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The Hydraulic lock
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jan.mevis(at)informavia.b
Guest

Posted: Thu Jul 22, 2010 2:08 am Post subject: The Hydraulic lock

Anyway, since I recently hand-started the engine unwillingly (one hot mag,

no P-Lead connected, my stupid error!), I'm very reluctant to stand just in

front and swing the prop by pulling on the blades in the middle. Since this

bad experience, I'm again very suspicious about touching props on an engine.



So I pull the blades at the tip, keeping a good distance, and I do it

slowly! It takes a few minutes more. But I'm mentally prepared for an

unwanted start of the engine.



Second, I want the parking brakes checked, and if I'm alone and there's

nobody in the cockpit, I even prefer to put big blocks in front of the main

wheels. All too often I've seen a Yak move forward as soon as the engine

starts.



And for what it's worth: if you can manage to have someone being in the

neighborhood when starting up (and when shutting down), it's better. Give

them a fire extinguisher, just as the military did and still do. I've also

seen an M14P take fire several times. When you're alone and in the cockpit,

it 'll take a while before you notice that!



Exagerated? Maybe.

Only my 2 cents,



Jan

YK50 RA2005K

YK52 RA1453K



--

dsavarese0812(at)bellsout
Guest

Posted: Thu Jul 22, 2010 4:11 am Post subject: The Hydraulic lock

Intake manifold drains do not "prevent" hydraulic lock from  occurring.  They are there to reduce the possibility of hydraulic lock  occurring by draining any oil that accumulates in the intake tubes.   Draining the intake tubes reduces the possibility of oil being sucked into  the lower cylinders when the engine is started.

  

 Take a lesson from the T6 guys.  Have you ever noticed at  various air shows or fly ins that some T-6's have a tube/small hose with a milk  jug or something similar under the cowl?  It is to drain the sump after  shutdown.  On an M14, if you connect a hose on the sump drain where the  chip detector screen is located and allow the oil to drain into a CLEAN  container, the oil that typically causes hydraulic lock by spilling over into  the lower cylinders, will be drained into the container.  Then during  pre-flight, pour the oil back into the oil tank and close the sump  drain.

  

 A friend of mine came up with a really neat sump drain and we  have installed this very simple sump drain on other M14's.  It really  works!  Using a 90 degree AN fitting on the sump drain (1/8 NPT to 1/4"  hose barb), tap the sump drain and install the AN fitting with the barb end  pointing to the right (when looking at the front of the engine).  Then  attach 1/4" blue silicone hose (secure with a small hose clamp) from the barb  end of the AN fitting and run it back to the firewall through the opening  between the cowl pads on the engine baffling.  Next, install/mount a fuel  quick disconnect available from Aircraft Spruce on the mount of the coarse  (yellow) fuel screen using two Adel clamps.  Connect the blue, 1/4" hose to  the fuel quick disconnect and secure with hose clamps.  On the open end of  the fuel quick disconnect, attach another piece of hose and place the open end  into a clean 2 gallon/8-10 liter plastic gas container available at your local  auto supply store.  The quick disconnect is the neat part.  Press the  button on the quick disconnect, and the end with the long hose into the drain  container is removed.  When you land, simply press it back into the other  end of the quick disconnect and it snaps (literally) in place.  You can  reach through the cooling louvers on the cowl to open and close the sump drain  and reinstall the safety clip.

  

 This sump drain only fits on the straight sump drains.   Not the 90 degree sump drains which are attached below the chip detector.   The AN fitting won't clear the cowl.

  

 The root of the problem is of course the oil  leaking down after engine shut down through the oil pump.  It can be  stopped by installing the Jim Kimball oil shut off kit OR by having the oil pump  repaired, which is why the oil is leaking down in the first place.  There  is an internal valve in the oil pump which Jill so nicely described in the RPA  magazine last year that may not fully close.  When it does not close,  it allows the oil from the tank to flow through the oil pump and into the engine  which then ends up in the sump.  When the sump fills, the oil spills over  into the lower cylinders.  And everyone knows what that means.

  

 If anyone wants pictures of this simple sump drain  installation, email me off list and I will be happy to send some pictures of the  installation.

 Dennis

  

 [quote]   ---

viperdoc(at)mindspring.co
Guest

Posted: Thu Jul 22, 2010 4:47 am Post subject: The Hydraulic lock

If you do not want to go to all the trouble of tapping, fitting and mounting this system described by Dennis (which is pretty slick) you can do what another friend did with his 50.  

He simply drilled a ¼ in hole in the chin of his cowling under the sump drain. He slides a ¼ in hose through that hole at the end of each flight, pops the retaining clip on the sump drain lever, and opens it to run into a 5 gallon “clean” gas can. Whatever drains out before the next flight is then put back into the oil tank.  He of course has the intake drains installed also to keep any excess from accumulating there. As Dave says, it is kind of hard to push the plane out of the hanger with all that crap hanging off the chin and it really makes a big mess that you have to clean up when you knock the oil can over with the tail of the 50 if you got stupid and forgot to disconnect the system.   

Of course nothing is fool proof. This method introduces the least number of “gotcha’s” into the equation though. Not real fond of drilling holes in my skin but after watching Dave’s system work over the years now it has definitely conformed to the KISS principle.  

Doc  

       

From: owner-yak-list-server(at)matronics.com [mailto:owner-yak-list-server(at)matronics.com] On Behalf Of A. Dennis Savarese

 Sent: Thursday, July 22, 2010 7:11 AM

 To: yak-list(at)matronics.com

 Subject: Re: Re: The Hydraulic lock  

  

  

     

Intake manifold drains do not "prevent" hydraulic lock from occurring.  They are there to reduce the possibility of hydraulic lock occurring by draining any oil that accumulates in the intake tubes.  Draining the intake tubes reduces the possibility of oil being sucked into the lower cylinders when the engine is started.  

    

   

    

Take a lesson from the T6 guys.  Have you ever noticed at various air shows or fly ins that some T-6's have a tube/small hose with a milk jug or something similar under the cowl?  It is to drain the sump after shutdown.  On an M14, if you connect a hose on the sump drain where the chip detector screen is located and allow the oil to drain into a CLEAN container, the oil that typically causes hydraulic lock by spilling over into the lower cylinders, will be drained into the container.  Then during pre-flight, pour the oil back into the oil tank and close the sump drain.  

    

   

    

A friend of mine came up with a really neat sump drain and we have installed this very simple sump drain on other M14's.  It really works!  Using a 90 degree AN fitting on the sump drain (1/8 NPT to 1/4" hose barb), tap the sump drain and install the AN fitting with the barb end pointing to the right (when looking at the front of the engine).  Then attach 1/4" blue silicone hose (secure with a small hose clamp) from the barb end of the AN fitting and run it back to the firewall through the opening between the cowl pads on the engine baffling.  Next, install/mount a fuel quick disconnect available from Aircraft Spruce on the mount of the coarse (yellow) fuel screen using two Adel clamps.  Connect the blue, 1/4" hose to the fuel quick disconnect and secure with hose clamps.  On the open end of the fuel quick disconnect, attach another piece of hose and place the open end into a clean 2 gallon/8-10 liter plastic gas container available at your local auto supply store.  The quick disconnect is the neat part.  Press the button on the quick disconnect, and the end with the long hose into the drain container is removed.  When you land, simply press it back into the other end of the quick disconnect and it snaps (literally) in place.  You can reach through the cooling louvers on the cowl to open and close the sump drain and reinstall the safety clip.  

    

   

    

This sump drain only fits on the straight sump drains.  Not the 90 degree sump drains which are attached below the chip detector.  The AN fitting won't clear the cowl.  

    

   

    

The root of the problem is of course the oil leaking down after engine shut down through the oil pump.  It can be stopped by installing the Jim Kimball oil shut off kit OR by having the oil pump repaired, which is why the oil is leaking down in the first place.  There is an internal valve in the oil pump which Jill so nicely described in the RPA magazine last year that may not fully close.  When it does not close, it allows the oil from the tank to flow through the oil pump and into the engine which then ends up in the sump.  When the sump fills, the oil spills over into the lower cylinders.  And everyone knows what that means.  

    

   

    

If anyone wants pictures of this simple sump drain installation, email me off list and I will be happy to send some pictures of the installation.  

    

Dennis  

    

   

   	  Quote: 	
		      

----- Original Message -----   

    

From: psb777 (matronics.com(at)beardsell.com)   

    

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

    

Sent: Thursday, July 22, 2010 4:36 AM  

    

Subject: Re: The Hydraulic lock  

    

   

  

--> Yak-List message posted by: "psb777" <matronics.com(at)beardsell.com (matronics.com(at)beardsell.com)>

 

 Francois's very unfortunate experience was a consequence, it is acknowledged, of there being an accumulation of oil in the inlet manifold, and the anti-lock procedure used now known not to be comprehensively correct.  I do not think the idea to modify this procedure next time to again swing the prop after replacing the plugs would have helped, necessarily.  Cold possibly congealed oil in the inlet manifold might not have been cleared by the extra swinging (the air path not being completely blocked, or air bubbling through), and the oil would still have been sucked in just after the start.

 

 Hydraulic lock is such a worry to us all. Whereas the oil tank tap and the scavenger pump would be nice things to fit to my 18T there are unintended consequences, perhaps, to doing such mods. They themselves can, potentially cause things to break. E.g. The tap could be left switched off and that will ruin your engine also.  And the the starter interlock to prevent this could stop working - how would you know?  It would be another thing to test periodically. Certainly I would want to put checking that the starter doesn't work with the tap off into my startup checklist.  I think that the addition of extra bits and pieces can sometimes make the whole assembly more prone to failure.

 

 A case in point - at the time I bought my 18T inlet manifold drains were fitted so as to help prevent hydraulic lock.  But twice now I have got back on the ground to find they had been open throughout the flight.  OK, no big consequence, but I am an idiot, and there is no compensating for that.  

 

 I left my 18T unflown in a hangar five months over the Winter.  On returning to it there was a large pool of oil in the drip tray. The oil dipstick read 5.  The a/c was dragged out into the sun.  I added 5 litres of oil, all that I had.  I swung the prop and what looked like another litre of oil emerged from exhaust pipes and inlet drains.  I waited and swung again.  More oil, but not as much.  I waited and swung again.  A few drops only.  I closed the inlet drains, alternated each primer stroke with a prop blade pull, and depressed the drains momentarily to let excess liquid fuel escape.  After the second unsuccessful start attempt I started again, opening the drains, swinging the prop, repriming etc etc.  The engine started on the third attempt, just as the air was about to be exhausted, in an unsually large cloud of smoke.  I went flying.

 

 Before the next flight I dipped the oil tank to find it reading more than 12.  5+5=10.  So over two litres of oil had been in the sump and/or cupped inside the lower pistons when I had started the engine the first time.

 

 But had that constituted a risk of hydraulic lock?  No, I suggest, not if you follow the procedure I did.  There was no substantial oil in the cylinder heads, and there was not enough time given for any meaningful quantity to leak past the rings.  And the inlet manifold was clear.  

 

 I cannot see how the combination of swinging the prop (and repeating if oil emerges) and fitting inlet manifold drains (and leaving them open between flights) should fail to prevent hydraulic lock.  Also, no matter how much extra kit I fit, the swinging of the prop and the inlet drains would remain necessary.  So I think I won't be fitting other stuff that might break.

 

 I worry that I am tempting fate, and that my next posting could be to report a disaster.  [On the other hand we're so worried about hydraulic lock that we think it possible or even simple to bend a con rod by pulling on the end of the prop - surely that is a nonsense!?!]  Anyway, I'm very willing to listen to all dissenting opinion.

 

 --------

 Paul Beardsell

 HA-YAB http://beardsell.com/flying/ha-yab

 Yak-18T http://beardsell.com/flying/yak18t

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=305905#305905

 

 

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dsavarese0812(at)bellsout
Guest

Posted: Thu Jul 22, 2010 4:53 am Post subject: The Hydraulic lock

What Doc describes is definitely the KISS method and certainly  works very well.  It's also the same thing the T6 guys do which, according  to Dave, is where his idea came from.

 Dennis

 [quote]   ---

psb777

Joined: 12 Aug 2009
Posts: 34
Location: UK

Posted: Thu Jul 22, 2010 6:01 am Post subject: Re: The Hydraulic lock

I haven't seen the T6 guys. do they still swing their props before starting?



[quote="dsavarese0812(at)bellsout"]What Doc describes is definitely the KISS method and certainly  works very well.  It's also the same thing the T6 guys do which, according  to Dave, is where his idea came from.

 Dennis

  	  Quote: 	
		     ---

_________________
Paul Beardsell
G-PYAK http://beardsell.com/flying/g-pyak
Yak-18T http://beardsell.com/flying/yak18t

bu131(at)swbell.net
Guest

Posted: Thu Jul 22, 2010 6:19 am Post subject: The Hydraulic lock

Always 9 turns

Snj5 777hl

---

psb777

Joined: 12 Aug 2009
Posts: 34
Location: UK

Posted: Thu Jul 22, 2010 6:26 am Post subject: Re: The Hydraulic lock

So the sump drain device is not enough, in the T6, by itself, to prevent hydraulic lock?

_________________
Paul Beardsell
G-PYAK http://beardsell.com/flying/g-pyak
Yak-18T http://beardsell.com/flying/yak18t

viperdoc(at)mindspring.co
Guest

Posted: Thu Jul 22, 2010 7:44 am Post subject: The Hydraulic lock

No, you still have to get your exercise pulling the blades.

Doc



--

dougsappllc(at)gmail.com
Guest

Posted: Thu Jul 22, 2010 8:25 am Post subject: The Hydraulic lock

Guys,I'm amazed (or maybe I missed the post) that no one has bothered to mention that either pre heating or elec heat pads will help the situation and GREATLY lessen the chances of having cold thick oil clinging to the ID of the intake pipes.  This small amount of cold stiff oil is easily capable of causing a hyd lock as it will be sucked off the walls and into the cyls as soon as the engine fires.  Cold weather operations without some form of heat is very, very risky business, even if you fly every day the odds of a hyd lock are great without some form of heat.  IMHO if you let your engine set for a period of time in the cold and then (without some form of heat), expect to do the standard "pull the plugs and rotate" routine you are flirting with disaster.  You may think you are getting away with it, but it is very possible that you will suffer some degree of lock, micro or major, but the odds are that it will happen.  Your just playing Russian roulette ---don't do it!  We all  need to realize that just because your engine did not suddenly go THUNK and stop during start up that it does not mean that you did not bend a rod.  There are all degrees of bends from the very slight to the extreme where in the rod contacts the skirt an stops the engine.

 



Best from Omak

Doug





On Thu, Jul 22, 2010 at 2:36 AM, psb777 <matronics.com(at)beardsell.com> wrote:

 [quote]--> Yak-List message posted by: "psb777" <matronics.com(at)beardsell.com>

  

 Francois's very unfortunate experience was a consequence, it is acknowledged, of there being an accumulation of oil in the inlet manifold, and the anti-lock procedure used now known not to be comprehensively correct.  I do not think the idea to modify this procedure next time to again swing the prop after replacing the plugs would have helped, necessarily.  Cold possibly congealed oil in the inlet manifold might not have been cleared by the extra swinging (the air path not being completely blocked, or air bubbling through), and the oil would still have been sucked in just after the start.

  

 Hydraulic lock is such a worry to us all. Whereas the oil tank tap and the scavenger pump would be nice things to fit to my 18T there are unintended consequences, perhaps, to doing such mods. They themselves can, potentially cause things to break. E.g. The tap could be left switched off and that will ruin your engine also.  And the the starter interlock to prevent this could stop working - how would you know?  It would be another thing to test periodically. Certainly I would want to put checking that the starter doesn't work with the tap off into my startup checklist.  I think that the addition of extra bits and pieces can sometimes make the whole assembly more prone to failure.

  

 A case in point - at the time I bought my 18T inlet manifold drains were fitted so as to help prevent hydraulic lock.  But twice now I have got back on the ground to find they had been open throughout the flight.  OK, no big consequence, but I am an idiot, and there is no compensating for that.

  

 I left my 18T unflown in a hangar five months over the Winter.  On returning to it there was a large pool of oil in the drip tray. The oil dipstick read 5.  The a/c was dragged out into the sun.  I added 5 litres of oil, all that I had.  I swung the prop and what looked like another litre of oil emerged from exhaust pipes and inlet drains.  I waited and swung again.  More oil, but not as much.  I waited and swung again.  A few drops only.  I closed the inlet drains, alternated each primer stroke with a prop blade pull, and depressed the drains momentarily to let excess liquid fuel escape.  After the second unsuccessful start attempt I started again, opening the drains, swinging the prop, repriming etc etc.  The engine started on the third attempt, just as the air was about to be exhausted, in an unsually large cloud of smoke.  I went flying.

  

 Before the next flight I dipped the oil tank to find it reading more than 12.  5+5=10.  So over two litres of oil had been in the sump and/or cupped inside the lower pistons when I had started the engine the first time.

  

 But had that constituted a risk of hydraulic lock?  No, I suggest, not if you follow the procedure I did.  There was no substantial oil in the cylinder heads, and there was not enough time given for any meaningful quantity to leak past the rings.  And the inlet manifold was clear.

  

 I cannot see how the combination of swinging the prop (and repeating if oil emerges) and fitting inlet manifold drains (and leaving them open between flights) should fail to prevent hydraulic lock.  Also, no matter how much extra kit I fit, the swinging of the prop and the inlet drains would remain necessary.  So I think I won't be fitting other stuff that might break.

  

 I worry that I am tempting fate, and that my next posting could be to report a disaster.  [On the other hand we're so worried about hydraulic lock that we think it possible or even simple to bend a con rod by pulling on the end of the prop - surely that is a nonsense!?!]  Anyway, I'm very willing to listen to all dissenting opinion.

  

 --------

 Paul Beardsell

 HA-YAB http://beardsell.com/flying/ha-yab

 Yak-18T http://beardsell.com/flying/yak18t

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=305905#305905

 

 

 

 

 

 

 

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 [b]

dsavarese0812(at)bellsout
Guest

Posted: Thu Jul 22, 2010 9:20 am Post subject: The Hydraulic lock

Some do and some don't.  Many have a scavenge pump  installed to pump the oil from the sump back into the oil tank.  I've  seen one installation with an attempt to do the same thing on an M14  and it was a disaster.  You had to remove part of the additional tubing, 2  rocker covers, an adapter plate and hoses BEFORE you could remove and  inspect the chip detector screen.  

 [quote]   ---

fish(at)aviation-tech.com
Guest

Posted: Thu Jul 22, 2010 11:23 am Post subject: The Hydraulic lock

Sir,



Yes the T-6's still swing the prop before start up.

We have the fitting on some of the T-6's (Condor Squadron), for the sump drain.

The clean kit, keeps excess oil from getting down the side of the aircraft.

But all props still get swung by hand before start up.



Laterrrrrr

Avn-Tech

Member, Condor Squadron

Crew, T-6, #42 Honest Entry, Reno Air Races



At 07:01 AM 7/22/2010, you wrote:

 	  Quote: 	
		  



I haven't seen the T6 guys. do they still swing their props before starting?



[quote="dsavarese0812(at)bellsout"]What Doc describes is definitely 

the KISS method and certainly  works very well.  It's also the same 

thing the T6 guys do which, according  to Dave, is where his idea came from.

  Dennis



 >    ---

--------

Paul Beardsell

HA-YAB http://beardsell.com/flying/ha-yab

Yak-18T http://beardsell.com/flying/yak18t





Read this topic online here:



http://forums.matronics.com/viewtopic.php?p=305932#305932

tigeryak18t

Joined: 26 Sep 2009
Posts: 233
Location: PARIS FRANCE

Posted: Thu Jul 22, 2010 2:55 pm Post subject: The Hydraulic lock

Hello Dennis,



I never heard about this system for draining the oil. I have intalled a draining system with the plugs you sent me. If I can add this draining system I will be most pleased to have a look on your installation.

  

Thanks a lot Dennis



best regards from Paris



Didier



2010/7/22 A. Dennis Savarese <dsavarese0812(at)bellsouth.net (dsavarese0812(at)bellsouth.net)>

  [quote]       Intake manifold drains do not "prevent" hydraulic lock from  occurring.  They are there to reduce the possibility of hydraulic lock  occurring by draining any oil that accumulates in the intake tubes.   Draining the intake tubes reduces the possibility of oil being sucked into  the lower cylinders when the engine is started.

  

 Take a lesson from the T6 guys.  Have you ever noticed at  various air shows or fly ins that some T-6's have a tube/small hose with a milk  jug or something similar under the cowl?  It is to drain the sump after  shutdown.  On an M14, if you connect a hose on the sump drain where the  chip detector screen is located and allow the oil to drain into a CLEAN  container, the oil that typically causes hydraulic lock by spilling over into  the lower cylinders, will be drained into the container.  Then during  pre-flight, pour the oil back into the oil tank and close the sump  drain.

  

 A friend of mine came up with a really neat sump drain and we  have installed this very simple sump drain on other M14's.  It really  works!  Using a 90 degree AN fitting on the sump drain (1/8 NPT to 1/4"  hose barb), tap the sump drain and install the AN fitting with the barb end  pointing to the right (when looking at the front of the engine).  Then  attach 1/4" blue silicone hose (secure with a small hose clamp) from the barb  end of the AN fitting and run it back to the firewall through the opening  between the cowl pads on the engine baffling.  Next, install/mount a fuel  quick disconnect available from Aircraft Spruce on the mount of the coarse  (yellow) fuel screen using two Adel clamps.  Connect the blue, 1/4" hose to  the fuel quick disconnect and secure with hose clamps.  On the open end of  the fuel quick disconnect, attach another piece of hose and place the open end  into a clean 2 gallon/8-10 liter plastic gas container available at your local  auto supply store.  The quick disconnect is the neat part.  Press the  button on the quick disconnect, and the end with the long hose into the drain  container is removed.  When you land, simply press it back into the other  end of the quick disconnect and it snaps (literally) in place.  You can  reach through the cooling louvers on the cowl to open and close the sump drain  and reinstall the safety clip.

  

 This sump drain only fits on the straight sump drains.   Not the 90 degree sump drains which are attached below the chip detector.   The AN fitting won't clear the cowl.

  

 The root of the problem is of course the oil  leaking down after engine shut down through the oil pump.  It can be  stopped by installing the Jim Kimball oil shut off kit OR by having the oil pump  repaired, which is why the oil is leaking down in the first place.  There  is an internal valve in the oil pump which Jill so nicely described in the RPA  magazine last year that may not fully close.  When it does not close,  it allows the oil from the tank to flow through the oil pump and into the engine  which then ends up in the sump.  When the sump fills, the oil spills over  into the lower cylinders.  And everyone knows what that means.

  

 If anyone wants pictures of this simple sump drain  installation, email me off list and I will be happy to send some pictures of the  installation.

 Dennis

  

 [quote]   ---

_________________
Didier Tiger YAK18T
Member of Commemorative Air Force
French Wing

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