Sport Pilot Talk

SportPilot Fans: Having never (after purchasing my airplane) been satisfied with the existing information and videos on this subject, I set out on a mission 16 months ago to learn as much as I could. Much of my new knowledge has come from "burping" my own engine for over 250 first-flights of the day. This video sets forth what I have found--and learned.

If you find any errors or omissions, serve them up right here, so I can fix them in subsequent editions of the video.--RD

http://www.youtube.com/watch?v=HsIfNt7_SB4

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Sting Sport Videos
http://www.youtube.com/user/9162069934/videos

Some days 20 or 30 hand props work.
Other days 100+ hand props just isn't going to do it!

The worst thing you can do is overfill the oil because it never burped.
So if you pull 30 times, no burp, and reasonably believe the oil level is fine, how about running the motor for 2 or 3 minutes. Shut down.
Let it sit for 5 min.
Then hand prop 20 pulls or so... and viola oil level is checked!

P.S. Love the T-shirts!!

My habit is to always check the oil after each flight. When I do that, it takes about 10 blades.

My plane sits in a hangar, so I think its safe to assume no one would sneak in and drain oil out of it before the next flight, and an oil leak would be obvious on the hangar floor.

If others flew the plane, or if it sat out, I'd probably force myself to check it before the next flight.

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Fast Eddie B.
Sky Arrow 600 E-LSA • N467SA
FastEddieB@mac.com

Good thinking FastEddie! I'll add that to my post flight routine.

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Dave

What many don't know is why it may take more prop turns on one plane than another or from one day to another on the same plane.
It really has nothing to do with compression since it takes very little to return the oil and propping one way over another we are all pretty close to the same compression, so take your pick on your preferred method.
The main reason is the amount of oil that settles back in the crankcase. This is determined by several factors between different setups like oil tank position, hose lengths, siphoning back to the case, ect... This is the reason that you get a gurgle with more or less prop turns at different times (i.e. plane sat a long time, sat only 1 day, just run and checked, ect... It all changes the oil amount in the crankcase.
If you have a small amount of oil to return (i.e. .5 - 1.5 oz) then you will get a fairly quick gurgle. If more oil has seeped back into the crankcase then it will take many turns and sometime you may never get a gurgle because you never really got all the oil out. It isn't a real issue.
How much oil could possibly leak back? How about almost an entire tank. I have seen this and when the owner thought he was very low on oil he added more oil and then of course when he started the engine oil flowed freely out the oil tank vent. Some engines and engine setups are more consistent than others and will hear the gurgle fairly quickly most of the time. Others will always turn the prop until they are blue in the face.
If in doubt just start the engine, check the oil pressure and after a few minutes top and then check the oil.
Don't get too hung up because your plane doesn't gurgle as fast as the other guys or even at all.
If you rotate the prop and hear no gurgle then you have checked for hydra lock in a cylinder and then it is okay for a start.

The oil level from day to day may look like it changes, but it is only these inconsistencies that frustrate you. Don't get frustrated just know it is inconstant and with some planes more than others.

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Roger Lee
Tucson, Az.
Light Sport Repairman - Maint. Rated
Rotax Repair Center - Heavy Maint Rated
(520) 574-1080 (Home) Try Home First.
(520) 349-7056 (Cell)

Here's what I can say for sure: Following the guidelines in the video, my oil level is now always in the exact same place on the dipstick, each day when I check it. All the dipstick variability I had, checking oil the first few months after airplane purchase, is gone. That means I know if there is a leak, heavy oil usage, or oil still stuck in the crankcase...just waiting to do me in with hydraulic lock.

Also, by following the secrets at the end of the video over the past four months (for 75 first-flights of the day), I have never gone past 12 prop pulls to a burp--and usually, it is closer to 3 or 4. That compares with 80, 100, 125, or even 200, sometimes with NO burp being achieved at all, in the past.

Yep, it's only an "anecdotal" sample size of one, but I'm convinced I'm on to something here. Either that--or all the hours I'm racking are shaving down my engine's internal tolerances, causing more air to blow past the rings, and making burping quicker and easier. But I don't think so.

We'll know, when some of you try the secrets and start reporting back your results, huh?

_________________
Sting Sport Videos
http://www.youtube.com/user/9162069934/videos

I just watched the video - good job, and I like the t-shirts!

I took a short flight yesterday*.

I propped up my iPhone and video'd my post-flight burping:

http://www.youtube.com/watch?v=NfK40Th7K9s

Two observations:

1) I don't feel the oil level change with temp is that large. Engines are routinely checked at operating temp, and I've never noticed a difference between hot and cold.

2) Can of worms here, but I don't think having oil in the tank prior to engine start is necessarily an advantage. Dry sump engines have routinely been started without oil in the tank for a long, long time with no apparent ill effect. It will take a certain number of turns to get oil into the tank and to build oil pressure, and there's no advantage to doing it slowly - bare metal scraping over bare metal is bad whether done fast or slow. Best thing is to get oil pressure and temps up as soon as possible, which is best done by just starting the engine.

I believe both Continental and Lycoming have moved away from recommending their engines be "pulled through", even when cold starting.

But like I said, a can of worms and whatever works for you!


*over Lake Blue Ridge to watch the moonrise. Can barely make out the moon in the second two photos, but in real life it was gorgeous!

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Fast Eddie B.
Sky Arrow 600 E-LSA • N467SA
FastEddieB@mac.com

Eddie: For me, one of the important three purposes for burping (front half of the video) is to check the oil level on the dipstick to detect changes, even small ones, that could mean something is "up." In this regard, I am thus considering these two points:

1) One of the reasons the oil level can very so much between a hot and cold engine has to do with foaming. Depending on the additives inside the oil, some oils will foam easier than others. This foaming can trap residual oil inside the case and not allow it to return to the sump until foaming has subsided, which can take a few minutes. Folks tend to under-estimate how much is actually coated on the engine internals after shut down. The oil galleries inside the engine will start to weep as soon as the engine is shut down and there is no longer a source of pressure. This weeping oil also migrates to the bottom of the case, causing various level differences on the dipstick, depending on when (how long after) the engine is burped.

2) Rotax used to mandate all 912 engines be burped before starting. This was primarly to ensure proper oil protection at start up. Up until last year factory Rotax oil filters did not have an anti-drain valve installed, so, up to a 0.3 qt of oil could drain out of the filter and result in the filter having to fill first, before sending oil to the vital parts of the engine. This has since not been a problem, with the new 825-012 filters. However, checking for hydraulic lock (by burping before the day's first flight) is always a good thing. Moreover, a 10.5:1 compression engine doesn't last long with any oil in a cylinder. So why take the chance?

Excuse me now, I'm headed to the airport to pre-burp (see video) my baby, so she burps faster tomorrow, when I go flying!
Rich D.

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Sting Sport Videos
http://www.youtube.com/user/9162069934/videos

Hi Rich,

The comment on Rotax oil filters not having an anti drain back device since last year isn't quite right. I have done extensive research on oil filters over the years and I have several oil filters cut open from Rotax that date back quite a few years. They did indeed have anti drain back membranes, but this last filter upgrade changed the material they used to make it better and less likely to seep oil out when just sitting. They also added a new check valve to help prevent this, which was highly influenced by the Kit Fox folks in the way they mount the oil reservoir.

The 10.5:1 compression ratio was always a misprint and has finally been change to the correct 11:1.

The burping was indeed for oil level check and hydra-lock because many engine installs had the oil tank in too high a position compared to the engine and the older anti drain back membrane did allow some seep at times.

Using one of today's quality oil is nothing like it was even 10 years ago much less longer than that and oil foaming was and can be an issue if you use the wrong oil, especially a straight mineral oil. The synthetics are far better at keeping foaming at bay or at least reducing it. They are better under high pressure between metal parts, have better staying power and better temp. properties. Amsoil motorcycle oil is the best oil on the market for anti foaming, but there are 3 others that are also good in this category. The foaming issues years ago is why Rotax raised the oil level in the reservoir 30% with a new dip stick to keep any foaming bubbles from possibly getting into the system and causing a lifter failure.

Prop burping revolutions is still dependent on how much oil is left in the crankcase. If it is a lot it may take 100 turns and if it is a little then 3-5 turns.

_________________
Roger Lee
Tucson, Az.
Light Sport Repairman - Maint. Rated
Rotax Repair Center - Heavy Maint Rated
(520) 574-1080 (Home) Try Home First.
(520) 349-7056 (Cell)

Rich,

In no way do I mean to be argumentative. And I appreciate the time and effort that went into your video. I'm just trying to apply logic in an area where Old Wive's Tales abound and data tends to be rarer than anecdote.

1) I could make a case that by always checking the oil when warm, there's less variation in temperature. When cold, "cold" could mean a range of 100ºF, depending on where you live and time of day. Warm should be a narrower range. In any case, I get consistent readings now, doing it when warm. When I used to do it cold, I'd sometimes get a low reading, add oil, then have it show overfilled the next flight. Now, I'll get very consistent readings, right now about 3/4 of the way up the flats. I would definitely be able to see a sudden drop.

2) In the absence of data, I still feel that the wear will be the same whether pulled through or cranked and started, dependent only on "number of revolutions required to get oil pressure. If anything, I think a case can be made that starting is the quickest way to get oil pressure.

I'll gladly bow to studies, experiments or data - this logic thing can easily lead one astray!

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Fast Eddie B.
Sky Arrow 600 E-LSA • N467SA
FastEddieB@mac.com

The idea of burping and checking oil after flight is interesting and I may start experimenting with that.
It would seem to me that hydra-lock is not very likely on an engine with the oil tank at the same or lower level than the crankcase, as the Flight Design seems to be. I'm not saying don't check for it, especially if your oil tank is above the cylinder level so that oil could flow into the cylinder from gravity.
Today, I talked with two old, old time mechanics and asked them if they had any personal or first hand accounts of hydralock in a flat opposed aircraft engine. They both said no. Of coures, they were familiar with it on radials.
But, one had an interesting observation. He is an old BMW motorcycle man and said he knew of a case where a worn out BMW had hydralock when the bike was set on a stand, leaned over, all winter so oil leaked into the cylinder and then kicked over in the spring. It can happen.
Cylinder wear is going to be influenced by how long it has sat since last flight. Oil has some residual lubricity for about a week. That is why some say you should get the engine to operating temperature and run it for an hour once a week. (Ground running isn't good enough, they say.) The oil additive CamGuard which generally has good reviews addresses this problem.
FAA certificated engines like Cont & Lyc are required to operate fully at 1/2 the minimum oil level. Does anyone how Rotax engines fit in this matrix, if at all? What is the minimum oil level for satisfactory long term operation? If the level is in fact quite flexible, then we might not need to be quite so anal about running a little below the full line on oil.
My inclination is to not get anal about running a little low on a local, short flight. On a long one, of course I want to be right up there with adequate oil.

Small world.

A long time ago I had a 1960's /2 BMW fall over on its side at my parent's house. It sat that way for at least a week. It was the opposed cylinder design, so one cylinder was pointed straight down.

When I went to kick start it (no electric start back then), it was as if the engine had been welded tight. I guess the kick starter did not have enough leverage to bend anything. Took the spark plug out and kicked it and oil came shooting out.

No relevance to our engines, unless you lay you plane on its side for an extended period! In that case crank it over with the lower plugs out to clear it first!

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Fast Eddie B.
Sky Arrow 600 E-LSA • N467SA
FastEddieB@mac.com

Jim, the hydro lock would most likely come from fuel with the over cylinder intakes.

Yes, I agree with that.

Ahhhh..., another pause that refreshes! A few days ago, I noticed that more prop pulls were being required to burp my baby and the oil was noticeably thicker (starting to hang on the stick like honey) and darker. Coming up on the majic number, I surmised. Sure enough, 31 hours had elapsed since the last oil change.

So, today, whilst it was too hot here to fly, I changed the oil. It's nice to know she's gonna burp in 3-6 pulls tomorrow morning, the cleaner, thinner oil pushing back up the return line with less friction, you know?

Anyway, fly safe and have a good one!

_________________
Sting Sport Videos
http://www.youtube.com/user/9162069934/videos