of the existing ground-based air traffic control system. It is also apparent
that a single, ground-based ATC system cannot meet the requirements of all flight
conditions because of the absence of coverage in oceanic and other low traffic-density
airspace. Thus, there is a need to provide an air -to-air collision avoidance capability on
aircraft, which is independent of the ground-based system. Such a system must remain
compatible with the ATC system when operating in controlled airspace. As a minimum,
equipment providing this capability must achieve the following operational goals:
a. The system must be capable of providing timely and effective resolution advisories to
a pilot to permit avoiding other air traffic equipped with an ATCRBS or Mode S
altitude reporting transponder. This capability must be assured throughout airspace
having a maximum traffic density of 0.3 transponder-equipped aircraft per square
b. Operation must be compatible with the existing ATC system and with planned
evolution of the ATC system.
c. The system design must ensure that the system does not have characteristics that
could adversely affect the safety of flight or interfere with other aircraft systems on
the aircraft or installed on other nearby aircraft.
d. Maneuvers expected in response to resolution advisories provided by the system
should be acceptable to both pilots and air traffic controllers.
e. The system must contain a comprehensive performance monitor function that will
monitor automatically, on a continuous basis, the operating integrity of the system.
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