gmcjetpilot
Well Known Member
I was thinking of a better way to wire the aircraft. It seemed over kill to have three solenoids under the cowl:
FW Master: Has to be large to handle up to 300 amps flow thru to the starter
FW Starter: It is redundant.
Starter: Modern aircraft starters (SkyTec) all have their own solenoid
If you wire the battery to the starter direct you will by pass the firewall starter relay, which is not longer needed. Also since you no longer have to feed the starter current thru the master you can use a small relay (solid state) to supply the "switch" master buss in the cockpit. The mess on the fire wall has always looked terrible and has many large connections. This alternate way will save +2 lbs and almost 1 amp of wasted current (12 watts) in wasted power to the master contactor. Picture below:
I think this will work with no loss in function or safety. I suppose you could argue that the starter engages and back-drives as a generator. What is the chance of that? Slim or nil. Well if it is a concern add the firewall starter relay back. I see no reason to have a big old firewall master relay.
George
Her is a little more detail with NipponDesno ALternator (I-VR) wired in:
FW Master: Has to be large to handle up to 300 amps flow thru to the starter
FW Starter: It is redundant.
Starter: Modern aircraft starters (SkyTec) all have their own solenoid
If you wire the battery to the starter direct you will by pass the firewall starter relay, which is not longer needed. Also since you no longer have to feed the starter current thru the master you can use a small relay (solid state) to supply the "switch" master buss in the cockpit. The mess on the fire wall has always looked terrible and has many large connections. This alternate way will save +2 lbs and almost 1 amp of wasted current (12 watts) in wasted power to the master contactor. Picture below:
I think this will work with no loss in function or safety. I suppose you could argue that the starter engages and back-drives as a generator. What is the chance of that? Slim or nil. Well if it is a concern add the firewall starter relay back. I see no reason to have a big old firewall master relay.
George
Her is a little more detail with NipponDesno ALternator (I-VR) wired in:
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