We have three RV-12’s here with ULS power and one RV-12iS under construction. One of our flying airplanes has had a series of 3 failures of the A ignition module in the last 250 hours of operation. It has 550 hours TT. The last failure resulted in the engine running rough on the A circuit when B was switched off during a “mag” check.
After this last failure we did more research, watched the Rotax Owner ignition troubleshooting video, and consulted the Rotax Guru at Lockwood Aero. It was determined that one of the ignition coils was not firing it’s 2 plugs. Using an inductive timing light confirmed that 1-top and 2-top spark plugs were not firing. There are 4 coils, each coil fires 2 plugs and the A ignition circuit fires 2 of the coils. Plugs 1-T and 2-T are fired by one of those A circuit coils.
An ohmmeter check of the coil showed the proper resistance in the secondary but the primary was open. After a bit if invasive surgery to get to the coil we found the blue power wire had been chaffing and was separated. Picture attached.
Earlier we suspected that something was killing the A modules and the issue was not the module themselves. But we didn’t act on those suspicions at the time and had we done so we probably could have saved the A/C owner a considerable sum. Lesson learned.
The coils are located on top of the engine in a rather confined space and there are a number of coil wires with potential for chaffing. This area is hard to get to and is probably overlooked during routine inspections.
After this last failure we did more research, watched the Rotax Owner ignition troubleshooting video, and consulted the Rotax Guru at Lockwood Aero. It was determined that one of the ignition coils was not firing it’s 2 plugs. Using an inductive timing light confirmed that 1-top and 2-top spark plugs were not firing. There are 4 coils, each coil fires 2 plugs and the A ignition circuit fires 2 of the coils. Plugs 1-T and 2-T are fired by one of those A circuit coils.
An ohmmeter check of the coil showed the proper resistance in the secondary but the primary was open. After a bit if invasive surgery to get to the coil we found the blue power wire had been chaffing and was separated. Picture attached.
Earlier we suspected that something was killing the A modules and the issue was not the module themselves. But we didn’t act on those suspicions at the time and had we done so we probably could have saved the A/C owner a considerable sum. Lesson learned.
The coils are located on top of the engine in a rather confined space and there are a number of coil wires with potential for chaffing. This area is hard to get to and is probably overlooked during routine inspections.
