5.21 ELECTRICAL (continued)
EMS
Problem: My EMS display values randomly spike causing warnings.
Solution: If for example the value of an EGT is randomly going high enough to generate a warning on the EFIS, check the quality
of all the harness connections. Check if wiggling the spade connector between the thermocouple wires and the wires going back
through the firewall recreates the problem. Also move the harness back and forth that goes into any d-sub type connection. If the
connection is severed some EFIS systems we default to an error value that is very high, which will in turn generate a warning. If you
have a bad connection that intermittently becomes disconnected you will then be generating intermittent warnings.
Some values that spike can be fixed by changing the sampling rate of a signal or by changing how the data collected is averaged
and over what amount of time the average takes place. Consult the instructions provided with your EFIS system or the EFIS
manufacture.
Problem: My EMS values randomly spike during transmit.
Solution: RFI leakage from the com antenna may affect the EGT or MP wires. This is a common issue with the Van's gauges and
has not been a major problem.
If using a Dynon Avionics SkyView system, and the CHT and EGT readings spike during COM transmit: This is a known issue with
older SkyView SV-EMS-220 modules, which Dynon can fix. Contact Dynon Technical Support. Mention that you have a SkyView
system and CHT/EGT is spiking during COM transmissions.
GPS
Problem: My EFIS is not detecting a GPS signal.
Solution: Check that the output format of the GPS signal is set correctly. You may have no control of the output format of a GPS
puck but for a device like a Garmin handheld GPS etc. there will be a menu driven option allowing different formats.
Check that the wire carrying GPS data to the ELT has not been accidentally grounded by
a) crimping the shield to main wire conductor (Refer to Section 5 in your builder manual for the proper termination of shielded
wires)
b) no connection to the ELT thus the wire is dangling and grounding out on aircraft structure. Cover the end of the conductor
in heat shrink.
Trim
Problem: Trim motor does not move, or low voltage present at trim motor
Solution: The trim speed is controlled by a pulsed voltage (ie the power is turned on and off quickly - the longer it is off the slower
the motor moves). Adjust the trim potentiometer CCW to increase the speed. Most voltmeters will average the pulsed voltage as
something less than buss voltage (for example a pulsed voltage with a peak voltage of 12V off 50% of the time would be seen as
6V on a typical voltmeter).
PAGE
REVISION:
DATE:
VAN'S AIRCRAFT, INC.
PAGE
REVISION:
DATE:
09/24/13
05-28 RV-ALL
1
Glossary of Electrical Terms
These definitions are not meant to be “scientifically” correct but rather a definition understandable to someone not
technically familiar with electrical systems.
EMI and EMR (RFI): Electro Magnetic Interference. A magnetic field if oriented correctly near a wire will move electrons within the
wire inducing a current and causing electrical “noise”. This is referred to as “near field” since the effect falls off rapidly. This is why
moving wires relative to or away from a source may solve an EMI problem. A common source would be a wire carrying a fluctuating
high current.
Electro Radiation Interference (or Radio Frequency Interference when in the radio frequency spectrum) is energy absorbed or
emitted from a charged particle and will continue to travel through space away from the source. This is referred to as “far field” and
in such cases a solution should if possible be applied to the source of the radiation. A common source would be a COM and the
transmit wire / antenna.
With any electromagnetic radiation interference small signals such as audio are more likely to be affected.
Gain: Amplification of a signal (for the sake of this manual audio signal)
Impedance: The equivalent resistance of an electrical device.
Quiescent Current Consumption: Power consumed by a device in the idle state.
Side tone: Sound from a headset microphone fed back into the earpiece of that same headset or the level at which you hear your
own voice in the head set when transmitting. For more information consult your COM radio installation and user manual.
Squelch: A level setting used to cancel background noise so that only signals above the set level will be heard. The term “breaking
the squelch” means that an incoming signal has a level high enough to be above this level and will be heard.
