Schottky Diode failure mode

[Strikhedonia]

I can't see a scenario where I could get a load dump on my system but I prefer to add protections when possible. If anyone wondering what to buy, I have Littlefuse SLD15U-017 on order for my plane.

 

[dmn056]

The Cirrus example below. Without measurement, we don't know if they are actually needed.

Thank you. That's very interesting, not quite the way I expected it.

 

[RVDan]

This is the voltage spike waveform from RTCA DO-160 that we would typically test avionics and other equipment to. It is meant to cover bus transients from multiple bus/ source switching and relay coil spikes and such. The baseline voltage is bus voltage and then the 600 v spike is applied. Your design should employ diodes that would be able to deal with this.
I work projects for lightning protection of prop deicing, and we employ TVSs in the design to deal with the potential for large spikes. The thing to consider is that we require TVS replacement after a known lightning strike. Performance of TVSs declines after they have performed their function.

 

[clutch22]

Update:

I've been meaning to give an update on my situation, but have been putting it off. Dan reached out to me so, I'll update publicly.

I received my new replacement diode pair & heat sink in the mail last week, and went to install it the next day.

Side note: I recently moved 3 hours away from where the project is located.

Due to the size of the heat sink, I spent about 3 hours getting everything installed. It was late at night and things were looking hopeful for a first flight the following morning.
I went to do one last "torquing" of the terminal screws, and like a sign from above, I felt a sudden 'pop' as the diode housing material broke away, leaving a flimsy terminal post behind!
I shouted some 'words', but after a few minutes my tunnel vision opened on this whole Diode situation.

Many of you had me not feeling very confident in the use of a diode. It is the last pathway before voltage hits my engine bus. And if it were to fail in a way to where insufficient voltage could reach the bus, then well you know....

After the new diode broke I decided to do away with the idea of both batteries always feeding that bus (see previously posted sketch). Now, Battery one feeds the avionics (vp-x), and Battery two feeds the engine bus.
There is still a cross-feed contactor used so that if either alternator goes down or some other Battery fault, I can close the bus-tie switch and kill either battery master and everything should be fine.

So, the following morning, I modified the wiring per that plan and made my First Flight by 10 AM !