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ORIGINAL 20-66
NAVAIR 01.F14AAD-1
CHAPTER 21
Identification
21.1 IDENTIFICATION TRANSPONDER
(AN/APX-100)
21.1.1 IFF Transponder. The APX-100 IFF
transponder system is capable of automatically reporting
coded identification and altitude signals in response
to interrogations from surface (or airborne) stations so
that the stations can establish aircratl identification, control
air traffic, and maintain vertical separation. The
system has five operating modes (1, 2,3/A, C, and 4).
Modes 1 and 2 are IFF modes, mode 3 (civil mode A)
and mode C (automatic altitude reporting) are primarily
air traffic control modes, and mode 4 is the secure (encrypted)
IFF mode. The IFF control panel is in the rear
cockpit (Figure 21-I).
21 .l .I .l Master Switch. The MASTER switch applies
power to all the transponder system components
except the altimeter components. It is a four-position
rotary switch placarded OFF, STBY, NORM, and
EMER. The switch must be lifted over a detent to switch
to EMER or to OFF. STBY should be selected for 2
minutes prior to switching to LOW or NORM to allow
the transpondetro warm up. In NORM, the transponder
system is operational at normal receiver sensitivity. In
EMER, the transponder transmits emergency replies to
mode 1, 2, or 3/A interrogations. The mode 3/A emergency
reply includes code 7700. When EMER is selected,
a ll modes are enabledr egardlesso f the position
of the selector switches. When the front seat ejects, a
switch is tripped that automatically selects the emergency
mode if the MASTER switch is in any position
other than OFF.
21.1.1.2 Antenna Select Switch. The position of
fhe antenna select switch determines APX-100 antenna
reply logic. Although the system is designed to receive
an interrogation on either antenna at all times regardless
of switch position, with TOP or BOT selected, it will
only reply on the selecteda ntenna,a ndo nly ifthe strongest
interrogation signal was received on that antenna.
For example, if BOT were selected and the interrogation
signal was strongerf rom the top antenna,n o reply would
be transmitted. In the DIV (diversity) position, an antenna
diversity comparator identities which antenna received
the strongest interrogation signal and automatically
selects that antenna to transmit the reply. It is
therefore recommended that the antenna select switch
be left in DIV at all times.
IfeitherTOPorBOTisselectedon the APX-
100 antenna select switch, a Mode IV reply
will be transmitted only if the Mode IV interrogation
signal is strongest on theantenna
selected. If the stronger of the two antennas
was not selected at the time of interrogation,
the aircrew will not have any indication that
theiraircrafi was interrogated or that no reply
was made.
21.1.1.3 IDENT-OUT-MIC Switch. The IDENTOUT-
MIC switch is a three-position toggle switch. The
spring-loaded IDENT adds an identification of position
pulse to mode 1,2, and 3/A replies for a period of 15 to
30 seconds. In MIC, the identification of position function
is activated for 15 to 30 seconds each time the UHF
microphone switch is pressed.
21.1.1.4 Mode 1,2, and 3/A Code Selectors The
two mode-l thumbwheel selector switches allow selection
of 32 mode-l codes and the four mode-3/A
thumbwheel selectors allow selection of 4096 mode-
3/A codes. The mode-2 code that is set on the four
MODE 2 selector switches may be read by moving the
sliding cover. The code may be reset by inserting a
pointed object like a pen tip or a paper clip to rotate the
thumbwheel. Mode 2 codes are not normally changed
in flight.
21.1.1.5 Mode Switches. The four mode switches
(M-l, M-2, M-3/A, and M-C) each have OUT, ON, and
spring-loaded TEST positions. The center position ON
of each switch enables that mode. To test the transponder,
press the mode switch of each mode to TEST.
21-1 ORIGINAL
NAVAIR Ol-F14AAD-1
/-i/- II;: ‘u’ - I I I, II
h 18
IFF !,-
!--.-.....-....-.---J
NOMENCLATURE FUNCTION
1. TEST light (GO) Illuminates when respective MODE switch TEST position is actuated;
indicates proper (GO) operation of modes 1, 2, 3/A. and C. Master switch
must be set to NORM.
2. TEST/MON light (NO GO) The light has two functions, Illuminates when respective MODE switch
TEST position is actuated: indicates failure (NO GO) of modes 1,2,3/A and
C. Master switch must be set to NORM.
3. ANT switch Selects upper (TOP), lower (BOT), or both (DIV) antennas. DIV (diversity)
permits the IFF to switch automatically for transmission to the antenna that
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F-14D 飞行手册 Flight Manual 3(38)
