Employing The AGM-88 HARM

Employing The AGM-88 HARM

What is the AGM-88 HARM?

The HARM (high-speed anti-radiation missile) is a weapon designed to destroy hostile ground radar emitters. A Superhornet can carry up to 6 HARM.

HARM is one of the most useful stores available in Jane’s F-18. It is a weapon for which target designation can be performed quickly and simply, can be automatically targeted at an imminent threat, and can be fired in a forgiving engagement envelope. No matter what your other stores, it is almost always a good idea to have some HARM on board.

HARM can be employed in one of three modes, selected with PB3, PB4, and PB5 of the HARM SMS MDI page.

Using the AGM-88 HARM in TOO mode

TOO (target of opportunity) mode is the most common method of targeting HARM. In TOO mode, when a HARM is the active weapon, the SMS MDI page displays the emitters that are viewable in the HARM seeker’s FOV (field of view). If additional emitters are detected by aircraft EW systems but they do not fall in the HARM seeker’s FOV, an arrow is displayed on the right and/or left side of the MDI display, indicating in which direction to point the aircraft in order to bring those emitters within the FOV.

The currently designated HARM target is boxed on the SMS MDI display. In addition, if the emitter is located at a point in space that is within your HUD constraints, the emitter’s location on the ground will be boxed in the HUD. Note that the manual indicates that the MDI box can be dashed; it is actually a solid box at all times. To change the designated HARM target, place the TDC in the SMS MDI display (click on the MDI or use the TDC keyboard commands to move the TDC) such that the TDC indicator diamond is displayed in the upper right corner of the MDI. Once the TDC is assigned to the SMS MDI, the TARGET_UNDESIGNATE command (mapped to the backspace key by default) will cycle the target designation box through all visible emitters on the MDI page. It can sometimes be difficult to distinguish exactly which emitter is currently selected for HARM targeting, especially when a number of emitters are  closely grouped. There are a number of methods that aid this process.

1. Selecting the LIMIT option (PB20) will display the top 5 threats instead of a maximum of 15.
2. PB12 will cycle the displayed emitters between land and sea (L/S) targets, land targets only (LAND), or sea targets only (SEA).
3. Zooming in on the SMS MDI using the ZOOM_LEFT_MDI and ZOOM_RIGHT_MDI commands will make the MDI image take up more of your monitor.

Note that the manual states that pressing the RSET (reset) button (PB15) automatically selects the highest priority HARM target; this feature is not implemented.

Occasionally an emitter will stop emitting after a HARM has been fired. In this case the HARM remembers where the emitter is and will aim for the last known point. The farther away the HARM is from the emitter at the time emissions cease, the less likely the HARM is to destroy its intended target.

Using the AGM-88 HARM in SP mode

SP (self-protect) mode is an automatic targeting mode of the HARM. When the HARM SP mode is selected and the Superhornet’s EW system detects that a ground-based radar is guiding a missile at your aircraft, a HARM will automatically be selected for firing and the intended target will be boxed on the HUD and in the SMS MDI display. No other emitters will appear in the MDI. The next press of the weapon pickle button will release a HARM.

If a hostile radar is guiding a missile intended for your aircraft, the HARM SP mode will activate even if another weapon, or even another master mode, is currently selected. This condition is called an “SP pullback”, indicating that the current master mode and weapon selection has been pulled back and replaced with an active HARM. When a pullback condition exists, “HARM” will appear in the middle of the HUD. If the release of a HARM is currently inhibited, “HARM” will appear. HARM release will be inhibited if the landing gear is down, the Master Arm is OFF, or if the release of another weapon is currently in progress. 

The only time a HARM pullback will not occur in SP mode is if the HRM-OR (HARM Override) option is boxed on the SMS or EW MDI pages. This option is toggled with PB16 on either of these two MDI pages; when the HRM-OR text is boxed the override is active. HARM Override is useful for the terminal stages of weapons deployment, when an SP pullback would interrupt weapons delivery.

Like TOO mode, HARMs fired in SP mode will attempt to strike their target even if target emissions cease while the HARM is in flight.

Using the AGM-88 HARM in PB mode

PB (pre-briefed) HARM mode is used to launch HARM at pre-designated targets. In this mode HARM is guided by GPS and it does not matter if the target is emitting. PB mode uses the HARM as a medium-range guided missile with a warhead specially designed to kill radar equipment.

To select pre-briefed targets for HARM, box the TGT option on the SMS MDI by pressing PB1. Once TGT is boxed, use the UP and DWN buttons (PB12 and PB13, respectively), to change the selected target. You will see the target number and label change in the lower right portion of the MDI. Be sure to only select radar targets for HARM launch, as the missile will be ineffective against most other vehicles and structures.

Once a target is selected, a time displays next to the TOF line in the upper right of the MDI. TOF stands for time of flight and indicates how long a HARM would be in the air, in minutes:seconds format, if it were launched at that moment. This is useful for calculating when to launch a missile so that it destroys a target at a specific time. When your aircraft is in range of the currently selected PB target, an IN RNG indication appears at the top right of the MDI. At this point a HARM fired will reach the target.

Once a HARM is fired, the time next to the FLT indication activates. This is the flight time of the last launched missile and indicates the time remaining before it reaches its target. This is useful for knowing how long it will be until a radar stops emitting (and guiding). The bottom time line indicates the difference between these two times.

HARM Employment Considerations

With the exception of PB mode, there is no range indicator for HARM targets. This means that it can be difficult to tell when you are in range of an emitter. There is no in-range indicator in a real F-18 either; HARM detects emitter strength and thus a determination of range is not possible.

A simple rule-of-thumb will do you well when targeting HARM in TOO or SP mode.  If the emitter box on your HUD is at or below -5 degrees on the horizon , a HARM fired at that point in time will reach its target before running out of energy. Be sure to use the -5 degree line on your HUD pitch ladder since Jane’s F-18 uses haze to ease the lanscape rendering load and the visible horizon is not the true horizon.

It is also very helpful to know that the Jane’s F-18 HARM outranges all SAMs in the game with the exception of the SA-10. That means that if missiles from a launcher are reaching you, you can reach the launcher with a HARM if that launcher is not an SA-10. This is the reason that the SA-10 is one of the two hardest SAM threats to overcome in Jane’s F-18. The other is the SA-11 because SA-11s can still guide even if their main radar is destroyed (although they will do so at shorter ranges); completely neutralizing an SA-11 site requires the destruction of all radars and missiles.

In the beginning of campaigns in which hostilities are in full swing (such as the stock campaign) it is a good idea to load lots of HARM if possible. At the end of a mission, remaining HARM can be fired at targets of opportunity in order to reduce the number of active SAM radars on subsequent missions.

Jane’s F/A-18 Manual References to HARM

• Page 4-67: Available hardpoints.
• Page 5-129: HARM Mode and Override: (EW PB 16) The current HARM mode is indicated above the HRM OR option and displays SP for Self-Protect mode, TOO for Target of Opportunity mode, and PB for Pre-Briefed mode.
• The HRM OR (HARM Override) option allows you to override the HARM Self-Protect pullback mode so that delivery of the selected weapon continues without interruption. This option is available on all stores pages whenever a HARM is loaded on the aircraft.
• Page 5-140: The AGM-88 High Speed Anti-Radiation Missile (HARM) is designed to seek out and destroy enemy land- and sea-based radar systems. Even if the radar stops transmitting before the HARM reaches it, the missile still has a fair chance of hitting within lethal distance of the radar. It is a vital weapon when you have been assigned the mission of SEAD (Suppression of Enemy Air Defenses). The HARM is a complex weapon with three different launch modes. They are Target Of Opportunity (TOO), Self-Protect (SP), and Pre-Briefed (PB).
• Pages 5-141 to 4-144: HARM HUD and MDI symbology.
• Page 5-144: The HARM is only effective against radar emitting targets. The TOO mode is the primary launch mode you should use during SEAD missions unless the mission briefing specifically instructs you to attack a known target using PB mode. For all other mission types, if you have HARMs loaded you should have the SP launch mode selected to give you a quick reaction means to deal with threat radars.