FMEA - RV14 Dual Alt / Dual BATT / SDS EFI

[TASEsq]

I thought i would share the FMEA i have been working on for my RV-14. It will be an electrically dependent aircraft.

This was a pretty useful process - it highlighted some operational checks i realised i needed to add (some at each flight, some monthly (occasionally) and some at the 100 hourly). It also showed me i think i need to go with 2 seperate firewall ground blocks for redundancy - otherwise everything is coming back to one bolt!

I still have to decide if i want to dual feed my essential bus with diodes (i have a couple there so it wouldn't be hard). But it is only guarding against a single failure (the shorting of the essential bus feed wire), so may not be worth it.

If anyone is bored and wants to take a look the whole docuement is here:

FMEA VH-TBA SDS-EFI.xlsx

docs.google.com

Otherwise, the printouts are attached.

Welcome any feedback!

 

[lipper03]

Think with a little moving around it can be used on a VPX system, non elec. dependent (dual pmags, not sds)?

 

[Carl Froehlich]

Trent,

Is engine start with both batteries in parallel?

Carl

 

[TASEsq]

Trent,

Is engine start with both batteries in parallel?

Carl

Not unless there is a need.

The engine bus and essential bus would be on one battery, the main bus (secondary power feeds) and starter on the other.

Normal start highlighted in green.

The wire sizes would support starting with both batteries if I opened the x-tie. (Highlighted in red) The GAD27 Keep alive would keep all the main items going throughout the start.

 

[Carl Froehlich]

Not unless there is a need.

The engine bus and essential bus would be on one battery, the main bus (secondary power feeds) and starter on the other.

Normal start highlighted in green.

The wire sizes would support starting with both batteries if I opened the x-tie. (Highlighted in red) The GAD27 Keep alive would keep all the main items going throughout the start.

I suggest you consider the normal POH starting procedure with the batteries in parallel. Easier on the starter, easier on the batteries, easier on the avionics (less buss voltage droop) and no down side. Split them out after start if you want.

Carl

 

[N10KE]

The cross tie breaker is pretty easy to install. Engine starts easily anyway with SDS, but as Carl said - you have two batteries and using them both for start is easier on all of the electrical components. I used Gigavac mil-spec contactors (electrically dependent like you) and for the cross-tie - used one with an additional contact for feed to an input on the GEA/GDU for alerting so I don't forget to open the cross-tie after start.

 

[TASEsq]

Thanks for the input. I’ll mull that over.

My thinking was that the one earthx should be capable of starting by itself, and by keeping them seperate I’m leaving a battery with little or no abuse on the engine bus side. I can swap it into the other side every couple of years and replace the engine bus side battery with a new one.

If the starting battery is starting to struggle then it’s time to go!

Just where my brain was at - not saying this thinking is correct.