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Burping the Engine before starting

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So for the last 5 years I have been burping my CT to check the oil before flying. That works fine and gives an accurate oil level check. Then I meet a fellow pilot who has a 912 in an ultra light and he does the following. After each flight he checks the oil and then before the next flight he does not have to check it but unlike the CT he can leave the mags off and crank the engine for a few seconds before starting to fill the oil resevoir. The CT does not have an independent mag switch that allows that procedure but if I did not choke it first it would not start right away and would then turn over for a few seconds and pump up the oil to the tank. So the question is do we burp it to get the oil out of the sump and up to the tank or are we burping it only to get an accurate oil level reading.

What does happen if you don’t burp it and just go ahead and start it before any cranking it over?

Larry

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It is my belief that the burping is only for getting an accurate oil reading.  I seldom burp mine any more, but instead look closely for any signs of oil loss.  Having had a seepy gasket, I can attest to the fact that a drop or two of oil can make a BIG mess, and is easily seen.  Otherwise, in 700ish hours of flying the 912, I've not seen enough oil used to add any between changes or annuals.

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Hi Larry,

 

The answer to your question....Nothing. Some guys like doing it after a flight, no big deal. I don't care for turning the engine over with the ignitions off. It takes too long, wears on the starter for no reason and you're also pumping raw gas into the cylinders to just sit. Rotax says before a flight that's good enough for me. If you pull the dip stick before a flight and it reads half way up the only thing rotating the engine does is pump some of the oil left sitting in the bottom of the crankcase back to the tank. The only thing now is you'll always have a higher level. More accurate than just sitting yes, accurate all the time , no. There are many times this can lie and especially when its cold outside. If you don't have an oily exhaust pipe or oil all over the bottom of the plane from oil usage or a leak you are not using any oil. The first place poil always goes is on the bottom of the plane and it's not very often people look under their plane. 

 

Too many people have hangups about this tuff. Rotation was used for hydra lock checks too when the filters were different and because Kitfox mounted their oil tanks to high. This is a rare situation for today's engines, new oil filters and oil tanks positioned as spec'd by Rotax. 

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Thanks for the quick replys about the burping of the engine. I guess for the most part now I won't do that any  more. It always seemed to me to be a lot of stress on the base of the prop blades  yanking on each blade 7 or 8 times to make it gurgle. 

I had thought that the oil sitting in the bottom of the engine would cause damage if not purged to the tank before starting.

Larry

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So for the last 5 years

 

Burping ensures the oil is fully collected back into the cannister (dry sump).   The best time to check the oil is preflight because then you are assured you have oil for the flight (suppose you had an oil leak overnight and didn't notice it?)   And it give you a preflight chance to check each blade of the prop and to feel the compression levels in the engine.   And the factory says to do it, so why not do it?

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When I check the oil before flight, if the level is below the the flat on the stick, I will burp to make sure the level comes up onto the flat.  Otherwise I don't bother.  

 

Personally, I think checking the oil after flying and then not doing it again before the next flight is a poor practice --  if you have an oil leak somewhere where the oil flows out and pools somewhere you don't see it, you could get yourself into trouble.  Checking oil takes about thirty seconds, even if you have to burp, and I think it should always be done before the first flight of the day.

 

YMMV of course, everybody has their own way of doing things.

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Jim, thanks for the comments on the burping. I do not use that method, I do as I was taught by pulling it through by hand and have done so since I got the plane. It does only take a minute or so. I posted that to see what others were doing and to get comments which are always well thought out and interesting.

Larry

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One little thing to add, and it's not a big thing... but your oil level will show at a different level if the oil is hot or cold. I usually aim for mid way up the flat spot when cold, this will show as around the top of the flat if you burp and check after shutdown (hot). Oil expands with temperature. Just something to think about if you check after shutdown....

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One other point about manually pulling the engine through before start..while we are doing it to get an accurate oil level reading, it also supplies a slight bit of fuel pressure to the fuel lines.  I had no indications of a fuel line leak until burping the engine during a preflight when fuel poured out the bottom of the cowling.  The main line from the pump was leaking around a fitting. (Tightening its clamp didn't get it; I had to have the line rebuilt.)  Was much happier to have discovered this while standing on the ground with the engine off than in the cockpit where I couldn't see it and starting the engine.

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GravityKnight - I have observed the same phenomenon.  I thought it was due to colder oil being more viscous and less likely to return completely to the oil tank.  Seems like a lot of expansion due to heat, but I don't know the actual thermal expansion of oil.  

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Oil levels on the stick are not always accurate and should be used as a guide. It can be different for different engines and sometimes it takes a longer time to burp because there is more oil in the bottom of the case.  Cold weather burping usually gives different results than hot oil does due to flow qualities.

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Oil levels on the stick are not always accurate and should be used as a guide. It can be different for different engines and sometimes it takes a longer time to burp because there is more oil in the bottom of the case.  Cold weather burping usually gives different results than hot oil does due to flow qualities.

 

It still remains best to simply follow factory guidance on this pre-flight routine. 

 

Before first flight of the day make sure the key is out and the panel is off...open the oil check door and remove the cap...pull the stick and clean it put the stick back...rotate the prop slowly check it and listening for the burp...pull the stick and add oil if below the half way mark on the flat part of the stick..put the oil cap back...  close the oil check door.

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It still remains best to simply follow factory guidance on this pre-flight routine. 

 

Before first flight of the day make sure the key is out and the panel is off...open the oil check door and remove the cap...pull the stick and clean it put the stick back...rotate the prop slowly check it and listening for the burp...pull the stick and add oil if below the half way mark on the flat part of the stick..put the oil cap back...  close the oil check door.

 

Your description is different than the factory guidance for my CTLS.

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Tom, thank you for your comments.  I would caution all those who are new to our forum to verify advice given here before following it, especially in critical areas.  Maintenance of engine oil reservoir level is one of these areas.

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Your description is different than the factory guidance for my CTLS.

 

My direction is from the POH and from Lone Mountain and Tom Peghiny of FD USA.  Where does yours come from?

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My direction is from the POH and from Lone Mountain and Tom Peghiny of FD USA.  Where does yours come from?

 

The airplane operating instructions (POH) that were delivered with my airplane, and as written by Flight Design.

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Checking the oil doesn't have to be done in any rigid way. So long as it gets done. Mfg's have to write something and they may not all be exactly the same way.

So long as the engine is powered down. Take the dipstick out, turn the prop and listen for the gurgle and dip the oil. Oil levels can and many times be different between a hot check and a cold morning check. The first gurgle especially on a cold engine may not be the best as the oil is moving slower so you may want to gurgle a few more times. Remember the straw in the glass of soda. You get air and gurgling then you reposition the straw and get more soda.Same with the oil in the bottom of the case. Just because it gurgled doesn't mean there isn't more flowing towards the hole.

 

This check on the dipstick is not 100% accurate so use it as a guide and not an absolute.

 

Rotation of the prop is to double check on any possibility of a hydrolock situation from oil that has seeped back into a cylinder that will not compress. Those are kind of a thing of the past except for older engine set ups and  could be real for people that use a non Rotax oil filter due to a different internal design.

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Does a pre flight burp help with needless cold start wear on a engine that's been sitting long? Someone said on this forum that pulling the prop gets metal replenished with oil, seals oiled and whatever else the mind can conjure up.

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The airplane operating instructions (POH) that were delivered with my airplane, and as written by Flight Design.

 

We are both using the factory POH.  How is what I said different from what is in your factory POH?

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Does a pre flight burp help with needless cold start wear on a engine that's been sitting long? Someone said on this forum that pulling the prop gets metal replenished with oil, seals oiled and whatever else the mind can conjure up.

 

I don't think that helps nearly as much as a good preheat in cold weather.

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It still remains best to simply follow factory guidance on this pre-flight routine. 

 

Before first flight of the day make sure the key is out and the panel is off...open the oil check door and remove the cap...pull the stick and clean it put the stick back...rotate the prop slowly check it and listening for the burp...pull the stick and add oil if below the half way mark on the flat part of the stick..put the oil cap back...  close the oil check door.

 

Re: "pull the stick and clean it..."

 

I know that our ancestors taught us to "clean the stick" when 

checking the automobile oil, but now I am thinking that what

you use to clean it ( rag, pants, etc ) could leave some 

foreign material on the stick; same goes for the fuel dipstick.

Over time, could you accumulate significant non oil/fuel bits

in the tanks.

 

I still can see the top of the oil / fuel level on the dipstick; no

need to touch anything.

 

BTW, you can still catch the drip with paper or a rag.

 

Comments ?

 

RH

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