Brent has written much on this topic including "In my "Glazed and
Confused" presentation on "Glass Cockpits" I say that flying an
aircraft with a non-certified, non TSO'ed glass standby (Dynon et al)
is like jumping out of an airplane with only your main parachute and
your standby plan is the fact you are wearing real soft socks."
I concur.
When I was young and stupid (not long ago) I had thoughts of long
overwater (think trans-Pacific) flights. I also have experience
with failure modes assessment analysis (FMEA) which frequently shows
up failure modes easily over looked. After reviewing various
electrical and instrument configurations I arrived at a system design
which is shown in simplified form in the attached sketch. It
consists of two alternators, two batteries, four busses, and a lot of
opportunities for cross tie. I use dual Chelton screens, with
PFD off the essential buss (many sources of power), the MFD off of the
avionics bus (which has many sources of power), and back up electric
attitude indicator (on essential buss), turn and bank (essential
buss) and air speed and altitude indicators.
You show me the failure and I can show you the automated or
manual work around. And critical stuff is all double protected
with circuit breakers and surge arresters (not shown).
But even this diagram is not as safe as it could
be. What about something simple like: a battery relay
decides to go flotch? (One already has done so.) That
causes a main bus to go south forcing you to a cross tie solution, not
ideal. So not shown are by-pass switches and fuses around the
relay solenoids I added "just in case" to provide redundancy on all
supply routes.
I have a mechanical and electrical fuel pump. And I have an
electronic ignition and a magneto.
Two of everything, independent power modes, independent pathways,
cross connects, multiple layers of electrical spike and surge
protection and independent and different principles of gyroscopic
display and electrical power supply. Now one begins to
achieve realistically (and defensible) high levels of
reliability.
If I could only achieve the same with the pilot.
Fred Moreno