Below Radar

Below Radar is an aircraft specialization in Battlefield 3 and Battlefield 4. It is a permanent upgrade, meaning that it does not have to be selected at the Customization screen unlike other specializations. It is also a passive upgrade - it is not activated via pressing a button like IR Flares for example, instead it takes effect when flying at a low altitude.

Battlefield 3

Below Radar
Vehicle type	Attack Helicopter Scout Helicopter Jet
Customization slot	Permanent Upgrade
Progression
◄	Laser Painter (AH) Guided Missile (SH) Extinguisher (Jet)
►	ECM Jammer (AH) Laser Painter (SH) Maintenance (Jet)
Unlocked at	37000 AH score 32000 SH score 15000 Jet score
Effect
Special feature	Protection from heat-seeking and spotting at low altitude

"When flying at low altitudes your heat signature is decreased, hiding you from enemy radar and preventing enemy air-to-air missile systems from locking onto you."

— Battlelog description

Below Radar decreases the thermal signature of all aircraft flying at low altitude. It hinders spotting and prevents weapon lock from heat-seeking weapons from aircraft and anti-air missile mounted aboard Mobile-Anti-Aircraft and Mobile Artillery. It is activated instantaneously when flying a lowest set altitude, preventing enemy heat-seeking air-to-air missiles from locking on to any aircraft below said altitude.

Below Radar does not protect against shoulder-launched anti-air weapons (Stinger/Igla), nor was it designed to. The user must decide whether the threat from enemy air vehicles outweighs the threat from ground forces.

Compared to Stealth, it allows helicopters to be more effective at close ground support. Low-flying aircraft are, however, more vulnerable to ground fire, including unguided or wire guided rockets, as well as fire from armored vehicles. Because of this, pilots of aircraft and encouraged to open, heavy-traffic areas when going below radar to avoid ground fire.

Activation of Below Radar can be identified in mainly 3 ways: Below Radar will activate once the aircraft is within 30 meters or feet (whether altimeter measurement in metric or imperial units is currently unknown, not even mentioned by the developers) from surface level (altimeter measurement is based on sea level, not surface level). Pilots equipped with Air Radar will also witness the HUD symbol of their aircraft disappear when they are below the minimum altitude of activation and re-appear again when above the minimum altitude of activation. For Attack and Scout Helicopters, the specialization is activated at 25 or below, which also turns the aircraft's altimeter red, signifying both a dangerously low altitude, and Below Radar active. Pilots equipped with Air Radar will also witness the HUD symbol of their aircraft disappear when they are below the minimum altitude of activation and re-appear again when above the minimum altitude of activation. Another peculiar, but more inconsistent way of identifying whether Below Radar is activated, is to fly within Air-Radar-Range of enemy aircraft, particularly other hostile Jet Aircraft. More experienced, dog-fighting professional pilots may appear to be oblivious to the enemy aircraft's presence when below radar, especially when trailing them from behind at extremely low altitudes where Below Radar automatically activates. This can be identified somewhat accurately when the pilot of the targeted aircraft fails to initiate evasive combat manoeuvres to counter the aircraft trailing them from behind with Below Radar activated, therefore revealing the targeted aircraft's pilot ignorance of the enemy aircraft's presence. However, the targeted aircraft may also simply be pre-occupied with other tasks such as ground-attack and fails to acknowledge the trailing aircraft anyway, sometimes leading to confusion. This is further compounded with the fact that there is no rear-facing aircraft camera in Battlefield 3, making it very hard to tell if another jet is following the player.

Gallery

Below Radar activated (Note absent vehicle symbol within Air Radar HUD)

Below Radar deactivated (Note presence of vehicle symbol within Air Radar HUD)

Battlefield 4

Below Radar
Vehicle type	Attack Helicopter Scout Helicopter Transport Helicopter Stealth Jet Attack Jet
Customization slot	Permanent Upgrade
Progression
Unlocked at	Default
Effect
Special feature	Protection from heat-seeking missiles at low altitude

Below Radar is a permanent vehicle specialization introduced to Battlefield 4 with the Community Operations expansion, and is enabled by default for all air vehicles. It functions almost identically to its Battlefield 3 counterpart, but it is available by default and does not hinder Spotting. Below Radar will protect against weapon locks from all anti-air vehicle missiles, including those from Mobile Anti-Air vehicles.

Below Radar is automatically activated once the aircraft is below 25 meters in all Helicopters and below 50 meters in all Jets. Unlike its Battlefield 3 predecessor, the piloting aircraft's HUD symbol will not disappear from the Air Radar but will however, disappear from enemy and friendly ground and air vehicle's Air Radar and thus, making it somewhat more difficult to identify whether the aircraft is below radar quickly at any given time without having to refer back to the vehicle's altimeter. Another peculiar, but more inconsistent way of identifying whether Below Radar is activated, is to fly within Air-Radar-Range of enemy aircraft, particularly other hostile Jet Aircraft. More experienced, dog-fighting professional pilots may appear to be oblivious to the enemy aircraft's presence when below radar, especially when trailing them from behind at extremely low altitudes where Below Radar automatically activates. This can be identified somewhat accurately when the pilot of the targeted aircraft fails to initiate evasive combat manoeuvres to counter the aircraft trailing them from behind with Below Radar activated, therefore revealing the targeted aircraft's pilot ignorance of the enemy aircraft's presence. However, the targeted aircraft may also simply be pre-occupied with other tasks such as ground-attack and fails to acknowledge the trailing aircraft anyway, sometimes leading to confusion.

Below Radar presents an effective counter to Passive Radar missiles, as they will be unable to continue tracking once the aircraft is low enough. However, Heat Seekers and Active Radar missiles will continue tracking if they have already been fired after a lock is achieved. Active Radar missiles are a more peculiar case, as they cannot automatically obtain lock-on to vehicles below radar, but will still automatically guide themselves towards the target once the target vehicle flies above radar, and will continue tracking past that point.

Like its predecessor, Below Radar does not protect against shoulder-fired Anti-Aircraft and Vehicle missiles, like the FIM-92 Stinger, SA-18 IGLA and HVM-II. Low-flying aircraft are, however, more vulnerable to ground fire, including unguided or wire guided rockets, as well as fire from armored vehicles. Because of this, pilots of aircraft are encouraged to avoid open, heavy-traffic areas when going below radar to avoid ground fire.