Primarily for general aviation discussion, but other aviation topics are also welcome.
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By Flyin'Dutch'
#1786861
@Shoestring Flyer

You don't seem to get it; the usual reason people give for Lycos/Continentals being Carp is their old designs; this gurgling stuff is reminiscent of stuff made at the same era, Rotaxes I think are designed a lot later - why accept as a manufacturer something as unsuitable as this. How do they do this on their snowmobile engines?

Anyway, the gurgling is only necessary then, if I understand it correct, when the dipstick shows low/too low. If the reading is in the normal range you can just jump in and go. Innit?
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By PeteSpencer
#1786863
[quote="Sooty25]

....................also turning the engine with no oil pressure which removes some of the residual layer of oil sitting on bearing surfaces, right before cold starting.[/quote]

Isn’t that true of most small GA engines?

It’s certainly the reason I stopped pulling through our cold arrer many years ago.

Also removed risk of decapitating myself /losing an arm if the mag earth lead has dropped off..

Peter :roll:
By Shoestring Flyer
#1786864
Flyin'Dutch' wrote:@Shoestring Flyer

You don't seem to get it; the usual reason people give for Lycos/Continentals being Carp is their old designs; this gurgling stuff is reminiscent of stuff made at the same era, Rotaxes I think are designed a lot later - why accept as a manufacturer something as unsuitable as this. How do they do this on their snowmobile engines?

Anyway, the gurgling is only necessary then, if I understand it correct, when the dipstick shows low/too low. If the reading is in the normal range you can just jump in and go. Innit?


That is the point!..It won't be in the normal range after standing say overnight. A large proportion of the oil will have drained from the tank into the sump.
Last edited by Shoestring Flyer on Wed Jul 29, 2020 8:45 am, edited 1 time in total.
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By Miscellaneous
#1786869
@Shoestring Flyer lease explain where this falls over:

I check my oil level without purging and see the the level is 7/8 the distance between min and max, I have confirmed I do not have a shortage of oil and the level is sufficient for my 90min flight. Why do I need to purge it to either discover no change in level, or it brings it up to max?

The purpose of checking the oil level is to establish that thee is sufficient for the flight. Unless you are worried someone crept in through the night and overfilled your engine there's no need to know exactly what the level is. So, sorry, I am not talking rubbish, indeed I think you'll find a large 5age of Rotax operators who have actually thought it through follow the procedure I describe.

I say yet again, there is no need to gurgle every time. :D
Last edited by Miscellaneous on Wed Jul 29, 2020 8:49 am, edited 1 time in total.
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By Miscellaneous
#1786871
Shoestring Flyer wrote:Sorry, lost the will to live in trying to explain...!

That's usually what people say when they are wrong. For goodness sake there's no harm in acknowledging you have been pointlessly gurgling all this time. Every day is a school day. :wink:
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By carlmeek
#1786873
Some of the comments above are not appreciating that it can differ SIGNIFICANTLY across aircraft. Over my experience of 8 different Rotax engines I have seen:

1. Engines that already have a good reading on dipstick from cold. This means that due to the heights and angles of engine versus tank, the oil did not drain back to sump.

2. Engines that gurgle really easily - just 5 blades.

3. Engines that are absolute nightmares - 40 blades, still no gurgle sometimes. Could be slightly low compression perhaps?

4. An engine in a Kitfox that pretty much refused to gurgle if the weather was cold. I turned it until I saw oil on dipstick, then gave up (exhausted)

5. Also don't forget 80 versus 100hp, different compressions means different effort required to gurgle!

Edited to add: I consider "Normal" to be ZERO reading on dipstick - like below minimum. In this case, a gurgle or equivalent MUST be done to verify it actually has oil in it!
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By Miscellaneous
#1786875
carlmeek wrote:Edited to add: I consider "Normal" to be ZERO reading on dipstick - like below minimum. In this case, a gurgle or equivalent MUST be done to verify it actually has oil in it!

Of course it has to be gurgled if the level is showing low, no one is suggesting otherwise.

I'll ask again, given my scenario above, why would a pilot want to gurgle and engine showing a level with which the pilot was happy to fly with before gurgling? :?

By all means gurgle away every time, but most of it is a complete waste of time.

Not gurgling can ONLY result in flight with more oil than verified, NEVER less. :D
Flyin'Dutch' liked this
By Nick
#1786880
One point that has has not been mentioned, surprisingly, is the position of the oil tank in the aircraft. If you have a build which places the oil tank high, ie above the crankshaft, then the oil will siphon into the sump thereby filling the sump and the sump therefore will definitely require purging before checking the oil level or you stand a very great chance of overfilling. Also in an extreme case, if you were to just spin it over on the key you may get a hydraulic lock which could cause damage. If you have an application with the oil tank low then it won't siphon. Get to know your aircraft !

HtH
Nick.
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By Miscellaneous
#1786882
@Nick that's likely to be the differences @carlmeek refers to. Given his experience on how many 'turns' it is taking to purge the engine I'd argue it is even more important to only gurgle if necessary. Otherwise one is simply scraping the bores very clean with multiple turns of the prop for no benefit. Fair enough if the initial dip shows low, however if the level is okay on initial dip then not only is turning the prop through unnecessary, it's also potentially detrimental to the engine.
Flyin'Dutch' liked this
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By ArthurG
#1786886
A lot of Rotax 912 engines are used in microlight instruction. When I was learning, it was normal to gurgle every flight. Engines used in this manner that I know of last multiple 1000s of hours without much work. This may be a function of the more modern oils used in Rotax, but my experience is that regular gurgling is not deleterious, despite some of the posts above. My aircraft had a high-mounted oil reservoir and showed no oil on the dipstick every time, so gurgling was essential to ascertain whether there was oil in the system.

Just my experience of 300+ hours of 912 operation, still got both arms and all fingers.
Flyin'Dutch' liked this
By Nick
#1786891
Agreed Misc. I don't know what aircraft Carl fly's, but if say a C42 that has the tank high up. Easy to fill and top up but they do drain back. A Eurofox if it has been well built the tank should be fairly low, so this will not drain back, especially if it is a taildragger or kept wings folded as in that configuration the oil tank is even lower effectively, when hangared. But it is a real pain to top up without dribbling it down the oil tank. A good tip here is to carry one of those sauce, or honey, containers with a sphincter like gland on it. (filled with oil). You can then invert it while reaching down inside the cowling and not spill a drop.

Again HtH
Nick.
By Aerials
#1786893
Nick makes a really good point about oil tank position. All of you relating your different experiences of where the oil is on the dipstick are quite right, for the reason he says.
Here is a very informative video explaining the Rotax 912 series engines and the oil system is explained at about 3 minutes in.
By oldbiggincfi
#1786914
Why do pilots stand in front of the prop when gurgling ?

Standing with your back to the tail the prop turns clockwise .

Stand, back to tail , alongside fuselage , anchor your leftarm/hand, right hand on prop .

Very slowly pull prop up to compression , wait and keep pulling slowly until the next cylinder compression .

You are using piston by pass into the crankcase to return the dry sump oil to the filler reservoir .
As long as you are not left ear deaf the gurgle will be quite audible with the oil filler cap off.

I know RF3 will do the same only with anticlockwise propeller using left hand on prop to start and right hand on throttle .

For the Rotax , when securely seated in the cockpit , the engine can be turned over, with Mags off, on the starter to check fuel & oil pressure build up.

Alright , not possible with a Chipmunk , but at least keep the non used hand tucked firmly behind your back clutching your belt .
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