Charlie, I divided the leading from trailing under the cowl near coils & installed two 20A spade fuses in covered fuse holders, if a trailing coil shorted internally it would cause fuse for both trailing to stop working & I fly on leading coils to landing. David R. Cook RV6A Rotary Lansing Michigan.
From: "Charlie England" <flyrotary@lancaironline.net>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Thursday, July 17, 2014 2:14:43 PM
Subject: [FlyRotary] power circuit design, was: actual current use by a rotary?
Well, time for some followup.
My 1st draft for circuit protection looked a lot like what Steve describes (thanks, Steve), with individual fuses for virtually everything, including an individual fuse for each injector and each ignition coil. After ruminating over the actual loads for the injectors & coils, I'm having second thoughts. The GM coil harness I have in hand has a single DC power wire for all four coils that it feeds (obviously isn't a part intended for flight, but included in Tracy's installation manual).
The obvious concern is whether an individual coil or injector failure has a statistically significant risk of taking out the power supply that's fused for the total load. If there's no statistically significant danger, weight & complexity could be reduced by feeding the coils and injectors as groups.
So, is there any consensus on how to handle injector & coil wiring? IIRC, there have been some coil failures in flight; were those planes wired with a single fuse/breaker protecting all the coils, or with individual fuses/breakers for each coil? What about the injectors?
Any failure modes I'm missing? (other than a dead short on a supply wire, of course)
Thanks,
Charlie
On 7/1/2014 10:13 PM, Stephen Izett wrote:
Charlie
Don’t know if it is wise but I have wired our electron traffic management as follows:
1. A Main 32 way blade fuse block which is broken into two busses: A & B being -
(The blade fuse block enables me to patch a current meter to any circuit to see whats happening. Helpful when setting up or trouble shooting but just nice and compact otherwise BUT I can’t just re-energise a circuit like with circuit breakers, though blade size circuit brakes do exist nowadays. This main fuse block is mounted directly below main system switches so is very accessible)
A. FLIGHT CRITICAL (16 fuses) fed by a keyswitch:
EC2(A), EC2(B), EM3, O2, Prop Pitch, Engine Fuel Pres Pump, Engine Backup Fuel Pres Pump, Fuel Transfer Pump, Backup Fuel Transfer Pump, Pri Fuel Injectors, Sec Fuel Injectors, Leading Coils, Trailing Coils.
Notes 1. All engine fuel is fed from a header tank of 8 gallons with the transfer pumps feeding the header from the main wing tank
Note 2. Separate power and return feeds to Pri and Sec Inj & Leading and Trailing Coils, fuel pumps.
B. AVIONONICS (16 fuses) feb by Avionoics master switch:
RHS Dynon EFIS, FHS Dynon EFIS, Flight Computer of my own, Com Radio, Transponder, Autopilot servos, Position Lights, Strobe Lights etc,
C. LANDING GEAR PUMP switched through seperate breaker (this mongrel draws ~30 amps)
Our airplane is plastic so return lines are very important. We have separate main return paths - quiet and noisy.
Steve
Wow, Steve, that's great detailed info; I was just hoping to get the total. I was expecting the injectors to draw more than the coils, but with all the coils together under 5 amps (and even better for the injectors), then my wiring architecture can get a lot simpler.
Many thanks,
Charlie
On 7/1/2014 7:19 PM, steve Izett wrote:
Hi Charlie
I think these are in the ball park but not measured under flying conditions only idle.
ENGINE
EC2 .3
EM3 .5
COILS (D585) 5
INJECTORS (Renesis) 2
FUEL PRESSURE PUMP x 1 8.4
FUEL TRANSFER PUMP x 1 1.6
O2 SENSOR 0.6
Total Engine 18.4
Steve Izett
Has anyone with an ammeter installed measured their engine's actual current draw (controller, injectors, plugs, fuel pump) with everything but the engine shut down, and the alternator offline? IIRC, Bernie Kerr once did a battery duration test & discontinued after ~40 minutes, but I don't recall seeing any actual current measurements.
Thanks,
Charlie