Mailing List flyrotary@lancaironline.net Message #67767
From: Stephen Izett stephen.izett@gmail.com <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] N214FL forced landing
Date: Wed, 1 Jan 2025 16:43:31 +0800
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Yes. You’re right, another single point of failure. There are many!

I ranked this switch as a lower risk of failure than say a set of relays that then introduces other fuse/circuit breakers, connections, switches etc.

I originally had tracy’s switching to the injectors that turned off the Primary or Secondary injectors doubled the fueling to the others.
I removed this feature as I decided the risk of an injector failing as being lower than the risk of the switches failing or being knocked and not noticing.

I questioned having the backup Engine pump trigger circuit except I have had a failure of a pump and noticed how often I forgot to turn on the backup pump. 

I originally used a Narva automotive ignition switch feeding all engine power and single point of failure. It died from too much current for its spec - my very foolish mistake, which is why I now have the Primary and Backup Engine Power Switches.

I realised I have many single points of failure eg. My soldering of the D37 EC2 wiring being one of many. A number of these wires/pins breaking will ruin my day and I wonder if I have tied these looms well.

I would appreciate peoples thoughts on where they see the higher risk points in their systems.

I suppose we must choose our poison. 
An example was it appears to me that Fuel management failure stops engines at a comparatively high rate, so I went with the Engine pumps drawing from the 8 Gal Header tank with circulation pump/backup from main wing tank.
No Fuel Switching BUT complexity of pumps needed to keep the header/reserver tank full at all times.

Happy New year

Steve











On 1 Jan 2025, at 12:13 pm, Charlie England ceengland7@gmail.com <flyrotary@lancaironline.net> wrote:

# Twin 25Ah batteries connected via dual battery isolator switch Off / A / B / BOTH

Single point of failure? If that's the only path for electrons, switch mechanical failure takes both batteries.

On Dec 31, 2024, at 6:56 PM, "Stephen Izett stephen.izett@gmail.com" <flyrotary@lancaironline.net> wrote:
Sorry to hear of your mishap Finn, glad your Ok.

Much appreciate your reflection and to revaluate my own risk

I agonised over the electrical risk / failure modes. Opting to ‘kiss' and not seek full redundancy.
Your experience brings a sober reconsideration of my assumptions and decisions which I’m trying to recollect and would value others critique.

My system:
# Single automotive Alternator - Fused B-lead - NO Over-voltage Crowbar circuit
# Twin 25Ah batteries connected via dual battery isolator switch Off / A / B / BOTH.
# Engine Power through Primary SPST switch with backup SPST upstream of current shunt
# Primary and Backup Fuel Pumps with automatic backup activation on low fuel pressure
# Engine Fuel pumps fed from Header/ReserveTank. Header fed via single wing tank via Primary and Backup transfer pumps
# EC2 redundant ECU's
# Armoured CAS wiring
# ‘Audible' EFIS Alarms for Volts, Amps, Fuel Pressure, Transfer Fuel Flow, Fuel Level, Gear etc.

Pre Flight Testing
Before Engine Start
# Measure individual battery volts while 2 x main 25Ah batteries disconnected (Isolator switch in Off position) via EFIS on its own battery backup  delta V < 0.3v if OK then switch isolator to Both
After Engine Start
# Check Alternator Charging Both A, B and back to Both batteries.
# Test Both Primary and Backup Engine Power Switches
# Test Engine Fuel Pumps - Switch Off Main Pump to test auto activation of backup, reset/arm
# Test Fuel Transfer Pumps - Switch Off Main Transfer Pump to test auto activation of backup, reset/arm
# Test ECU B and Coils
After Engine shut down
# Turn battery Isolator Switch to Off position and note Battery delta V before turning Off EFIS

My Key Failure mode consideration / assumptions
Alternator -
Short Circuit (Low risk but catastrophic) must be protected against via fuse
Over Voltage (Low risk) - EFIS Alarm - On reflection perhaps I ought include a Crow Bar but it does introduce complexity/danger
Batteries -
Open Circuit (Significant risk) - Solution - two batteries tied together reducing chances of failure and protects should failure occur
Shorted Cell (Low risk) - Outcome ???? Battery fire - Halon extinguisher 
Testing before and after flight picks up failure and lowers risk 
Keep Batteries away fro heat and vibration
Second battery provides more air time in case of Alternator failure though introduces significant weight
Crank Angle Sensor - 
Failure is catastrophic so armour and attention added 
Power Switching - 
Failure (High risk) therefore backup required 
No Relays as they introduce complexity

Key Questions
Crow Bar on Alternator?
Should I have gone with AeroElectriic circuit with Backup Buss etc. ?


Appreciate peoples thoughts.

Steve Izett - Perth Western Australia
Glasair Super II RG 
Renesis 4 port EC2 EM3 RD1C Prop MTV 7 Elec









Steve Izett.



On 1 Jan 2025, at 3:55 am, Finn Lassen finn.lassen@verizon.net <flyrotary@lancaironline.net> wrote:

Not sure if I should re-post the following and its two referenced threads here.

https://vansairforce.net/threads/n214fl-forced-landing.232017/

The battery failure mode must definitely be made well-known for electrical-dependent engine installations.

Finn



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