Home' RTCA Documents for Review : C2 Link Systems MASPS_Draft Contents Appendix D
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Scheduled Break Before Make Switchover
Since an interruption in the C2 Link System’s ability to transfer information does occur
during this BbM Switchover situation, then the OPA SMEs determined that the TET for
this type of Switchover is equal to the shortest TET for all the other remote pilot activities
in the airspace in which the UA is operating.
Unscheduled Make Before Break Switchover
As discussed in APPENDIX E, Unscheduled Switchovers will be primarily performed to
mitigate a Lost C2 Link state from occurring. So, the Unscheduled Switchover must be
completed prior to the TET being exceeded during the most demanding pilot activity being
supported by the C2 Link System. Consequently, to be an effective mitigation, the
Unscheduled Switchover must be triggered soon after the interruption begins and be
successfully completed prior to the Lost C2 Link being declared. However, to avoid
unnecessary Switchovers being made, the Unscheduled Switchover should not be triggered
in a time less than the shortest interruption time for the most demanding remote pilot
activity being supported by the C2 Link System.
Unscheduled Break Before Make Switchover
Since an interruption in the C2 Link System’s ability to transfer information occurs
during this Switchover situation, the TET for this Switchover is equal to the shortest TET
for supporting any of the other remote pilot activities in the airspace in which the UA is
operating. Additionally, just as described in Section E-184.108.40.206.3, the Unscheduled
Switchover should not be triggered until after the short interruption time has elapsed for
the most demanding remote pilot activity being supported by the C2 Link System.
Because the OSA determined that the end result of a Misdirected Switchover (Scheduled
or Unscheduled and for BbM or MbB) in Use Cases C1-S1-UC2.1c and C1-S1-UC5.3c
resulted in a hazard with a Major severity, the OPA determined that, based on Table E-1,
the Risk Class 3 UAS Allowable Quantitative Probability of a Misdirected Switchover of
any type is 1 x 10-4.
Considerations on the C2 Link System’s Support of the Switchover Aspects of the
Support of the Remote Pilots Mange C2 Link Activity
The following lists examples of where Scheduled Switchovers should not be scheduled so
that the 1-minute time described in E.220.127.116.11.1 is not exceeded.
1. When the UA is going to be too close to the current link’s GRS/GES service volume
limit. This is because the UA may fly beyond the range of the current link and thus
would be unable to switch back to the current link if the Switchover fails.
2. When the UA is going to be too close to a controlled/uncontrolled airspace boundary.
This boundary is based on published data and known before the flight. This example
is included because the remote pilot may need to call or get called by ATC when near
3. When the UA is going to be too close to another aircraft. For example, during takeoff,
landing or in any other planned area of operation where a high density of aircraft is
anticipated, the DAA system may issue a DAA Warning Alert requiring an urgent
remote pilot Aviate activity.
4. When the UA is going to be too close to the ground. This includes taking off and when
in the landing pattern.
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