Interim Guidance for UAT Avionics Operating with Safe Flight 21 ...

8 bytes
UAT -Specific Header
I-Frame 1 I-Frame 2 I-Frame 3
Length
9 bits
Res.
3 bits 4 bits
Transmission order
2.2.3.1 UAT-Specific Header
Frame Type
432 bytes (message payload)
424 bytes
Application Data
. . .
Frame Data
Length
I-Frame N
Figure 2-1: Decomposition of the Ground Uplink Message Payload
15
fill as needed
The UAT-Specific Header is an 8-byte field that contains information on the location of
the broadcasting ground station, the time slot used to send the present message, validity
flags for position, time, and application data, and other fields as described in Section
2.2.3.2.2 of [UAT MOPS].
2.2.3.2 Application Data
The Application Data is a fixed-length field of 424 bytes. The Application Data consists of
Information Frames, and always consists of an integral number of bytes. Any remaining
unused portion of the field is zero-filled (i.e., all bits set to ZERO).
Note: The Application Data should be discarded if the Application Data Valid field
is set to “0” in the UAT-Specific Header, as specified in [UAT MOPS].
2.2.3.3 Information Frames
Each Information Frame consists of ‘N’ bytes, comprising four fields formatted as shown
in Table 2-1.