190-01115-01
G3X/G3X Touch Installation Manual - GMU 11 Installation
Rev. AC
Page 14-3
Ensure that any electrical conductor that comes within 10 feet (3.0 meters) of the GMU 11 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 11, 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 wing tips
with nonmagnetic stainless steel screws).
In general, wing mounting of the GMU 11 magnetometer is preferred (unless as noted in
Fuselage mounting is less desirable because of numerous potential disturbances that interfere with accurate
operation. For installations with dual GMU 11 magnetometers, co-locating the two magnetometers close
to each other in the tail or in one wing is recommended as this reduces the likelihood of heading splits or
miscompares when operating on the ground in the vicinity of local magnetic anomalies.
Mechanical mounting fixtures for the GMU 11 must be rigidly connected to the aircraft structure. Use of
typical aircraft-grade non-magnetic 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 11 to within 3.0° of the in-flight level cruise attitude.
Align the GMU 11’s forward direction to within 0.5° of the any of the 4 cardinal directions with relation
between its connector and the nose of the aircraft.
Table 14-4 Recommended Distance from Magnetic Disturbances
Disturbance Source*
Minimum Distance
from GMU 11
Electric motors and relays, including servo motors
10 feet (3.0 meters)
Ferromagnetic structure greater than 1 kg total (iron, steel, or cobalt materials,
especially landing gear structure)
8.2 feet (2.5 meters)
Ferromagnetic materials less than 1 kg total, such as control cables
3 feet (1.0 meter)
Any electrical device drawing more than 100 mA current
3 feet (1.0 meter)
Electrical conductors passing more than 100 mA current [(should be twisted
shielded pair if within 10 feet (3.0 meters)]
3 feet (1.0 meter)
Electrical devices drawing less than 100 mA current
2 feet (0.6 meter)
Magnetic measuring device other than another GMU 11 (e.g. installed flux
gates, even if unpowered)
2 feet (0.6 meter)
Electrical conductors passing less than 100 mA current [(should be twisted
shielded pair if within 10 feet (3.0 meters)]
1.3 feet (0.4 meter)
*Disturbance sources listed in table do not apply to a second installed GMU 11
