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Fluctuating oil pressure during prop braking.

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bluesidedown

Joined: 30 May 2008
Posts: 9
Location: Charlotte

Posted: Mon Apr 06, 2009 4:16 am Post subject: Fluctuating oil pressure during prop braking.

My oil pressure is fluctuating considerably when prop braking and I think it is because of my prop governor but I am not sure. Now the oil pressure is 80 lbs at full throttle and only drops to 50 (at) 800 rpm when fully warmed up and on the ground is as strong and steady as you could want. Even fast taxing back and forth is is fine. But when I am flying what happens is when I pull back the throttle the oil pressure fluctuates considerably. It only happens in the air when I pull back the throttle and the prop is braking and only after the temperature reaches 200. Now on the ground I can't reproduce it and all is normal, only in the air when the prop braking can I reproduce it. Another thing I noticed is that it will not go to 2700 but only about 2600 and I adjusted it out but no effect. On the ground when I cycle the prop the pressure drops from 80 to 60 or so.  



The engine is an AEIO-360-A1E with a front mounted Hartzell governor and the prop is a new Whirlwind 200c.



Any ideas? Anyone have a oil flow diagram for A Lycoming? 



Thanks

Mike

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khorton01(at)rogers.com
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Posted: Mon Apr 06, 2009 5:04 am Post subject: Fluctuating oil pressure during prop braking.

On 6 Apr 2009, at 08:16, bluesidedown wrote:



 	  Quote: 	
		   My oil pressure is fluctuating considerably when prop braking and I  

 think it is because of my prop governor but I am not sure. Now the  

 oil pressure is 80 lbs at full throttle and only drops to 50 (at)  

 800 rpm when fully warmed up and on the ground is as strong and  

 steady as you could want. Even fast taxing back and forth is is  

 fine. But when I am flying what happens is when I pull back the  

 throttle the oil pressure fluctuates considerably. It only happens  

 in the air when I pull back the throttle and the prop is braking and  

 only after the temperature reaches 200. Now on the ground I can't  

 reproduce it and all is normal, only in the air when the prop  

 braking can I reproduce it. Another thing I noticed is that it will  

 not go to 2700 but only about 2600 and I adjusted it out but no  

 effect. On the ground when I cycle the prop the pressure drops from  

 80 to 60 or so.



 The engine is an AEIO-360-A1E with a front mounted Hartzell governor  

 and the prop is a new Whirlwind 200c.



 Any ideas? Anyone have a oil flow diagram for A Lycoming?


	


Mike,



Is this an aerobatic prop that goes to coarse pitch if the oil  

pressure drops, or a normal prop that goes to fine pitch with no oil  

pressure?



Is your positive g oil pickup at the very back of the oil sump?  If  

so, when the prop is braking, the oil may be moving far enough forward  

in the oil sump so the oil pickup is starting to suck some air.  Try  

running with more oil in the sump.  The inverted oil system oil  

separator should keep the engine from losing too much oil through the  

breather.



If this is a normal prop, be very, very careful.  I've got an IO-360- 

A1B6 with a Christen inverted oil system in my RV-8.  I too was seeing  

occasional oil pressure fluctuations when I pulled the power back, but  

I increased the oil quantity in the sump, and believed the issue was  

resolved.  Then one day I pulled the back sharply at 200 kt in a  

descent, and all hell broke lose.  The oil pressure plummeted, the  

prop went to full fine pitch and the rpm hit almost 4000.  I pulled  

the nose up, and the oil pressure came back up, and the rpm came back  

down.  I followed the Lycoming and Hartzell overspeed recommendations  

- I had Aero Sport Power do an engine inspection + replace connecting  

rod bolts and crankshaft counterweight bushings.  I replaced the  

Christen oil pickup with one from Raven Aircraft that has the pickup  

nearer the middle of the sump.  I scrapped the prop and bought a new  

aerobatic prop and prop governor.  This was a very expensive episode,  

plus the aircraft was on the ground for about four months.



I have since learned from several sources in the aerobatic community  

that the long oil sump on the IO-360-A series Lycomings in combination  

with the Christen oil pickup is known to have issues in steep  

descents, or when the power is pulled sharply back.  Not a huge  

problem with an aerobatic prop, but a real big deal with a normal  

prop.  Be careful.



--

Kevin Horton (Grounded)

RV-8 (Flight Test Phase)

Ottawa, Canada

http://www.kilohotel.com/rv8

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g4mech(at)sbcglobal.net
Guest

Posted: Mon Apr 06, 2009 7:04 am Post subject: Fluctuating oil pressure during prop braking.

How did you try to adjust it to get 2700 rpm? Just FYI 180 is the target oil 

temp, 200 is fine but it would be better to try to get it to 180.

---

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chaskuss(at)yahoo.com
Guest

Posted: Mon Apr 06, 2009 1:05 pm Post subject: Fluctuating oil pressure during prop braking.

Mike,

 I am going to send you a diagram of the oiling system off list. I'm also going to send you a photo of a special tool you can easily make yourself to check for possible air leaks in the system between the governor and the prop. The photo I'm sending is of the tool I made. These should help you troubleshoot your problem.

Charlie Kuss

--- On Mon, 4/6/09, bluesidedown <mbick(at)carolina.rr.com> wrote:



 	  Quote: 	
		   From: bluesidedown <mbick(at)carolina.rr.com>

 Subject: Fluctuating oil pressure during prop braking.

 To: rv-list(at)matronics.com

 Date: Monday, April 6, 2009, 8:16 AM

 

 <mbick(at)carolina.rr.com>

 

 My oil pressure is fluctuating considerably when prop

 braking and I think it is because of my prop governor but I

 am not sure. Now the oil pressure is 80 lbs at full throttle

 and only drops to 50 (at) 800 rpm when fully warmed up and

 on the ground is as strong and steady as you could want.

 Even fast taxing back and forth is is fine. But when I am

 flying what happens is when I pull back the throttle the oil

 pressure fluctuates considerably. It only happens in the air

 when I pull back the throttle and the prop is braking and

 only after the temperature reaches 200. Now on the ground I

 can't reproduce it and all is normal, only in the air

 when the prop braking can I reproduce it. Another thing I

 noticed is that it will not go to 2700 but only about 2600

 and I adjusted it out but no effect. On the ground when I

 cycle the prop the pressure drops from 80 to 60 or so.  

 

 The engine is an AEIO-360-A1E with a front mounted Hartzell

 governor and the prop is a new Whirlwind 200c.

 

 Any ideas? Anyone have a oil flow diagram for A Lycoming? 

 

 Thanks

 Mike

 

 

 

 

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