The International Rafale forum

Thank you Nicolas10 for having translated this part :

Dossier Rafale :


Total sensor fusion and NAS

1/ Total integration

The utmost degree of integration of the systems was required from the beginning in order to reduce the workload of the pilot, and also to benefit fully of the aircraft’s systems (higher survivability, better precision of the NAS (Navigation and attack system).

Everything on the rafale is networked: sensors, flight control system, engine FADEC, displays, armaments, communications, and various systems of the plane including start up, hydraulics, electrical, fuel and air conditioning system. Everything is interchangeable, with synchronised joint treatment and a capability to transmit all the data.

This integration which is not a mere “sensor fusion” (fusion of the sensors’ data) is managed by two very powerful calculators: the MPDU (Modular Data Processing Unit).

The integration of those data works the following way: creation of a “track” file, sharing of those information to compensate for the limits of certain sensors, treatment of the “false track” and redundant tracks.

This allows to increase the range of every sensors (RBE-2, OSF, SPECTRA, L16, and missile –Mica IR-), to display all the information to the pilot under the most clear picture as possible (on the VTM (Visualisation tête moyenne or Head Level Display: a sort of “god’s view” of the situation)), to employ stealthy tactics, and also to make maintenance much easier.

Thus with the fusion of the information between SPECTRA, OSF, L16 (but not necessarily all at once), it is possible for a Rafale to fire a Mica IR missile in a completely passive manner (no use of the indiscrete radar), even at longer ranges, and even if the target is behind the Rafale.

2/ Navigation

To reach the best level of survivability while being able to attack the most highly defended targets, several features of modern warfare had to be grasped: first, as long as you are not totally undetectable, the higher altitudes are always under the threat of long range SAMs (Surface to Air Missile). Flying at very low level remains a very good way of penetrating hostile territory while remaining undetected, by avoiding radars and by hiding in the ground clutter. However in very low level, portable SAM systems become a threat. Hence the need to fly at night or under low visibility weathers as much as possible (fog, clouds). Lastly the only means to avoid AAA (anti aircraft artillery) is to fly at high subsonic speeds, speed at which these systems have much difficulty tracking a plane.

While the Rafale can use the Scalp missile for high risk missions, there are probably missions in which it will be forced to fly at high speed and very low level, with the worst weather as possible.

Global integration is the root of the very powerful autopilot equipping the plane. Let’s talk navigation. To find its way in the skies, the Rafale is equipped with a ring-laser inertial navigation system, coupled with a GPS receiver.

- INS that can be started in 4 minutes for precise calibration, and 1min30sec for quicker calibration. It allows navigation with an error of 0,8 NM per hour.


- GPS: the precision of the GPS gives a position within 10 m
The Rafale M adds the TELEMIR system to find it’s position thanks to the position of the aircraft carrier

Because those systems are not yet precise enough, the RBE-2 is capable of mapmaking, allows for recalibrating the navigation system if its use is possible in the mission without compromising the aircraft’s quietness.

To navigate in terrain following mode at high subsonic speeds, the Rafale has a 300 000 km² digital map in memory. The terrain following mode on a digitalised map is the best in terms of quietness. However it is not accurate enough to allow a safe flight in very rough (or unknown) terrain while flying at 30 meters from the ground at high speed and with accelerations of 5.5G. Therefore the RBE2 takes over with its own 3D mapmaking ability. It combines with the CET (Calculateur d’élaboration de trajectoire or Trajectory Making Calculator) that prepares complex trajectories up to 10km in advance, while coupling with the fire control system in order to best use the plane’s weapons. The CET is also used for automatic approach on the aircraft carrier.

Over the sea, the terrain following is done very close to the waves thanks to a LPI (low probability of intercept) radio altimeter efficient from 0 to 10500 feet.