Definition
A data communication service in which information is broken into small units called packets, each routed independently across a network, and reassembled at the destination. In aviation, PSS is used as part of the data link infrastructure that carries digital messages between aircraft and ground systems.
Plain English
A way of sending digital information by chopping it into small chunks, sending each chunk across the network, and putting them back together at the other end. It is the same basic idea behind how the internet moves data.
Context Anchor
Seen in FAA acronym lists and in technical descriptions of aviation communication or data systems.
Derivation
The word 'packet' is used because the data is bundled into small parcels — like little packages — instead of being sent as one continuous stream. 'Switched' refers to the network choosing a path for each packet at the moment it is sent, rather than holding open a fixed line between sender and receiver.
Why Pilots Care
PSS underlies many of the digital messaging services pilots rely on, such as clearance delivery, weather updates, and controller-pilot data link messages. Knowing it is a packet-based network helps explain why messages may arrive in bursts or with slight delays rather than as a continuous stream.
Analogy
It is like mailing a long document in several numbered envelopes. Each envelope may travel through the mail system separately, but the receiver puts them back in order.
Intuition Check
Do not read packet here as a physical paper packet, and do not read switched as simply turned on or off. In this term, packet means a small unit of data, and switched means routed through a network.
Example Sentence 1
The aircraft's data link messages are carried over a packet switched service, allowing text clearances to reach the cockpit reliably even on long oceanic routes.
Example Sentence 2
Ground systems rely on PSS to handle multiple simultaneous flight data transmissions efficiently.