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Countermeasures on military aircraft: DASS

Picture of Enrique Ponce

Enrique Ponce

AERTEC / A400M Flight Test Center


A military aircraft and its crew constitute a very valuable “asset” for air forces in mainly two aspects. On the one hand, due to the possibilities they offer (transport, in-flight refuelling, air superiority, supply drops in areas which are difficult to access, etc.) and, on the other due to economic costs (manufacturing the equipment) and because of time and resources (the crew and their instruction and training). It is therefore logical and necessary to safeguard such an “asset” (crew and aircraft) from any possible threats as effectively and efficiently as possible when they perform their tasks.

The greatest threat arises from a conflict with other air forces and armies which, in the event of combat, will use all means at their disposal to shoot aircraft down. Among these, air-to-air missiles and surface-to-air missiles should be highlighted. The Defensive Aids Sub-System (DASS) was developed to counteract them.

Very simply put, the DASS is a system equipped with a central intelligence unit that can detect and classify any possible threats and consequently act on them.

The notion of “guided” should be underlined on this point, which is the means by which missiles locate the target and change their trajectory to reach it. It includes technologies like infrared-guided technology, which is based on the heat trail left by an aircraft’s engines, or radar-guided technology, which locates the target through how previously transmitted electromagnetic pulses bounce off the target. It is therefore essential to identify the type of guided missile in question in order to evade it.

Such identification is carried out by different kinds of sensors strategically distributed throughout the aircraft which inform the system’s central intelligence unit of the existence of a threat, the kind of threat it is and possibly the direction from which it comes. The system alerts the crew of this information and can also take decisions automatically like, for instance, launching flares to deal with infrared-guided missiles or chaff to counteract radar-guided missiles. In both cases the underlying idea is the same: to confuse the missile by showing a large number of targets to its guided system. In the former case, the flares are a heat source which hide the trail left behind by the engines, while in the latter the fragments making up the chaff produce a large number of pulses bouncing around which appear on the missile’s radar as possible targets.

However, the above is no more than a simplification of the DASS, which is equipped with other functionalities to alert the crew, such as suggesting evasive manoeuvres and automatically deploying countermeasures like silencing the aircraft’s radio transmissions.

There is no doubt that the DASS is a highly effective tool to ensure the protection and safety of aircraft and their crews when they are deployed in hostile environments.



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