Uplink Message Formats, ACARS Peripherals - Label H1
Provisions have been made for avionic subsystems (peripherals) to operate as End Systems and to accept messages from
the AOC users’ host systems or ATC facility on the ground. These messages will be routed through the ACARS
Management Unit (MU) for delivery. Uplink messages to these avionics subsystems will contain Label characters H1.
Label H1 messages may contain additional addressing information to facilitate delivery of the message. Sublabels are
used to enable the MU to identify the specific avionics subsystem (e.g. FMC) to which uplink message is to be passed.
A general format example is shown below. The following subsections define, in greater detail, the format of messages
exchanged across the air-ground medium that are to be delivered to an avionics subsystem by the ACARS Management
Unit (MU).