July 2019 – Jersey Sherwood Ranger

I’ve had an annoying little crackle in the headsets for a while now but have had trouble pinning it down .. at first it was just a low level occasional click but has increased over recent flights to being quite invasive.

When I transmit or receive the radio goes clear as a bell.

Chatting with our visiting avionics specialist he suggested trying to isolate it by turning off circuits and devices and checking to see what happened .. problem was it was definitely more noticable airborne … so not so easy to start wholesale switch offs !

In the end .. the progressive nature of change … I noticed that if I turned the right mag off the click pretty much stopped .. so we had an area to focus on .. but no one in Jersey has a Jabiru and the forums are flooded with conflicting advice …

I also noticed on the last flight that the right mag drop suddenly increased to about 100 .. where the left was only showing about 40 drop ..

Time to ground her and check before any more flying ….

Time to call Paul H Smith at TLAC for a quick bit of advice…

Given the symptoms, he advised to check the Jabiru remanufactured HT lead and fitting out of the mag and, if that looked ok, double check distributor cap and rotor arm

In 5 minutes I’d located the problem … the right rotor arm was clearly not seated firmly and could move ever so slightly ..

At the first 25 hours of engine run time I had been super cautious and changed oil, filter, plugs, rotor arms and distributor caps. The arms were very difficult to get off .. later found they are epoxied in place ..

I had applied epoxy .. sparingly but, I guess, too sparingly … and this arm could move fractionally on its squared stem drive shaft.

Removed, and temporarily put back the original 25 hour unit having cleaned and epoxied

Engine start and run up … radio clear as a bell again …

Also .. Left and Right mag drops back to evenly matched at about 40 rpm each 😉