Air-to-Air weapons

AN/APQ-72 RADAR set

The AN/APQ-72 is a mechanically operated air intercept RADAR with detection ranges of up to 200 nautical miles. It can scan an azimuth of 60 degrees in either direction and its elevation can be adjusted to a maximum of +/- 60 degrees off boresight.

The AN/APQ-72 is equipped with a continuous wave illuminator (CWI) that is used to guide the AIM-7 sparrow missile. The CWI is automatically activated the moment a contact is selected by the RIO and turned off when the target is destroyed, deselected or outside the RADAR scan limits.

The RADAR boresight line (RBL) is 2 degrees below the aircraft nose and 0 degrees in azimuth. All elevation and azimuth references are based on RBL.

To operate the AN/APQ-72 the RIO uses the RADAR control panel, RADAR scope and RADAR stick located below the flight instruments in the rear cockpit. The equipment is visible in that order from left to right on the image.

Note: the RADAR scope in early F-4B aircraft can be unstowed to provide a better view. On later F-4B and F-4N aircraft the scope is locked in an unstowed position.

The stick needs to be unstowed in order to be operated. This is done by pulling the metallic lever located above it.

RADAR control panel

The RADAR control panel allows the RIO to change between the settings of the AN/APQ-72 RADAR:

• POWER knob
  • OFF: turns the RADAR set off
  • TEST: not simulated
  • STBY: RADAR set is powered but not emitting
  • OPR: RADAR set is operational and emitting
  • EMER: same as OPR
• MODE knob
  • BOMB: INOP
  • IR: not installed on F-4B/N aircraft
  • RDR: standard RADAR operating mode
  • MAP: INOP
  • BST: boresight mode. RADAR is locked at the BRL and range is set to 5nm. The RADAR scans an area of 6.7 degrees in azimuth and a vertical line is shown on the scope.
• DISPLAY knob:
  • EXP: expanded search mode. RADAR azimuth is limited to 10 degrees on each side. Antenna is moved left right using the EXP SW knob on the aft RADAR scope
  • NAR: narrow search mode. RADAR azimuth is set to 30 degrees on either side. Elevation is controlled using the elevation wheel on the RADAR stick.
  • WIDE: wide search mode. RADAR azimuth is set to 60 degrees on either side. Elevation is controlled using the elevation wheel on the RADAR stick. * scan
• SCAN switch
  • 1 BAR: the RADAR scans an area of 4.8 degrees of total elevation
  • 3 BAR: the RADAR scans overlapping areas of 7.55 degrees of elevation alternating from one to the other. This results to a total coverage area of 12.3 degrees of elevation.
• RANGE knob:
  • 5-10: sets the RADAR to a maximum range of 10 nautical miles. When a locked track comes to within 5nm miles the range is automatically reduced to 5nm. This setting belongs to the air intercept range.
  • 25-50: sets the RADAR to a maximum range of 50 nautical miles. When a locked track comes to within 25nm miles the range is automatically reduced to 25nm. This setting belongs to the air intercept range.
  • 100: sets the RADAR to a maximum range of 100 nautical miles.
  • 200: sets the RADAR to a maximum range of 200 nautical miles.

Keystrokes

TAB is used to go into half-action when no target is locked. When already in half-action pressing TAB again will take the RADAR into full-action.

CAPS LOCK is used to unlock targets.

Scope symbology

Search mode

Search mode is the default RADAR operating mode, allowing the operator to scan for targets at ranges up to 200 nautical miles.

• Horizon line: the horizon line is used as a reference for the RADAR attitude relative to the horizon. It is visible when the RADAR is operating in horizon-stabilized mode.
• Scan bar: represents the scanning RADAR beam
• Target acquisition brackets: this is the pair of brackets the RIO uses to select a target return on the scope. It is moved using the RADAR stick.
• Elevation strobe: appearing on the right side of the scope, this is used to indicate the current elevation the RADAR is scanning. Its full range of motion is +/- 60 degrees up or down and is changed using the wheel on the RADAR stick
• Target returns: displayed as dashes on the RADAR scope, target returns represent aircraft as detected by the RADAR beam.

Track mode

Track mode is initiated once the cursor is over the target and half-action has been initiated. The RADAR then enters Single Target Track mode (STT) and tracks the target along the azimuth axis.

For the RADAR to enter track mode the target must be at a range of 50nm or less.

• Range strobe: once the target acquisition brakets are enclosing the target and half-action is initiated the range strobe appears at the bottom of the RADAR display. To advance to Intercept mode, RIO must move the range strobe over the target using the stick and initiate full-action for a successful target lock.

Intercept mode

Intercept mode is used to guide the AIM-7 missiles to the target, which must remain locked until the missile scores a hit. Symbology is as follows:

• VC circle: once a target track is selected the VC circle shows the closing speed of the target.
  • Clockwise: 12’ o clock position means that the relative velocity is 0 thus the target is not closing nor separating. Clockwise positions up to 9 o’ clock are used to indicate closure of up to 900 kts.
  • Counterclockwise: 11 o’ clock is used to indicate separation at 100 kts, 10 o’ clock at 200 and up to the 9 o’ clock limit which would be 300 kts.
• ASE circle: the allowable steering error circle is an expanding circle that helps achieve optimum firing conditions. The circle expands as the target closes within optimum firing range and shrinks again as it moves closer than the optimum threshold. In the picture to the right the ASE circle is fully shrinked as the target is beyond maximum firing range.
• Steering dot: the steering dot needs to be within the Allowable Steering Error (ASE) circle to be able to fire the AIM-7 missile. The closer to the center the better the chances it will successfully hit the target.
• Weapon release envelope symbols:
  • Raero strobe: the Raero strobe indicates maximum aerodynamic range for the selected air-to-air weapon. When a target is beyond Raero the missile will not be able to reach it to score a kill
  • Rmin: the Rmin strobe is the minimum engagement range required for successful and safe deployment of the selected air-to-air weapon. When a target crosses the Rmin strobe the BREAK light will illuminate on both RADAR scopes accompanied by an X symbol on the display.
  • When the target is between Raero and Rmin, an IN RANGE light will illuminate on both scopes. The ASE circle will expand until the target is in the optimum range based on the flight and interception parameters.
  • A weapon cannot be released outside of its engagement envelope unless the pilot moves the INTLK switch to OUT (all aircraft) or DOGFIGHT (late F-4B and F-4N only

AIM-7 deployment

Rear cockpit

• RADAR OPR and mode to RDR or BST

Forward cockpit

• Missile tuning
  • Weapons control panel
    • FCS POWER: RADAR STBY or ON
    • Arming switch: OFF
    • HEAT/RADAR switch: RADAR
  • Missile Status Panel
    • SELECT lights: lit green
    • READY lights: lit after 15 seconds
  • Firing
    • FCS power: ON
    • Arming switch: ARM
    • When target is within engagement envelope press the trigger

AIM-9 deployment

Forward cockpit

• Optical sight unit: 35 mils
• Weapons control panel:
  • FCS power: ON
  • Arming switch: ARM
  • HEAT/RADAR switch: HEAT
• Auxiliary armament panel:
  • Increase AURAL TONE volume until sound is clearly audible
• Missile status panel:
  • SEL lights: LIT
  • READY lights: LIT
• If a lock has been achieved, aural tone increases in volume and pitch to indicate lock. Hold trigger for 1.5 seconds and verify successful launch
• To cycle between available AIM-9 missiles, right click on HEAT/RADAR switch to move it to HEAT REJECT

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