Garmin G3X Installation Manual page 36

Table 3-7. Required Distance from Magnetic Disturbances
Disturbance Source
Electric motors and relays, including servo motors
Ferromagnetic structure greater than 1 kg total
(iron, steel, or cobalt materials, especially landing
gear structure)
Ferromagnetic materials less than 1 kg total, such
as control cables
Any electrical device drawing more than 100 mA
current
Electrical conductors passing more than 100 mA
current [(must be twisted shielded pair if within 10
feet (3.0 meters)]
Electrical devices drawing less than 100 mA current
Magnetic measuring device (e.g. installed flux
gates, even if unpowered)
Electrical conductors passing less than 100 mA
current [(must be twisted shielded pair if within 10
feet (3.0 meters)]
Ensure that any electrical conductor that comes within 10 feet (3.0 meters) of the GMU 44 is installed as a
twisted shielded pair, not a single-wire conductor. (If possible, the shield should be grounded at both
ends.)
Use nonmagnetic materials to mount the GMU 44, and replace any magnetic fasteners within 0.5 meter
with nonmagnetic equivalents (e.g. replace zinc-plated steel screws used to mount wing covers or
wingtips with nonmagnetic stainless steel screws).
In general, wing mounting of the GMU 44 magnetometer is preferred (unless as noted in Appendix C).
Fuselage mounting is less desirable because of numerous potential disturbances that interfere with
accurate operation.
Mechanical mounting fixtures for the GMU 44 must be rigidly connected to the aircraft structure. Use of
typical aircraft-grade materials and methods for rigid mounting of components is acceptable, so long as
adequate measures are taken to ensure a stiffened mounting structure.
Level the GMU 44 mounting rack to within 3.0° of the in-flight level cruise attitude.
Align the GMU 44 mounting rack's forward direction to within 0.5° in heading of the aircraft forward
direction (longitudinal axis). If it is not possible to guarantee this accuracy, installation alignment to
within 2.5° in heading is acceptable in combination with a post-installation heading alignment of the
aircraft to a precise heading to determine and set a heading offset. The heading offset procedure is
described in Section 8.3.4.
It is strongly preferred that the GMU 44 alignment is within 0.5° of the aircraft longitudinal axis, rather
than using the heading offset procedure.
Page 3-4
Revision E
Minimum Distance from GMU 44
10 feet (3.0 meters)
8.2 feet (2.5 meters)
3 feet (1.0 meter)
3 feet (1.0 meter)
3 feet (1.0 meter)
2 feet (0.6 meter)
2 feet (0.6 meter)
1.3 feet (0.4 meter)
G3X Installation Manual – GMU 44
190-01115-01