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Re : wiring

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Gilles.Thesee(at)ac-greno
Guest

Posted: Wed Jul 26, 2006 9:24 am Post subject: Re : wiring

why not wire the  

 	  Quote: 	
		   essential fuel pump directly off the battery - would you not then  

 have  a working pump to get the aircraft down.

 


	


Hi Paul,



This is a good question. The diagram suggested by Rotax is far from being satisfactory. It does not provide electrical redundancy for the fuel pumps. Don't know about the Europa schematic, but chances are they followed Rotax.



It is far safer to run the pumps direct from a more reliable power supply, eg a battery.

This is what I did in our 914. For those interested, there are some details on my website.



Regards,

Gilles Thesee

Grenoble, France

http://contrails.free.fr

josok-e(at)ukolo.fi
Guest

Posted: Wed Jul 26, 2006 10:38 am Post subject: Re : wiring

And i would like to repeat myself:

The chance that the (too?) small capacity generator on the rotax would  

"run away" and fry something is less then an OV protection killing a  

healthy system.



OV protection on the rotax setup is only introducing more failure prone  

components.



In the Europa supplied circuit diagram, one pump is switched from the main  

bus, so will keep working if the alternator switch is off, and the master  

switch on. The other pump is fed directly from the regulator output, and  

will keep running as long as the engine runs, whether or not the master  

and or the alternator switches are on or off. In my humble opinion this  

seems to be reasonably redundant, because i can't think of a single  

component that would kick both pumps out of operation.

The only addition that i would like to have here is a switch or pullable  

breaker for the directly connected pump, because in case of an engine fire  

while flying, it would not be possible otherwise to kill both pumps to  

stop the fuel flow.

The only thing i would leave out is the master relay. The master switch is  

easily rugged enough to switch the full load of this low capacity system.



Is there somebody under us who could redraw the Europa supplied diagram to  

something easier readable? It is a beast to understand the way it is  

presented.

-- 

Kind Regards,



Jos Okhuijsen



workshopcam http://www.okhuijsen.org/plane

http:www.europaowners.org/kit600

mono xs, top on, gear in, tail wheel in, wings set, flapdrive in, tail  

closed, tailwheel in, tail top in, blue stuff filled, sanded and primed,  

fuel system in, doors done, windows in, sanding and filling the fuse and  

wings.

m.j.gregory(at)talk21.com
Guest

Posted: Wed Jul 26, 2006 2:13 pm Post subject: Re : wiring

Jos,



The principal reason why there is no switch for the fuel pump supplied

directly from the alternator is so that it cannot be inadvertently turned

off -- this would require the breaker to be pulled (or fuse removed). 



Issue 4 of the circuit diagram was developed following an incident

experienced by Andy Draper when giving a demonstration flight in a

914-powered Europa.  During the pre-landing checks the handling pilot

switched OFF the number one pump, instead of switching ON the number two

pump, with a result that Andy did not wish anyone else to experience...



Mike



--

josok-e(at)ukolo.fi
Guest

Posted: Wed Jul 26, 2006 3:57 pm Post subject: Re : wiring

Hi Mike,



 	  Quote: 	
		   The principal reason why there is no switch for the fuel pump supplied

 directly from the alternator is so that it cannot be inadvertently turned

 off -- this would require the breaker to be pulled (or fuse removed).


	


I said, switch or pullable breaker.

Of course if the choice is a switch then it would have to be properly  

marked and secured and understood, as a few other switches too. An  

instructor told me, that his only emergency landing followed after a  

student turned and pulled the ignition key and dropped it on the floor. Is  

that a reason to remove ignition locks? Maybe it is 



What frightens me is that some of us, with apparently no understanding of  

the possible consequences make changes in the proposed electrical system.  

And the specialists make it worse by adding too many choices and options  

with the result that the electrically handicapped are completely lost. My  

ten cents: Stick to the factory design, unless you are absolutely sure  

what is involved.



 	  Quote: 	
		   914-powered Europa.  During the pre-landing checks the handling pilot

 switched OFF the number one pump, instead of switching ON the number two

 pump, with a result that Andy did not wish anyone else to experience...


	


The demonstrator had 2 switches for 2 pumps on Andy's last day at Europa.  

Number one secured, yes.



-- 

Kind Regards,



Jos Okhuijsen



workshopcam http://www.okhuijsen.org/plane

http:www.europaowners.org/kit600

mono xs, top on, gear in, tail wheel in, wings set, flapdrive in, tail  

closed, tailwheel in, tail top in, blue stuff filled, sanded and primed,  

fuel system in, doors done, windows in, sanding and filling the fuse and  

wings.

europa flugzeug fabrik

Joined: 13 Feb 2006
Posts: 65
Location: North Coast, USA

Posted: Wed Jul 26, 2006 4:12 pm Post subject: Re: Re : wiring

 	  josok-e(at)ukolo.fi wrote: 	
		  Of course if the choice is a switch then it would have to be properly marked and secured and understood... 	


A locking toggle switch (pull to move up or down) is another approach.



Fred F.

Gilles.Thesee(at)ac-greno
Guest

Posted: Thu Jul 27, 2006 1:30 am Post subject: Re : wiring

Hi Ron and all,



 	  Quote: 	
		   2) I don't absolute agree with Gilles, if wired as per Europa, if 

 for any

 reason battery is not putting out, 1 pump will run off of generator

 (provided it is excited, which would have happened upon start up)


	


That's the main point concerning the circuit : you have redundancy PROVIDED  the regulator is working. I played the "What if game" before designing the pump circuit, and made some investigations.



The Rotax regulator needs a definite voltage to continue providing power. Disconnect it, or have it fail, or run your battery down, and you're left with very few option to keep your engine running.



Of course, things are different if you have an additional power source such as a second alternator.



I paid much attention to the number of switches : except for the E-bus switch (which is not mandatory), there is no special switch to operate the airplane : the behaviour is the same as in any Lyco-Conti aircraft.

Turn off the Master switch, do anything, the engine keeps running, unless you turn off the ignition keyswitch. No risk of inadvertently switching of the main pump.



By the way, the airplane runs without any problem with a 7 Ah only Hawker battery.



Regards,

Gilles

http://contrails.free.fr

nwcmc(at)tiscali.co.uk
Guest

Posted: Thu Jul 27, 2006 1:57 am Post subject: Re : wiring

 	  Quote: 	
		  The Rotax regulator needs a definite voltage to continue providing

power. Disconnect it, or have it fail, or run your battery down, and
	


you're left with very few option to keep your engine running.<



Not true. If you disconnect the battery with the engine running the

generator continues to supply the electrical system until the revs drop

to idle. Even then, restoring the revs above idle results in the

generator picking up the load.



Nigel Charles

BEBERRY(at)aol.com
Guest

Posted: Thu Jul 27, 2006 2:18 am Post subject: Re : wiring

>The Rotax regulator needs a definite voltage to continue  providing

power. Disconnect it, or have it fail, or run your battery down,  and

you're left with very few option to keep your engine  running.<



Not true. If you disconnect the battery with the engine  running the

generator continues to supply the electrical system until the  revs drop

to idle. Even then, restoring the revs above idle results in  the

generator picking up the load.



Nigel Charles



 True Nigel but I find I need to get the rpm back over about 2500 to get the  voltage reg to cut in again once it has dropped out at low rpm (which it does  not always do.)

  

 Constant problems of this nature have caused some anxieties, but there is  no fear that it will result in an engine failure.

  

 Patrick

rparigor(at)suffolk.lib.n
Guest

Posted: Thu Jul 27, 2006 9:49 am Post subject: Re : wiring

Hello Gilles



One more time:



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~



2) I don't absolute agree with Gilles, if wired as per Europa, if 

for any

reason battery is not putting out, 1 pump will run off of generator

(provided it is excited, which would have happened upon start up)

That's the main point concerning the circuit : you have redundancy

PROVIDED  

the regulator is working.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~



If using 1 battery and Rotax generator, if both pumps are wired to main

bus, both would be dead if:

Master switch failed or was turned off

Battery isolator failed 

30 amp slow blow fuse in series with main bus feed opened



If wired as per Europa, primary will run as long as generator and

regulator is functioning.



Take a look at Europa 914 schematic so we are on same page:

http://www.europa-aircraft.biz/pdfs/buildersmanuals/CBM%20-%2025%20-%20ELECTRICAL%20SYSTEM.pdf

On page #11



Unless B+ was shorted at regulator, by closing alternator output switch

power to primary pump will be provided from the battery should the

regulator fail, or OVP take it off line.



In other words you can run both pumps off battery with an added bonus of

being able to run 1 pump exclusive off generator.



Ron P.

Gilles.Thesee(at)ac-greno
Guest

Posted: Thu Jul 27, 2006 11:59 pm Post subject: Re : wiring

Hi Ron and all,



 	  Quote: 	
		   If wired as per Europa, primary will run as long as generator and

 regulator is functioning.

 

Failure of the regulator is not an unlikely event. That's why I considered this case when designing the circuit.
	


My purpose was to prevent a regulator failure from becoming an engine emergency.



 	  Quote: 	
		   Take a look at Europa 914 schematic so we are on same page:

 http://www.europa-aircraft.biz/pdfs/buildersmanuals/CBM%20-

 %2025%20-%20ELECTRICAL%20SYSTEM.pdf

 On page #11

 

 Unless B+ was shorted at regulator, by closing alternator output 

 switchpower to primary pump will be provided from the battery 

 should the

 regulator fail, or OVP take it off line.

 


	


How is your OVP wired ? If it is of the crowbar type, doesn't it disconnect the offending generator/regulator unit from the ship's circuit ?

How is the "OV regulator failure" case managed ?



Of course, it is up to each builder to chose the degree of redundancy he is willing to build into his systems.

Best regards,

Gilles

htttp://contrails.free.fr

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