Upgrade from LARUS Essential to Dual-GNSS

Influence of the heading accuracy on the wind calculation in forward flight

As described above, the LARUS Essential (uBlox M9N single-frequency receiver) already achieves a high heading accuracy of 1-2° (under optimal installation conditions, see below).

In contrast, the accuracy of heading determination with the Dual-GNSS variant is outstanding at 0.05°. This is particularly advantageous at high airspeed in level flight. As the wind triangle illustrates, at an airspeed of 200 km/h, 2° corresponds to a 7 km/h inaccuracy in the crosswind component, while 0.05° corresponds to only a 0.2 km/h inaccuracy.

In addition, the accuracy of the dual GNSS version is not affected to the same extent as LARUS Essential if iron parts or magnetic fields in the vicinity of the LARUS sensor unit cannot be avoided due to the installation situation. Due to the two GNSS receivers, only a small part of the measured values from the IMU flows into the algorithm.  

Installation Instructions

Explanations regarding LARUS Essential

A requirement for the high accuracy of LARUS Essential is that the disruptive influence of magnetic fields in the vicinity of the sensor unit is minimized. This is particularly high priority for LARUS Essential. In particular, the correct operation of the inertial measuring unit IMU, which among other things measures the magnetic induction, is severely impaired by magnets, changing magnetic fields or iron parts. We recommend keeping the LARUS sensor unit as far away as possible (at least 20 cm), especially from speakers and magnets (often contained in GPS / GNSS antennas, simply check with magnets). In addition, the fastening elements in the immediate vicinity of the sensor should be made of stainless steel, brass, plastic, aluminum or fiber composite materials and the usual nuts and bolts made of steel should be avoided. Iron parts are unsuitable because they generate a variable interference field with every movement of the aircraft.

The GNSS antenna, on the other hand, is not sensitive to magnetic fields.

Explanations regarding LARUS Dual-GNSS

Bei LARUS Dual-GNSS ist dagegen wichtig, dass die beiden GNSS Empfänger einen Abstand von mind. 1,0 Metern zueinander aufweisen.

The master GNSS antenna should be mounted on the inside of the fuselage tube (luggage compartment / end of the canopy) approximately above the center of gravity of the aircraft. Because the shorter the distance between the antenna and the center of gravity, which is also the center of rotation of the aircraft around the pitch axis, the less the influence of pitching movements (forward or backward movement of the stick) on the measured altitude.

The second antenna (slave GNSS antenna), on the other hand, is mounted at the level of the instrument panel or in front of it in the nose of the aircraft.

Für alle GNSS-Antennen ist wichtig, dass das Laminat oberhalb der Antennen aus GFK und nicht aus CFK besteht, da ansonsten aufgrund der elektrischen Leitfähigkeit von Kohlenstofffasern die Dämpfung zwischen GNSS Satellit und Empfänger im Flugzeug zu groß wäre. Bei Flugzeugen mit CFK-Rumpf kann allerdings auch eine Montage der Antennen im vorderen und hinteren Bereich der Haube in Betracht gezogen werden, sofern die Antennen dann einen ausreichenden Abstand (ca. 1,0 m) zueinander aufweisen.

LARUS License