SHEARWATER AVIATION MUSEUM

Home of Canadian Maritime Military Aviation

  • AIRCRAFT OPERATING INSTRUCTIONS
  • PART 1 – GENERAL DESCRIPTION – AIRCRAFT AND SYSTEMS
  • Section 11 – Navigational Aids
  • RADAR IDENTIFICATION SYSTEM (IFF) (AN/APX-77A)

    • IFF Caution Light

    The caution light illuminates whenever the caution light circuitry detects an inoperative MODE 4 capability, provided that:

    a. The KI-1C/TSEC computer is installed.

    b. The aircraft power is on.

    c. The IFF MASTER switch is not OFF.

    Discrepancies or faults which cause the caution light to illuminate are:

    a. MODE 4 codes zeroized.

    b. Transponder failure to reply to proper interrogation.

    c. Automatic self-test function of the computer reveals a faulty computer.

    NOTE

    If the interrogation signals are not valid (incorrect code of the day, etc.), the signal is ignored and the caution light will not illuminate.

    Illumination of the IFF caution light warns the pilot that the equipment will not respond to MODE 4 interrogations. To attempt correction the pilot should place the IFF MASTER control switch to NORM, check that the MODE 4 ON-OUT toggle switch is ON, and that the proper A or B code has been selected for the current time period.