BMS F-16C/D 4.34, Flight Manual

Page: 158 / 234

T.O. BMS1F-16CM-1 BMS 4.34 Change 2.00
BMS 4.34 Dash 1
© Red Dog 2012-2019
Page: 158
1.16.5. IFF use in backup mode
Backup IFF operation is done with the switches on the IFF panel, when the C&I switch is in BACKUP.
It is possible to control Mode 1, 3, and S; the active modes are decided by the IFF ENABLE Switch
position. It can toggle between: OFF (centre), M1 & M3 (down), and M3 & MS (up).
Remember, Mode S is only implemented as eye-candy.
With the switch out of the OFF position, the M1 code broadcasted is set with the two MODE 1 manual
digits. The Mode 3 code first two digits are set with the MODE 3 digits on the IFF panel
– the last two
digits being 00. As an example, in the picture above, the backup Mode 1 code would be 10 and the
backup Mode 3 code would be 6600.
Mode 2 and C operation is not possible in BACKUP. No reply will be transmitted to any interrogation in
these modes in BACKUP.
Mode 4 operation is decided by the MODE 4 REPLY Switch, toggling between: OUT (no Mode 4
reply), A (reply with A key) and B (reply with B key). Please note it is up to you to know which key is
supposed to be active according to the briefed switch time.
The MODE 4 MONITOR Switch defines the audio cue which sounds when the IFF is unable to answer
a Mode 4 request. Please note for the audio cue to sound, this switch must be placed in AUDIO, even
for normal operation with the C&I switch in UFC.
The M4 CODE Switch allows you to manage the secret keys for Mode 4. It is a 3-position switch
labelled: ZERO, A/B and HOLD.
A/B is for normal operation of Mode 4, with the A and B keys.
ZERO when held for two seconds erases both keys from the
aircraft memory (before ejecting the pilot should zero the IFF
keys to avoid it falling into enemy hands
but it’s not critical in
BMS). With no key available for Mode 4 the IFF caution light
will be on and a relevant IFF PFD message will be displayed
as well.
The HOLD position allows the key to be retained in memory even after a shut down.
Normally the key is automatically erased upon system shut down.