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Bob says,
"When the failure manifests itself by opening the breaker or
fuse likelihood of recovering the system by replacing a
fuse or pushing in a breaker is very, very small."
Beneath it all, this is what all the fuse versus circuit breaker discussions hinge on. It is an incorrect assumption, in my experience.
A very large percentage (but by no means all) of electrical problems in vehicles are intermittent in nature. You can very often reset the breaker and restore the critical system long enough to safely land the aircraft. A fuse does not give you this option, at least not in a timely manner.
To be realistic, don't most of the multi-reset stories start in old/poorly maintained/poorly designed/etc aircraft?
Since our airplanes do not come off an assembly line with millions of hours on identical prior production aircraft, they might possibly fall under the category of "poorly designed" since each of our airplanes is pretty close to a prototype with none of the bugs worked out (at least during the fly-off hours.) None of our freshly-built airplanes, especially those with a one-off non-standard engine installation could be called a "mature" design. I would never call a design "complete" until there were many failure-free hours on the prototype. You always change something in the design after the prototype is built and you often find out the design flaws the "hard way."
Even well-designed, well-maintained aircraft have electrical problems. To quote "The Breakfast Club", "The world is an imperfect place. Sometimes screws just fall out."
Both Tracy and I (and others) have given examples of how resetting a CB made all the difference in averting (or at least deescalating) an in-flight emergency. These examples may be anecdotal, but the fact that several people in a small group have had similar experiences strongly suggests that resettable CBs add some degree of safety. They certainly do not detract from safety.
I really think that the cornerstone(s) of his endorsement is more along the lines of 1. you don't have to have a 50 year old design & 'aircraft (poor) quality' factory electrical system in a homebuilt
A 50 year old design is a "well-proven" "well-tested" and "mature" design that has stood the test of time. Unexpected failures are less likely in such a product. There is a Darwinistic culling of critical design flaws in mass-produced (or oft-built) aircraft. :^)
and 2. you can design critical-to-flight systems to have automatic or flip-a-switch backups. The reality is (as he's stated many times) *nothing* is failure proof. His philosophy is that you design the system with redundancy to trump any single failure.
The desire to go with fuses is primarily motivated by cost and weight, not by safety. Breakers are safer. That is why there are no fuses in commercial aircraft. If fuses were safer, that is what they would put in commercial aircraft.
Many (by no means all) homebuilders are motivated primarily by cost, and not so much by safety. That is why fuses appeal to many homebuilders. If circuit breakers were as cheap (and small) as fuses, almost no one would select fuses. In an aircraft application, there is no advantage to a fuse aside from cost and weight.
Everyone's got to make their own choices but it helps to start with the right assumptions.
It is more about deciding on what is most important to you, cost (weight) or safety. The safety difference is not non existent, contrary to what is suggested by Bob. You must determine what that additional degree of safety actually is, and then decide if it is worth the money and weight to use a CB instead of a fuse.
As much as the safety folks hate to admit it, it always comes down to the cost/benefit ratio. At some level, you must choose accept a given degree of risk for a given degree of cost savings. I personally think that CBs add a degree of safety that is worth the extra money they cost for flight-critical systems. For things like the CD player, a fuse would be OK with me, but not for the fuel pump.
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