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Oil temperature for take-off


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There seems to be little standardization about this. Jabiru say that the oil temp should be over 15 degrees C, while I was taught to see the needle move  off the stop ( at about 50 degrees.)

The Lancair with the Lycoming 360 has a much higher temp specified.n Yes its funny old units on the meter, but for sure its a lot hotter.

In neither case do they have a lower allowed temperature if using a multigrade oil, but it seems that 15/50 would lubricate cold much better than straight w100. So I would lower the specified temperature for the Lycoming if using 15/50.

Of course, we don't have real cold here in Australia, and I have never heard of any damage as a result of taking off too fast before the oil is hot enough for the spec. I can just imagine wrecking an engine if the oil was too viscous to flow to the bearings and full power was used.

What do you guys do?

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According to the lycoming operating instructions the carburetor models are sufficiently warmed up when they do not falter with throttle application, no mention of oil temperature. I like to see about 30°C oil temp before run up. 

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Generally stick to the makers figure. IF multigrade or synthetic I might crib 10 degrees. Those oils are better flowing than the original straight 50's (W-100). Nev

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SECTION 3 LYCOMING OPERATOR’S MANUAL
OPERATING INSTRUCTIONS O-360 AND ASSOCIATED MODELS
a. Fixed Wing.
(1) Head the aircraft into the wind.
(2) Leave mixture in “Full Rich”.
(3) Operate only with the propeller in minimum blade angle setting.
(4) Warm-up to approximately 1000-1200 RPM. Avoid prolonged idling and do not exceed 2200
RPM on the ground.
(5) Engine is warm enough for take-off when the throttle can be opened without the engine faltering.
Take-off with a turbocharged engine must not be started if indicated lubricating oil pressure, due
to cold temperature is above maximum. Excessive oil pressure can cause overboost and
consequent engine damage.

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Gosh there is different stuff out there...  I have read " 100 degrees F minimum oil temperature for take-off" in the Lancair stuff. I can dig out the reference if you like. 

I wonder why " the engine not faltering on throttle application" means that the oil is warm enough to lubricate properly.

 

 

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If the oil is too thick to flow properly (indicated by too high an oil pressure) it will rise rapidly with RPM increase .You can shear oil pump drives when this is happening or split an oil filter case.. In the earlier engines like the Gypsy  Majors the oil flow is much less than later engines use and starvation or an inadequate flow is more likely.  Many of the Lycoming sumps have the inlet manifold going through them and that slows warm up.  IF you had Cowl gills you would close them (in my view) so why not warm up facing downwind if the ambient is low. I spent a full 15 minutes getting my 0- 320 near the min figure at Corryong last time there.. Nev

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Thanks Nev, just 3 questions:

1. What temp do you remember aiming for?

2. were you using straight or multigrade oil ?

3. do you know of incidents in Australia due to this?

 

I too have spent time waiting for the oil to warm up. And yes I wished I had cowl flaps. And I can see why engine heaters are used in cold climates. 

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Whatever the book said Can't recall what that was  I've sold the Plane. Maybe 30 degrees C ?. I had rough Country to fly over. AeroShell100 plus. In cold climates I would recommend the multigrade. Just as Jabiru do. It was quite frosty. Nev

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ENGINE HEATERS! .

Not only do heaters warm your engine, it Will also stop condensation, inside, as well as outside your motor.

That was the uptake from, lots of happy car owners when they, Chopped up mums electric iron, to use on the sump of the car, one very cold pommie winter.

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No engine (aviation or otherwise) should be operated at full power until it "warms up". - Petrol engines seem to be unable to deliver full power from cold/start and I have no doubt that the potential for accelerated wear is highly likely if you try.

 

The engine manufactures advice on this matter, is invariably the minimum temperature that need to be achieved befor full power /TO is applied. If you value your engine, you will allow the engine to reach substantially higher temperatures, befor pushing the go lever

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The latest Jabiru manual JEM002-8 dated 22 May 2019 has these instructions. Note that full power should not be applied until the oil temperature has reached 40deg C. The earlier manual stated 50deg C. 15deg C only applies for the mag check. I warm my engine up for a bit longer and always wait till the oil is at 50 deg C before takeoff. CHT is always above 100 deg C by the time the oil temp is at 50 deg.

 

5.3 Warming Up Period
• Start the warming up period with the engine running at 1200 RPM for around 1 minute.
• Continue at 2000 RPM depending on ambient temperature, until oil temperature reaches 15°C (59°F).
• Check the two ignition circuits at 2000 RPM
Note: Engine RPM should not drop by more than 100 RPM when 1 ignition is turned OFF.
WARNING
DO NOT apply full power until CHT reaches 100 °C (212°F)
DO NOT apply full power until Oil Temperature reaches 40°C (104°F)
DO NOT allow cylinder heads to rise above 180°C (356°F) during ground running.

 

5.5 Take-Off
• Ensure all temperatures and pressures are within limitations before applying take-off power.
• Climb with the engine at maximum continuous power.
• Observe Oil & Cylinder Head Temperatures & Oil Pressure.
• Max RPM at Full Throttle is 3300 RPM

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If only JEM002-8 was the latest, which it aint, but the info is still correct.

The 40 degree thing came in at issue 4 in 2014. Was 50C prior to that.

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Oil temp is just an indicator for the temperature of the bottom end, CHT is the top end. If you start a cold engine and go to full power, the engine wil warm up unevenly (cylinder head and barrels warm up nearly instantly under full power) while the crank case is still cold. The different temperatures lead to different expansion of the components and many joints will be subject to minute movements. Over time, this will lead to oil leaks.

VW cars were quite well know for this. Drivers who gave the engine time to warm up had clean engines, the drivers who jumped in and floored it had oil leaks from the barrel base and case.

Same for the Alfa Romeo all alu engines. Once warm, you couldn't kill them but don't try a cold start and then full power.

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General recommendations for motor vehicles these days is don't warm up by running at no load Idle. Run at a bit above till oil is definitely circulating and then drive at moderate speed and load till temps are in the normal range. Modern engines this only takes about 1 KM or less unless it's a diesel with the heater on . The flying situation has always concerned me a bit as you ARE using 100% power for about 5 minutes after a fairly limited warm up. Not many engines get that sort of treatment.  Alfa's used a thick oil and insisted on a definite warm up. Idle speed is too slow to fling oil. That applies to aero engines as well They can be decidedly "Unsmooth" unless a few revs above idle are put on. Nev

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Motor vehicle advice does not apply here. One of the causes of two stroke failures was getting the CHT up and taking off. The barrels expanded slower than the pistons and as soon as you reduced power the piston could seize or possibly just leave aluminium coating the bore. I have seen pistons with tear marks down the full depth. I have also seen a seized piston which moved OK when the plane was recovered and sitting nice and cool in the hangar.

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In my long life engine idle has never been the recommended way of warming an engine - assuming normal start and systems operating it has always been warm up under light load conditions (not nil load) - my understanding of this is -

Ground based engines gentle acceleration, keeping the engine speed above max torque (do not lug), but not high revs, until temperature stabilises. Most but not all ground based engines will also have some additional  load from the "cold" transmission.

Aircraft engines fitted with Fixed Pitch props are loaded from the start, In Flight Adjustable will be lightly loaded as they taxi & perform run ups,  so revs should be kept below mid range, until manufacturers temperatures are met or exceeded. 

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Diesels are not smupposed to be left idling as it Glazes the cylinder,s.

BUT

turbo diesels have a timer to let the turbo bearings cool down !.

spacesailor

 

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43 minutes ago, spacesailor said:

Diesels are not smupposed to be left idling as it Glazes the cylinder,s.

BUT

turbo diesels have a timer to let the turbo bearings cool down !.

spacesailor

 

It is good practice for all engines to be idled or be driven/operated under minimal load for a few minutes before shut down - I favour the latter  for my vehicles, as I have 3 km of very quite, almost level road befor I get home. Low load driving has the benefit of good air flow helping to cool the engine. The former (fast idle) is what I use on my aircraft engine. Fast, as it facilitates air flow, oil and coolant flow encouraging engine to cool - a long taxi would have similar beneficial impact.

 

As for turbo chargers (petrol or diesel) - turbo chargers get very hot under load. They used to have bearing lubrication that ceased as soon as the engine stopped (delivering pressurised oil). So you have a very hot (can glow red) turbo, shut off the oil supply and you get cooked oil & a dry bearing. Do this often enough and you "bugger" the bearing  - very expensive.

Don't know much about aircraft turbos but land based ones now tend to have a cooling system and some have after shut down oil delivery - both help to minimise the effects mentioned above - still I would maintain the good practise & allow for a cool down period.

 

Note: I am not a big supporter of turbo timers (usually fitted as an after market - not standard) - lazy drivers/operators and technically illegal, as a running motor vehicle is not supposed to be left unattended, on a public street (the latter point is of little consequence).

 

Glazing of the bore is usually associated with extended idling (well above the few minutes to allow cool down), lugging the engine, incorrect engine oil, operating at below optimum running temperature (city cars)etc etc

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Is there an add-on electric oil pump? This could also be used before start-up to ensure there was no time where the bearings went dry. I have never heard of such a thing, but the idea is so obvious that it must have been used.

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17 minutes ago, Bruce Tuncks said:

Is there an add-on electric oil pump? This could also be used before start-up to ensure there was no time where the bearings went dry. I have never heard of such a thing, but the idea is so obvious that it must have been used.

Pre start oil pumps are used on very large engines. I am guessing on aircraft and automotive engines the bearing clearance is small enough to retain sufficient oil for the next start up, think capillary action. The oil pump does not "pump the metal apart" it just replenish's cool oil to the bearing. Google "oil wedge". 

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55 minutes ago, Bruce Tuncks said:

Is there an add-on electric oil pump? This could also be used before start-up to ensure there was no time where the bearings went dry. I have never heard of such a thing, but the idea is so obvious that it must have been used.

Here......

 

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

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1 hour ago, Bruce Tuncks said:

Is there an add-on electric oil pump? This could also be used before start-up to ensure there was no time where the bearings went dry. I have never heard of such a thing, but the idea is so obvious that it must have been used.

 

34 minutes ago, Thruster88 said:

Pre start oil pumps are used on very large engines. I am guessing on aircraft and automotive engines the bearing clearance is small enough to retain sufficient oil for the next start up, think capillary action. The oil pump does not "pump the metal apart" it just replenish's cool oil to the bearing. Google "oil wedge". 

As Thruster said  - have been available for large engines for a long time - usually in the form of a "pilot" starter motor that will rotate the large engine for a period to raise oil & fuel pressures pre start.

 

I would speculate that the, pre first start of the day, hand/prop rotation of an aircraft engine would have some of the same benefits.

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For the bigger industrial diesels, you can buy Delco-style starters that are fitted with a prelube pump on the end of the starter housing.

 

As soon as you turn the start switch to "start", an electrical circuit is opened that spins the prelube pump, and sends pressurised oil through the oil galleries.

 

As soon as operating oil pressure is reached, a pressure switch sensor actuates the switching arrangement to turn off the prelube pump and actuate the starter motor.

 

I seem to recall a number of vintage aircraft and cars had a hand-operated prelube pump?

 

China Starter for Prelube 50mt Str2611pl 3603868pl 6956 - China Starter  Motor, Auto Starter

 

https://www.flocomponents.com/sln_engine_prelubrication_systems/

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Some if them were probably total loss oil systems. Give them a bit to get to when the other has put out enough to sustain it.  Nev

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9 hours ago, onetrack said:

For the bigger industrial diesels, you can buy Delco-style starters that are fitted with a prelube pump on the end of the starter housing.

 

.............................................................

Onetrack - I can certainly see the merit of such a system helping engines that are expected to go from cold start, to full power & load, within a few seconds/minutes , such as generators and emergency pumps. May also be a good investment for the little used marine engine but cant see that it would be helpful for regularly used equipment/vehicles and hand "propping" of small aircraft engines befor the first start of the day, while not quite as good, is infinitely cheaper, significantly less complex and lighter.

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