Tactical Data Links - Link 4/TADIL C
Key words and phrases: tactical data links, link 4, TADIL C, UHF band, link 4A, link 4C, controller to aircraft, fighter to fighter, STANAG 5504, ADatP 4
Link 4/TADIL C
Link 4 is a non-secure data link used for providing vector commands to fighters. It is a netted, time division link operating in the UHF band at 5,000 bits per second. There are two separate "Link 4s": Link 4A and Link 4C.
Link 4A
Link 4A is the controller to aircraft data link which uses V-series messages and R-series messages to support the Automatic Carrier Landing System (ACLS), Air Traffic Control (ATC), Air Intercept Control (AIC), Strike Control, Ground Control Bombing System (GCBS) and Carrier Aircraft Inertial Navigation System (CAINS).
It has a limited data throughput, has no ECM resistance, and can cater for a limited number of participants (up to 8). It was, however, the first data link to be integrated with fighters to provide a digital C2 unit to fighter communication path.
Link 4 has been fitted to USN ships, US AEWC aircraft and several fighters, fighter/bombers and supporting platforms. Because the NATO E-3s, UK E-3D & French E-3F are based on the US E-3, they also implement Link 4 although they do not use it operationally. However, the French E-3F does use it and in addition the French Ground environment has been equipped with a capability to forward Link 4 messages.
Link 4C
Link 4C is a fighter-to-fighter data link which is intended to complement Link 4A although the two links do not communicate directly with each other. Link 4C uses F-series messages and provides some measure of ECM resistance. Link 4C is fitted to the F-14 only and the F-14 cannot communicate on Link 4A and 4C simultaneously. Up to 4 fighters may participate in a single Link 4C net.
It is planned that Link 16 will assume Link 4A's role in AIC and ATC operations and Link 4C's role in fighter-to-fighter operations. However Link 16 is not currently capable of replacing Link 4A's ACLS function and it is likely that controlled aircraft will remain equipped with Link 4A to perform carrier landings.
Message standards are defined in STANAG 5504 while standard operating procedures are laid down in ADatP 4.
Data Link descriptions: Tactical Data Links | Link 16 | Link 11 | Link 22 | IJMS | Link 1 | Link 14 | Link 4 | Other protocols | CDL, TCDL & HIDL | Satellite Link 16 | Variable Message Format - VMF
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