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The Hydraulic lock
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viperdoc(at)mindspring.co
Guest

Posted: Wed Feb 24, 2010 3:05 pm Post subject: The Hydraulic lock

Another way is to simply drain the sump into a sealed 5 gal fuel can (plastic of course). The oil can then be poured back into the main tank before the next flight. Dennis Savarese can provide the details for making this simple but effective modification. One of my hanger mates has made this simple mod. He leaves his plane un-flown for 2-3 months using this sealed system. He does not have a drop of oil in the intake drain over flow catch bucket nor the exhaust stack drain buckets at 2 months currently. It was cheaper than the $700 oil cut-off kit.   

Doc  

       

From: owner-yak-list-server(at)matronics.com [mailto:owner-yak-list-server(at)matronics.com] On Behalf Of Chris Wise

 Sent: Wednesday, February 24, 2010 4:03 PM

 To: Francois Davel

 Subject: Re: The Hydraulic lock  

  

  

     

G'Day Francois,  

    

   

    

You are spot on.  

    

A friend of mine has a 52. He went to fly it after standing for 2 1/2 weeks and found 2 litres of oil in the tank.  

    

We have had similar problems and have refaced the oil non return valve.  

    

In spite of that, we then also had a locked up engine 3 weeks ago after not flying for 3 weeks.  

    

There are others in Australia that sing the same tune.  

    

   

    

To solve the problem, my mate with the 52 and I have already bought the oil shut off valve and scavenge pump set up from Jim Kimball and as we speak are busy installing these items to our aircraft.  

    

   

    

I think that the shut off valve on its own should suffice, but we both decided to fit the oil scavenge pump as well as an extra safeguard.  

    

You may think that US$300 plus $300 for the pump = US$700 is too expensive, but it is a small price to pay to prevent that dreaded bang of hydraulic lock and an engine strip and rebuild.  

    

   

    

Good luck with it all Francois.  

    

   

    

Cheers, Chris.  

    

   

    

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

   	  Quote: 	
		      

From: Francois Davel (fdavel(at)senninger.biz)   

    

To: annie(at)flygal.co.za (annie(at)flygal.co.za) ; adamsfamily(at)telkomsa.net (adamsfamily(at)telkomsa.net) ; lushd(at)mweb.co.za (lushd(at)mweb.co.za) ; gpw678(at)aol.com (gpw678(at)aol.com) ; greg(at)rwa.co.za (greg(at)rwa.co.za) ; skywrite(at)iafrica.com (skywrite(at)iafrica.com) ; ecapea(at)telkomsa.net (ecapea(at)telkomsa.net) ; roger(at)spikeapparel.co.za (roger(at)spikeapparel.co.za) ; williamo(at)iafrica.com (williamo(at)iafrica.com) ; mcarstens(at)mweb.co.za (mcarstens(at)mweb.co.za)   

    

Cc: tmo34003(at)bigpond.net.au (tmo34003(at)bigpond.net.au) ; Chris Wise (wise(at)txc.net.au) ; Golfcartpro (info(at)golfcartpro.co.za) ; lushd(at)mweb.co.za (lushd(at)mweb.co.za)   

    

Sent: Thursday, February 25, 2010 6:52 AM  

    

Subject: The Hydraulic lock  

    

   

  

Hi there Fellow aviators, Friends and Yak owners  

   

As the subjects of the e mail shows, this is something serious….  

   

The one thing we all fear is the Hydraulic lock......  

   

I must say that when it happens it is really frightful.....so we should all fear it!!!  

   

So we do many things to save ourselves from this most horrible experience:  

   

We pull blades  

   

We have manifold drains  

   

We run the engine at 65% for 20 seconds at shutdown…..  

   

All in an attempt to stop this from happening to us.  

   

Well while all this helps it does not solve the problem…..I am now speaking from experience so I would like to share what has happened to me and offer you another solution.  

   

I did what we all know what we should do, pulling blades through and making sure there is no oil in the cylinders, and when I find or feel a “lock” I do the right thing and removed the cowls remove the plugs and allow the oil to drain, we even pull the blades through with the plugs out, so making sure there is no oil hidden anywhere. Well this was what I did AND I got a hydraulic lock and am living with the results of that…. However can you spot the mistake?  

   

While I had the plugs out and was pulling the blades the cylinders 5 + 6 were getting air from the open plug hole. While had a let the oil drain out, and replaced the plugs and then pulled the blades I would have sucked air through the inlet valve and so also sucked the oil in that was in the inlet manifold……while I do have a manifold drain and it was open, there must have been oil there. Since this what I did:  

   

The plugs are replaced, since I thought all was fine since  no extra oil came out. Bearing in mind that I had not replaced the plugs while pulling the blades.  

   

So no oil meant I could get in and prime and start the engine, the engine fired a couple of times and comes to sudden halt.  

   

This is when you know all is not as it should be.  

   

Now the question why? I did the right things, everything I have been taught to do.  

   

Simple I did not get the oil out…..and oil causes the “Lock”.  

   

So to stop the Lock we need to exclude the reason for the Lock, OIL!!!!  

   

I do not take any credit for this since the guys on the forum (follow this link - http://forums.matronics.com/viewforum.php?f=60&sid=9517d1dd056024aec1842940271d50fa ) have done the thinking.  

   

We need to install an oil shut off valve. See the picture below:  

   

[img]cid:image001.jpg(at)01CAB571.80134980[/img]  

   

This is a cable operated valve that is manually closed after shut down and in the closed position it cut the start circuit by means of a micro switch (not shown) so if it closed the engine cannot start……  

   

I am in the process of looking into having this made here in SA (this one is from the USA and costs $300), so if you are interested, I will put you in contact with the right people since I am sure we could make it cheaper.  

   

However, the purpose of the e mail is to tell you guys that we are all living dangerously……we are all allowing oil to get into the engine, and we all doing what we have been taught to do, but this is not good enough……get rid of the oil!!!  

   

I must just add that I can say we are a tight band of brothers and sister, in this time I have been offered help with parts, advice, and contacts, for all of which I am eternally grateful. Thank you friends.  

   

I am also in the process of working on a system by which you can remove the bent rod from the engine and replace it without removing the engine from the plane. This has not been completed yet, so once we (the AMO and I) have done this I will send out the method to those that are interested. This has been done before but it seems the method has been very closely guarded.   

   

Keep safe keep oil free, and please be careful of the Lock…..  

   

Cheers  

   

Francois  

   

   

   

Regards,  

   

Francois Davel  

   

=================  

Regional Manager  

Senninger Irrigation, Inc.  

fdavel(at)senninger.com (fdavel(at)senninger.com)  

+27 82 414 3762 (Cell)  

+27 86 600 7583 (Fax)  

www.senninger.com  

=================  

NOTICE: This Senninger Irrigation Inc. e-mail message (including any file attachment) is intended only for the use of the individual or entity to which it is addressed, and may contain information that is privileged and/or confidential. If you are not the intended recipient, any dissemination, distribution or copying of this communication is strictly prohibited. If you have received this communication in error, please notify the sender immediately by reply e-mail or a collect telephone call and delete or destroy all copies of this message and any file attachment. Thank you!  

       

  

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plus2s

Joined: 30 Nov 2006
Posts: 65
Location: NEW ZEALAND

Posted: Wed Feb 24, 2010 4:45 pm Post subject: The Hydraulic lock

The easiest fix is to fly at least every 2 weeks !!!



--- On Thu, 25/2/10, Roger Kemp M.D. <viperdoc(at)mindspring.com> wrote:

  	  Quote: 	
		  

From: Roger Kemp M.D. <viperdoc(at)mindspring.com>

Subject: RE: Re: The Hydraulic lock

To: yak-list(at)matronics.com

Date: Thursday, 25 February, 2010, 11:53 AM



       

Another way is to simply drain the sump into a sealed 5 gal fuel can (plastic of course). The oil can then be poured back into the main tank before the next flight. Dennis Savarese can provide the details for making this simple but effective modification. One of my hanger mates has made this simple mod. He leaves his plane un-flown for 2-3 months using this sealed system. He does not have a drop of oil in the intake drain over flow catch bucket nor the exhaust stack drain buckets at 2 months currently. It was cheaper than the $700 oil cut-off kit. 

 

Doc

 

 

   



	
  [quote][b]

viperdoc(at)mindspring.co
Guest

Posted: Wed Feb 24, 2010 6:50 pm Post subject: The Hydraulic lock

Shack…better to fly it weekly…the RU manual calls for pulling a min. of 8 blades every couple of weeks if the aircraft is going to sit. It calls for pulling the plugs if it is going to sit longer than a month.  

From: owner-yak-list-server(at)matronics.com [mailto:owner-yak-list-server(at)matronics.com] On Behalf Of Keith Pickford

 Sent: Wednesday, February 24, 2010 6:02 PM

 To: yak-list(at)matronics.com

 Subject: RE: Re: The Hydraulic lock  

The easiest fix is to fly at least every 2 weeks !!!

   --- On Thu, 25/2/10, Roger Kemp M.D. <viperdoc(at)mindspring.com>   wrote:   

   From: Roger Kemp M.D. <viperdoc(at)mindspring.com>

   Subject: RE: Re: The Hydraulic lock

   To: yak-list(at)matronics.com

   Date: Thursday, 25 February, 2010, 11:53 AM         

Another way is to simply drain the   sump into a sealed 5 gal fuel can (plastic of course). The oil can then be   poured back into the main tank before the next flight. Dennis Savarese can   provide the details for making this simple but effective modification. One of   my hanger mates has made this simple mod. He leaves his plane un-flown for   2-3 months using this sealed system. He does not have a drop of oil in the   intake drain over flow catch bucket nor the exhaust stack drain buckets at 2   months currently. It was cheaper than the $700 oil cut-off kit.    

Doc   

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       [quote][b]

Francois Davel

Joined: 19 Jan 2009
Posts: 24

Posted: Wed Feb 24, 2010 11:08 pm Post subject: Re: The Hydraulic lock

I can take 3 days for a Hydraulic lock to form......That translates into a lot fun flying, but a huge fuel bill....

_________________
Round Engines RULE!

william(at)netpros.net
Guest

Posted: Thu Feb 25, 2010 7:06 am Post subject: The Hydraulic lock

Somewhere I recall that when oil leaks from the sump, it could be an 

indicator the oil pump's seals are wearing out.  It that what is 

causing the oil to drain into the intake pipes?  Did I recall that correctly?



Also my manual calls for running the engine at about the same power 

setting as used for the pre-flight engine run up for about 20 seconds 

to suck oil out of the sump and shove it back into the oil tank.  I 

love it when crowds gather to see what's causing all that noise in a 

hangar row ....  so far the EPA truck has not showed up.





At 11:08 PM 2/24/2010, Francois Davel wrote:

 	  Quote: 	
		  



I can take 3 days for a Hydraulic lock to form......That translates 

into a lot fun flying, but a huge fuel bill.... 



--------

Round Engines RULE!

dsavarese0812(at)bellsout
Guest

Posted: Thu Feb 25, 2010 8:59 am Post subject: The Hydraulic lock

There is an internal "valve" in the oil pump which may remain  open.  Jill of M14P, Inc. did an excellent article in one of the recent  issues of the RPA magazine about this problem.  See the Fall of 2009 issue,  page 15.  If this valve remains open even slightly, oil will drain  from the oil tank into the engine which may cause the hydraulic  lock.   Although Jim Kimball's oil shut off and drain kit are  outstanding, the root of the problem is internal to the oil  pump.

 Dennis

  

 p.s. The Fall of 2009 issue is too big to attach.

  

  

  

 [quote]   ---

kurt(at)scitechsys.com
Guest

Posted: Thu Feb 25, 2010 9:19 am Post subject: The Hydraulic lock

If you're an RPA member - archived copies are available here:

http://flyredstar.org/magazine-archive.php

-- 

Kurt "It" Howerton

N923YK

http://cj6.scitechsys.com



On 02/25/2010 08:59 AM, A. Dennis Savarese wrote:

 	  Quote: 	
		   There is an internal "valve" in the oil pump which may remain open. 

 Jill of M14P, Inc. did an excellent article in one of the recent

 issues of the RPA magazine about this problem.  See the Fall of 2009

 issue, page 15.  If this valve remains open even slightly, oil will

 drain from the oil tank into the engine which may cause the hydraulic

 lock.   Although Jim Kimball's oil shut off and drain kit are

 outstanding, the root of the problem is internal to the oil pump.

 Dennis

  

 p.s. The Fall of 2009 issue is too big to attach.

threein60(at)yahoo.com
Guest

Posted: Fri Feb 26, 2010 1:51 pm Post subject: The Hydraulic lock

Keep in mind.. Even with an oil shut-off valve, the splash and ported oil in the top cylinders and gears will still drip down to the lowest point in the engine.  So the long and short is.. You must always pull your engine through, with of without and external mods.



Larry Pine



 	  Quote: 	
		  



	


         [quote][b]

Francois Davel

Joined: 19 Jan 2009
Posts: 24

Posted: Sat Feb 27, 2010 5:46 am Post subject: Re: The Hydraulic lock

Hi there Larry, point taken, but the less oil you have the less is the chance for the LOCK.



I am not sure and hopefully there is wisdom on this list that can answer the question:



Is there enough oil in the upper part of the engine that could drain into the lower cylinders, to cause a hydraulic lock?



Cheers



Francois

_________________
Round Engines RULE!

viperdoc(at)mindspring.co
Guest

Posted: Sat Feb 27, 2010 6:01 am Post subject: The Hydraulic lock

Yes. The prudent pilot will always pull blades before starting this engine.

doc



--

rick(at)rvairshows.com
Guest

Posted: Sat Feb 27, 2010 6:32 am Post subject: The Hydraulic lock

And pull it through even after a fifteen minute fuel stop. You will also occasionally get a lock five hours after a run on a hot day, that requires pulling bottom spark plugs to clear. 

Rick Volker

---

william(at)netpros.net
Guest

Posted: Sat Feb 27, 2010 1:42 pm Post subject: The Hydraulic lock

Agreed!  Also good excercise!

+--

mark.bitterlich(at)navy.m
Guest

Posted: Sat Feb 27, 2010 2:52 pm Post subject: The Hydraulic lock

Yes?  

 

My answer would be that it is very hard to tell what oil comes from the top of the engine and what oil has leaked through a poorly seated ball check valve.  

 

If you have a oil shut off valve, and turn it off immediately after you land, ... along with a lower sump pump.... I would be curious to know how much oil came out of ANYTHING... plugs, sump, you name it... after landing, turning off the valve, using the sump pump, letting it sit for a MONTH and then coming back to see exactly how much is in it.  

 

My few experiences with engines set up like this is ... nothing.   Less than maybe a few ounces.  NONE in the cylinders.  NONE!  

 

However, without having these devices, it is very very possible to have an engine hyd. lock even in 15 minutes to 30 minutes, with the right conditions, as was mentioned. 

 

You also must pull it through ... as was mentioned.  

 

But the few engines I have had experience with that had both a sump pump and a shut-off valve, that were used directly after shutdown, have never had a drop of oil come out of ANYPLACE a month after just sitting there.  

 

I guess if you had cracked rings and stacked rings, the oil could just run down right into the cylinder it might be possible.  

 

Bottom line it becomes a moot debate, or discussion.   If you don't have the sump pump and you don't have the oil shut off valve, ... the amount of oil that gets into cylinders on exactly what engine and exactly after so many minutes, is going to vary from one engine to another and there is no way to predict exactly how much.  

 

mgb



________________________________



From: owner-yak-list-server(at)matronics.com on behalf of Roger Kemp M.D.

Sent: Sat 2/27/2010 9:00 AM

To: yak-list(at)matronics.com

Subject: RE: Re: The Hydraulic lock






Yes. The prudent pilot will always pull blades before starting this engine.

doc



--

kjkimball(at)aol.com
Guest

Posted: Sat Feb 27, 2010 4:32 pm Post subject: The Hydraulic lock

Guys



I have followed this discussion as it refers to our clean kit  

components.



First, to be clear, we developed this items for the model 12. Using  

them on yaks and cj aircraft among others is being done as well.



Our "system" includes 3 parts:

Shut off valve

Scavenge pump

Intake drains



Full benefit is realized only if installing and properly using all 3.



Example operational use:



Prior to start, intake drain is open left this way from previous shut  

down program. Leave it open. Check mags off pull prop through 3 revs.  

Close drain complete typical prefight checks. Prime engine. Open oil  

shut off valve via cockpit control cable. Start engine and go fly.



After landing and at shut down area, kill engine as normal. Pull cable  

to close shut off valve. Turn on scab pump and run until it skips.  

This eturns the sump oil to the tank above the now close oil valve.  

Exit aircraft as normal. Open intake drain. Store airplane.



Repeat for every flight.



We have all of these components in service now more than 10 years.  

Some with 700 plus hours in service. We fly the model 12 to advanced  

and unlimited level acro and have never failed one of these parts,  

sump fitting, oil tank bung, etc.



Sent from my iPhone sitting in Carabas Italian grill.



Kevin kimball

Jim kimball enterprises, Inc.



On Feb 27, 2010, at 5:51 PM, "Bitterlich, Mark G CIV Det Cherry Point,  

MALS-14 64E" <mark.bitterlich(at)navy.mil> wrote:



[quote] 

 Point, MALS-14 64E" <mark.bitterlich(at)navy.mil>



 Yes?



 My answer would be that it is very hard to tell what oil comes from  

 the top of the engine and what oil has leaked through a poorly  

 seated ball check valve.



 If you have a oil shut off valve, and turn it off immediately after  

 you land, ... along with a lower sump pump.... I would be curious to  

 know how much oil came out of ANYTHING... plugs, sump, you name  

 it... after landing, turning off the valve, using the sump pump,  

 letting it sit for a MONTH and then coming back to see exactly how  

 much is in it.



 My few experiences with engines set up like this is ... nothing.    

 Less than maybe a few ounces.  NONE in the cylinders.  NONE!



 However, without having these devices, it is very very possible to  

 have an engine hyd. lock even in 15 minutes to 30 minutes, with the  

 right conditions, as was mentioned.



 You also must pull it through ... as was mentioned.



 But the few engines I have had experience with that had both a sump  

 pump and a shut-off valve, that were used directly after shutdown,  

 have never had a drop of oil come out of ANYPLACE a month after just  

 sitting there.



 I guess if you had cracked rings and stacked rings, the oil could  

 just run down right into the cylinder it might be possible.



 Bottom line it becomes a moot debate, or discussion.   If you don't  

 have the sump pump and you don't have the oil shut off valve, ...  

 the amount of oil that gets into cylinders on exactly what engine  

 and exactly after so many minutes, is going to vary from one engine  

 to another and there is no way to predict exactly how much.



 mgb



 ________________________________



 From: owner-yak-list-server(at)matronics.com on behalf of Roger Kemp M.D.

 Sent: Sat 2/27/2010 9:00 AM

 To: yak-list(at)matronics.com

 Subject: RE: Re: The Hydraulic lock



 

 >



 Yes. The prudent pilot will always pull blades before starting this  

 engine.

 doc



 --

harley(at)siriusconinc.co
Guest

Posted: Sat Feb 27, 2010 5:59 pm Post subject: The Hydraulic lock

Rick,



I was trained never to pull the prop thru when the engine is warm??



Martin



---

radiopicture

Joined: 23 Jun 2008
Posts: 263

Posted: Sat Feb 27, 2010 7:21 pm Post subject: The Hydraulic lock

That's only when it's very recently shut down. I had heard the reason  

was to avoid scoring the cylinders, but the primary reason is so it  

doesn't fire on you. Fifteen minutes is long enough.

On Feb 27, 2010, at 8:58 PM, Martin (Home) wrote:



[quote] 

 >



 Rick,



 I was trained never to pull the prop thru when the engine is warm??



 Martin



 ---

rick(at)rvairshows.com
Guest

Posted: Sat Feb 27, 2010 7:57 pm Post subject: The Hydraulic lock

Martin,

    There is a CHT below which it is safe to move the prop. I use 250 degrees F .   After a 15 minute fuel stop, you are always well below that, especially if you have used proper shut-down procedure.

Rick Volker

On Feb 27, 2010, at 10:18 PM, Eric Wobschall wrote:

[quote] 

 That's only when it's very recently shut down. I had heard the reason was to avoid scoring the cylinders, but the primary reason is so it doesn't fire on you. Fifteen minutes is long enough.

 On Feb 27, 2010, at 8:58 PM, Martin (Home) wrote:

> 

> 

> Rick,

> 

> I was trained never to pull the prop thru when the engine is warm??

> 

> Martin

> 

> ---

Francois Davel

Joined: 19 Jan 2009
Posts: 24

Posted: Wed Jul 21, 2010 11:43 am Post subject: Re: The Hydraulic lock

Well as an update I would like post the following.



Due to a lot of support from friends and a very good engineer we managed to replace the bent rod, on #5

Below is what would consider a safe procedure, any comments? or additions?



I have been thinking a lot about the that fateful day and how the lock occurred what could have been done to prevent it and what would I do differently?



We here is what I have come to think of good procedure, to prevent this happening to myself again, and happening to one of you.



Never pull the prop on the end, always pull the prop half way along the blade, this gives you less leverage and so limits the problem of bending a rod with the prop. Which I believe is possible. 

Always stop when ANY resistance is felt. Do not try and “squeeze” through the oil. It is quite possible to “squeeze” the oil past the rings and so get through a small lock.....but it HUGELY dangerous. With the leverage you have in your hand through the prop you could easily damage the connecting rod. 

NEVER TRUN THE PROP BACKWARDS!!!!!! This is arguably the most dangerous thing to do, since it could allow the oil to go up into the intake manifold, ready to be sucked into the cylinder and cause damage. 

So as soon as there is any resistance felt stop turning the prop, and open the two bottom cylinders,and allow time for the oil to drain, do NOT rush. Once the oil has stopped draining then you MUST screw the plugs back in!!! Then pull another full set of blades, I usually pull 16 blades. And if there any resistance, then you need to stop and remove the plugs again. Allow time for the oil to drain.....do NOT RUSH. 

As soon as you can pull your blades and there is no resistance then you are ready to fly.



There are options, like and oil shut off valve that allows you to shut the oil off after you have stopped the engine, and this valve has a switch that will cut the ignition circuit so you cannot start the engine with out the oil valve being open. Part of the kit is a oil pump to pump the engine empty. The danger here is the mounting of the oil valve could damage the oil tank.



It does not take a lot of oil to cause a lock, I have not worked it out but I would guess that 100 ml will be enough. What ever the accurate figure is, it is not a lot.

_________________
Round Engines RULE!

dsavarese0812(at)bellsout
Guest

Posted: Wed Jul 21, 2010 1:48 pm Post subject: The Hydraulic lock

If there is an intake drain kit installed in the intake tubes  of cylinders 4,5 and 6 and you turn the prop backwards when you feel the "stop",  you will be opening the intake valve and allowing the oil to run out of the  locked cylinder through the drain kit.  No harm will be done using this  technique.  But as Francois has stated, DO NOT DO THIS UNLESS YOU DO HAVE  AN INTAKE DRAIN KIT INSTALLED.

 Dennis

 [quote]   ---

psb777

Joined: 12 Aug 2009
Posts: 34
Location: UK

Posted: Thu Jul 22, 2010 1:35 am Post subject: Re: The Hydraulic lock

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

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