Electrical System

JetExec Electrical Wiring Diagram.
Overall wiring arrangement, looking from front toward back of the helicopter.
      I spent 4 or 5 years working out the instruments, wiring diagrams and electrical details. I started with the RotorWay Exec standard wiring drawing. I incorporated the KISS turbine wiring details. I got my Private Pilot license so I would understand what instruments, gauges and avionics were needed and how I should lay out the panels. (It seemed like a good idea.) I drew wiring diagrams for the complete JetExec. I read Bob Nuckolls' book The AeroElectric Connection and reworked all of my electrical drawings. And finally, I started building the panels and wiring the helicopter.

      Power to all circuits is fused with BUSS automotive fuses. The lower fuse block (bottom 12 fuses) receives main battery power from a 30A self-resetting breaker (SRB) off of the ammeter shunt. I split the upper BUSS fuse block strip in half. The upper left 4 fuses are fed from the Instrument Power fuse and switch, and the upper right 4 fuses are fed from the Avionics Power fuse and switch.

      Here is a partial diagram of the main power circuits, showing how power is supplied to the Main Power, Instrument and Avionics Bus circuits.

      The instrument and switch panels were wired with Molex connectors for easier installation and removal.
      Here is the main panel with alarm LED's wired (red and black wires) to the central LED board. The green and white wires are from four Nulite light ring bezels used to illuminate the 3-1/8" airspeed, dual tachometer, altimeter and VSI gauges. I bought internal lamp kits for all of the 2-1/4" Westach gauges for the JetExec, which can be seen wired in the following panel pictures.
      Finished wiring and air connections, with a few more close-ups of the main panel: Instr10.jpg; Instr11.jpg; Instr12.jpg; and Instr13.jpg; and lower panel wiring Instr14.jpg and Instr15.jpg.
      This is the initial mounting plate I fabricated from 0.063" 4130 CrMo steel for the Main and Aux battery. (The legs were a little flimsy so I added a triangular side piece seen in the picture below.)
      The finished mounting plate, with rubber pad and straps to keep the batteries in place, fastens onto the existing tub support mount tubes.
      The Main battery, contactor and Auxilliary battery mounted to the support plate. The Main battery is an Odyssey PC925. It and the alternator provide all main power to the helicopter. The Aux Batt, a PowerSonic PS-1250, provides power to the governor, and additional voltage for the turbine ignitor and Start Fuel solenoid during the turbine start sequence.

      Here is a partial diagram of the Turbine Starter Relay circuit, showing how the M-Gov/Starter switch and the starter relays put the Main battery and the Aux battery in series to provide 24VDC to the turbine igniter and Start Fuel solenoid during the turbine start sequence.

      In 2016, another JetExec builder came up with the idea of using a 12VDC to 24VDC voltage converter to power the Turbine Exciter and Start Fuel Solenoid during the start sequence. This is an excellent idea and I highly recommend it, as it eliminates the two relays that put the two batteries in series and it really simplifies the starting circuit. My helicopter was complete by this time though so I have not gone back and modified my own wiring nor have I changed any of my electrical drawings to reflect this.

      The main power circuit (battery and alternator) also provides power to the turbine governor and to recharge the Aux Batt, through the M-GOV switch. The Aux Batt provides power directly to the turbine governor through the A-GOV switch. When both the M-GOV and A-GOV switches are on, the main power circuit is connected to the Aux Batt and governor through a Schottky power diode, which allows the Aux Batt to be charged and protects the governor power circuit from any main power failure. (I used the Schottky diode in lieu of a third relay, R3, used in the standard JetExec turbine wiring diagram.)

      Here is a partial diagram of the Governor Power circuit. The diagram also shows how the Fuel Pump switch, A-GOV switch, the JetExec governor overspeed relay and the RotorWay inertia switch all interface with the Fuel Boost pump and Fuel Shutdown solenoid valve.

      The wiring is nearly complete here, with Velcro to hold the Molex connectors down. I do still need to add a landing light and relay and run coax for the radio and transponder antennas.

      Upper right in the picture is an AeroElectric Connection LR3C-14 Alternator Regulator used to control the alternator voltage and to provide overvoltage protection and high/low voltage warning indication.

      Here is a partial diagram of the LR3C-14 Voltage Regulator circuit.

      Just inside to the left of the alternator regulator is an AeroElectric Connection DIM 15-14 Instrument Light Dimmer module. It provides power to all of the Nulite ring bezels, and Westach gauge, magnetic card compass, and radio and transponder internal lighting.
      The alternator is an Autozone Duralast / Schucks 14668 ND100211-203 or 10021-757, rated 67 Amps at 13.7 Volts. I removed the internal voltage regulator and wired the field coil to ground and to the Ig (Field) terminal using the method described in Lynn French's EAA Experimenter article One-Wire Alternator Conversion.
      A double junction box mounted on the passenger side of the helicopter has a few main power components on top and provides RF isolation for the governor below. (Lids to both boxes are removed in this picture.)
      The governor RF isolation box, before I attached it upside down to the power box below. Connections to the governor RF isolation box are accessed inside the power box.
      Main Battery power from the contactor feeds into the power box through an insulated terminal in the upper left, which connects through an ammeter shunt block to three BUSS 30A self-resetting circuit breakers (SRB's). Two of the SRB's receive power from the alternator and the third SRB provides Main power to the instrument console fuse block.

      The Turbine Starter relays R1 and R2 are on the right. Connections to the govorner RF isolation box are along the bottom.

      An additional covered junction box (lid removed) is mounted directly above the fuel pump on the pilot side of the helicopter. It is a convenient place to centralize and test all of the wiring connections for the fuel pump, oil cooling fan, lighting, pressure and temperature senders and switches, the fuel shutdown (Divert Fuel) valve, chip detectors and thermocouples. The diodes are isolation and flyback diodes for the shutdown valve, fuel pump and oil cooler fan.
Whelen Nav/Strobe Light       The Nav/strobe lights are Whelen MicroBurst III LEDs. Boy are they bright!
Last Updated: March 18, 2017
Send Mail to: pete@swanstrom.net
Return to: | Pete's | Helicopter | Home Page