The third part covers the IFF Interrogator, the ASPECT switch and the TCS.
As mentioned already, this is more a collection of tips and ideas rather than explanation. Details are, as usual, in the manual.
VI. AN/APX-76 IFF Interrogator
The antenna of the AN/APX-76 IFF Interrogator is located on the gimbals of the AWG-9 antenna gimbal platform. The IFF antenna is a separate radar system, independent from the AWG-9. It can therefore detect targets not spotted by the AWG-9. If this is the case, the IFF return will not have the radar echo mark inside it.
The AN/APX-76 can be used to complement the AWG-9 in specific situations.
The IFF is displayed on the DDD in Range vs Azimuth. It can be combined with the PD mode (Closure rate vs Azimuth) to better understand the situation and increase the SA. The IFF range can be modified by means of the same range buttons used by the Pulse radar.
IFF and PD modes share the Azimuth on the abscissa and it can be used to identify each target both in range and closure rate, as displayed in Plate 5.1. Note the radar return in the middle of the IFF mark.
By locking in STT mode, the DDD switches from normal range to a ±10 NM display to enable display of multiple returns in case of closely grouped targets.
Multiple close targets, aligned one behind the other relative to the F-14, can appear as a single target. Locking and using the IFF antenna is not a reliable way to separate such targets.
VII. ASPECT Switch
The operating range of the doppler filters can also be configured by the ASPECT switch on the same panel, NOSE sets 600 knots opening to 1 800 knots closing, BEAM sets 1200 knots closing to 1200 knots opening and TAIL sets 1 800 knots opening to 600 knots closing. This allows the RIO to optime the doppler filters for a known target closing speed and this affects the whole radar processing unlike the Vc switch which only affects the DDD.
The ASPECT switch controls the PRF of the Pulse radar. It can be effectively employed WVR to make the radar more resistant to countermeasures.
The ASPECT switch is a 3-way switch located on the right of the DDD. It has 3 possible positions:
If the target is aspect hot, setting the ASPECT to NOSE will make the radar more resistant to chaffs, which will be trailing behind the target.
NOTE: Aspect Switch tests are on halt due to the new incoming implementation of the AWG-9 WCS and AIM-54. Partial tests show quite similar outcome when the target is cold by setting BEAM and TAIL. If the target is beaming, BEAM is the only efficient setting. If the target is HOT, there is little difference between the settings.
In all tests, the target is flying along a constant path, deploying only chaffs.
VIII. Television Camera Set
The TCS is used by default to enhance SA when WVR, ID targets, in AG-mode. The TCS has three main sets of controls: FOV, ACQ and SLAVE (Sensors Control Panel).
FOV is a 2-way switch, it controls the Field of View (Wide or Narrow).
ACQ is a 3-way switch and controls how the lock is acquired:
- AUTO SRCH: the TCS moves in a small pattern; it locks automatically.
- MANUAL: the TCS locks only to a target if controlled by the HCU.
- AUTO: the target locks to whatever enter its field of view.
AUTO SRCH is enabled by holding full-action with the HCU to IR/TV mode.
SLAVE is a 3-way position switch which defines which sensor (Radar or TCS) is slaved to the other.
- RDR: The Radar is slaved to the TCS line of sight.
- INDEPL: Radar and TCS act independently.
- TCS: The TCS is slaved to the RADAR.
Default setting is TCS slaved to the Radar. WVR, when the identification is not required or flying at a low level, the TCS can automatically slave to any aircraft, helicopter, missile, or any other heat source flying through its field of view or it’s scanning pattern. IROT turns on if a positive track is seen by the TCS.
Set A/A mode, SLAVE to RDR before locking with the TCS, otherwise the cue on the HUD is not shown.
Plate 7.1 shows a successful TCS lock, the STEERING filed shows OPTTRK (Optical Track).
This mode should allow the employment of missiles (see Manual):
The resulting submode entered is equivalent to an STT mode where the TCS is instead used to track the targets angle rather than the radar itself. The radar is still used to track range and rate, on the DDD the IROT lights instead of the ANT ROT, IROT relating to ir tracking which has been replaced by the TCS in the F-14B.
This mode can be used to guide missiles, active and cw modes if in pulse and in PD if in pulse doppler. If the SLAVE switch is set to INDEP from this mode the system reverts to true pulse STT or pulse doppler STT depending on current mode.
At the moment the radar looks to be slaved but RDROT is off and the trigger is not HOT, so missiles cannot be employed. It is still a useful mode to steer the pilot towards the target.
TCS for Radar-less intercept and ID
The TCS can be used to ID and IR-Lock targets without using the radar. By default, the TCS is boresighted to the armament datum line (ADL) on the Pilot’s HUD. The RIO can either look for the target by means of the HCU or the pilot can superimpose the ADL to the target so the RIO can immediately lock the target.
Plate 7.2 shows the ADL placed near the barely visible target, whereas the TCS shows a clear picture of the target aircraft.
Unless the radar is slaved to the TCS, the target will not be locked by the radar.
This function is useful to quickly ID targets within visual range without alerting the target.