190-02087-10
GDL 50(R)/51(R)/52(R) Installation Manual
Rev. 2
Page 2-9
2.11 Noise
To reduce noise on the audio lines, care must be taken to minimize effects from coupled interference and
ground loops.
Coupled interference can sneak into audio system interconnecting cables when they are routed near large
AC electric fields, AC voltage sources, and pulse equipment (strobes, spark plugs, magnetos, EL displays,
CRTs, etc). Interference can also couple into audio system interconnecting cables by magnetic induction
when they are routed near large AC current-carrying conductors or switched DC equipment (heaters,
solenoids, fans, autopilot servos, etc).
Ground loops are created when there is more than one path in which return currents can flow, or when
signal returns share the same path as large currents from other equipment. These large currents create
differences in ground potential between the various equipment operating in the aircraft. These differences
in potential can produce an additive effect at an audio panel signal input.
The audio panel may "see" the desired input signal plus an unwanted component injected by ground
differentials, a common cause of alternator-related noise. This is the main reason why all audio jacks
should be isolated from ground. Terminating audio shields just at one end eliminates another potential
ground loop injection point.
Single-point grounding cannot be overstressed for the various avionics producing and processing audio
signals. Single-point, in this context, means that the various pieces of equipment share a single common
ground connection back to the airframe. Good aircraft electrical/charging system ground bonding is also
important.
The wiring diagrams and accompanying notes in this manual should be followed closely to minimize noise
effects.
2.12 Mounting Requirements
The GDL 5X/5XR mounting surface must be capable of providing structural support.
The GDL 5X is mounted using a GDL 5X mounting bracket (
Appendix A-4
). See
Section 3.5
for
installation instructions.
The GDL 5X/5XR includes a sensitive attitude measurement sensor. Consider the following when
selecting a mounting location:
•
Mount the unit with the FWD arrow aligned to within 3.0° of the longitudinal axis of the aircraft
(LED bezel parallel to the wing spar). Mount the GDL 5XR so that the connectors point in the aft
direction.
•
The unit can be mounted with the serial tag pointing straight up or straight down, within 30
degrees of a level flight position.
•
Using the connected display, cage the gyros while the plane is in a level flight position.
•
For proper attitude performance the unit should be rigidly mounted to the aircraft.
•
The unit should be mounted to the aircraft with the LED bezel facing toward the rear of the
aircraft.
•
To prevent degraded accuracy, avoid placing the unit near areas that are prone to severe vibration.
•
The mounting location for the unit should be protected from rapid thermal transients, in particular
large heat loads from nearby high-power equipment.
