Home' RTCA Documents for Review : C2 Link Systems MASPS_Draft Contents Appendix D
© 2018 RTCA, Inc.
OPA for the Remote Pilot’s Integrate Activity
The remote pilot activity of “Integrate” describes their ability to maintain traffic and hazard
awareness and inform other airspace users of their UA’s presence in the airspace. The
remote pilot would accomplish this by interacting with both the DAA and UA surveillance
(e.g., transponder) equipment located in the UA and CS. In this MASPS, the UA DAA
and surveillance equipment are assumed to be connected to the CS by only the C2 Link
System. The remote pilot’s Integrate activity includes all interactions with these systems
to include suitable Aviate and Navigate responses to Traffic Alert and Collision Avoidance
System (TCAS) Resolution Advisories (RAs), DAA alerts, and warnings as well as the
setting of appropriate transponder codes when required. This Subsection describes the
development of the performance requirements to support OR-1.4 and OR-2.3 using the
Linear Sensing and Aerial Survey CONOPS and the selected scenarios and Use Cases C1-
S1-UC3.1a, C1-S1-UC3.1b and C1-S1-UC6.1 as described in B.8.1 in the OSED and listed
in Table E-2 in this OPA’s introduction section.
Note D-17: This section may not be completely applicable to the C2 Link System if the
UAS uses an alternate architectural means of meeting the DAA requirements
that do not rely wholly on or only partly on the C2 Link System (e.g., Ground-
Based DAA (GBDAA)).
In all of the encounter model simulations used for DO-365 , the CNPC Link System was
assumed to have a latency of 0.5 seconds. In the simulations performed for this MASPS,
it was determined that a latency of 1.0 second for the entire C2 Link System would be
acceptable. This longer latency, based on the estimates in Subsectio n E.2, allows for the
lessening of the requirements placed on the C2 Link System to include when it is using
either satellite-based or terrestrial links as well as possible networks supporting those links
(see Figure 1-3) when compared to just the point-to-point link of the CNPC Link System
described in DO-362 .
Short C2 Link System Interruptions
Since the DAA update rate, sent over the C2 Link System, is once per second , short C2
Link System interruptions will only cause one or two DAA updates to be lost.
Consequently, DAA Subject Matter Expert opinions have determined that such short
interruptions would only cause a slight but acceptable degradation in safety. This is
because the DAA system’s awareness of potential intruders is only slightly delayed by such
short interruptions. Conversely, long interruptions (which should occur less frequently)
may need to force a Lost C2 Link state because it will most often be “safer” to declare a
Loss C2 Link state than to leave the UA in an interrupted C2 Link System state for too
Long C2 Link System Interruptions
The effect of long C2 Link System interruptions was simulated by MITRE using the MIT
Lincoln Laboratories DAA encounter model . Since interruptions on the C2 Link
System do not introduce additional latency but cause certain information to never be
delivered, the original encounter model was modified with the ability to temporarily block
and delete the flow of DAA tracks; thus, effectively representing C2 Link System
interruptions. It should be noted that as soon as a C2 Link System interruption ceases,
information again begins to flow, but that information is not the information that was not
delivered (i.e., buffered) during the interruption but is up-to-date information only delayed
by the C2 Link System’s latency.
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