I think if I had fuses on something as critical as my coils, I would have a blown fuse indicator LED/neon lamp so I would know what was going on.  A popped circuit breaker you can see or feel.

Mike

At 20:54 2004-06-05, you wrote:

Yes, John,  I have also read Bob's well thought out and reasoned philosophy about fuses and circuit breakers.  However, after over 2000 hours of military flying there is no question that temporary conditions have caused circuit breakers to pop and they have successfully reset. Having had access to the military maintenance reports on such and with all respect to Bob (who I do respect, indeed) there was never ONE case where it was the circuit breaker malfunctioning.   I disagree that there is danger to the wiring by resetting a circuit breaker, if it is a sustained overload (wire shorted to ground), the circuit breaker will not stay engaged (even if you hold it in - I know I've tried) so the wire will not melt.  On the other hand, if it was a temporary situation then a reset may well get you your equipment back.
 
However, I do agree, that you certainly should go with the philosophy you feel most comfortable with.  That's certainly why I stay with circuit breakers and others chose fuses.  Hopefully a fuse will never blow and a circuit breaker will never pop {:>)
 
 
Ed Anderson
RV-6A N494BW Rotary Powered
Matthews, NC

----- Original Message -----

From: John Slade

To: Rotary motors in aircraft

Sent: Saturday, June 05, 2004 11:29 PM

Subject: [FlyRotary] Re: LS1 Coils - amp draw?

Ed said:

 John,  I don't know the current draw, but I would strongly suggest that you replace fuses in critical circuits like ignition with quality circuit breakers.  Fuses are OK and have their place and I used them in my aircraft but,  in my opinion they do NOT belong in a critical circuit.  I have never reset a fuse, but I have reset circuit breakers that popped due to a temporary overload and got the system back in operation.  FWIW

 

Ed,

As always I appreciate you're input. As you probably know, this is an age old discussion which has been played out ad nausium by people far more qualified than I.  Bob Nuckolls had a very comprehensive paper on the subject on his web site http://aeroelectric.com

 

I think the logic goes something like this:

 

1. It is better to plan for a failure and be able to complete the flight without the offending item, than it is to try to ensure that the item never fails. It WILL fail sometime. Take a look at his product "guarantee".

 

2. If a circuit breaker pops, either you have a bad breaker, or there's a reason for the overload. Resetting it in the second case is a bad thing, since you could now be overloading the wire.  If it had been a fuse, then you wouldn't have had to reset it in the first case.

 

3. If a fuse blows, or a breaker pops, then the right thing to do (according to Bob) is to continue with you're backup plan and fix the problem on the ground. In this case that meant run home on trailing coils only. (not that I knew this at the time)

 

Of course, many old and bold flyers have stories of saved bacon from resetting breakers. We've all heard them, and I believe them. Bob would [and does] argue that these incidents were mostly bad breaker incidents, and there should have been a backup plan that didn't involve resetting the breaker. Given this argument, a fuse is more reliable.

 

In my case, maybe the coils take 7 or 8 amps each. I'd designed the circuit for one coil, forgetting that there was double the draw because there were 2 coils on each circuit. So, perhaps I was in danger of seriously overloading the wire. Had I reset a breaker maybe I'd have had a fire to deal with instead of just a rough engine. Not a bad example of Bob's point.

 

Understand, I'm not so much arguing for one side or the other, as I am making sure that both sides are presented. I chose to follow Bob's logic. However - trying to cover my back (in case he was wrong) my fuses are within reach during flight, and I have spares lined up on the back of the fuse panel. :)

 

Regards,

John