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Bill3558

Cause of oil pressure loss.

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I’ve got the ok to share some pics and info with you guys. This is what we saw under the cowling. Oil lines were off both sides of the oil temp sensor. 
Hose would slip onto the barb and slid off just as easily.  This might account for the sudden pressure loss and no indicated increase n oil temp. 

Mechanic told NTSB he never touched them. 
 

I flew 170 hours behind this engine in the last 12 months. It failed 40 minutes after picking it up from annual. After he had replaced oil cooler mounts. 
 

Thoughts?  

F230222F-4DD9-4EA5-BB9F-7DAE9F14C110.jpeg

DA2A225B-FCA7-45A8-AB76-04C6C4C338DF.jpeg

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That is the oil thermostat. That top line on the rear should be the one that supplies oil to the oil pump.

I have a couple old thermostats laying around here, and I can't even get the hose to pull off without a clamp installed. I wonder if at the last hose change someone substituted an oil hose other than Rotax.

I also don't like how they did the ends on the hoses. I like the firesleeve to cover the complete hose if at all possible, like this.

Thermostat.jpg

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The other thing I would like to add is there is no pressure in the oil lines to blow them off. It would have to be some external force pulling on the lines, improper hose, improper clamping pressure, or loss of tension on the rubber hose due to heat exposure. I would also bet there was very little loss of oil from the tank, unless it was from the position of the airplane in the tree.

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They generally say that when the parachute is deployed the aircraft is totaled. That is not to say that it can't be repaired, it depends on the cost of the repairs compared to the salvage cost of the aircraft. The airplane landing in the tree is not typical outcome, so it will depend on the damage from the tree and that caused during retrieval. If the spars in the wing are not damaged, and the attachment to the fuselage is okay it may have a chance.

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I have seen CTs with more damage repaired, but you also need a $25K engine. My prediction is that someone down the road will repair it.

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4 hours ago, Tom Baker said:

The other thing I would like to add is there is no pressure in the oil lines to blow them off. It would have to be some external force pulling on the lines, improper hose, improper clamping pressure, or loss of tension on the rubber hose due to heat exposure. I would also bet there was very little loss of oil from the tank, unless it was from the position of the airplane in the tree.

Your right Tom. Oil showed on the dipstick. 

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4 hours ago, Tom Baker said:

The other thing I would like to add is there is no pressure in the oil lines to blow them off.

Really?

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4 hours ago, Tom Baker said:

That is the oil thermostat. That top line on the rear should be the one that supplies oil to the oil pump.

I have a couple old thermostats laying around here, and I can't even get the hose to pull off without a clamp installed. I wonder if at the last hose change someone substituted an oil hose other than Rotax.

I also don't like how they did the ends on the hoses. I like the firesleeve to cover the complete hose if at all possible, like this.

Thermostat.jpg

He did the hoses last years annual.

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1 hour ago, GlennM said:

Really?

Yes! The pump is on the engine, and it sucks oil from the tank. The engine has pressure internally. The most pressure would be the oil return line from the bottom of the sump, and that is just from crankcase pressure from piston blow bye. 

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5 hours ago, Tom Baker said:

I also don't like how they did the ends on the hoses. I like the firesleeve to cover the complete hose if at all possible, like this.

Thermostat.jpg

Not only are they supposed to be done like this, but the ends are also supposed to be RTVd as possible to properly comply with spec.

 

6 hours ago, Bill3558 said:

I’ve got the ok to share some pics and info with you guys. This is what we saw under the cowling. Oil lines were off both sides of the oil temp sensor. 
Hose would slip onto the barb and slid off just as easily.  This might account for the sudden pressure loss and no indicated increase n oil temp. 

Mechanic told NTSB he never touched them. 
 

I flew 170 hours behind this engine in the last 12 months. It failed 40 minutes after picking it up from annual. After he had replaced oil cooler mounts. 
 

Thoughts?  

F230222F-4DD9-4EA5-BB9F-7DAE9F14C110.jpeg

DA2A225B-FCA7-45A8-AB76-04C6C4C338DF.jpeg

There shouldn't have been a need to touch this to replace oil cooler mounts. They are easily replaced just by dismounting the radiator, spinning new ones on, and remounting, without removing a single hose.

Also, those oil lines are suction based, only the return line to the crank case has any pressure.

Unfortunately, the reality is that sometimes hoses can slip off. I had a coolant line slip off the water pump of an aircraft. They were on final and landed, the temp alarm sounded, but since it was the old style engine where the probes sensed CHT and not actual coolant; the logs showed that it wasn't a true overheat.

What I DO see though, are improper clamps on the oil hoses. In my experience, screw clamps loosen over time. Fuel injector and worm drive hose clamps do not belong on lines that require fire protection, and in addition, nor do they belong on any non-beaded fitting. The heat that will loosen them over time, and the one in your image additionally looks to be too large for the application; when they have to be screwed that tight, they don't really clamp right.

Those lines are supposed to be clamped with something much more secure, such as a band clamp or crimp clamp as imaged below:

https://static.grainger.com/rp/s/is/image/Grainger/2LPG2_AS01image.jpeg.11be1c6264729c2ae069dec87ffc2c67.jpeg

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1 hour ago, Bill3558 said:

Your right Tom. Oil showed on the dipstick. 

As soon as the line that attached to the pump came off it stopped sucking oil from the tank.

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8 minutes ago, Anticept said:

Not only are they supposed to be done like this, but the ends are also supposed to be RTVd as possible to properly comply with spec.

Not RTV'd, they are supposed to be end dipped. I had a customer once who shafted me on a bill for a hose change, and one of their complaints were that the ends of the hoses were not gooped up with silicone like the previous person had done.

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The issue now is subrogation by the insurance company.  If the mechanic has insurance, then I would predict the aircraft insurer will allege the mechanic was negligent and will approach the mechanic's insurer.  Arbitration between the insurers will result. If the mechanic has no insurance, then it will die on the vine.

Either way, Bill gets a check. Glad you are OK, Bill.

There, but by the grace of God, go I. 

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9 minutes ago, Tom Baker said:

Not RTV'd, they are supposed to be end dipped. I had a customer once who shafted me on a bill for a hose change, and one of their complaints were that the ends of the hoses were not gooped up with silicone like the previous person had done.

Haven't heard that one. It has been a long time, but I believe that RTV was acceptable. But now you got me questioning myself. Got the spec lying around?

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I’m slow here, what does the open oil thermostat have to do with the recently replaced oil cooler mounts in relation to loss of oil?  Sorry if I’m confusing the discussion, just trying to keep up.

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46 minutes ago, Anticept said:

Haven't heard that one. It has been a long time, but I believe that RTV was acceptable. But now you got me questioning myself. Got the spec lying around?

There are people who use RTV, but the idea is for it to soak into the fibers to prevent the ends from being able to soak up fuel or oil. The end dip is just a liquid silicone. 

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Under ASTM standards they do not have to have END DIP on them. It isn't actually RTV and using RTV is a major mess and PITA to deal with later if applied wrong like 90% of the people do. END DIP which is about $375+ per quart and once dipped they need to sit overnight to dry. That's why very few people ever use it. There are other acceptable methods like END WRAP. The coating or wrap is only there to prevent fluids from going up or out in the fire sleeve. The fuel Injectioin clamps on the hose are perfectly okay and come that way from FD. These are not the cheap crappy serrated garden hose type clamps. These are used in cars in fuel injection hoses with ratings to 100 psi when properly used. When used correctly these clamps will stay on a barbed fitting like the thermostat right up to destruction when you try to pull them off.

 

p.s.

You're right that the oil hoses on that thermostat should have had nothing to do with vibration mount replacement. 

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49 minutes ago, BugBuster (BB) said:

Bill, my hats off to your 1st problem BRS solution, but if you wish to say, how did you finally get on the ground safely? That’s a ways up there, it looks!

Bill, disregard my question, I found the answer. Again hats off and thank you for sharing. Best Wishes!

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On 10/15/2021 at 8:38 PM, Tom Baker said:

Yes! The pump is on the engine, and it sucks oil from the tank. The engine has pressure internally. The most pressure would be the oil return line from the bottom of the sump, and that is just from crankcase pressure from piston blow bye. 

So the pump sucks the oil from the tank and through the cooler?  You learn something new every day...

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