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  #1  
Old 08-09-2020, 11:56 AM
jdeas's Avatar
jdeas jdeas is offline
 
Join Date: Mar 2006
Location: SoCal
Posts: 633
Default Sudden temporary change in oil pressure

On a flight last week I had a -19psi change in my oil pressure, the majority of change in 6 seconds!

No alarms sounded as the oil pressure was still in range but picked up on it and made an immediate turn to more favorable landing zones as it was still slowly trending down. During the turn I was also changing power settings and looking for oil when I noticed the pressure coming back up! Located a safe path to the nearest airport but the pressure was rock solid from then on. On landing the oil level was at 5.5q, about where expected so there was no unexplained oil loss. The event lasted over a minute and I see nothing in the data that would suggest this was instrumentation.
The only conclusion I can reach is the oil pressure regulator must have gotten something on the seat or just didn't seat properly until I shook it loose with power and g load. Weird considering this was 10+ minutes after establishing a climb profile.
I attached the Savvy flight (11 minutes in) for those who may have more insight into this anomaly.
https://apps.savvyaviation.com/fligh...e-b277f8b8505e
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JD
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RV-7 N314SY (KWHP)
IO-360-B1B
A&P


CANbus based trim/flaps and electrical

Last edited by jdeas : 08-09-2020 at 08:08 PM.
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  #2  
Old 08-10-2020, 12:50 PM
Kent Ashton Kent Ashton is offline
 
Join Date: May 2010
Location: Concord, NC
Posts: 137
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Yup, I flew the other day (Lyc O-360) and the oil pressure was about 10-12 psi higher than I usually see. After landing I tapped on the housing for the regulator ball. Next flight it was back to normal.
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  #3  
Old 08-10-2020, 01:39 PM
lr172 lr172 is offline
 
Join Date: Oct 2013
Location: Schaumburg, IL
Posts: 5,870
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Quote:
Originally Posted by jdeas View Post
On a flight last week I had a -19psi change in my oil pressure, the majority of change in 6 seconds!

No alarms sounded as the oil pressure was still in range but picked up on it and made an immediate turn to more favorable landing zones as it was still slowly trending down. During the turn I was also changing power settings and looking for oil when I noticed the pressure coming back up! Located a safe path to the nearest airport but the pressure was rock solid from then on. On landing the oil level was at 5.5q, about where expected so there was no unexplained oil loss. The event lasted over a minute and I see nothing in the data that would suggest this was instrumentation.
The only conclusion I can reach is the oil pressure regulator must have gotten something on the seat or just didn't seat properly until I shook it loose with power and g load. Weird considering this was 10+ minutes after establishing a climb profile.
I attached the Savvy flight (11 minutes in) for those who may have more insight into this anomaly.
https://apps.savvyaviation.com/fligh...e-b277f8b8505e
Unless you have a good deal of bearing wear, the ball should be well off the seat at 2400 RPM. Improper seating, due to debris, in the ball seat area, at those RPMs, is a pretty unlikely reason for a low pressure indication. A problem with the cage or spring could cause that though. My engine had the wrong adapter (i.e. no cage present) and the pressure would fall only at high RPMs (ball was falling off to the side). Further, typical sendor errors and anamolies usually report high vs low readings. While a bad sender or wiring issue is absolutely possible, I would keep a close eye on it to confirm it is not a mechanical issue.

Larry
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N11LR - RV-10, Flying as of 12/2019

Last edited by lr172 : 08-10-2020 at 01:44 PM.
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  #4  
Old 08-10-2020, 01:54 PM
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Carlos151 Carlos151 is offline
 
Join Date: Jan 2008
Location: Lebanon, TN
Posts: 334
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What type of oil pressure sensor? Dynon recently issued a service bulletin for the Kavlico sensors.
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RV-8
N151TK "La Otra Chica"
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  #5  
Old 08-10-2020, 05:05 PM
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AlexPeterson AlexPeterson is offline
 
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Location: Maple Grove, MN
Posts: 2,405
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Here's the affect a piece of debris in the relief valve seat has on oil pressure. Larry is right, your observation does not seem to fit debris in the seat.
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  #6  
Old 08-10-2020, 08:17 PM
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jdeas jdeas is offline
 
Join Date: Mar 2006
Location: SoCal
Posts: 633
Default Low PSI

Guys,
Thanks for the input. This is a one time anomaly after almost 500hrs of use. The engine is far from new so no idea how far the ball is off the seat at 2400.


A point of reference, Switched to 120wt oil and removed a washer from the regulator around 20hrs ago. It has given me more consistent psi but perhaps the regulator is not quite happy with the washer/spring stack and/or missing the cage.
This is the tall hat fixed regulator. I'll have to see if a cage should be there.
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IO-360-B1B
A&P


CANbus based trim/flaps and electrical
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  #7  
Old 08-10-2020, 10:20 PM
lr172 lr172 is offline
 
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Quote:
Originally Posted by jdeas View Post
Guys,
Thanks for the input. This is a one time anomaly after almost 500hrs of use.
Please don't take comfort in that. Most engines will go 1000's of hours without ever having an indication like this. It may be something simple like a loose connector. However, your engine is whispering to you, please don't ignore it. A failed oil system, typically results in a very bad day.

You need to find the cause.

Larry
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  #8  
Old 08-10-2020, 10:29 PM
Earl Findlay Earl Findlay is offline
 
Join Date: Jul 2019
Location: Sandpoint, Idaho
Posts: 85
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Quote:
Originally Posted by lr172 View Post
Please don't take comfort in that. Most engines will go 1000's of hours without ever having an indication like this. It may be something simple like a loose connector. However, your engine is whispering to you, please don't ignore it. A failed oil system, typically results in a very bad day.

You need to find the cause.

Larry
Point taken, BUT sometimes “it just is”. I had a 20+ psi drop for a few flights and added a quart of oil and it took care of the OP drop. Pressure has been back to normal since. On here I was told that adding oil wouldn’t solve the OP issue and something else is wrong. Well, it did and there wasn’t. So where I’m going with this is if your OP is back, sometimes it is OK to assume it was a transient excursion and you may never know why, but you can be satisfied that the problem is gone.
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  #9  
Old 08-11-2020, 08:06 AM
lr172 lr172 is offline
 
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Location: Schaumburg, IL
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Quote:
Originally Posted by jdeas View Post
G
This is the tall hat fixed regulator. I'll have to see if a cage should be there.
Two styles for this. One has the cage on the block, in which case, you need the derby hat style cap(not sure if they ever made an adjustable regulator for this style). The other has no cage on the block and it requires the abe lincoln hat style that has a cage built into the cap. To be clear, I don't believe that this is your issue, as it would have presented a long time ago.

Larry
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  #10  
Old 08-11-2020, 08:09 AM
lr172 lr172 is offline
 
Join Date: Oct 2013
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Quote:
Originally Posted by Earl Findlay View Post
Point taken, BUT sometimes “it just is”. I had a 20+ psi drop for a few flights and added a quart of oil and it took care of the OP drop. Pressure has been back to normal since. On here I was told that adding oil wouldn’t solve the OP issue and something else is wrong. Well, it did and there wasn’t. So where I’m going with this is if your OP is back, sometimes it is OK to assume it was a transient excursion and you may never know why, but you can be satisfied that the problem is gone.
pressure drops that can be tied to a low oil level is a completely different matter and is to be expected. OP stated that he confirmed a proper oil level at the time of the event. No one should ever ignore irregular oil pressure drops. These are remarkably stable systems with VERY FEW intermittent excursions from normal patterns. The exception being instrument/sensor issues.
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Last edited by lr172 : 08-11-2020 at 08:16 AM.
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