News: Added Links For Twin Commander and Facebook Pages

Login  |  Register

Author Topic: Start Auxiliary Bus on 690 series  (Read 269 times)

Roberto Serrano

  • Newbie
  • *
  • Posts: 10
Start Auxiliary Bus on 690 series
« on: December 17, 2022, 12:08:09 pm »
What is purpose of the start auxiliary bus on the electrical system on the Commanders 690 A/B series.

Roberto Serrano

donv

  • Administrator
  • Hero Member
  • *****
  • Posts: 2957
Re: Start Auxiliary Bus on 690 series
« Reply #1 on: December 17, 2022, 03:23:53 pm »
We really need Barry Lane to answer this one... even though I was flying a 690A this summer.

donv

  • Administrator
  • Hero Member
  • *****
  • Posts: 2957
Re: Start Auxiliary Bus on 690 series
« Reply #2 on: December 19, 2022, 04:51:30 pm »
After looking at my FlightSafety manual, I believe the purpose is to prevent 48 volts from going into the electrical system during a series start. During a parallel start, power goes from the #1 battery through the start auxiliary bus and powers the left side of the aircraft, while power from the #2 battery powers the right side.

In a series start, the start over voltage relay opens and only the #2 battery is powering the distribution busses, through the start bus and the diode protecting the start aux bus.

The JetProps (840/980/900/1000) have a simplified system where the batteries don't have to go through the start bus to power the distribution busses in normal operation.

Roberto Serrano

  • Newbie
  • *
  • Posts: 10
Re: Start Auxiliary Bus on 690 series
« Reply #3 on: December 19, 2022, 07:17:43 pm »
Thanks appreciate your time !!
Roberto Serrano

donv

  • Administrator
  • Hero Member
  • *****
  • Posts: 2957
Re: Start Auxiliary Bus on 690 series
« Reply #4 on: December 27, 2022, 11:53:46 am »
When they developed the JetProp series (840/980/900/1000), they really took a hard look at the systems. The 690B is an evolution from where they were with the 680 series, with things tacked on here and there and everywhere... the JetProps took a clean look, and really simplified and improved a lot of stuff.