A few weeks ago Ed Anderson reported a failed circuit breaker feeding both coils.  He urged that we make our systems redundant where possible, with separate circuits and circuit protection to each.  I second his plea and share my recent experience as reinforcement.

I have about 60 flight hours and about 15 ground hours on my RV8.  It is powered by a 13B with the stock Mazda coils.  Tracy recently updated my EC2 and I installed it Saturday.  After a half hour ground run adjusting the MAP table I shut down and installed the cowl.  Taking Tracy’s advice I took off, stayed near the airport and did the Mode 9 programming at altitudes of 7,000’ to 10,000’ AGL.  I did several simulated approaches and landings at altitude enjoying the smoother running engine compared with the previous iteration of the program.  Also spent time among the puffy clouds and cooler air above the haze layer!  After 1.5 hours I began simulating another approach but when I pulled the power to idle the engine quit.  Emergency procedures were fruitless.  Even shutting down the entire system and attempting a power-up didn’t result in an engine start.  I was several miles from the field at about 7,000 AGL.  I set up an 85 KT glide, and decided to land on a runway with a six KT tailwind to avoid flying over a residential area or over a lake on the approach to an alternate runway.  I arrived over the approach end of the runway on a crosswind leg with 1500’ to lose so I began a tight pattern flying a descending left turn to lose altitude and position myself for the landing.  I lost 500 feet in the first 180 degrees and about the same in the second 180 degrees.  I rolled out on final high and hot, shut off all the electrics, landed long but without incident.  It all went pretty well other than the fact I forgot to roll in flaps when I could have used the drag to get me down sooner.

I use fuses for circuit protection so the first troubleshooting step was to check the fuses – all were OK!  I suspected the coils were involved because the tachometer was reading zero even though the engine was windmilling.  The tach is driven by a signal from the trailing coil.  Using the new diagnostic features,  the injectors were clicking OK but there was no spark.  Tracy reminded me of Ed Anderson’s post about the failed breaker feeding both coils.  Upon close examination the fuse had not blown but apparently it has been warm because it had warped.  It was in the fuse holder but somehow was not making contact.  Replacing the fuse cured the problem.

I am now a firm advocate of redundancy!  I have added a circuit to power the coils separately and plan to replace the essential bus fuse panel with circuit breakers.  I share this experience to urge those of you who use a single circuit to power your coils, your fuel pumps, your EC2 or any other critical systems to modify your wiring so a single circuit failure doesn’t place you in a dangerous position.  Mine ran for about 75 hours.  It was just a stroke of good fortune that the failure occurred while near the airport at an altitude higher than I usually fly. 

Here are a couple of data points that may be of interest:

          The fixed pitch wood prop windmilled at a 100 KT glide, rate of descent about 1000 FPM.

          The prop stopped at about 90 KT.

Fly safe!

Gaylen Lerohl

RV8

Alexandria, Minnesota