These have been around in the homebuilt world for a long time; various previous threads here.
What are the main certification challenges?
Single point of failure
Indeed, but
I looked at the VP-X when designing the electrical system for my IMC-capable RV-10. There were several reasons why I didn’t go for it:
However, I do think they have a place in the market. If you are building a VFR aircraft and you don’t want to get into the details of electrical systems, this is a pre-packaged solution for you. Many builders are comfortable with mechanical work but eschew anything electrical and this is for them. Another (minor) advantage is that you have a wider choice of switches for the panel, because they are low current. It also works for those who love gizmos.
As to solid state breakers in general, they sound like a good idea to me, it’s when you integrate them all under a single controller that I become uncomfortable.
That’s very interesting – many thanks Raiz.
I was wondering how I would design such a product. It’s not trivial. You have to deal with 1000+ amp currents, which is OK but the MOSFET has to be turned off really fast, so it can’t be done with a micro, in software. The overcurrent trip needs to be analog. But then you need programmable trip levels, so the trip level has to be set with a DAC. You also need a “memory” that a circuit has tripped so the trip event needs to be stored (by a microcontroller) in an EEPROM. I sat down and worked out a circuit for it and it is a lot of items for every protected output
The microcontroller etc is likely to be a big single point of failure. If it crashes, you should still get “crude” short circuit protection but only at the highest programmable current level, and the trip state will be lost at power-down.
If they do have an ADC (to monitor the current drawn) per channel, it would not surprise me if they implement the overcurrent trip wholly in software. It’s really tempting to do that… but very dodgy.
Microcontrollers crashing is a whole lot more likely in “plastic” homebuilts with no antistatic layers in the composite, whole-airframe bonding, static wicks, etc. It was bad enough in Diamonds, and others, in the early days. An RV would be fine, of course.
A solid state breaker of any kind needs a microcontroller and an EEPROM to store the “tripped” state. How do the new airliner breakers display the state? Is it an LED? If so, it must have power to display the state. That’s an interesting problem in itself. I wonder if @antonio has come across these.
I believe they must be using these ST E-fuse or similar from a different manufacturer.
You don’t necessarily need the DAC – if you’ve already got an ADC, you can use pure logic for the trip and not require software.
How would an ADC do anything useful without a CPU reading it? The only way I see is a parallel output one and a comparator, but parallel ADCs are rare these days.
You don’t need a parallel ADC – even a small CPLD has enough logic resources for a few shift registers and the clock generation – I’ve done it.
Some low cost FPGAs have enough resources to implement not just the above, but a full blown OpenRISC CPU with onboard RAM as well.
Of course, everything is possible. 6 months’ work 
I’ve spent years as an FPGA design consultant (Xilinx) so yeah it’s all possible. But it would be a very awkward way to do it.
Doing it so it is reliable, especially against static issues, is another thing.
I do think one needs a two-level current trip. A very fast (1 microsecond or so) trip at say 100A, implemented in hardware for max reliability, and then the software-programmed one which can have a different value for each virtual CB.
The fast one could be a single global trip; no need to do it per-channel. But then you lose one of the major benefits.
