AN/APX-72 IFF AIMS System

Introduction

The AIMS system, which utilizes an AN/APX-72 receiver/transmitter (transponder), is used to automatically identify the aircraft in response to coded interrogations. Depending on interrogation mode, the reply is transmitted in modes 1, 2, 3/A, 4, or aircraft altitude reporting in mode C.

Controls

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  1. Mode 4 Function Switch
  2. Master Switch
  3. Reply Light
  4. Test Light
  5. Mode 4 Indication Switch
  6. Mode Selection Switches
  7. Monitor-Radiation Test Switch
  8. Mode 4 Selector Switch
  9. Identification Switch
  10. Mode 1 Code Selectors
  11. Mode 3/A Code Selectors

Note

Settings on the IFF panel have no effect in DCS, but they can be exposed to external tools (for example, SRS).

Mode 4 Function Switch

The mode 4 CODE selector has the following positions: | Selection | Function |---------------|--------- | A | Code A | B | Code B | HOLD | Provide a means of retaining the mode 4 code for an additional flight (unless intentionally retained, the code is automatically returned to zero when power is removed after landing) | ZERO | Manually zeroize mode 4 code

Note

The mode 4 code selector knob must be pulled out to be moved to ZERO.

Master Switch

Selection Function
OFF System off
STDBY Powered on, in standby
NORM Normal receiver sensetivity
LOW Low receiver sensitivity
EMER Activates emergency operation

Note

The master switch knob must be pulled out to be moved to the EMER position.

Reply Light

When the transmitter-reciever responds properly to a mode 4 interrogation, the mode 4 REPLY light (green) illuminates.

Test Light

A green TEST light illuminates to indicate proper operation of each tested mode during the self-test, or when the (radiation) monitor switch is set to the MON (monitor) position.

Mode 4 Indication Switch

The audio/light switch has been moved from OFF to AUDIO or LIGHT (no audio signal provided).

Mode Selection Switches

The mode selection switches M-1, M-2, M-3/A, and M-C have three positions:

Selection Description
TEST (forward, momentary) Initiates a self-test of the mode (provided the airborne test set is installed)
ON (center)
OUT (aft)

Monitor-Radiation Test Switch

The RAD TEST position is used by maintenance personnel during ground checks. In flight, leave this switch in the OFF position.

Mode 4 Selector Switch

Mode 4 is selected by placing the mode 4 enable switch from OUT to ON. Mode 4 codes are preset in the mode 4 computer prior to missions via a code changer key.

Identification Switch

The identifier switch enables transmission of identification of position (I/P) signals in response to interrogations in modes 1, 2, or 3/A, for 15–30 seconds. Transmission of I/P signals can be accomplished in three ways:

  • When the switch is momentarily placed in the IDENT position
  • When the switch is in the MIC position, and the microphone button is momentarily pressed
  • When the switch is in the MIC position, and the command radio tone button is pressed (while command radio is on)

Mode 1 Code Selectors

The two mode 1 selectors provide 32 possible code selections.

Mode 3/A Code Selectors

The four mode 3/A selectors provide for 4096 code selections.

Normal Operation

Information forthcoming.