INSTALLATION MANUAL
CMA-5024 GLSSU
This document includes Proprietary Information and shall not be reproduced or communicated to third party
without prior written permission by CMC Electronics Inc.
Page D.6
November 21, 2008
equipment does not output these particular data labels and is not faulty and its wiring is correct, please
consult the system integrator and CMC's Customer Support.
1.4 CORRECTIVE ACTIONS FOR ELECTROMAGNETIC COMPATIBILITY
If harmful RF interference effects are detected, double-check first for external factors such as mobile
radios and cellular phones, nearby vehicles and other aircrafts, etc...
Typical causes of on-board RF interference are the HF/ VHF radios and defective radio transmitters.
The conventional fault isolation procedure consists in cycling off/on and operating in turn each
suspected equipment, one at a time, until finding the interference source. Refer to the EMI testing
information in section III. If these checks are unsuccessful, investigate further as follows:
- Inspect the RF and electrical cable shields, grounds and connectors for defects
- Inspect and tighten the electrical connections and grounds.
- Check that the antenna cables are not tied along with other cables that carry significant RF energy
since this may cause spurious cross-coupling due to imperfect RF shields.
- Swap the antenna for a known-good one, since active antennas may fail in odd ways (i.e. self-
oscillation).
- Check for evidence of corrosion or poor ground continuity on electrical and mechanical/structural
parts and hardware, especially in the vicinity of antennas.
Rationale: It is known that harmful "passive intermodulation" RF by-products may be caused by
oxidized or corroded metal contacts such as on nuts, bolts and stainless steel parts. This is because
such junctions may possess non-linear semiconducting properties, hence they may rectify the RF
currents circulating on the aircraft body. In such cases, clean, tighten or replace the suspect
hardware.
- Check for spurious signals in the RF frequency spectrum at the output of the antenna connector.
The requirements in Appendix C of RTCA DO-229D should apply to both RF Continuous Wave
(CW) and wideband noise interference.
Note: The DO-229D Appendix C levels are specified ahead of the preamplifier inside the active
antenna. Adjust the levels for preamplifier gain and the antenna cable losses.
Should the interference problem persist, the system integrator or installer should be consulted to modify
the installation and/or the aircraft interwiring, such as by adding RF filters and shields or by changing
antennas location to improve the RF isolation between antennas. CMC should be contacted for
support.
1.5 LIGHTNING INDUCED TRANSIENT SUSCEPTIBILITY
As indicated in section I, the GLSSU includes lightning protection circuitry that will protect safely
against the indirect effects of lightning strokes, provided the installation conforms to the requirements
herein.
1.6 GUIDANCE TEST UP/RIGHT DEVIATIONS
If the deviations remain at up/right during the guidance test, verify the following:
1) SDI setting of the GLSSU;
2) APD selection of the GLSSU;
3) Attitude data inputs (IRS/FMS inputs) or source equipment (typically IRS) when Attitude Data
Used APD parameter is enabled;
The document reference is online, please check the correspondence between the online documentation and the printed version.
To Next Page
Loading...
Need help?
General
