| 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:
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