Warming your engine?

[Who has control?]

Whats the best way to get the engine up to temperature?

I went flying with another group member last weekend and he was careful to ensure that the oil temperature was starting to creep into the bottom of the green before taking off.

Normally, I just do power checks and then leap into the wide blue yonder, but it got me thinking.

I have a book that states 'a cold engine will deliver only deliver 90% of its rated power' which means that on take off, I've only got 90% of my horses working for me, when I really coudld do with all of them.

So what is the best way to warm the engine, do you sit gently at idle and run the risk of the plugs foulling or rev the nuts of it at 2000rpm and risk increasing the wear rate due to lack of lubrication from thick oil.

The best way to warm a car engine is to drive it, as normal urban driving involves varying the revs until the engine has reached operating temperature.

Suggestions please.

[poetpilot]

Well, leaping off into the wild blue without warming up is not recommended. Remember you've got an aircooled engine there, not a cosseted, water-jacketed engine, so heating up and cooling is not as uniform as your car.

Just revving up and going could result in a cracked cylinder or something, just as you are in the climbout. Not recommended. Really, you should be warmed up reasonably well prior to power checks.

But it aint easy on a cold day. Damn things just dont want to warm up. On my 172 (RR O-300D), the book suggests 800 rpm for first minute (ie until pressure comes up) then 1200 rpm to prevent plug fouling. I'd use say 1400-1500 once I'm at the hold and on the brakes.

Sometimes I do the pre-takeoff checks once slowly before the engine checks - then I do 'em again after the engine checks. It double checks and it uses up some time, allowing the engine to warm up a bit more.

...and I know first hand what can happen. I flew a VP1 on a very cold day in the '80s, and on climbout the crankcase cracked. I got a bucket load of oil over the screen, the exhausts and even on my legs (seeped through holes in the bulkhead). Luckily I was at 1500 feet and circled back to land on the airfield.

Once over the first few seconds of sheer fright (the oil was smoking off the exhaust & I thought I was on fire), and checking the oil pressure guage, I decided to leave the engine on idle in case I needed a burst of power to get over the hedge. If your engine loses all its oil, it may be worth remembering this.

The oil cools as well as lubricates, so reduce the load right away - if you dont use power, i.e. leave it on idle, it wont get TOO hot, and it may (but I stress MAY) be able to give you a brief boost when you need it. In a situation like this, your engine will have to be stripped anyway so dont think about engine preservation as much as conserving what's left for a safe landing.

[sennadog]

I've never been comfortable with a cold engine so I tend to pootle around a bit during the taxi and given the undulations at Redhill the power comes on and off gently to avoid prop strikes which seems to be the kindest way of waking him up.

[FlyingForFun]

Surely this must depend very much on the specific engine type, and also aircraft type? The only advice I can suggest is to read the POH, and do what it says.

Personally, I can't move off until the engine is at least a bit warm, but then I have an unusual engine. The Rotax has water-cooled cylinder heads, so it has a choke which must be pulled out for cold-starting (much the same as older cars do, except the choke on older cars stays out so you can drive off, whereas on my Europa it's spring-loaded to return to the normal position).

So, after starting (which really requires four hands - although I can just about cope with two if I don't have a pax to help me), I grip the stick between my knees, use my right hand to hold the choke out, gradually letting it in as the engine warms, and my left hand to keep the RPM at about 2000 as I push the choke in. Usually takes about 2 or 3 minutes, but I haven't had the 'plane long enough to try it on a really cold day yet. If I were to try to taxy, I'd need to use my feet, which I couldn't do without letting go of the stick!

Also, the checklist states to ensure an oil temperature of 50 degrees C before doing the power checks. So, by the time I've done the power checks, the oil temperature is usually up to at least 60 or 70 degrees before I line up on the runway.

Of course, this won't be applicable to most engines...

FFF
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[Kermit 180]

Most engines shuoldnt be run up until the temperature is at least at the bottom of the green. However, in hot conditions, idling for too long can cause plug fouling. Taxiing is the same, if you require a lot of power to get moving, try to avoid doing so until the temps have at last started to rise and the pressure has stabilised. As was said, consult the POH/AFM, and there is also some good stuff from the engine manufacturers at their respective websites.

Kerms

[LowNSlow]

Au contraire FFF, ALL engines should be warmed up before being asked to produce full power. Suddenly asking a motley collection of aluminium, brass, cast aluminium, cast steel, forged steel, spring steel etc etc with widely differing coefficients of expansion to work in the manner the designers intended is just asking for trouble. Ensuring the oil has reached a minimum temerature is a guide that at least most of the engine is at a relatively constant temperature. Also cold engines have a greater tendancy to cut when cold if the throttle is closed.
The reason that cars are driven away straight from starting the engine is more to do with fuel efficiency than conserving the engine. Even so, all manufacturers handbooks I've read recommend not exceeding a certain speed/rpm until the temperature gauge has made some kind of indication or if one is not fitted they specify a distance or time.

Who has control no offence mate but if you were renting an aeroplane off me and you were handling the engine as you describe we would be having words ;) Revving cold engines at least keeps the engineers in business........Good that you posted this though as it appears that nobody has explained the principle behind warming engines to you and probably a lot of other peeps out there. Hopefully this will increase your engine's life and therefore reduce your group's long term maintenance bills. :)

[Genghis the Engineer]

I tend to start at idle, and incrementally increase revs over several minutes, timed right I usually get a sensible oil / CH temp around the time I get to something roughly equivalent to cruise revs.

Having about 400hrs with Rotax engines, and not yet had one stop in the air, I think this approach probably works.

Incidentally, there's nothing to stop you leaning on the ground to avoid plug fouling, just make sure your checks take you back to rich before t/o.

G

[FlyingForFun]

LowNSlow, I agree - engines should be warmed before doing power checks. Although, re-reading my post, I didn't make that very clear. What I was trying to get across is that the method of warming the engine will certainly vary from type to type.

FFF
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[Who has control?]

Thanks for the responses -

The engine is a Lycoming 0-540 160HP and I've just discovered a note in the POH:-

Engine must be run at 1200 rpm or less until oil temp of 104deg F (40 degC) is attained.

So it looks as though as though sitting at idle is the way to go.

[LowNSlow]

FFF sorry, missed your point! Yes, I would agree that different types of engines may need a different warm up regime although I can't see there would be that much change between different types except for possibly certain rpm's that must be avoided because of resonance or for engines that heat up quickly eg Merlins & Griffons when fitted to Spits (wish I had that problem :D) or conversly big air cooled radials that take an age to warm up (wish I had that problem too :D :D). Anybody out there with complex engine experience such as big radials, GITSO's etc to enlighten us??

Personally for Lycomings, Continentals and Cirrus engines I've just pointed them into wind and run at a fast idle around 1,000 - 1,200 rpm until the needle in the temperature gauge moves off it's stop which is usually around the 40C mark. Once the gauge shows some indication then I do my power checks which further warms the engine and hopefully clears any plug fouling during the 1,500rpm power check. Finally taxiing to the takeoff position should get the whole shebang warm enough to take full power safely so it's up to full power to check for plug fouling and off to the big blue sky!
I face into wind because the inefficient part of the prop near the hub doesn't throw a lot of air through the air intakes and the cylinder heads get hotter faster than the rest of the engine and still need a flow of cooling air over them as the rest of the engine warms up.

In the Hewland water-cooled engine in the ARV I was taught to do the same although facing into wind wasn't as important as the heat generated by the heads was circulated rapidly through the engine to warm it up. Also the radiator scoop was under the belly and got (marginally) better airflow from the prop compared to the more common nose intakes. All in all the process was far quicker than for an air cooled engine especially on a cold day. Much more car-like except for the old Beetle of course :D

[QDMQDMQDM]

I believe my 0-320 handbook says you shouldn't run for more than four minues on the ground and that the engine is warm enough to take off when the throttle can be advanced without the engine coughing. It says nothing about having oil temp in the green.

QDM

[sexybeets]

I find a quick hug, and a few whispers in the right place get her nice and warm before I turn her on............:D
She's treated me right so far!!!!!

[LowNSlow]

QDMx3 only 4 minutes on the ground? Don't go to Southampton, you'd exceed that taxiing out! Are you sure that doesn't mean 4 minutes without the cowls and/or cooling baffles in place cos hot spots would easily be created in those conditions within about 4-5 minutes.

Regarding the advancing throttle, how long does it usually take you to get to the stage where you can advance the throttle without any splutters?

[Lowtimer]

LowNSlow,

You asked about radials. It's not a _big_ radial, but the M14P in the Yak takes quite a bit of warming and has to be treated very gently in terms of revs until the CHT and oil temps reach certain levels. I try to do the actual start at low revs (around idle, which is around 750 rpm (around 25%), and as soon as I confirm oil pressure I let it gradually pick up to around 1200 (40%, a little more as time goes by). (It often does this semi-automatically as additional cylinders chime in.) It is especially important not to rev too hard when the oil is cold in the winter as this tends to promote cavitation of the oil pump, with the pressure falling as the revs rise.

In most M14P installations the pilot has the considerable benefit of being able to close and open the cooling gills in front of the engine, and open / close the oil cooler. After start you can shut off the cooling to encourage the CHTs to start moving into the green in reasonable time, and thereby help to get the oil warmed up as quickly as possible. The CHTs come up quicker than the oil, so once the CHTs are up you start opening the gills again while you wait for the oil to come the rest of the way. On the Yak I fly, on a temperate autumn day or cooler, opening the gills all the way on the ground at 1200 rpm will make the CHTs drop back out of the green, so ithe intermediate settings are not just for show. In the winter, all of this can take a lot of ground running, 15 mins or even more. Pre-heating would be nice to have!

On really big radials there are usually controllable cooling gills at the rear edge of the cowling. From conversations and observations at Duxford over the years, getting big radials to stable core temperatures before flight is a major deal for the operators. There's a lot of metal in those very large engines and the sheer size means it takes longer to get all the temps nice and even, and all the internal clearances and tolerances in the best ranges. The Blenheim folk, and probably others, go to great trouble to pre-heat both the oil and the Pegasus engines themselves before starting, actually pumping hot oil all around the lubrication system, as cold starts are the time when almost all engine wear takes place in normal use.

With Merlins, Allisons and other liquid cooled engines you have the advantage that the coolant heats up quickly and then rapidly carries the heat around the engine, so even temperatures can be achieved much more quickly.

(edited for silly spelling)

[Final 3 Greens]

Who has control

O-540 = 160hp?

On our Pup we try and run her at 800rpm for the first minute, then 1000, then 1200 - but it's sometimes easier said than done on a cold day as the engine needs at least a 1000 to idle when very cold.

[QDMQDMQDM]

It definitely says four minutes and I don't have any fancy cooling flap thingies.

Regarding the advancing throttle, how long does it usually take you to get to the stage where you can advance the throttle without any splutters?

About a minute, maybe two. On one of the runways at my home base, I start up, taxi 20 yards, do the run-up and vital actions and take-off.

QDM

[LowNSlow]

QDMx3 4 minutes, how bizarre. It is a 150hp Super Cub with a Lycoming O-320 engine right? Surely you haven't had the O-540 conversion with 310 hp! If you have, can I have a ride please? :D :D

If it is the O-320 then it's one of the most reliable engines in the business as fitted to AA-5s, C-172s and PA-28s the world over. I am amazed that they would be restricted to 4 minutes ground running. As I said earlier Southampton, (for one) when busy should have PA-28s and Grumman AA-5s with cooked engines all over the place. :eek:

Lowtimer nice insight into the operation of radial engines. I'd thought the cooling shutters on the MP-14 were to ward off Siberian cold in the winter. I didn't realise that the airflow would cool the heads that quickly on the ground. I remember the AeroStar display team at North Weald last year taking forever to warm up (after their well flash sychronised startup :D), now I know why, cheers ;)

[RotorHorn]

Part of the start-up procedure for an R22/R44 is to allow the engine to warm up.

After starting the engine (and letting the clutch engage), the engine is run up to 75%-80% operating ERPM and held there whilst the temp climbs into the green. This can take a few minutes on a cold day. Once there we carry on with the engine checks (magneto's, carb heat, needle-splits, etc.)

Note the engines are de-rated, so that even at 100% ERPM its still only about 80% of what the engine is capable of....

[Rod1]

One thing which stops our engines warming up is fuel. At full rich and 1200 rpm the engine is receiving too much, which acts as a cooling agent. On a cold day if you point into wind, set the rpm recommended in the book and lean the engine off it will warm up at a rate much closer to normal.

The IMPORTANT thing to do is make sure you set mixture back to full before takeoff!

Rod

[Who has control?]

F3G I've double checked the POH & its definitely 0-540 - 160 HP.


I thought that the 3-digit number in a Lycoming engine 320, 540 etc was the cubic capacity in inches and the 540 was a 6-cylinder engine. Am I wrong here?

[A and C]

The heart of the walming up problem is the "low tech " oils that aviation still uses most of you are using single grade oils such as W100 or W80 these are not good lubricants when they are cold and so to avoid damage to the engine it should be run at low RPM untill the bottom of the green arc on the temp gauge is reached.

The most common damage resulting from high RPM when cold is worn camshafts , normaly the lobes furthest from the oil pump are the first to have the case hardening worn through this distrbutes small steel particals around the engine , most of them seem to get embeded in the "softer! alloy of the pistons below the rings.

My recomendation is to use a multi-grade oil and warm the engine at low RPM not more than 1200RPM untill 40 C sounds good to me , thease are the numbers for the Lycoming O-540 an engine with a reputation for eating camshafts if ill treated.

[Lowtimer]

Who Has - I believe you, but it does sound as if you have a weird typo in your POH. 0-540 = 6 cylinders and 235 bhp minimum. If it's 160bhp it must be a four-banger. How many cylinders do you have?

LnS - When I started flying the Yak I too imagined that in "standard" UK weather compared to the frozen wastes, the operation of the cooling gills would be pretty much "open fully and locked". In fact I was surprised just how much scope there is for using them. In this autumnal weather, standard cruising will be at a part-closed position, and in anticipation of a prolonged climb I would open them , then if descending a couple of thousand feet I would pull them closed a little more. Even if not making huge power reductions it still cools down quite noticeably when you're swooping down for an overhead join.

Another advantage is that when you stop for fuel (something you get LOTS of practice at), you can close the shutters after shut-down, and the engine stays nice and warm while you refuel, grab a cuppa, etc, so the restart is easier and you don't have to wait around for ages again for it to warm up before departure. Oh yes, and leaving it in the hangar with the shutters closed can only discourage little nesting creatures, and those peculiar individuals at air shows who seem to find the oddest places to dispose of put their crisp packets, Mars Bar wrappers etc.

So there's lots to do with those odd-looking levers on the right sill of the cockpit, but we make up for the workload by having automatic mixture control, no tanks to change, etc.

[Who has control?]

Lowtimer - I'm inclined to believed your typo idea. Its only a 4 cylinder BUT there is a 235HP variant available.

One page in the POH states :- 0-320 4 cyl 160hp, but has been amended, the new sheet states:- 0-540 4 cyl 160hp.

A later chapter on engine limitations states :- engine : 0-320

So apart fom ripping the cowlings off to find the data plate, I think I'll accept its a 0-320.

Fortunately its the only mistrake I've found.

[Final 3 Greens]

Who has Control

You are right - the number doe smean cubic inches.

The 0-320 is usually 140-160HP, whereas the 0-360 is 180HP.

Both are 4 cylinder - I am not expert, but I believe that the 0-360 is basically a longer stroke 0-320.

The 540, as others have pointed out, is the big 6 cylinder 235-300HP block that hangs off the front end of the PA28-235/6 and the PA32 range.

If your a/c is a Koliber, it is available with a larger 0-540 engine as an option - giving 235HP.

Perhaps this is the explanantion - my original query was that an 0-540 giving 160HP seemed VERY de-rated - and as there is a 260HP carb version, I wondered if you had done a typo - but apprently someone else had!!!!!

BTW, I am a Squadron member and fly the Pup with 69 on the nose ... we may have bumped intp each other at some stage.

[Shaggy Sheep Driver]

Agree with everyting Lowtimer says about the M14P in Yaks - in winter, it can be a very long wait before you can taxi.

I found the oil cooler flap didn't need much attention in flight, but those engine gills were something else, and an eagle eye had to be kept on the CHTs. After a while you could actually smell when the engine was getting hot enough to require a tad more opening of the gills; there was no such warning for overcooling.

But reading my car handbook, it says NEVER to warm up the engine by pre-drive idling. Start it and drive away immediately, it says (Omega V6). I wonder why? Is it something to do with not having cold and rich exhaust gasses soaking the catalytic convertor?

SSD

[LowNSlow]

SSD, sounds about right regarding the cat.

SSD & Lowtimer, pity there isn't an automatic option for the gills :D

who has control and QDMx3, looks like I got your posts mixed up in my befuddled mind :rolleyes: regarding the hp of QDMx3's engine and the type of who has control's engine.

Now that I'm straight again, what kind of system allows two different aircraft types with the same model of engine to have such different criteria for such an important part of their operations:

QDMx3 quoted from his POH (Super Cub)
I believe my 0-320 handbook says you shouldn't run for more than four minues on the ground and that the engine is warm enough to take off when the throttle can be advanced without the engine coughing. It says nothing about having oil temp in the green.

who has control quoted from his POH (PZL Koliber)
Engine must be run at 1200 rpm or less until oil temp of 104deg F (40 degC) is attained.

Surely the operating criteria are unique to the engine rather than the airframe. I realise that different cooling capabilites in the cruise could be reflected in the POH but surely they will all start up/warm up the same! I don't recall seeing a Super Cub with a LoPresti style cowling with teeny weeny cooling air inlets :D

[QDMQDMQDM]

Nope I didn't quote from the Super Cub POH, which is notoriously sketchy, but the engine handbook. But I've temporarily, er 'misplaced' it. I'll get back to you when I find it and quote exactly.

QDM

[E1453]

My procedure for engine warming is idle plus lean mixture. That way, I don`t get fouled plugs.

I strongly recommend everone to always lean the mixture after start until the run up. But if you pull the red knlb, pull it hard. You must have the mixture so lean that the engine will immediately quit when you apply takeoff power. It`s safer to pull hard than being timid and forget it leaned before the takeoff.

The mags check is much more valuable if you do it with the mixture leaned. With the mixture leaned, any ignition problem will show soon, before it gets worst. Doing this, I learned that, if a standard rich mixture mag check shows a discrepancy, you have a big problem. With the mixture leaned, the problem shows earlier.

[andyb79]

poet that sounds like a katana or at least a rotax 912???

i usually find that start up then take your time taxying(which with its taxying abilitys aint hard) power checks then a back track usually gets it up to temp. it has however been drilled into me that you should never commence rolling until all gauges are reading normally


edited to say that i am pretty low hours so i normally take my instructers word as gospal but i shall be watcjing this thread with interest

[A and C]

As far as I can see there are two issues to deal with the first is thermal shock this is best avoided by warming the engine at a fast idle speed untill the whole engine has had the chance to walm up to a point at which the rapid diferental expantion of the engine parts will be minimised.

The second issue is lubrication as we all know aircraft piston engine oil technology seems to be frozen in the 1940,s with most of us still using mono grade oils.
These oils do NOT work well untill up to near working temperature and will flow freely between the working parts , this is critical in the highly loaded parts of the engine.
This damage is most commonly seen on the cam lobes and cam followers and is known as "spalling" This is a direct result of lubrication breakdown usualy as a result of the engine being run to fast before the lubrication system has had a chance to build up the "splash lubrication " and the oil is to cold to flow freely.

As the cam and follower spall and small particals of steel are released into the engine , the particals that are not caught in the oil filter normaly embed themselfs in the pistons below the rings and score the barrels this leads to the release of more steel particals flowing around the engine and a rapidly increasing amount of engine damage.

There are two things that can be done to first and most important is to keep the RPM at or below 1200 untill the temp gauge starts to move and then dont do the run-up checks untill you have 40c oil temperature.

The other thing that you can do is use a multi grade oil , these provide better lubrication at low tempertures and some have an anti scuffing agent to help reduce spalling ( this is agent is required for the Lycoming "H" series engines)

[LowNSlow]

Sliding slightly off topic:

A & C I've been thinking about using multigrade oil once my rapidly dwindling stock of 100W is finished. I have been led to believe that they provide better protection to engines that stand for a while (mine can be idle for at least a month at a time). What concerns me is that they might not be appropriate and / or approved for an ancient engine like a Cirrus Minor II with it's oil flinger front crank seal and ancient design oil seals.

Hopefully I am avoiding the spalling effect caused by overly viscous cool oil as I wait until the oil temp needle is off the stop (100F / 40C) before giving the engine any welly. However, I have seen my oil temp getting up to 180F during the summer when I was in a fast, for an Auster, cruise. I was surprised at how long it took for the oil to cool down to a more normal 150-160F after reducing the power. Would a multi grade help in these circumstances?

[M14P]

Good tip - if you lean on the ground (in my view absolutely essential) then lean far enough so that you cannot get more than 2000RPM out of the engine; you can't damage the engine like that and you certainly can't take off with it leaned!

Has anybody ever seen REAL Russian oil? I have - I can tell you that all of the min temps for the M14 etc suddenly seemed very sensible. This was new oil. I can only describe it as a grey amorphus blob of cloying mush.The chap turned his glass jar upside down, counted to about five and the whole lot plopped to the bottom. The chances of that stuff lubricating below 40 deg C is NIL! The Russians are also very proud of their non-leaking engines. I wonder why they don't leak!

Koilber - 160hp O-320 (BZAJ at NW) but it is also available with an 0-540 pushing out 235hp.

Another contentious issue - Lengthy power checks cause much more harm than good on 'everyday' Lycs and Contis.

m

[146fixer]

LowNSlow,
There could be a small problem with multigrade oils not being approved for older out of production engines.The manufacture would usally approves a new type of oil for use with its engine after testing or making sure that it meets the required spec's MIL/SAE etc. by some other way.If its not approved then it can be regarded as using a non approved part with all the safty and legal problems that brings.Or the oil may just not work with the materials used in that engine.Check your POH/AMM.You could try the oil manufactures to.
You could try doing your oil/filter changes earlier and using a good quality oil.But warm up the engine before any high RPM.That is one of the best ways of reducing ware and tear on any engine.

:ok:

[A and C]

I would not use a multi grade in your engine , however Shell have now started to market "W100 plus".

This is W100 with the anti scuff agent and a corosion inhibiter added that I would think would be the best thing for your "old" engine.

[ROB-x38]

On the 230hp IO-540 (C-182) i tend to leave the cowl flaps closed while getting up to temperature - every bit helps.

And on the topic of piston engine temperatures i've got a question re: shock cooling. I have no experience with water-cooled engines. On descent i tend to close the throttle and give the mixture a twist every 1000' or so to minimise any sudden temp changes. Am i right in saying this is unnecessary in water-cooled engines - could someone explain?

Rob.

[LowNSlow]

146fixer and A and C thanks for the advice. I don't think multigrades were in common usage when the POH for my 1946 Cirrus was written. I'll go for the W100 plus I think.

[411A]

Oil does several things in aircraft engines (cooling, lubrication etc) but if you have a TCM turbocharged engine, oil also assures that the wastegate operates properly.
For this to happen, the oil must be hot.
Watched in amazement some years ago as the president of Pacific Airmotive in KBUR taxied out for takeoff in a Cessna 402, did not bother with a runup( his usual forte)...and on takeoff, shoved the throttles full forward (recommended by the POH) only to find that three cylinders on the left engine, and two cylinders on the right engine separated from the case, leaving bits of metal all over the runway.

Hot oil was very necessary to ensure that the turbo wastegate operated properly, limiting the MP to the proper number.

[LOMCEVAK]

LowNSlow, I see that many moons ago you asked about warming up big radials. The principles are the same as with any piston engine, but you do have to be very thorough with the procedures or significant mechanical damage will occur. My comments below relate to the PW R-1340 engine in the Harvard and the PW R-2800 engine in the Hellcat and Corsair. Other combinations, such as the Centaurus engine in the Sea Fury or R-2800 in the DC6, may be markedley different.

After starting with cold oil, the oil pressure will initially be very high, with a quoted maximum limit for most engines of 100 psi. With the PW R-1340 you can keep the pressure down to 100 psi by running at around 700 - 800 RPM then, as the oil temp increases, progressively increasing the RPM to maintain 100 psi until the normal warm up setting of 1200 RPM is reached. With the PW R-2800 you may see pressures as high as 200 psi after start. Pilots' Notes states that the RPM must not exceed 1000 until the oil pressure is less than 100 psi.

As with most engines, the RPM must not exceed the "warm up" setting (1200 R-1340, 1000 R-2800) until the oil temp reaches 40 deg C and the CHT reaches 120 deg C. This inevitably precludes taxying on grass but should allow you to taxy on hard surfaces if reasonably level. Also, although it may seem logical to warm up the engine with the cowl gills closed, in the Hellcat this can cause heat damage to the ignition harness so they must stay open on the ground.

Some engines have a lower maximum CHT limit on the ground than in flight, presumably due to the reduction in cooling airflow to certain cylinders without the airflow into the cowling.

Big radial engines do not like sudden large temperature changes. Therefore, you do not go straight from a display (continuous rich) setting to very low power for the approach. You always aim to spend a few minutes at a cruise power setting before an approach to land to let the engine temperatures stabilise at a lower value.

Prior to shutdown you run the engine at 800 - 1000 RPM for at least a minute to let the temperatures throughout the engine stabilise. Also, there is a maximum temperature for shutdown which is less than the normal ground maximum temperature. This is because the CHT initially rises after shutdown due to the loss of propwash over the cylinders.


So far on this thread, no-one has mentioned the problems of warming the engine in flight if the CHT cools below the minimum value. In the Harvard, this occurs easily during prolonged flight at idle (stalling, spinning, high speed dives), and I have often seen it with the IO-540 in the Beagle 206/Basset during descents and after engine shutdown during airtests and training. If you fly an aircraft that is prone to this and the POH does not tell you the power setting for warming up, you must use the minimum power that will give a CHT increase without losing too much altitude. Work it out in advance, remember it and use it!

I was somewhat alarmed when I first read this thread that minimum oil and cylinder head temperature limits were not being strictly adehered to. This comment is not a criticism of those who have posted here. In fact, it was heartening to find the interest in researching this field. However, it does raise two questions in my mind. Firstly, are POHs adequate in the promulgation of engine limits and advice on how to adhere to them? Secondly, is engine husbandry emphasised adequately during PPL training by flying instructor? I suspect that this might stimulate more debate!

Hope that this is of interest.

[Dale Harris]

411A - Same on the TIO Lycomings

[Circuit Basher]

Had an interesting one a couple of days ago, flying out of Perth in the club Fuji FA200 (IIRC, an O320 powered beast).

Ambient temperature at ground level was -3 deg C and the engine (aircraft had been in unheated hangar overnight) was run up very gently, progressively increasing revs to around 1500 whilst at the hold, waiting for oil temp to reach 40 deg C (bottom of yellow arc). After around 10 mins running, the temp was still only 30 deg C. The pilot I was checking out (as part of club currency rules) and I agreed to proceed with the power check as the temp had not moved at all in 3 mins. After the power check, the oil temp was still only 30 deg C. We then did a couple of circuits, during which time, the oil temp dropped to 25 deg C.

I then had the aircraft booked for an XC and flew at FL60 over the Cairngorms to Inverness and back (1 hr flight either direction). At cruise power, the oil temp never rose above 25 deg C and I estimate OAT at around -16 deg C.

On paper, the flights should not have proceeded - anyone think I was doing damage to the engine by continuing?? I felt that I'd done my best to warm the engine and that a transducer positioning error was causing erroneous readings.

[IO540]

Circuit Basher

I would check the CHT gauge.

[Tinstaafl]

Have you considered cold weather blanks fitted to the oil cooler &/or cowling?

[sycamore]

CB,
It may be worth your , and the clubs while , changing to a thinner grade of oil during the winter season, even if ground temps remain somewhat lower than normal.

I also concur with the others that a gauge temp check should be carried out, and maybe a small blanking plate over part of the oil cooler may help to keep temps. up. If the oil pressure is normal
then it is probably ok, but I`d get an engineer to check it out.

[ShyTorque]

A couple of things to consider before giving full throttle to a cool engine.

1. Application of full throttle causes rapid heat exansion of the pistons. If the CHT isn't up, the cylinder bores haven't yet reached their full working diameter. This results in a reduction of clearance between piston / bore and might result in bore scuffing or piston ring area damage.

2. If the oil is too cold, the oil pressure is likely to go high enough to force the oil filter bypass off its seat so you are running cold, unfiltered oil around your engine at full power.

Neither of the above is likely to result in good engine longevity. :uhoh:

[aidanruff]

I have been running a cherokee-6 with an IO-540, 300 HP lycoming for about a year. I sought out the advice of a very helpful guy who had run the same type of a/c as a parachute jump plane and had achieved TBO and beyond with it.

His recommendations seem to work well and my engineer agrees that my engine is in great condition, certainly I haven't - yet - had any nasty surprises (fingers crossed).

Immediately after startup, lean aggressively at no more than 1000RPM. This warms the engine as rapidly as possible, still taking several minutes, giving me time to check out all four tanks and run through the checklist, tune radios, etc.

Never exceed 1000RPM until the CHT is well off the stop.

If you are parked on grass, for a tarmac runway, pull the a/c off the grass by hand so that you don't have to over-rev to get moving.

If you've got the runway length available, open the throttle progressively rather than just firewalling it, this also stops stones, etc, being sucked into the the prop - don't forget to richen the mixture.

Although its off subject, after landing I also do a scavenge run on the engine for a couple of minutes at 1200 RPM with the mixture leaned back until the RPM just starts to droop.

The last endoscopic check showed the cylinders in good condition and the plugs just seem to go on and on...

[overclock]

The POH for my 182 (Continental O470) recommends 2 to 5 mins running at 1000rpm after start in cold weather, and a check on oil pressure to ensure it remains normal during run ups. The big problem, apart from insufficient lubrication is, I understand, that if the oil is very cold and viscous the pressure relief valve may not be able to "dump" sufficient oil, the pressure rises to a level which burst pipes or joints leading to total loss of oil pressure - not good!

I generally ensure the oil temp is in the green before take off, on cold mornings starting the engine first and running for 5 mins very lean before I do the airframe checks (engine stopped!) generally means the heat soak from the engine has nicely warmed the oil on restart.

[Kolibear]

To put this into some sort of perspective.

The group aircraft's engine holds 8 quarts of oil, thats 2 gallons. Last weekend the temperature was 2deg C. So imagine a domestic bucket full of oil just above freezing point - I certainly wouldn't want to put my hand in it. It would be painfully cold and stiff like treacle.

The POH recommends keeping the revs below 1400 until the temperature reaches 40deg C, which is the maximum temperature recorded in the UK last summer.

So what we are asking the engine to do is to take a bucket of treacle from just above freezing to midsummer temperature - its not surprising that it can take 10 minutes.

But its definately worth taking the time to do it.

[MLS-12D]

To each his own, but I wouldn't start (let alone fly) an airplane in the winter without first pre-heating. In my view, this is advisable whenever the temperature is below freezing, and an absolute requirement whenever the temperature is minus 7 C. Pre-flight idling is insufficient, and may itself damage the engine.

See further:

(1) AvWeb (http://www.avweb.com/news/maint/182846-1.html);

(2) F.E. Potts' advice (http://www.fepco.com/BF.chapter12.html) (note this comment: "Mike Busch, the Cessna Pilots Association's engine specialist, claims that one cold start at the lower temperature extremes can cause as much wear as 500 hours of normal cruise operation. This takes into consideration the metal-to-metal contact between the piston and cylinder walls caused by the uneven expansion of the aluminum pistons and steel cylinders as the engine goes rapidly from very cold to very hot");

(3) Peter Tanis' SAE paper (http://www.tanair.com/article6.html).

On the other hand, see also this contrary view (http://www.aviation-consumer.com/newspics/pdfs/31-3-Oversold.pdf).

[I have control]

Well I just read through all those 40-odd posts and was wondering when someone would recommend a pre-heater - MLS-12D just beat me to it! Tanis is the way to go for sure, heats the entire engine. You can even get a system to switch it on by cellphone, so you don't even need to stop by the hangar to turn it on a few hours beforehand.

[Chuck Ellsworth]

I know its not all that relevant on this thread...but for what it is worth here is what we do with the PBY.

Each engine oil tank holds 55 imperial gallons of oil. 100 weight in winter and 120 weight in summer. ( That is 990 pounds total for the oil. )

We cannot use more than high idle RPM until oil temp shows 40 degrees C.

We must pre heat if the ambient temperature is plus 2 degrees C or lower.

Note:

There is an oil thremostat that ensures no oil will be taken from the oil tank until the temp of the engine oil reaches the proper temp....otherwise it would take forever to heat all the oil.

Chuck

[six-sixty]

I fly a Yak-52 and echo everything already said about the M14-P, but once when sitting in the AC on a very cold day waiting for the temps to come up, I had the owner of my maintenance org and supplier of the plane in the back and he suggested pulling the prop back. His words went along the lines of it would make the engine work harder and warm up quicker.

Has anyone come across this technique before, either for radials or other types? Though the actual RPM is going to be low the engine will be under a relatively increased load before it's warmed up. I must admit I don't do this, preferring to do it the hard way - waiting!

[Dale Harris]

660, I would have thought increasing the load on the cold engine would simply result in increasing the wear on the engine. After all, increasing the rpm really just increases the load on the engine too. Kind of defeats the purpose, doesn't it?

[Circuit Basher]

IO540 - sorry it's taken a week to post, but you were right!! From an email sent to club members last Weds:
Sorry folks but I have today grounded the aircraft following an afternoon at Perth trying to produce a fix for a problem xxx encountered yesterday. The oil temperature guage has ceased to function and there is no way of monitoring engine temp. I have managed to source one which we can borrow until ours is fixed - the new one is yes you have guessed a Fuji part and as readily available as rocking horse jobbies. It is a borden tube type so they apparently are repairable and recalibrated- more on this as it unfolds.

So I was blaming the ambient temperature, when it appears that all the time, there was a gauge problem!!

Moral of The Story: Never Assume, CHECK!! :D

Thanks, guys!!