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Technical Provisions for Mode S Services and Extended Squitter

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DRAFT - Working Paper ASP TSGWP11-01 <strong>for</strong> review by the TSG during the meeting in June 2011 in Paris<br />

Appendix B B-11<br />

B.2.3.9 RESERVED FOR TARGET STATE AND STATUS INFORMATION<br />

The target state <strong>and</strong> status in<strong>for</strong>mation squitter shall be <strong>for</strong>matted as specified in the definition of register 6216 <strong>and</strong> in the<br />

following paragraphs:<br />

B.2.3.9.1 TRANSMISSION RATE<br />

The Target State <strong>and</strong> Status Message shall be broadcast at r<strong>and</strong>om intervals uni<strong>for</strong>mly distributed over the range of 1.2<br />

to 1.3 seconds <strong>for</strong> the duration of the operation.<br />

B.2.3.9.2 MESSAGE DELIVERY<br />

<strong>Extended</strong> <strong>Squitter</strong> Message delivery shall be accomplished using the event-driven protocol (see §A.2.3.7).<br />

B.2.3.9.3 VERTICAL DATA AVAILABLE/SOURCE INDICATOR<br />

This 2-bit (ME bits 8 — 9, Message bits 40 — 41) subfield shall be used to identify if aircraft vertical state in<strong>for</strong>mation is<br />

available <strong>and</strong> present as well as the data source <strong>for</strong> the vertical data when present in the subsequent subfields.<br />

Encoding shall be defined as specified in the following table. Any message parameter associated with vertical target<br />

state <strong>for</strong> which an update has not been received from an on-board data source with the past 5 seconds shall be<br />

considered invalid <strong>and</strong> so indicated in the Vertical Data Available/Source Indicator subfield.<br />

Coding<br />

(Binary) (Decimal)<br />

Meaning<br />

00 0 No valid Vertical Target State data is available<br />

01 1<br />

Autopilot control panel selected value, such as <strong>Mode</strong> Control Panel<br />

(MCP) or Flight Control Unit (FCU)<br />

Draft<br />

10 2 Holding altitude<br />

11 3 FMS/RNAV system<br />

B.2.3.9.4 TARGET ALTITUDE TYPE<br />

This one bit (ME bit 10, Message bit 42) subfield shall be used to identify whether the altitude reported in the “Target<br />

Altitude” subfield is referenced to mean sea level (MSL) or to a flight level (FL). A value of ZERO (0) shall indicate target<br />

altitude referenced to pressure-altitude (flight level). A value of ONE (1) shall indicate a target altitude referenced to<br />

barometric corrected altitude (mean sea level).<br />

B.2.3.9.5 TARGET ALTITUDE CAPABILITY<br />

This 2-bit subfield (ME bits 12 — 13, Message bits 44 — 45) shall be used to describe the aircraft’s capabilities <strong>for</strong><br />

providing the data reported in the target altitude subfield. The target altitude capability subfield shall be encoded as<br />

specified in the following table.<br />

DRAFT - Working Paper ASP TSGWP11-01 <strong>for</strong> review by the TSG during the meeting in June 2011 in Paris

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