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mhilderbrand

Joined: 28 Sep 2006
Posts: 36

Posted: Fri May 01, 2009 1:08 pm Post subject: Switch

Hi everyone, 

  

 I bought a handful of 1-2 switches for various items i.e., landing lights, strobes, left & right mag, etc.  My question is can I use the same switch for the master and alternator? Looks like sometimes people are using the 2-3 and only having one switch - being multifunctional. Since I now have a small surplus of 1-2 switches, I thought I might just use them instead. This will be on the Jab 3300 engine. As you can tell I am ignorant to this area... but I am trying to learn! Thanks!  

 

Michael Hilderbrand

Derby, Kansas

Http://www.kansasflying.com  



 [quote][b]

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nuckolls.bob(at)aeroelect
Guest

Posted: Sat May 02, 2009 5:24 am Post subject: Switch

At 04:05 PM 5/1/2009, you wrote:

  	  Quote: 	
		  Hi everyone, 

  

 I bought a handful of 1-2 switches for various items i.e., landing lights, strobes, left & right mag, etc.  My question is can I use the same switch for the master and alternator? Looks like sometimes people are using the 2-3 and only having one switch - being multifunctional. Since I now have a small surplus of 1-2 switches, I thought I might just use them instead. This will be on the Jab 3300 engine. As you can tell I am ignorant to this area... but I am trying to learn! Thanks!  

  	


     The first batteries to go into aircraft were

     charged by generators. Unlike many if not

     most alternators, generators would come on line

     and run by themselves as a useful power source.

     

     It was common and practical to control the

     generator and battery with their own separate

     switches.



     When alternators began to replace generators

     in the 60s . . . we found that product of the

     day was best operated with a battery on line.

     This insured that (1) the alternator would have

     excitation power available to go to work and

     (2) there was a battery always available to

     avoid stalling a self-excited alternator when

     hit with a hi-inrush load (like landing gear

     motors and/or landing lights). 



     Hence the development of the infamous "split-

     rocker" master switch for single engine light

     aircraft.



 [img]cid:.0[/img]



     This product's rockers were mechanically interlocked

     to prevent an alternator from being on line

     without a battery . . . yet allows the battery

     to be on without the alternator.



     This functionality is emulated by the use of the

     progressive transfer 2-10 style switch. Alternatively,

     some Z-figures show a 2-3 that brings the battery

     and alternator ON and OFF together. This is okay

     too as long as you have a means by which the

     externally excited alternator can be shut OFF for

     ground maintenance activities.



     In the case of Z-13/8 I suggest a 2-3 switch

     when paired with the crowbar ov protection that

     calls for a pullable circuit breaker co-located

     with the DC POWER MASTER switch. In the switch

     panel options drawing at . . .



  http://www.aeroelectric.com/PPS/Switch_Panels/spanel.pdf



      . . . all configurations illustrated show a 2-3

     DC PWR MASTER and a 5A pullable breaker. In this

     drawing . . .



  http://www.aeroelectric.com/PPS/Switch_Panels/Switches.pdf



      . . . the 2-10 switch is suggested for a DC PWR

      MASTER. The pullable breaker allows for disabling

      the alternator for extended ground operations of

      the electrical system with the engine not running.



      You can certainly used independent switches to

      control the battery and alternator. However, it

      is incumbent upon you to understand the limitations

      of the equipment items you've installed and to

      educate yourself (and anyone else who might fly

      your airplane) as to the proper operation of those

      switches consistent with those limitations.



 

        Bob . . .



        ----------------------------------------)

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

        ----------------------------------------

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