We just lost oil pressure

[skippydiesel]

It's recommended to pre-pressurise a lot of motors including aviation ones after an overhaul prior to running it. Also to fill a screw on oil filter when it's replaced..Caterpillar graders had a 2 cyl Delco auxiliary engine that warmed the manifold and pressures the oil before firing it up. Where you have metal to metal completely dry you risk metal welding (scoring) of the surfaces. Pressured oil doesn't do the whole job, it's relative movement of the two surfaces that generates the very high pressures in a film of oil that keeps the friction down, separates the parts and reduces wear in PLAIN bearings. Nev

Amazing Nev - years ago I found an abandoned Cat (4 cylinder) powered grader, on a research station I was managing. Except for glass in cab windows and drivers seat cushion, the grader appeared complete (with pilot motor). After a bit of research I found one long serving staff member who had actually operated the machine (mechanical not hydraulic systems) and a Cat maintenance facility, who would renovate the "old girl" for the cost of parts alone. as an apprentice project.. Many months later the grader was returned in operational condition (except for tyres which were very hard to find/replace). The "senior" employee then used the grader for the next 3 + years of my posting. It was great to see the process of starting - if I remember correctly, the pilot motor was a hand start, once going it engaged the main (decompressioned) motor, brought fuel and oil pressure up - when at a satisfactory level , decompression ended and main engine would fire & away she went (very satisfying). The cost far all this - about the same as one annual visit from a contractor coming on station to do the grading work.

[facthunter]

The best time to grade your tracks around the farm is the right wait after a good shower of rain. The only way to do that is to have your own equipment BASIC stufF won't send you broke.. Nev

[danny_galaga]

One of these could be handy:-)

 

http://infinityaerospace.com/product/other/pre-oiler-and-back-up-engine-oil-pump/

 

Been around in heavy industry for years. You could actually get a kit for Delco starters etc for your Caterpillar or whatever engine so that turning the key one way spins the starter without engaging the pinion but engages a pre oil pump instead. Then a normal start after that.

[Geoff_H]

There only needs to be the smallest amount of oil between the bearing and the journal for an oil wedge to happen. So as long as the wedge is higher than the roughness of the bearing and journal no wear should happen. Having said that I paid $1800 to have oil supposed to the camshaft on my Lycoming IO360. The standard arrangement is that splashing from oil in the engine lubricates the lifter/camshaft area. My engine had a valve lift around have the design lift from wear. The oil was wearing off the camshaft after sitting for extended periods of time. Hence no wedge on startup. Lycoming suggests that you use a "magnetic" oil to solve this problem. So I really wasted my money, I lost confidence in my judgement lol.

My father used to say that if his car ran out of oil he would put water in his sump to get him home. I once thought that it was a great idea, after all both form a wedge in the journal/bearing area. How once the fluid shearing heat had raised the temperature of the water steam would have formed. With steam's lower viscosity a very weak wedge would have formed. Steam also has much lower heat transfer coefficient than water so it would only have worked for a very short distance. OK if very close to home, maybe easier to push the car, ?

[Bruce Tuncks]

Water is a new one for me, but I like the idea. Surely a spare can of old sump oil would be better though.

If you are ever driving through aboriginal places, you should carry some old sump oil with you to give to people who flag you down asking for some oil. I have done this and the oil was gratefully received.

Apparently, the dipstick and the oil warning light are very early warnings and these can be ignored for a long time until the engine begins its " death rattle".

I have heard of water for emergency brake fluid.

[Geoff_H]

I could have found the Lycoming camshaft wear problem before I bought the aircraft had I done an oil condition check. we picked up the problem because we found an enormous amount of metal filings in the oil filter at the oil change. We found this metal with a magnet full stop when we found it there was an enormous amount of wear but how do I have a check for metals in oil we would have found it's a wrong before I bought it and I probably would have saved myself the $40,000 the engine overhaul cost. engine oil condition monitoring tells you many many things about the engine I I would recommend it to everyone who owns an engine particularly a person who owns an aircraft engine.

[Geoff_H]

Sorry for the few errors in the previous post I'm using voice to text because I'm a bit pressed for time. Please use your imagination

[onetrack]

It amazes me that engine manufacturers spend tens of millions on engine design, then fail to ensure critical components such as camshaft lobes don't have a simple sheetmetal cup under them, to retain a supply of oil, that the lobes would dip into on startup, to prevent camshaft lobe dry start wear.

[Geoff_H]

Lycoming did change their design they put in roller followers. I chose not to go this way because if you have a prop strike you have a sizeable bill because they have to be either inspected or replaced I can't remember, but it wouldn't involve more cost over the straight engine disassembly on a prop strike. Getting old so sure of my memory anymore

[Thruster88]

It amazes me that engine manufacturers spend tens of millions on engine design, then fail to ensure critical components such as camshaft lobes don't have a simple sheetmetal cup under them, to retain a supply of oil, that the lobes would dip into on startup, to prevent camshaft lobe dry start wear.

Onetrack, if you was a lycoming fan boy like myself ? you would know why lycoming did not do this, cups could fail and hit crankshaft and they would block the oil being flung off the crank, this is how the cam lobes are lubricated. Camshaft failure in a lycoming is always detected by the LAME (metal in oil filter) before the pilot will detect a loss of power, so not dangerous except to the wallet as Geoff found out.

[jackc]

Been around in heavy industry for years. You could actually get a kit for Delco starters etc for your Caterpillar or whatever engine so that turning the key one way spins the starter without engaging the pinion but engages a pre oil pump instead. Then a normal start after that.

My instructor always wants oil pressure on the guage, before an engine start on the Rotax, so I crank with ign switches OFF and watch the pressure guage rise thinking that‘S one less engine start on the life of the starter but the motor is pre lubed.

With a preluber at least I save the starter some cranking life to get oil pressure up before the actual start. IF there is an in flight oil pump failure (very rare), I have a backup., too. All this comes at a weight penalty..

[skippydiesel]

My instructor always wants oil pressure on the guage, before an engine start on the Rotax, so I crank with ign switches OFF and watch the pressure guage rise thinking that‘S one less engine start on the life of the starter but the motor is pre lubed.

With a preluber at least I save the starter some cranking life to get oil pressure up before the actual start. IF there is an in flight oil pump failure (very rare), I have a backup., too. All this comes at a weight penalty..

 

Hi Jack - This ignition off cranking sounds a but sus.

 

Rotax recommend "burping" (rotating the engine by hand, with aid of prop, ignition off ) the 912 befor first start of the day. This relocates any excess oil in the crankcase, to the reservoir AND importantly creates some oil pressure in the distribution system ie pre lubing.

[Geoff_H]

Oil pressure has little to do with the load carrying capacity of a journal bearing. Oil pressure just ensures that there is oil between the journal and the bearing. The load carrying capacity is a function of the oil wedge formed between the bearing and the journal.

[jackc]

Hi Jack - This ignition off cranking sounds a but sus.

 

Rotax recommend "burping" (rotating the engine by hand, with aid of prop, ignition off ) the 912 befor first start of the day. This relocates any excess oil in the crankcase, to the reservoir AND importantly creates some oil pressure in the distribution system ie pre lubing.

 

Do that on first pre flight for day, then check level in the reservoir, add oil IF needed.

[facthunter]

The burping is to make the oil level more accurate when you check it. If you top it up before returning the crankcase oil, it may be overfilled in the remote tank. The engine is a dry sump. What returns the oil is pressure in the crankcase from gas leaking past the piston rings. You need a positive pressure to return it. Most dry sump engines have a separate scavenge pump which is bigger than the delivery pump to ensure there is no build up of oil. in the engine.

The Lycoming CAMSHAFT is above the crank. The Continental is below it and doesn't have as much of a corrosion/scuffing problem but the manifolds have to go around the pushrods. ..Nev

[Jase T]

My local wreckers (back in the late '80s) used to hold Saturday afternoon refreshment drinking sessions that involved running engines without oil and water at WOT until they stopped. One could bet on how long they would last if one was that way inclined (in beer, of course, no money would change hands)... A holden red motor would regularly go longer than 20 mins before it started shedding bits of glowing metal... Morris engines less than 5..... The problem in the real world is that the cause of the oil loss is normally something a bit more serious than a loose line and is often the cause of the failure, not the loss of the oil it's self!

[facthunter]

On long ferry flights, low oil is not uncommonly the cause of the flight not making it. Inflight transfer is standard in some long range Pistons. Bent push rods or oil cooler failures or oil line failures, can empty oil. A high oil consumption motor may still function IF the oil was kept up to it. A motor without oil may have difficulty feathering the engine.. Sometimes a POT will blow, but usually that happens at the shrink band. Oil leakage is a real fire risk. On a red hot exhaust pipe it lights up better than lighter fuels do. Nev

[jackc]

Hi Jack - This ignition off cranking sounds a but sus.

 

Rotax recommend "burping" (rotating the engine by hand, with aid of prop, ignition off ) the 912 befor first start of the day. This relocates any excess oil in the crankcase, to the reservoir AND importantly creates some oil pressure in the distribution system ie pre lubing.

 

What the CFI wants....the CFI gets, its his aircraft:-)

[Bruce Tuncks]

Ignition off cranking is recommended for Jabirus if there is a likelihood of dry mains taking combustion loads. I don't think is a silly idea but as you guys have said, it is not without costs.

It's nothing to do with that Rotax burping business and a Rotax engine would be the same as a Jabiru with respect to combustion loads on dry mains, unless the Rotax uses ball bearings for mains.

[skippydiesel]

What the CFI wants....the CFI gets, its his aircraft:-)

 

If that's what the CFI/Owner want, who am I to question their policy for their aircraft/engine. However this is NOT a good practice, to routinely use the starter motor to crank the (ignition off) engine - its lazy and potentially damaging (mainly to starting system).

 

My training tells me that all aircraft piston engines benefit from a hand/prop crank befor the first flight of the day - gives the pilot an opportunity to assess compression and circulate a bit of oil to minimise the wear that occurs from a dry start.

[facthunter]

Starter wear is related to starter use. Any propping will help to prime the oil galleries and reduce the time to oil pressure rise. Making sure the throttle is not set too far off idle helps but the Rotax is rough if idled too slow after a start so it' needs to be set to a smooth running RPM ASAP. Engines with an "IMPULSE" mag should always be turned over with great care as you are relying on the switch earthing the live magneto when in the OFF position. Mechanics when working on them usually earth the mag more positively than relying on the switch alone. Nev

[Bruce Tuncks]

Good points. I agree that you should only turn the motor with the starter ( igns off ) if the motor has not been run for a week or more. And turning the prop by hand is a great DI thing to do, you should pick up quite a few things doing that, and the Jabiru is good for this with no impulse magneto. Thats a good tip Nev about an extra earth when working on an impulse magneto engine.

Turning by hand would not bring up the oil pressure would it?

[facthunter]

Bruce if the pump is good it will prime and with thick oil may produce pressure but I wouldn't expect it to be very effective in that regard, Gypsy Majors are very slow to show oil pressure rise. Some of that may be in the indication. (long capillary tube) but by todays standards, the oil pump flow is probably a bit on the low side.

I had fair pressure reading on a Continental C -90-16F with the mag points isolated to stop any contact. (as per the manual) on the starter and with hand swinging. I would never operate a new or serviced motor without priming the oil system before the engine ran.

Re the compressions , I've picked up quite a few issues that way. On a trip with a group, I turned a jab motor and recommended the owner check the tappet clearances which he did and found a couple too tight. Same with the DH gypsy motors. Report a soft pot and she goes in the Hangar for further checks. Nev

[facthunter]

There are limit's on how long a starter should be operated without allowing it to cool. With thick oil on a cold morning it's working harder and the internal windings may get much hotter than the heat you feel on the outside. Nev

[kgwilson]

I turn my engine by hand if it has not been run for more than 5 days or so. This is mainly to check compressions but also gets a bit of oil circulating. After an oil change & new filter I spin it up with Mags off to get oil pressure. This only take a few seconds on the starter & then I don't start it for some time later as at this stage it is still in the hangar.