Concerning the earlier question about chip lights preceeding a major failure, it would be hard to prove in many cases, but I'm aware of at least one case where the chip light probably did prevent a large bang.
I was FTE on an options development program using a brand new BK117-A3. We had one engine chip light at about 10 hours total airframe time. We found what we though was normal manufacturing fuzz on the magnetic plug. The plug was cleaned, and we pressed on. About 5 flying hours later, we had another light on the same engine.
This time we found some bigger chunks on the plug, and did a more thorough investigation of the helicopter. The first thing we found was slivers of turbine blade material imbedded in the tail rotor. The next thing we found was a crumbling bearing on the power turbine shaft, which was permitting enough radial slop on the shaft to allow the turbine to rub on the ID of its housing. The tips of the blades looked liked they had been chewed by rats.
This is exactly the failure mechanism that previously produced at least one fatal accident in an LTS 101 powered twin. The engine operated with the crumbling bearing long enough to cause the turbine to come apart completely, and chunks of it took out the other engine.
The only reason I'm able to tell you about this today is because our pilot was a "by the book" man, and he shut down the engine when the light came on (as per the FLM of that time).