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stopping engine

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kjohnsondds(at)yahoo.com
Guest

Posted: Tue Apr 27, 2010 8:48 am Post subject: stopping engine

Aircraft Electrical Gurus,

 This subject has been presented briefly recently, but I was looking for the opinion of several.  This may have an electrical solution of not.  The question is: "What is the best way to stop your aircraft engine?

  

 In the recent past, at this site I have seen recommended a switch to the fuel pump.  Turn off the fuel pump and eventually the engine stops.  

  

 I rent Cessna 172 and the prefered way to stop the engine is to minimize both the throttle and richness knobs by pulling them out.  Technically, what exactly does this do?  Could I place a simple ball valve on my fuel rail and phsically close it?  Is this what I do on the Cessna 172?  The Cessna fuel is fed throught a carburetor and my engine is fuel injected.  Does that make a difference?

  

 On the automobile engine, when we turn off the engine, are we just closing the switch that provides current to the spark plugs, or is something else involved?   Is this what should be done for the aircraft engine?

  

 Thanks for your advice.

  

 Ken Johnson

  

         [quote][b]

bgray(at)glasair.org
Guest

Posted: Tue Apr 27, 2010 9:22 am Post subject: stopping engine

In an Aviation carb’ed or injected engine, the shutoff method is the same- turn off the fuel. The reason for this is to prevent a fuel/air mixture being left in a cylinder. If a P lead wire is broken and the propeller is turned, it could fire and injure someone. From your question I assume you’re installing an auto engine.   

   

Auto engines kill the spark. Some might also kill the pressure in the fuel rail. You’re going to have to blasé your own trail here.  

     

Bruce

 www.Glasair.org   

  

--

Neal.George(at)hurlburt.a
Guest

Posted: Tue Apr 27, 2010 9:45 am Post subject: stopping engine

Depends on the engine and the application.  On most certificated systems,

pulling the mixture shuts off the fuel flow in the metering device

(injection servo or carb) - thus the term Idle Cut-Off (ICO).  The fuel

servo manufactured by Airflow Performance, popular among the experimental

crowd, DOES NOT completely stop fuel flow at the low idle stop.  Airflow

Performance incorporates a valve to shut off fuel between the servo and the

distribution spider.    



Generally speaking, to shut down an aircraft engine we turn off the fuel

supply to starve the engine.  The idea is to get the fuel out of the intake

system so that a hot cylinder or un-grounded mag won't fire unexpectedly and

hurt someone.  I've had more than one airplane fire a cylinder  when

positioning the prop after a run-up for maintenance - with the mags off and

keys in my hand.   



Just turning off the ignition is no guarantee and leaves fuel in the system.

Hot aircraft engines will diesel, and the higher the compression, the more

likely it is to happen. 



Neal

A&P/IA



--

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rlborger(at)mac.com
Guest

Posted: Tue Apr 27, 2010 9:59 am Post subject: stopping engine

 	  Quote: 	
		  Ken,



What kind of engine are you using or planning to use?  Makes a difference.



My Rotax 914 is shut down by shorting the ignition module output to ground preventing spark.  This method ensures you know that the ignition is properly grounding.



Traditional aircraft engines such as Lycoming and Continental are shut down by setting the throttle to idle and pulling the mixture control to Idle/cutoff.  This shuts off the fuel going into the engine from either the carb or F/I system.  Makes the engine safe as described by Bruce Gray.



Auto engines are shut down by turning off the key which removes the electrical source from the ignition, computers & fuel pump, shutting things down all over the place.



There are valid reasons for each method.  You should determine what would be best for your engine based on the manufacturers recommendations.  If you are doing an automotive conversion, I guess you'd use the automotive method.



Bob Borger

Europa XS Monowheel, Rotax 914 w/ Intercooler, Airmaster C/S prop.

Building a Little Toot Sport Biplane.



 

On Tuesday, April 27, 2010, at 11:45AM, "Kenneth Johnson" <kjohnsondds(at)yahoo.com> wrote:

 	  Quote: 	
		  	
    Aircraft Electrical Gurus,

  This subject has been presented briefly recently, but I was looking for the opinion of several.  This may have an electrical solution of not.  The question is: "What is the best way to stop your aircraft engine?
	


   

  In the recent past, at this site I have seen recommended a switch to the fuel pump.  Turn off the fuel pump and eventually the engine stops.  

   

  I rent Cessna 172 and the prefered way to stop the engine is to minimize both the throttle and richness knobs by pulling them out.  Technically, what exactly does this do?  Could I place a simple ball valve on my fuel rail and phsically close it?  Is this what I do on the Cessna 172?  The Cessna fuel is fed throught a carburetor and my engine is fuel injected.  Does that make a difference?

   

  On the automobile engine, when we turn off the engine, are we just closing the switch that provides current to the spark plugs, or is something else involved?   Is this what should be done for the aircraft engine?

   

  Thanks for your advice.

   

  Ken Johnson

   

 

 

     	  Quote:

jon(at)finleyweb.net
Guest

Posted: Tue Apr 27, 2010 10:18 am Post subject: stopping engine

Hi Ken,

  

 I too have seen that discussion.  For clarity - all of my comments are in regards to an automotive multi-point EFI engine (not to be confused with any carbureated engine or any mechanical fuel injection system).

  

 With my flying Subaru EJ-22, the ignition switch cuts power to the ECU (Real World Solutions EC2), injectors, and coils.  Has worked fine for 300 hours.

  

 I believe (but am not 100% positive) that most modern automotive EFI systems all shut down the ECU, coils, and injectors when switched off.  Talking specifically about automotive EFI engines, I see no value in starving the engine for fuel. I am told (but have no statistics or tests to prove) that this can harm a high pressure EFI fuel pump (running it dry).

  

 Jon

 



--

mprather(at)spro.net
Guest

Posted: Tue Apr 27, 2010 10:56 am Post subject: stopping engine

I think it's worthwhile to be precise (reduce ambiguity) in matters such

as this.



I believe many (most?) light airplane POH's specify that engine shutdown

is accomplished by moving the mixture control to idle-cutoff (ICO).

Usually this causes the engine to stop running fairly rapidly - in a

matter of a couple of seconds.  Selecting rich mixture and hitting the

starter usually allows the engine to restart very quickly/easily.



Certainly many airplanes still have Stromberg carbs (or similar) which

don't have a mixture control effective enough to cause "idle-cutoff".  I

have ridden with pilots of such airplanes who only use the magneto

switches to stop the engine.  One benefit of this procedure is that you

check to see if you have a "hot mag" on each flight.  If the engine stops

dead, you can be somewhat certain that the p-lead circuit is in working

condition.



Most (all?) light airplanes also have at least one fuel control valve

(selector), which can also be used to stop the flow of fuel to the engine.

 On the carbureted engines that I have operated, closing this fuel valve

does eventually stop the engine, though depending on how low the throttle

setting is, it might take a few minutes for the float bowl in the carb to

get low enough to cause the engine to lean-out and die.  Usually when I

pull up to a parking spot, I don't feel like waiting for the carb to

empty, so I never do this.



If the fuel valve was turned off, on carbureted airplanes with gravity

feed fuel, turning on the fuel valve and waiting a few moments will refill

the carb float bowl, at which point the engine may be restarted.  For an

airplane with pump driven fuel, turning on the electric pump will allow

restarting much faster/sooner than if only the engine driven pump is used.

 Turning on the electric pump is often in the engine start procedure.



In an airplane that depends on a high pressure electric pump, I'm not sure

it makes sense to "turn off the fuel," if that implies closing some kind

of fuel valve.  It might make more sense to turn off the electric pump(s).



My impression of automotive fuel injection is that turning the key off

stops power to both the ignition and the fuel pump(s).  This leaves

burnable mixture in the cylinders and intake manifold.  In an airplane,

this method of stopping the engine increases the risk of unexpected prop

motion.  Turning the key to run causes the fuel pump(s) to run until the

specified system pressure is reached, at which point the pump(s) turn off.



One other thing I have noticed is that some electronic ignition systems

may fire the spark plugs one time when the system is energized.  This will

likely cause the prop to turn if there is a burnable mixture in the

cylinders.  In fact, my Varieze has such a system.  A number of times I

have actually had the engine start spontaneously because of this effect -

prime with accelerator pump, walk the prop to pull fuel into the

cylinders, turn on the ignition, and away it goes.  So, magnetos aren't

the only things that will fire unexpectedly.  In fact, a mag without an

impulse couple isn't likely going to spark on its own..



So to get back to the original question,  I agree that stopping the fuel

delivery in some way is generally a good idea.  I think turning off the

pumps while leaving the ignition firing is the best bet, as that should

dump fuel system pressure, and yield the least burnable mixture in the

cylinders.



With all that said, everyone working around aircraft should be very

careful of the propeller, whatever method is used to stop the engine. 

Pilots need to be vigilant to not allow anyone to haphazardly move the

prop or stand in the prop arc.

Regards,



Matt-



[quote] In an Aviation carb’ed or injected engine, the shutoff method is the

 same- turn off the fuel. The reason for this is to prevent a fuel/air

 mixture being left in a cylinder. If a P lead wire is broken and the

 propeller is turned, it could fire and injure someone. From your

 question I assume you’re installing an auto engine.



 Auto engines kill the spark. Some might also kill the pressure in the

 fuel rail. You’re going to have to blasé your own trail here.



 Bruce

 www.Glasair.org

 --

kjohnsondds(at)yahoo.com
Guest

Posted: Wed Apr 28, 2010 8:12 am Post subject: stopping engine

Hi All,

 I would like to thank all who responded.  

  

 It would seem the best reason to stop an engine with fuel starvation would be to prevent possible danger from the prop.  If a prop was repositioned, fuel in a cylinder might ignite, which in turn would turn the prop and that might hurt someone.  In an automobile, if dieseling occurs, no is hurt.  The car is in "Park" or "Neutral."

  

 I have a Mazda rotary engine I will be using for my airplane.  Eventhough this is not a piston engine, the threat of danger from the prop with fuel left in the burn chamber still exists.  For safety reasons, fuel starvation would be the best way to stop the engine.  Turning off the ignition will stop current to the spark plugs, coils, and will turn off the high pressure fuel pump.  However, it would seem that turning off the fuel pump before turning off the ignition would be a safer way to eliminate fuel from the burn chambers.

  

 By using a valve on my fuel rail, I could stop fuel.  However, the fuel pump would still be working and could be damaged.  Again, it would seem that switching off the fuel pump before the ignition might be the best solution.  

  

 If anyone has a better solution, please post.

  

 Thanks,

  

 Ken Johnson  



 

   From: Matt Prather <mprather(at)spro.net>

To: aeroelectric-list(at)matronics.com

Sent: Tue, April 27, 2010 1:54:43 PM

Subject: RE: stopping engine



--> AeroElectric-List message posted by: "Matt Prather" <mprather(at)spro.net (mprather(at)spro.net)>



I think it's worthwhile to be precise (reduce ambiguity) in matters such

as this.



I believe many (most?) light airplane POH's specify that engine shutdown

is accomplished by moving the mixture control to idle-cutoff (ICO).

Usually this causes the engine to stop running fairly rapidly - in a

matter of a couple of seconds.  Selecting rich mixture and hitting the

starter  usually allows the engine to restart very quickly/easily.



Certainly many airplanes still have Stromberg carbs (or similar) which

don't have a mixture control effective enough to cause "idle-cutoff".  I

have ridden with pilots of such airplanes who only use the magneto

switches to stop the engine.  One benefit of this procedure is that you

check to see if you have a "hot mag" on each flight.  If the engine stops

dead, you can be somewhat certain that the p-lead circuit is in working

condition.



Most (all?) light airplanes also have at least one fuel control valve

(selector), which can also be used to stop the flow of fuel to the engine.

On the carbureted engines that I have operated, closing this fuel valve

does eventually stop the engine, though depending on how low the throttle

setting is, it might take a few minutes for the float bowl in the carb to

get low enough to cause the engine to  lean-out and die.  Usually when I

pull up to a parking spot, I don't feel like waiting for the carb to

empty, so I never do this.



If the fuel valve was turned off, on carbureted airplanes with gravity

feed fuel, turning on the fuel valve and waiting a few moments will refill

the carb float bowl, at which point the engine may be restarted.  For an

airplane with pump driven fuel, turning on the electric pump will allow

restarting much faster/sooner than if only the engine driven pump is used.

Turning on the electric pump is often in the engine start procedure.



In an airplane that depends on a high pressure electric pump, I'm not sure

it makes sense to "turn off the fuel," if that implies closing some kind

of fuel valve.  It might make more sense to turn off the electric pump(s).



My impression of automotive fuel injection is that turning the key off

stops power to both the ignition and the  fuel pump(s).  This leaves

burnable mixture in the cylinders and intake manifold.  In an airplane,

this method of stopping the engine increases the risk of unexpected prop

motion.  Turning the key to run causes the fuel pump(s) to run until the

specified system pressure is reached, at which point the pump(s) turn off.



One other thing I have noticed is that some electronic ignition systems

may fire the spark plugs one time when the system is energized.  This will

likely cause the prop to turn if there is a burnable mixture in the

cylinders.  In fact, my Varieze has such a system.  A number of times I

have actually had the engine start spontaneously because of this effect -

prime with accelerator pump, walk the prop to pull fuel into the

cylinders, turn on the ignition, and away it goes.  So, magnetos aren't

the only things that will fire unexpectedly.  In fact, a mag without  an

impulse couple isn't likely going to spark on its own..



So to get back to the original question,  I agree that stopping the fuel

delivery in some way is generally a good idea.  I think turning off the

pumps while leaving the ignition firing is the best bet, as that should

dump fuel system pressure, and yield the least burnable mixture in the

cylinders.



With all that said, everyone working around aircraft should be very

careful of the propeller, whatever method is used to stop the engine. 

Pilots need to be vigilant to not allow anyone to haphazardly move the

prop or stand in the prop arc.

Regards,



Matt-



[quote] In an Aviation carbâ€™ed or injected engine, the shutoff method is the

 same- turn off the fuel. The reason for this is to prevent a fuel/air

 mixture being left in a cylinder. If a P lead wire is broken and the

 propeller is turned, it could fire and  injure someone. From your

 question I assume youâ€™re installing an auto engine.



 Auto engines kill the spark. Some might also kill the pressure in the

 fuel rail. Youâ€™re going to have to blasÃ© your own trail here.



 Bruce

 www.Glasair.org

 --

mikef(at)apexconsultingse
Guest

Posted: Wed Apr 28, 2010 8:42 am Post subject: stopping engine

I have a GEO engine, EFI is the EC2 system, with 2 fuel pumps going into a

single line, then to the fuel rail. In that line is a 3 way valve that I can

use to bypass the rail and spill back into the fuel tank. Turning off the

engine by starving the fuel, yet keeping the pumps running smoothly works

quite well.



On Wed, Apr 28, 2010 at 10:11 AM, Kenneth Johnson <kjohnsondds(at)yahoo.com>wrote:



[quote] Hi All,

 I would like to thank all who responded.



 It would seem the best reason to stop an engine with fuel starvation would

 be to prevent possible danger from the prop.  If a prop was repositioned,

 fuel in a cylinder might ignite, which in turn would turn the prop and that

 might hurt someone.  In an automobile, if dieseling occurs, no is hurt.  The

 car is in "Park" or "Neutral."



 I have a Mazda rotary engine I will be using for my airplane.  Eventhough

 this is not a piston engine, the threat of danger from the prop with fuel

 left in the burn chamber still exists.  For safety reasons, fuel starvation

 would be the best way to stop the engine.  Turning off the ignition will

 stop current to the spark plugs, coils, and will turn off the high pressure

 fuel pump.  However, it would seem that turning off the fuel pump before

 turning off the ignition would be a safer way to eliminate fuel from the

 burn chambers.



 By using a valve on my fuel rail, I could stop fuel.  However, the fuel

 pump would still be working and could be damaged.  Again, it would seem that

 switching off the fuel pump before the ignition might be the best solution.

 If anyone has a better solution, please post.



 Thanks,



 Ken Johnson



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

 *From:* Matt Prather <mprather(at)spro.net>

 *To:* aeroelectric-list(at)matronics.com

 *Sent:* Tue, April 27, 2010 1:54:43 PM

 *Subject:* RE: stopping engine



 

 >



 I think it's worthwhile to be precise (reduce ambiguity) in matters such

 as this.



 I believe many (most?) light airplane POH's specify that engine shutdown

 is accomplished by moving the mixture control to idle-cutoff (ICO).

 Usually this causes the engine to stop running fairly rapidly - in a

 matter of a couple of seconds.  Selecting rich mixture and hitting the

 starter usually allows the engine to restart very quickly/easily.



 Certainly many airplanes still have Stromberg carbs (or similar) which

 don't have a mixture control effective enough to cause "idle-cutoff".  I

 have ridden with pilots of such airplanes who only use the magneto

 switches to stop the engine.  One benefit of this procedure is that you

 check to see if you have a "hot mag" on each flight.  If the engine stops

 dead, you can be somewhat certain that the p-lead circuit is in working

 condition.



 Most (all?) light airplanes also have at least one fuel control valve

 (selector), which can also be used to stop the flow of fuel to the engine

bbradburry(at)bellsouth.n
Guest

Posted: Wed Apr 28, 2010 9:11 am Post subject: stopping engine

Ken,  

You didn’t say if you have fuel injection or a carb on your Mazda rotary, but if you have FI, you can shut off the injectors and the engine will immediately stop due to fuel starvation.  No fuel will be left in the rotor faces.  The fuel regulator will then immediately open up to keep the fuel pressure at your set point, so the fuel pumps will not be adversely affected.  In fact, this is the condition you will have the regulator and pumps in when you set the fuel pressure.  This is the way it is designed to work so no damage will ensue.  After the engine stops you can leisurely shut everything else down.  There will be no fuel in the rotors so there will be no danger if you want to move the prop for whatever reason.  

If you have a carb, well, you are on your own..   :>)  

   

Bill B  

         

  

From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Kenneth Johnson

 Sent: Wednesday, April 28, 2010 12:11 PM

 To: aeroelectric-list(at)matronics.com

 Subject: Re: AeroElectric-List: stopping engine  

  

         

Hi All,  

    

I would like to thank all who responded.    

    

   

    

It would seem the best reason to stop an engine with fuel starvation would be to prevent possible danger from the prop.  If a prop was repositioned, fuel in a cylinder might ignite, which in turn would turn the prop and that might hurt someone.  In an automobile, if dieseling occurs, no is hurt.  The car is in "Park" or "Neutral."  

    

   

    

I have a Mazda rotary engine I will be using for my airplane.  Eventhough this is not a piston engine, the threat of danger from the prop with fuel left in the burn chamber still exists.  For safety reasons, fuel starvation would be the best way to stop the engine.  Turning off the ignition will stop current to the spark plugs, coils, and will turn off the high pressure fuel pump.  However, it would seem that turning off the fuel pump before turning off the ignition would be a safer way to eliminate fuel from the burn chambers.  

    

   

    

By using a valve on my fuel rail, I could stop fuel.  However, the fuel pump would still be working and could be damaged.  Again, it would seem that switching off the fuel pump before the ignition might be the best solution.    

    

   

    

If anyone has a better solution, please post.  

    

   

    

Thanks,  

    

   

    

Ken Johnson    

    

         

  

From: Matt Prather <mprather(at)spro.net>

 To: aeroelectric-list(at)matronics.com

 Sent: Tue, April 27, 2010 1:54:43 PM

 Subject: RE: AeroElectric-List: stopping engine

 

 --> AeroElectric-List message posted by: "Matt Prather" <mprather(at)spro.net (mprather(at)spro.net)>

 

 I think it's worthwhile to be precise (reduce ambiguity) in matters such

 as this.

 

 I believe many (most?) light airplane POH's specify that engine shutdown

 is accomplished by moving the mixture control to idle-cutoff (ICO).

 Usually this causes the engine to stop running fairly rapidly - in a

 matter of a couple of seconds.  Selecting rich mixture and hitting the

 starter usually allows the engine to restart very quickly/easily.

 

 Certainly many airplanes still have Stromberg carbs (or similar) which

 don't have a mixture control effective enough to cause "idle-cutoff".  I

 have ridden with pilots of such airplanes who only use the magneto

 switches to stop the engine.  One benefit of this procedure is that you

 check to see if you have a "hot mag" on each flight.  If the engine stops

 dead, you can be somewhat certain that the p-lead circuit is in working

 condition.

 

 Most (all?) light airplanes also have at least one fuel control valve

 (selector), which can also be used to stop the flow of fuel to the engine.

 On the carbureted engines that I have operated, closing this fuel valve

 does eventually stop the engine, though depending on how low the throttle

 setting is, it might take a few minutes for the float bowl in the carb to

 get low enough to cause the engine to lean-out and die.  Usually when I

 pull up to a parking spot, I don't feel like waiting for the carb to

 empty, so I never do this.

 

 If the fuel valve was turned off, on carbureted airplanes with gravity

 feed fuel, turning on the fuel valve and waiting a few moments will refill

 the carb float bowl, at which point the engine may be restarted.  For an

 airplane with pump driven fuel, turning on the electric pump will allow

 restarting much faster/sooner than if only the engine driven pump is used.

 Turning on the electric pump is often in the engine start procedure.

 

 In an airplane that depends on a high pressure electric pump, I'm not sure

 it makes sense to "turn off the fuel," if that implies closing some kind

 of fuel valve.  It might make more sense to turn off the electric pump(s).

 

 My impression of automotive fuel injection is that turning the key off

 stops power to both the ignition and the fuel pump(s).  This leaves

 burnable mixture in the cylinders and intake manifold.  In an airplane,

 this method of stopping the engine increases the risk of unexpected prop

 motion.  Turning the key to run causes the fuel pump(s) to run until the

 specified system pressure is reached, at which point the pump(s) turn off.

 

 One other thing I have noticed is that some electronic ignition systems

 may fire the spark plugs one time when the system is energized.  This will

 likely cause the prop to turn if there is a burnable mixture in the

 cylinders.  In fact, my Varieze has such a system.  A number of times I

 have actually had the engine start spontaneously because of this effect -

 prime with accelerator pump, walk the prop to pull fuel into the

 cylinders, turn on the ignition, and away it goes.  So, magnetos aren't

 the only things that will fire unexpectedly.  In fact, a mag without an

 impulse couple isn't likely going to spark on its own..

 

 So to get back to the original question,  I agree that stopping the fuel

 delivery in some way is generally a good idea.  I think turning off the

 pumps while leaving the ignition firing is the best bet, as that should

 dump fuel system pressure, and yield the least burnable mixture in the

 cylinders.

 

 With all that said, everyone working around aircraft should be very

 careful of the propeller, whatever method is used to stop the engine. 

 Pilots need to be vigilant to not allow anyone to haphazardly move the

 prop or stand in the prop arc.

 

 

 Regards,

 

 Matt-

 

 > In an Aviation carb’ed or injected engine, the shutoff method is the

 > same- turn off the fuel. The reason for this is to prevent a fuel/air

 > mixture being left in a cylinder. If a P lead wire is broken and the

 > propeller is turned, it could fire and injure someone. From your

 > question I assume you’re installing an auto engine.

 >

 > Auto engines kill the spark. Some might also kill the pressure in the

 > fuel rail. You’re going to have to blasé your own trail here.

 >

 > Bruce

 > www.Glasair.org

 > --

bbradburry(at)bellsouth.n
Guest

Posted: Wed Apr 28, 2010 9:54 am Post subject: stopping engine

Ken,  

If you are building a Mazda rotary for your plane you should really look into the rotary forum.  There is a tremendous amount of knowledge available there.  Come join us!  

   

http://mail.lancaironline.net:81/lists/flyrotary/List.html  

   

How to subscribe is at the lower right corner.  

   

Bill B  

         

  

From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Kenneth Johnson

 Sent: Wednesday, April 28, 2010 12:11 PM

 To: aeroelectric-list(at)matronics.com

 Subject: Re: AeroElectric-List: stopping engine  

  

         

Hi All,  

    

I would like to thank all who responded.    

    

   

    

It would seem the best reason to stop an engine with fuel starvation would be to prevent possible danger from the prop.  If a prop was repositioned, fuel in a cylinder might ignite, which in turn would turn the prop and that might hurt someone.  In an automobile, if dieseling occurs, no is hurt.  The car is in "Park" or "Neutral."  

    

   

    

I have a Mazda rotary engine I will be using for my airplane.  Eventhough this is not a piston engine, the threat of danger from the prop with fuel left in the burn chamber still exists.  For safety reasons, fuel starvation would be the best way to stop the engine.  Turning off the ignition will stop current to the spark plugs, coils, and will turn off the high pressure fuel pump.  However, it would seem that turning off the fuel pump before turning off the ignition would be a safer way to eliminate fuel from the burn chambers.  

    

   

    

By using a valve on my fuel rail, I could stop fuel.  However, the fuel pump would still be working and could be damaged.  Again, it would seem that switching off the fuel pump before the ignition might be the best solution.    

    

   

    

If anyone has a better solution, please post.  

    

   

    

Thanks,  

    

   

    

Ken Johnson    

    

         

  

From: Matt Prather <mprather(at)spro.net>

 To: aeroelectric-list(at)matronics.com

 Sent: Tue, April 27, 2010 1:54:43 PM

 Subject: RE: AeroElectric-List: stopping engine

 

 --> AeroElectric-List message posted by: "Matt Prather" <mprather(at)spro.net (mprather(at)spro.net)>

 

 I think it's worthwhile to be precise (reduce ambiguity) in matters such

 as this.

 

 I believe many (most?) light airplane POH's specify that engine shutdown

 is accomplished by moving the mixture control to idle-cutoff (ICO).

 Usually this causes the engine to stop running fairly rapidly - in a

 matter of a couple of seconds.  Selecting rich mixture and hitting the

 starter usually allows the engine to restart very quickly/easily.

 

 Certainly many airplanes still have Stromberg carbs (or similar) which

 don't have a mixture control effective enough to cause "idle-cutoff".  I

 have ridden with pilots of such airplanes who only use the magneto

 switches to stop the engine.  One benefit of this procedure is that you

 check to see if you have a "hot mag" on each flight.  If the engine stops

 dead, you can be somewhat certain that the p-lead circuit is in working

 condition.

 

 Most (all?) light airplanes also have at least one fuel control valve

 (selector), which can also be used to stop the flow of fuel to the engine.

 On the carbureted engines that I have operated, closing this fuel valve

 does eventually stop the engine, though depending on how low the throttle

 setting is, it might take a few minutes for the float bowl in the carb to

 get low enough to cause the engine to lean-out and die.  Usually when I

 pull up to a parking spot, I don't feel like waiting for the carb to

 empty, so I never do this.

 

 If the fuel valve was turned off, on carbureted airplanes with gravity

 feed fuel, turning on the fuel valve and waiting a few moments will refill

 the carb float bowl, at which point the engine may be restarted.  For an

 airplane with pump driven fuel, turning on the electric pump will allow

 restarting much faster/sooner than if only the engine driven pump is used.

 Turning on the electric pump is often in the engine start procedure.

 

 In an airplane that depends on a high pressure electric pump, I'm not sure

 it makes sense to "turn off the fuel," if that implies closing some kind

 of fuel valve.  It might make more sense to turn off the electric pump(s).

 

 My impression of automotive fuel injection is that turning the key off

 stops power to both the ignition and the fuel pump(s).  This leaves

 burnable mixture in the cylinders and intake manifold.  In an airplane,

 this method of stopping the engine increases the risk of unexpected prop

 motion.  Turning the key to run causes the fuel pump(s) to run until the

 specified system pressure is reached, at which point the pump(s) turn off.

 

 One other thing I have noticed is that some electronic ignition systems

 may fire the spark plugs one time when the system is energized.  This will

 likely cause the prop to turn if there is a burnable mixture in the

 cylinders.  In fact, my Varieze has such a system.  A number of times I

 have actually had the engine start spontaneously because of this effect -

 prime with accelerator pump, walk the prop to pull fuel into the

 cylinders, turn on the ignition, and away it goes.  So, magnetos aren't

 the only things that will fire unexpectedly.  In fact, a mag without an

 impulse couple isn't likely going to spark on its own..

 

 So to get back to the original question,  I agree that stopping the fuel

 delivery in some way is generally a good idea.  I think turning off the

 pumps while leaving the ignition firing is the best bet, as that should

 dump fuel system pressure, and yield the least burnable mixture in the

 cylinders.

 

 With all that said, everyone working around aircraft should be very

 careful of the propeller, whatever method is used to stop the engine. 

 Pilots need to be vigilant to not allow anyone to haphazardly move the

 prop or stand in the prop arc.

 

 

 Regards,

 

 Matt-

 

 > In an Aviation carb’ed or injected engine, the shutoff method is the

 > same- turn off the fuel. The reason for this is to prevent a fuel/air

 > mixture being left in a cylinder. If a P lead wire is broken and the

 > propeller is turned, it could fire and injure someone. From your

 > question I assume you’re installing an auto engine.

 >

 > Auto engines kill the spark. Some might also kill the pressure in the

 > fuel rail. You’re going to have to blasé your own trail here.

 >

 > Bruce

 > www.Glasair.org

 > --

mprather(at)spro.net
Guest

Posted: Wed Apr 28, 2010 10:09 am Post subject: stopping engine

Bill,



My only concern about this (and it's probably a remote concern) is that if

you have a leaking injector, it may dribble fuel into the engine after

shutdown.  Otherwise, this is very much analogous to pulling the mixture

to ICO on an aircraft carb or mechanical injection.

Matt-



[quote] Ken,



 You didn’t say if you have fuel injection or a carb on your Mazda rotary,

 but if you have FI, you can shut off the injectors and the engine will

 immediately stop due to fuel starvation.  No fuel will be left in the

 rotor

 faces.  The fuel regulator will then immediately open up to keep the fuel

 pressure at your set point, so the fuel pumps will not be adversely

 affected.  In fact, this is the condition you will have the regulator and

 pumps in when you set the fuel pressure.  This is the way it is designed

 to

 work so no damage will ensue.  After the engine stops you can leisurely

 shut

 everything else down.  There will be no fuel in the rotors so there will

 be

 no danger if you want to move the prop for whatever reason.



 If you have a carb, well, you are on your own..   :>)



 Bill B



   _____



 From: owner-aeroelectric-list-server(at)matronics.com

 [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Kenneth

 Johnson

 Sent: Wednesday, April 28, 2010 12:11 PM

 To: aeroelectric-list(at)matronics.com

 Subject: Re: stopping engine



 Hi All,



 I would like to thank all who responded.



 It would seem the best reason to stop an engine with fuel starvation would

 be to prevent possible danger from the prop.  If a prop was repositioned,

 fuel in a cylinder might ignite, which in turn would turn the prop and

 that

 might hurt someone.  In an automobile, if dieseling occurs, no is hurt.

 The

 car is in "Park" or "Neutral."



 I have a Mazda rotary engine I will be using for my airplane.  Eventhough

 this is not a piston engine, the threat of danger from the prop with fuel

 left in the burn chamber still exists.  For safety reasons, fuel

 starvation

 would be the best way to stop the engine.  Turning off the ignition will

 stop current to the spark plugs, coils, and will turn off the high

 pressure

 fuel pump.  However, it would seem that turning off the fuel pump before

 turning off the ignition would be a safer way to eliminate fuel from the

 burn chambers.



 By using a valve on my fuel rail, I could stop fuel.  However, the fuel

 pump

 would still be working and could be damaged.  Again, it would seem that

 switching off the fuel pump before the ignition might be the best

 solution.





 If anyone has a better solution, please post.



 Thanks,



 Ken Johnson



   _____



 From: Matt Prather <mprather(at)spro.net>

 To: aeroelectric-list(at)matronics.com

 Sent: Tue, April 27, 2010 1:54:43 PM

 Subject: RE: stopping engine



 

 <mprather(at)spro.net>



 I think it's worthwhile to be precise (reduce ambiguity) in matters such

 as this.



 I believe many (most?) light airplane POH's specify that engine shutdown

 is accomplished by moving the mixture control to idle-cutoff (ICO).

 Usually this causes the engine to stop running fairly rapidly - in a

 matter of a couple of seconds.  Selecting rich mixture and hitting the

 starter usually allows the engine to restart very quickly/easily.



 Certainly many airplanes still have Stromberg carbs (or similar) which

 don't have a mixture control effective enough to cause "idle-cutoff".  I

 have ridden with pilots of such airplanes who only use the magneto

 switches to stop the engine.  One benefit of this procedure is that you

 check to see if you have a "hot mag" on each flight.  If the engine stops

 dead, you can be somewhat certain that the p-lead circuit is in working

 condition.



 Most (all?) light airplanes also have at least one fuel control valve

 (selector), which can also be used to stop the flow of fuel to the engine.

 On the carbureted engines that I have operated, closing this fuel valve

 does eventually stop the engine, though depending on how low the throttle

 setting is, it might take a few minutes for the float bowl in the carb to

 get low enough to cause the engine to lean-out and die.  Usually when I

 pull up to a parking spot, I don't feel like waiting for the carb to

 empty, so I never do this.



 If the fuel valve was turned off, on carbureted airplanes with gravity

 feed fuel, turning on the fuel valve and waiting a few moments will refill

 the carb float bowl, at which point the engine may be restarted.  For an

 airplane with pump driven fuel, turning on the electric pump will allow

 restarting much faster/sooner than if only the engine driven pump is used.

 Turning on the electric pump is often in the engine start procedure.



 In an airplane that depends on a high pressure electric pump, I'm not sure

 it makes sense to "turn off the fuel," if that implies closing some kind

 of fuel valve.  It might make more sense to turn off the electric pump(s).



 My impression of automotive fuel injection is that turning the key off

 stops power to both the ignition and the fuel pump(s).  This leaves

 burnable mixture in the cylinders and intake manifold.  In an airplane,

 this method of stopping the engine increases the risk of unexpected prop

 motion.  Turning the key to run causes the fuel pump(s) to run until the

 specified system pressure is reached, at which point the pump(s) turn off.



 One other thing I have noticed is that some electronic ignition systems

 may fire the spark plugs one time when the system is energized.  This will

 likely cause the prop to turn if there is a burnable mixture in the

 cylinders.  In fact, my Varieze has such a system.  A number of times I

 have actually had the engine start spontaneously because of this effect -

 prime with accelerator pump, walk the prop to pull fuel into the

 cylinders, turn on the ignition, and away it goes.  So, magnetos aren't

 the only things that will fire unexpectedly.  In fact, a mag without an

 impulse couple isn't likely going to spark on its own..



 So to get back to the original question,  I agree that stopping the fuel

 delivery in some way is generally a good idea.  I think turning off the

 pumps while leaving the ignition firing is the best bet, as that should

 dump fuel system pressure, and yield the least burnable mixture in the

 cylinders.



 With all that said, everyone working around aircraft should be very

 careful of the propeller, whatever method is used to stop the engine.

 Pilots need to be vigilant to not allow anyone to haphazardly move the

 prop or stand in the prop arc.

 Regards,



 Matt-



> In an Aviation carb’ed or injected engine, the shutoff method is the

> same- turn off the fuel. The reason for this is to prevent a fuel/air

> mixture being left in a cylinder. If a P lead wire is broken and the

> propeller is turned, it could fire and injure someone. From your

> question I assume you’re installing an auto engine.

>

> Auto engines kill the spark. Some might also kill the pressure in the

> fuel rail. You’re going to have to blasé your own trail here.

>

> Bruce

> www.Glasair.org <http://www.glasair.org/>

> --

wschertz(at)comcast.net
Guest

Posted: Wed Apr 28, 2010 7:12 pm Post subject: stopping engine

I have Mazda Rotary with EC-2 and electric fuel  pump. shut down consists of shutting off the fuel pump, engine dies quickly, and  there is no residual pressure in the lines to leak past the injectors and cause  flooding or richness on the start.

  

 Bill Schertz

KIS Cruiser  #4045

N343BS

Phase I testing

  



  From: Bill Bradburry (bbradburry(at)bellsouth.net) 

 Sent: Wednesday, April 28, 2010 12:09 PM

 To: aeroelectric-list(at)matronics.com (aeroelectric-list(at)matronics.com)  

 Subject: RE: stopping engine

 



  

Ken, 

You didn’t say if you  have fuel injection or a carb on your Mazda rotary, but if you have FI, you can  shut off the injectors and the engine will immediately stop due to fuel  starvation.  No fuel will be left in the rotor faces.  The fuel  regulator will then immediately open up to keep the fuel pressure at your set  point, so the fuel pumps will not be adversely affected.  In fact, this is  the condition you will have the regulator and pumps in when you set the fuel  pressure.  This is the way it is designed to work so no damage will  ensue.  After the engine stops you can leisurely shut everything else  down.  There will be no fuel in the rotors so there will be no danger if  you want to move the prop for whatever reason. 

If you have a carb,  well, you are on your own..   :>) 

  

Bill  B 

     

 

From:  owner-aeroelectric-list-server(at)matronics.com  [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Kenneth Johnson

Sent: Wednesday, April 28, 2010 12:11  PM

To: aeroelectric-list(at)matronics.com

Subject: Re: stopping  engine

 

     

Hi All,

  

I would like to thank all who responded.   

  

 

  

It would seem the best reason to stop an engine with  fuel starvation would be to prevent possible danger from the prop.  If a  prop was repositioned, fuel in a cylinder might ignite, which in turn would turn  the prop and that might hurt someone.  In an automobile, if  dieseling occurs, no is hurt.  The car is in "Park" or  "Neutral."

  

 

  

I have a Mazda rotary engine I will be using for my  airplane.  Eventhough this is not a piston engine, the threat of danger  from the prop with fuel left in the burn chamber still exists.  For safety  reasons, fuel starvation would be the best way to stop the engine.  Turning  off the ignition will stop current to the spark plugs, coils, and will turn  off the high pressure fuel pump.  However, it would seem that turning off  the fuel pump before turning off the ignition would be a safer way to eliminate  fuel from the burn chambers.

  

 

  

By using a valve on my fuel rail, I could stop  fuel.  However, the fuel pump would still be working and could be  damaged.  Again, it would seem that switching off the fuel pump before  the ignition might be the best solution.   

  

 

  

If anyone has a better solution, please  post.

  

 

  

Thanks,

  

 

  

Ken  Johnson  

  

     

 

From: Matt  Prather <mprather(at)spro.net>

To: aeroelectric-list(at)matronics.com

Sent: Tue, April 27, 2010 1:54:43  PM

Subject: RE:  stopping engine



-->  AeroElectric-List message posted by: "Matt Prather" <mprather(at)spro.net (mprather(at)spro.net)>



I think it's  worthwhile to be precise (reduce ambiguity) in matters such

as this.



I  believe many (most?) light airplane POH's specify that engine shutdown

is  accomplished by moving the mixture control to idle-cutoff (ICO).

Usually this  causes the engine to stop running fairly rapidly - in a

matter of a couple of  seconds.  Selecting rich mixture and hitting the

starter usually allows  the engine to restart very quickly/easily.



Certainly many airplanes still  have Stromberg carbs (or similar) which

don't have a mixture control  effective enough to cause "idle-cutoff".  I

have ridden with pilots of  such airplanes who only use the magneto

switches to stop the engine.   One benefit of this procedure is that you

check to see if you have a "hot  mag" on each flight.  If the engine stops

dead, you can be somewhat  certain that the p-lead circuit is in working

condition.



Most (all?)  light airplanes also have at least one fuel control valve

(selector), which  can also be used to stop the flow of fuel to the engine.

On the carbureted  engines that I have operated, closing this fuel valve

does eventually stop  the engine, though depending on how low the throttle

setting is, it might  take a few minutes for the float bowl in the carb to

get low enough to cause  the engine to lean-out and die.  Usually when I

pull up to a parking  spot, I don't feel like waiting for the carb to

empty, so I never do  this.



If the fuel valve was turned off, on carbureted airplanes with  gravity

feed fuel, turning on the fuel valve and waiting a few moments will  refill

the carb float bowl, at which point the engine may be restarted.   For an

airplane with pump driven fuel, turning on the electric pump will  allow

restarting much faster/sooner than if only the engine driven pump is  used.

Turning on the electric pump is often in the engine start  procedure.



In an airplane that depends on a high pressure electric pump,  I'm not sure

it makes sense to "turn off the fuel," if that implies closing  some kind

of fuel valve.  It might make more sense to turn off the  electric pump(s).



My impression of automotive fuel injection is that  turning the key off

stops power to both the ignition and the fuel  pump(s).  This leaves

burnable mixture in the cylinders and intake  manifold.  In an airplane,

this method of stopping the engine increases  the risk of unexpected prop

motion.  Turning the key to run causes the  fuel pump(s) to run until the

specified system pressure is reached, at which  point the pump(s) turn off.



One other thing I have noticed is that some  electronic ignition systems

may fire the spark plugs one time when the system  is energized.  This will

likely cause the prop to turn if there is a  burnable mixture in the

cylinders.  In fact, my Varieze has such a  system.  A number of times I

have actually had the engine start  spontaneously because of this effect -

prime with accelerator pump, walk the  prop to pull fuel into the

cylinders, turn on the ignition, and away it  goes.  So, magnetos aren't

the only things that will fire  unexpectedly.  In fact, a mag without an

impulse couple isn't likely  going to spark on its own..



So to get back to the original  question,  I agree that stopping the fuel

delivery in some way is  generally a good idea.  I think turning off the

pumps while leaving the  ignition firing is the best bet, as that should

dump fuel system pressure,  and yield the least burnable mixture in the

cylinders.



With all that  said, everyone working around aircraft should be very

careful of the  propeller, whatever method is used to stop the engine. 

Pilots need to be  vigilant to not allow anyone to haphazardly move the

prop or stand in the  prop arc.

Regards,



Matt-



[quote] In an Aviation carb’ed or  injected engine, the shutoff method is the

 same- turn off the fuel. The  reason for this is to prevent a fuel/air

 mixture being left in a  cylinder. If a P lead wire is broken and the

 propeller is turned, it  could fire and injure someone. From your

 question I assume you’re  installing an auto engine.



 Auto engines kill the spark. Some  might also kill the pressure in the

 fuel rail. You’re going to have to  blasé your own trail here.



 Bruce

 www.Glasair.org

  --

ceengland(at)bellsouth.ne
Guest

Posted: Thu Apr 29, 2010 12:24 am Post subject: stopping engine

A couple of thoughts.



With electronic automotive injection, killing the injector power will 

stop the injectors, but the fuel rail will still be pressurized. If an 

injector is a bit leaky, fuel can still make it to the combustion 

chamber after shutdown. Some guys provide a tiny bleed hole that 

bypasses the regulator so the fuel rail will depressurize a minute or so 

after shutdown (probably overkill, but there it is).



On the subject of traditional a/c engines with carbs, there is a 

possible misconception buried below (I hate RPN posting....).  I read 

about the following somewhere & was surprised, but cutaway drawings of 

some a/c carbs seem to support the story.  I believe that the McNeilly 

(sp?) leaning block for Holley carbs works this way, too, and the 

technique has been used to lean some motorcycle carbs on alternative 

engines. Here's the 'story':



On at least some a/c carbs, the mixture control is actually controlling 

the vent to the fuel bowl on the carb. Pulling mixture to idle cutoff on 

those carbs just causes the 'head' (air pressure+fuel weight) on the 

fuel in the bowl to drop until it equals the absolute pressure in the 

venturi, stopping flow. Once the engine stops, pressure can equalize at 

ambient. If the prop spins after that happens, and the mags are on, the 

engine can fire because there's still fuel available & there's now a 

(short term) normal 'head' of ambient pressure on the fuel in the bowl.



Charlie



On 4/28/2010 11:32 AM, Mike Fontenot wrote:

[quote] I have a GEO engine, EFI is the EC2 system, with 2 fuel pumps going 

 into a single line, then to the fuel rail. In that line is a 3 way 

 valve that I can use to bypass the rail and spill back into the fuel 

 tank. Turning off the engine by starving the fuel, yet keeping the 

 pumps running smoothly works quite well.



 On Wed, Apr 28, 2010 at 10:11 AM, Kenneth Johnson 

 <kjohnsondds(at)yahoo.com <mailto:kjohnsondds(at)yahoo.com>> wrote:



     Hi All,

     I would like to thank all who responded.

     It would seem the best reason to stop an engine with fuel

     starvation would be to prevent possible danger from the prop.  If

     a prop was repositioned, fuel in a cylinder might ignite, which in

     turn would turn the prop and that might hurt someone.  In an

     automobile, if dieseling occurs, no is hurt.  The car is in "Park"

     or "Neutral."

     I have a Mazda rotary engine I will be using for my airplane. 

     Eventhough this is not a piston engine, the threat of danger from

     the prop with fuel left in the burn chamber still exists.  For

     safety reasons, fuel starvation would be the best way to stop the

     engine.  Turning off the ignition will stop current to the spark

     plugs, coils, and will turn off the high pressure fuel pump. 

     However, it would seem that turning off the fuel pump before

     turning off the ignition would be a safer way to eliminate fuel

     from the burn chambers.

     By using a valve on my fuel rail, I could stop fuel.  However, the

     fuel pump would still be working and could be damaged.  Again, it

     would seem that switching off the fuel pump before the

     ignition might be the best solution.

     If anyone has a better solution, please post.

     Thanks,

     Ken Johnson



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

     *From:* Matt Prather <mprather(at)spro.net <mailto:mprather(at)spro.net>>

     *To:* aeroelectric-list(at)matronics.com

     <mailto:aeroelectric-list(at)matronics.com>

     *Sent:* Tue, April 27, 2010 1:54:43 PM

     *Subject:* RE: stopping engine



     

     <mprather(at)spro.net <mailto:mprather(at)spro.net>>



     I think it's worthwhile to be precise (reduce ambiguity) in

     matters such

     as this.



     I believe many (most?) light airplane POH's specify that engine

     shutdown

     is accomplished by moving the mixture control to idle-cutoff (ICO).

     Usually this causes the engine to stop running fairly rapidly - in a

     matter of a couple of seconds.  Selecting rich mixture and hitting the

     starter usually allows the engine to restart very quickly/easily.



     Certainly many airplanes still have Stromberg carbs (or similar) which

     don't have a mixture control effective enough to cause

     "idle-cutoff".  I

     have ridden with pilots of such airplanes who only use the magneto

     switches to stop the engine.  One benefit of this procedure is

     that you

     check to see if you have a "hot mag" on each flight.  If the

     engine stops

     dead, you can be somewhat certain that the p-lead circuit is in

     working

     condition.



     Most (all?) light airplanes also have at least one fuel control valve

     (selector), which can also be used to stop the flow of fuel to the

     engine.

     On the carbureted engines that I have operated, closing this fuel

     valve

     does eventually stop the engine, though depending on how low the

     throttle

     setting is, it might take a few minutes for the float bowl in the

     carb to

     get low enough to cause the engine to lean-out and die.  Usually

     when I

     pull up to a parking spot, I don't feel like waiting for the carb to

     empty, so I never do this.



     If the fuel valve was turned off, on carbureted airplanes with gravity

     feed fuel, turning on the fuel valve and waiting a few moments

     will refill

     the carb float bowl, at which point the engine may be restarted. 

     For an

     airplane with pump driven fuel, turning on the electric pump will

     allow

     restarting much faster/sooner than if only the engine driven pump

     is used.

     Turning on the electric pump is often in the engine start procedure.



     In an airplane that depends on a high pressure electric pump, I'm

     not sure

     it makes sense to "turn off the fuel," if that implies closing

     some kind

     of fuel valve.  It might make more sense to turn off the electric

     pump(s).



     My impression of automotive fuel injection is that turning the key off

     stops power to both the ignition and the fuel pump(s).  This leaves

     burnable mixture in the cylinders and intake manifold.  In an

     airplane,

     this method of stopping the engine increases the risk of

     unexpected prop

     motion.  Turning the key to run causes the fuel pump(s) to run

     until the

     specified system pressure is reached, at which point the pump(s)

     turn off.



     One other thing I have noticed is that some electronic ignition

     systems

     may fire the spark plugs one time when the system is energized. 

     This will

     likely cause the prop to turn if there is a burnable mixture in the

     cylinders.  In fact, my Varieze has such a system.  A number of

     times I

     have actually had the engine start spontaneously because of this

     effect -

     prime with accelerator pump, walk the prop to pull fuel into the

     cylinders, turn on the ignition, and away it goes.  So, magnetos

     aren't

     the only things that will fire unexpectedly.  In fact, a mag

     without an

     impulse couple isn't likely going to spark on its own..



     So to get back to the original question,  I agree that stopping

     the fuel

     delivery in some way is generally a good idea.  I think turning

     off the

     pumps while leaving the ignition firing is the best bet, as that

     should

     dump fuel system pressure, and yield the least burnable mixture in the

     cylinders.



     With all that said, everyone working around aircraft should be very

     careful of the propeller, whatever method is used to stop the engine.

     Pilots need to be vigilant to not allow anyone to haphazardly move the

     prop or stand in the prop arc.

     Regards,



     Matt-



     > In an Aviation carb’ed or injected engine, the shutoff method is the

     > same- turn off the fuel. The reason for this is to prevent a

     fuel/air

     > mixture being left in a cylinder. If a P lead wire is broken and the

     > propeller is turned, it could fire and injure someone. From your

     > question I assume you’re installing an auto engine.

     >

     > Auto engines kill the spark. Some might also kill the pressure

     in the

     > fuel rail. You’re going to have to blasé your own trail here.

     >

     > Bruce

     > www.Glasair.org <http://www.glasair.org/>

     > --

bbradburry(at)bellsouth.n
Guest

Posted: Thu Apr 29, 2010 12:24 am Post subject: stopping engine

Matt,

One other consideration about the Mazda rotary vs a typical piston airplane

engine is the blade rotation involved.  If either whacked you in the head,

you would probably not be real happy about it. However... 

The 4 cycle piston engine will rotate the prop 180 degrees on one power

stroke, but the rotary will only rotate the crankshaft 120 degrees if all

three rotor faces fire and only 40 degrees if one face fires.  Since the

rotary has a PSRU on it which is probably either 2.17 or 2.85 to 1, this

would further reduce the prop movement to 18.5 to 14 degrees depending on

which PSRU.

The rotary would give you a good whack, but you would have to be standing

close to the blade for it to hit you.



Bill B



--

bbradburry(at)bellsouth.n
Guest

Posted: Thu Apr 29, 2010 4:23 am Post subject: stopping engine

Matt,

An injector with much of a leak will show up on the way the engine performs,

but some have installed a small orifice (.050") in a bypass line around the

fuel pressure regulator.  This small leak is not more than the pump and

regulator can handle, but when the pump is turned off, the line pressure

quickly bleeds off into the tank return line.  This would stop any possible

problems from a leaky injector.



Bill B



--

Ed Anderson

Joined: 10 Jan 2006
Posts: 475

Posted: Thu Apr 29, 2010 5:08 am Post subject: stopping engine

Ken, you didn’t say,  

   

But if you are using electronic fuel injectors with your rotary engine, a power cut off switch to the injectors will instantly stop injection even with your pumps still running.  That is the method I use for shut down and there is no fuel left in combustion chamber nor any potential to damage the fuel pumps by running them dry.  

   

http://www.flyrotary.com/  

You may want to consider joining our FlyRotary list – there are many flying who have solved most problems you are likely to encounter and the information is there.  

   

Ed  

     

Ed Anderson  

Rv-6A N494BW Rotary Powered  

Matthews, NC  

eanderson(at)carolina.rr.com  

http://www.andersonee.com  

http://www.dmack.net/mazda/index.html  

http://www.flyrotary.com/  

http://members.cox.net/rogersda/rotary/configs.htm#N494BW  

http://www.rotaryaviation.com/Rotorhead%20Truth.htm[/url]  

        

  

From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Kenneth Johnson

 Sent: Wednesday, April 28, 2010 12:11 PM

 To: aeroelectric-list(at)matronics.com

 Subject: Re: AeroElectric-List: stopping engine  

  

         

Hi All,  

    

I would like to thank all who responded.    

    

   

    

It would seem the best reason to stop an engine with fuel starvation would be to prevent possible danger from the prop.  If a prop was repositioned, fuel in a cylinder might ignite, which in turn would turn the prop and that might hurt someone.  In an automobile, if dieseling occurs, no is hurt.  The car is in "Park" or "Neutral."  

    

   

    

I have a Mazda rotary engine I will be using for my airplane.  Eventhough this is not a piston engine, the threat of danger from the prop with fuel left in the burn chamber still exists.  For safety reasons, fuel starvation would be the best way to stop the engine.  Turning off the ignition will stop current to the spark plugs, coils, and will turn off the high pressure fuel pump.  However, it would seem that turning off the fuel pump before turning off the ignition would be a safer way to eliminate fuel from the burn chambers.  

    

   

    

By using a valve on my fuel rail, I could stop fuel.  However, the fuel pump would still be working and could be damaged.  Again, it would seem that switching off the fuel pump before the ignition might be the best solution.    

    

   

    

If anyone has a better solution, please post.  

    

   

    

Thanks,  

    

   

    

Ken Johnson    

    

         

  

From: Matt Prather <mprather(at)spro.net>

 To: aeroelectric-list(at)matronics.com

 Sent: Tue, April 27, 2010 1:54:43 PM

 Subject: RE: AeroElectric-List: stopping engine

 

 --> AeroElectric-List message posted by: "Matt Prather" <mprather(at)spro.net (mprather(at)spro.net)>

 

 I think it's worthwhile to be precise (reduce ambiguity) in matters such

 as this.

 

 I believe many (most?) light airplane POH's specify that engine shutdown

 is accomplished by moving the mixture control to idle-cutoff (ICO).

 Usually this causes the engine to stop running fairly rapidly - in a

 matter of a couple of seconds.  Selecting rich mixture and hitting the

 starter usually allows the engine to restart very quickly/easily.

 

 Certainly many airplanes still have Stromberg carbs (or similar) which

 don't have a mixture control effective enough to cause "idle-cutoff".  I

 have ridden with pilots of such airplanes who only use the magneto

 switches to stop the engine.  One benefit of this procedure is that you

 check to see if you have a "hot mag" on each flight.  If the engine stops

 dead, you can be somewhat certain that the p-lead circuit is in working

 condition.

 

 Most (all?) light airplanes also have at least one fuel control valve

 (selector), which can also be used to stop the flow of fuel to the engine.

 On the carbureted engines that I have operated, closing this fuel valve

 does eventually stop the engine, though depending on how low the throttle

 setting is, it might take a few minutes for the float bowl in the carb to

 get low enough to cause the engine to lean-out and die.  Usually when I

 pull up to a parking spot, I don't feel like waiting for the carb to

 empty, so I never do this.

 

 If the fuel valve was turned off, on carbureted airplanes with gravity

 feed fuel, turning on the fuel valve and waiting a few moments will refill

 the carb float bowl, at which point the engine may be restarted.  For an

 airplane with pump driven fuel, turning on the electric pump will allow

 restarting much faster/sooner than if only the engine driven pump is used.

 Turning on the electric pump is often in the engine start procedure.

 

 In an airplane that depends on a high pressure electric pump, I'm not sure

 it makes sense to "turn off the fuel," if that implies closing some kind

 of fuel valve.  It might make more sense to turn off the electric pump(s).

 

 My impression of automotive fuel injection is that turning the key off

 stops power to both the ignition and the fuel pump(s).  This leaves

 burnable mixture in the cylinders and intake manifold.  In an airplane,

 this method of stopping the engine increases the risk of unexpected prop

 motion.  Turning the key to run causes the fuel pump(s) to run until the

 specified system pressure is reached, at which point the pump(s) turn off.

 

 One other thing I have noticed is that some electronic ignition systems

 may fire the spark plugs one time when the system is energized.  This will

 likely cause the prop to turn if there is a burnable mixture in the

 cylinders.  In fact, my Varieze has such a system.  A number of times I

 have actually had the engine start spontaneously because of this effect -

 prime with accelerator pump, walk the prop to pull fuel into the

 cylinders, turn on the ignition, and away it goes.  So, magnetos aren't

 the only things that will fire unexpectedly.  In fact, a mag without an

 impulse couple isn't likely going to spark on its own..

 

 So to get back to the original question,  I agree that stopping the fuel

 delivery in some way is generally a good idea.  I think turning off the

 pumps while leaving the ignition firing is the best bet, as that should

 dump fuel system pressure, and yield the least burnable mixture in the

 cylinders.

 

 With all that said, everyone working around aircraft should be very

 careful of the propeller, whatever method is used to stop the engine. 

 Pilots need to be vigilant to not allow anyone to haphazardly move the

 prop or stand in the prop arc.

 

 

 Regards,

 

 Matt-

 

 > In an Aviation carb’ed or injected engine, the shutoff method is the

 > same- turn off the fuel. The reason for this is to prevent a fuel/air

 > mixture being left in a cylinder. If a P lead wire is broken and the

 > propeller is turned, it could fire and injure someone. From your

 > question I assume you’re installing an auto engine.

 >

 > Auto engines kill the spark. Some might also kill the pressure in the

 > fuel rail. You’re going to have to blasé your own trail here.

 >

 > Bruce

 > [url=http://www.glasair.org/]www.Glasair.org

 > --

_________________
Ed Anderson
Rv-6A N494BW Rotary Powered
Matthews, NC
eanderson@carolina.rr.com

mprather(at)spro.net
Guest

Posted: Thu Apr 29, 2010 12:15 pm Post subject: stopping engine

We're off in the weeds a bit as far as Aero Electrics..



I'm pretty sure that the Marvel Schebler carbs pass all of the fuel

through the main metering valve - even the idle circuit.  Thus, pulling

the mixture to ICO on these units does, in fact, positively stop fuel

flow.



The Stromberg carbs, and those commonly installed on Rotax engines work as

you suggested.  I believe these carbs are known variously as "altitude

compensating".



My impression of the Manual Mixture Control for the Holley is that it

works much like the Schebler - positively controlling fuel flow, not by

controlling venting of the float chamber.  I could be mistaken here.

Regards,



Matt-



 	  Quote: 	
		   

 <ceengland(at)bellsouth.net>



 A couple of thoughts.



 With electronic automotive injection, killing the injector power will

 stop the injectors, but the fuel rail will still be pressurized. If an

 injector is a bit leaky, fuel can still make it to the combustion

 chamber after shutdown. Some guys provide a tiny bleed hole that

 bypasses the regulator so the fuel rail will depressurize a minute or so

 after shutdown (probably overkill, but there it is).



 On the subject of traditional a/c engines with carbs, there is a

 possible misconception buried below (I hate RPN posting....).  I read

 about the following somewhere & was surprised, but cutaway drawings of

 some a/c carbs seem to support the story.  I believe that the McNeilly

 (sp?) leaning block for Holley carbs works this way, too, and the

 technique has been used to lean some motorcycle carbs on alternative

 engines. Here's the 'story':



 On at least some a/c carbs, the mixture control is actually controlling

 the vent to the fuel bowl on the carb. Pulling mixture to idle cutoff on

 those carbs just causes the 'head' (air pressure+fuel weight) on the

 fuel in the bowl to drop until it equals the absolute pressure in the

 venturi, stopping flow. Once the engine stops, pressure can equalize at

 ambient. If the prop spins after that happens, and the mags are on, the

 engine can fire because there's still fuel available & there's now a

 (short term) normal 'head' of ambient pressure on the fuel in the bowl.



 Charlie

n801bh(at)netzero.com
Guest

Posted: Thu Apr 29, 2010 3:13 pm Post subject: stopping engine

I will add a correction to the Mc Neilly mixture block for Holley carbs..  Tom Mc Neilly designed the block to act like a variable main jet, not to alter float bowl pressure... Some 2 and 4 stroke snowmobile motors use the bowl pressure method to trick the carb into thinking it is at a different altitude.....     Just for the record....

Ps... I LOVE my Mc Neilly mixture block on my V-8 powered experimental. It works sooo good. !!!!!! 



Ben Haas

N801BH

www.haaspowerair.com



--------

Eric M. Jones

Joined: 10 Jan 2006
Posts: 565
Location: Massachusetts

Posted: Fri Apr 30, 2010 4:36 am Post subject: Re: stopping engine

In learning to fly in a C150/C172, the explanation was:



The fuel was gravity fed with a left-right- both selector (was there an OFF?), the spark was magneto. In the event that the prop was turned by hand, the magneto could start the engine if its P-lead to ground lead was defective. So throttle at idle, mixture pulled lean until engine quit, switch off.



Your mileage may vary.

_________________
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones(at)charter.net

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