My initial thinking for grounding of the AeroLEDs Pulsar series and Suntail lights was to run the ground wire all the way to the fuselage along with the power wires in the shielded wire bundle to keep RFI low. Recent testing has shown that it is actually much better to ground the light locally to stuctural ground along with the chassis of the light (heatsink).

With the ground run to the fuselage, the Pulsar NSP strobe function has some frequencies in the communications band where the RFI energy is 6db uV/m above the Cat M limit line.

Changing the grounding scheme such that both the black ground wire from the light and the chassis of the light are grounded locally to aircraft structural ground drops the emissions in the communications band by 30db uV/m which eliminates any potential for radio interference.

The most recent wiring diagram for the Pulsar and Suntail lights documents this change in grounding.   That diagram can be found in the Resources section of the AeroLEDs website.

The installation for minimum RFI emissions requires the following:

1.  Ground the black wire from the light to structure ground as close as reasonably possible to the mounting location of the light.

2.  Ground the chassis of the light to structure ground as close to reasonably possible to the mounting location of the light.   For the Pulsar it is important to strip away the clear anodization from the counter-sunk screw wells to ensure that the mounting screw heads make electrical contact to the mounting bracket.   For the Suntail, it is important to strip away the clear anodization from the counter-sunk screw wells on the chassis of the light to ensure the mounting screw heads make electrical contact to the body of the light.   If the mounting screws attach directly to grounded structure, nothing further is required.   If the lights are mounted to a non conducting surface, a ground strap wire needs to be run from the mounting screw to the nearest structure ground point, and it should be grounded at the same location as the black wire.

3.  Use three conductor 20 gauge shielded wire to connect the power to the red and yellow power inputs for the position and strobe functions.   The third conductor can be used to route the synchronization (green) wire to synchronize the strobes on multiple lights.

4.  The shield on the wire bundle should be attached to structure ground at both ends of the wire run to provide both electric and magnetic field shielding.

In a composite wing, if there is a heavy gauge chassis ground wire or strap that runs the length of the wing, that should be used for structural grounding.   If no such ground exists, the shield braid on the wire bundle will have to be used as the structural ground.

Failure to follow the above grounding installation recommendations can result in audible radio noise and interference, so I strongly recommend that all installations are completed as described above.

Dean Wilkinson

CTO, AeroLEDs LLC