IFF – MODE 1 and MODE 3

IFF – MODE 1 and MODE 3

Jan 26 Rob  
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IFF MODES what are they?

Most of if not all of you should already know what ‘IFF‘ is, that lovely ability to go ‘Are you Friend or Unknown?’ because really it being called Identify Friend or Foe is a little bit of a misdemener given that its more Identify Friend else we don’t know, but I’m getting off track here. IFF works in reality because it uses a series of ‘Modes’ or ‘Keys’ that allow things to identify what they are some of these are normally set on the ground or as part of the DTC others can be set on the fly but for our purposes in TGW on Training and mission nights we really only care about 3 of them, Mode 1, Mode 3 and Mode 4 but for the sake of being complete we will look at all 4 and what they are for.

Mode 1 – Mission Code

Mode 1 allows for the entry of 2 digits or ‘5-bits’ and is a military only transponder code used to convey mission type. For example a value of 11 might mean Fighter CAP, while 21 might mean Bomber etc. Typically these are generated for a specific period but TGW will normally use one set to cover everything, we also ’round’ some of the MODE 2 items into Mode 1 as currently you can not change MODE 2 in DCS.

Be Aware the F-16 is limited in what it can change on Mode 1 codes, see the mission for information on what MODE 1 codes are what and if they are in use.

Mode 1 in the Hornet.
Mode 1 in A-10C Warthog.

Mode 2 – Unit Code

Mode 2 allows for the entry of 4 digits or an ‘octal’ unit code currently as mentioned nothing in DCS or SRS allow a manual entry, this code is typically set on the ground for Fighters and can only be changed in the air on modern fighters or in ‘heavies’.


Mode 3 Entry in the A-10C Warthog.

Mode 3 allows for the entry of 4 digits or an ‘octal’ code (Octal meaning 0-7 for a total of 8 digits) like mode 2 and is used by both Civil and Military controllers to identify aircraft, in DCS Mode 3 can be set on almost every Aircraft and can also be set in the SRS overlay panel. For LOTATC Mode 3 is used to Automatically Assign your Callsign to your aircraft so for example 2110 will automatically id you as Warrior11. Mode 3 has an extra ‘item’ in some aircraft and the Transponder overlay of SRS allowing for you to ‘IDENT’ this sends out a special ‘pulse’ on the transponder code that makes you light up nice and red on the Radar Scope for the controller, it is not uncommon to be told to ‘Sqwark Ident’ when your first checking in after take off, or coming back under ATC control so they know who the hell you are. Mode 3 typically is turned ‘off’ as part of your EMCON checks.

Mode 4 – Friend or Foe

Mode 4 is a cryptogenerated code that identifies you to other Aircraft with the same Keyset as ‘friend’ or ‘Unknown’, In DCS this code is automatically generated and run, in most aircraft you can turn it off by either deboxing Mode 4 on the UFC or by turning off the M4 option on the IFF panel. In FC aircraft you can use the SRS Overlay to do the same.

Mode 4 Active.
Mode 4 in LOTATC
Mode 4 in the SRS overlay

MODE 3 Automatic Callsigns.


About Rob

Rob is the server monkey and founder of TGW, he grew up a RAAF brat, and has had a love of aviation from well as long as he can remember in large part thanks to his dad and mum. Sadly medical issues mean that dream won't ever come true, so instead he tries to recreate it in virtual space. He's programmed for Flight Sim, designed ATO/Tasking and simulation systems for VSOA's, made a virtual PC9 fly correctly and its systems run properly, Beta tested for P3D, done concept art and design work for a best selling author plus more. See more about Rob at his personal website http://robgraham.info

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