Engine preheat

[Pilot DAR]

Merry Christmas everyone!

A bit of thread drift, but I was asked...

My choice to not use multi grade oil in my aircraft, is based upon several bad experiences....

When I first bought my C 150, Phillips 20-50XC oil was easily available to me. I found sticking exhaust valves to be a problem (not that O-200's are not known for this anyway). As I worked at an aircraft engine shop at the time, engine teardwn and inspection were not a problem for me. I found that an unpeasant black glass like substance had formed all over the exahaust valve/stem/spring/rocker area. I cleaned it all out, and went again. Months later, same thing... I cleaned it out again.

This time, I switched to Aero Shell 15-50. No more black glass, or sticking valves. During this time, we had two big Continentals come in, both of which had experienced momentary prop runaways in cruise flight. This was accompanied by very low oil pressure indication, but reported normal temps, at cruise power. Both engines went through inspection with no defects found. Both owners changed to straight grade oil, and the problem was never reported again.

Then one day, I was orbiting a friend's place, so he could take pictures. I glanced at the oil pressure, to see with great alarm that it was near zero. Temp normal for a summer day. I pulled the power off, and landed on his runway. When I shut down, and checked the oil, it was the consistancy of a mineral solvent (we call it "Varsol" here). I was very surprised. I left the plane to cool for a few hours.

When I returned late in the afternoon, I checked the oil again, and all was "normal". I fired up for a tem minute flight home. Good oil pressure and temps. By the time I was arriving at home minutes later, the oil pressure was at zero again. After landing check, like Varsol again. The next day, I checked the oil, normal again, fired up, all normal, and flew up to my local airport to buy new oil. By the time I got there (less than ten minutes flight) zero oil pressure again, temps normal. That oil had less than 50 hours and a few months running on it, in an O-200, which does not work oil hard to begin with. Others I spoke with at the timep said they had heard of this too...

Since then, I have chosen straight grade 80 Aero Shell, and never had a problem. As I always preheat in cold weather, I never have a problem starting, and otherwise, with a winter kit when required, I have never had the slightest problem with oil.

I know that multi grades are popular, and to each their own, but I don't see myself using them again, inless the engine specifically requires them.

[S-Works]

I have used multigrade on 3 engines fir nealy 3000hrs combined without a problem.

[POBJOY]

15-50

Can not fault it as long as the motors in good order to start with.
Nothing wrong with the W80 or 100 but i think they favour warmer climes than the n europe average.

[Big Pistons Forever]

I think Pilot DAR is in the minority with his refusal to use Multigrade oil. Pretty much every commercial operator of piston aircraft I know uses either Red Ram (Philips) 20-50 or Shell semi-synthetic 15-50. Although the latter is more expensive so its use seems to restricted to turbocharged twins.

When I bought my little Grumman AA1B in the late fall 10 years ago the previous owner had used straight 80 oil. he had changed the oil 5 hrs prior to the sale so I flew the oil for another 20 hours. I then changed to 20-50. There was no question that on a typical Canadian West Coast winter day (ie +5 deg C) the engine was easier to crank and showed oil pressure as soon as it started as compared to a few second delay with the old straight oil. If there is any downside with Multi Grade oil I think it is on the hot side. Even though 20-50 is notionally a 100 weight oil on the hot side, engine do run seem to run cooler with staight 100. If the aircraft where based in a hot climate I would change to straight 100 during the summer, particularly for cooling challenged aircraft like the Grumman.

There is a aircraft mechanic at my home field who is widely considered to be an engine savant. He thinks there is no reason to preheat engines using Multigrade oil at temperatures at or above 0 deg C. After working on many hundreds of engines he has found no evidance that not preheating reduces engine life, a feeling that seems to mirror the experience of the UK piston aircraft fleet. Below 0 deg C however he thinks a whole engine heating system (not just the oil) should be used.

As an aside there does seem to be a fairly widespread problem with students and new pilots starting engines when it is cold. I think this is due to a reluctance to give the engine enough prime and is IMO a result of flying schools propagating the urban legands of aircraft which postulate that there is an exteme danger of having the aircraft burst into flame if one ml too much prime is used. At 5 deg C a C 172 needs 2.5 to 3 full shots of prime and at 0 deg 4 shots. An unsuccessfull start (ie the engine fires but then dies) will require more prime before cranking.

[IO540]

I use AeroShell 15W-50. It's expensive but trivial on the cost of flying - about £60 for the 50hr service.

I did a number of alternates with Exxon Elite and the oil analysis never showed any pattern, so I think the two are equivalent as far as straight wear is concerned. Now I just use Shell because it is a bit easier to get where I am.

The fuel injected engine starts immediately, every time, from any "cold" temperature. Hot starts are a different matter (as any FI owner knows) but with a powerful starter motor it is sorted anyway.

There is a separate issue here in the UK, caused by most school/club billing being WET and charged brakes-off to brakes-on. So renters do as much as they can before letting go of the brakes. They start the engine and do the engine tests as soon as they reach them on the checklist, while it is still cold (there is usually no properly working engine oil temperature gauge anyway) then they race like crazy to the runway... I see this all the time.

[SkyHawk-N]

I have a Tanis heater on my engine. A heating pad on the sump and heating probes on each cylinder. Plug it in and 30-60 minutes later the engine is pretty warm. Purchase and installation is cheap.

[bbrunton]

My preheat indicator is the engine dipstick.

If you pull out the dipstick and you can get a drop of oil to drip off of it, then the oil is will flow for start up. If the dipstick looks like a popcicle on a dipstick, and oil will not drip off, then you will need to preheat.

When you preheat in the usual fashion using external heaters, put them at the cowl flap area not in the intakes. Remember, heat rises. Block the air intakes so the heat will not escape and put a blanket over the cowl if you can.

Preheat usually takes a while.. Remember, if you reach in and the feel the engine, and it feels warm, that is not the crankshaft or the cam that you are feeling. It will take a few hours for the heat to reach them.

Electric heaters such as Tanus that are permenately installed are very good. Dip stick heaters tend to just heat the oil around the dipstick, and not the whole engine.

Turbo charged engines with their external plumbing to the turbo shaft bearings and the waste gate are another story. They should be preheated if the temperature is near or below freezing to prevent congealed oil in the external lines. Congealed oil in the right place in the waste gate line can mean you will be in for a big surprise on start up.

An airplane in a closed hangar can usually be much warmer than the outside overnight air temperature.


Bill

[CanAmdelta1]

Just a quick FYI on external heating and nose plugs.

I believe you will experience more efficient and quicker heat up if the external heat is placed towards the rear and low on one side of the engine (with the nose plug installed on that side) and the nose plug removed on the other side of the engine.

This causes a positive flow of hot air around the entire engine and allows it to exit on the unplugged side. This flow pretty much ensures even preheat.

Of course as mentioned in a previous post a insulated wrap is also used.

Cheers, very informative comments!

[SNS3Guppy]

Th crankcase and sump and made of aluminium, and I wonder if there is a product based on a heating element which could be attached to one of the (many) screws which are all over the place. Such a heater would be left permanently attached, and would be wired to a connector somewhere. A small device could easily dump 100-200 watts into the engine in this way.

Tanis Air Craft : Lycoming 6 cyl premium system: IO-540, TIO-540, LTIO-540 - $1,080.00

Oil Sump Elements : Tanis Air Craft

Cylinder Elements : Tanis Air Craft

Battery Heaters : Tanis Air Craft

Covers - Single : Tanis Air Craft

Various other systems are in common use, including systems that ring each cylinder to heat the engine prior to start. Used with a blanket or cover, these are effective means of heating the engine. Some use a portable generator, some use a propane or other fuel fired heater to inject hot air into the cowl.

Lycoming SI 1505 addresses preheat on Lycoming engines. While I realize that waves, carburetor heat, atmospherics, mixture settings, and of course preheat requirements are different within the geopolitical borders of the UK than the rest of the world, as told to us by genuine UK private pilots, what would happen if we looked to Lycoming for answers regarding Lycoming engines? Is it possible that Lycoming might have some input on the matter, even if it's within the borders of the UK (where physics and of course manufacturer input are artificially suspended)? Let's look:

http://www.tanisaircraft.com/UserFil...20Wx%20Ops.pdf

The use of pre-heat will facilitate starting during cold weather, and is required when the engine has been allowed to drop to temperatures below +10°F/-12°C (+20°F/-6°C for –76 series engine models).

Interesting, that word, "required." If someone has a dictionary, look it up. See if it still means what it used to mean, will you?

I recall mentioning that a heated dipstick can damage the oil, but let's see what Lycoming has to say:

The use of a heated dipstick is not approved because heat is not distributed throughout the engine, and concentrated heat may damage non-metal engine parts. Proper pre-heat requires a thorough decongealing of all oil.

Interesting. Imagine that. What does Continental have to say on the matter? SIL 03-1 addresses the subject:

http://www.tanisaircraft.com/UserFil...20Wx%20Ops.pdf

Preheating is required whenever the engine has been exposed to temperatures at or below 20° Fahrenheit / -7 degrees Centigrade (wind chill factor) for a period of two hours or more.

There's that word, "required," again. As we already looked it up, we needn't review it once more.

Continental is a little more direct and forceful with their comments regarding preheating, particularly with their opening warning (bearing in mind, of course, that aircraft registered in the UK, and the pilots operating them, are exempt from these conditions, and the laws and principles of engine operation, metallurgy, and physics from which these warnings are derived):

Failure to properly preheat a cold-soaked engine may result in oil congealing within the engine, oil hoses, and oil cooler with subsequent loss of oil flow, possible internal damage to the engine, and subsequent engine failure.

Superficial application of preheat to a cold soaked engine can cause damage to the engine. An inadequate application of preheat may warm the engine enough to permit starting but will not de-congeal oil in the sump, lines, cooler, filter, etc. Congealed oil in these areas will require considerable preheat. The engine may start and appear to run satisfactorily, but can be damaged from lack of lubrication due to the congealed oil blocking proper oil flow through the engine. The amount of damage will vary and may not become evident for many hours. However, the engine may be severely damaged and may fail shortly following application of high power. Proper procedures require thorough application of preheat to all parts of the engine. Hot air must be applied directly to the oil sump and external oil lines as well as the cylinders, air intake and oil cooler. Because excessively hot air can damage non-metallic components such as seals, hoses, and drives belts, do not attempt to hasten the preheat process.

Scary stuff, but fortunately, UK residents are exempt, right? These things don't happen in the UK, right?

Standby for more scary stuff (disregard if you're beyond the principles of mechanical motion, because this may not apply to you):

Attempting to start your engine with a partially discharged aircraft battery may result in damage to the starter relay, possible engine kick-back resulting in a broken starter adapter clutch spring.

Engine starting during extreme cold weather is generally more difficult. Cold soaking causes the oil to become thicker (more viscous), making it difficult for the starter to crank the engine. This results in slow
cranking speeds and an abnormal drain on the battery capacity. At low temperatures, aviation gasoline does not vaporize readily, further complicating the starting procedure. Always use an external power source when attempting to start your aircraft engine in cold weather.

"Always" sounds a lot like that "required" we read about a couple of times, earlier. Dictionary still available?

More warnings. Be forewarned that the second one is really, really scary. Harry Potter scary. Death, injury, all that. (Don't look those up. You don't want to know).

Do not operate the engine at speeds above 1700 RPM unless oil temperature is 75° Fahrenheit or higher and oil pressure is within specified limits of 30-60 PSI.

Operation of the engine above 1700 RPM before reaching minimum oil temperature may result in engine malfunction, engine failure, injury or death.

I added the last quote there, because I've read posters here telling us before that the engine will never reach operating temperature, and doesn't need to be, before takeoff. If we wait for the temperatures to get up there, we're sometimes told, we'll wait all day, and we can't do that when we're renting. it's too expensive. (Far more expensive than being fit for a casket, for example). Disregard if this doesn't apply to you.

Now, if you're using a combustion heater, Continental will (and does) tell you:

Proper procedures require thorough application of preheat to all parts of the engine. Apply preheated air directly to the oil sump, oil filter, external oil lines, oil cooler, coolant radiator and cylinder assemblies. Continue to apply heat for a minimum of 30 minutes.

If you're using an engine-mounted heater, Continental will (and does) tell you:

Engine mounted preheating systems should include individual cylinder head heater thermocouples, oil sump heater pad and crankcase heater pad. The use of a nacelle blanket will increase the effectiveness of engine preheating.

In other words, heat the whole engine. Go figure. Not just the oil, but the whole engine. If you own a Volkswagen vehicle, you're exempt, because you know better than Continental, and of course if you live in the UK, none of this applies to you, anyway.

Begin preheating of the engine at least 5 hours prior to expected departure. However, do not leave the engine preheating system in operation for more than 24 hours.

Five hours? What? You can't simply show up, jump in, and go? It requires some preparation? Some forethought? Not if you live in the UK, of course, but everywhere else, one may actually have to start preparing for this operation a little early.

Now...there's always the redneck engine heater, using the mechanic's trouble light with the lightbulb, sitting on top of the cylinders around the clock...doesn't actually warm the engine through, but it's cheap, in common use, and in many cases gets left on all the time. Setting aside the fire hazard issue, Continental does have something to say about leaving heaters on all the time. The redneck lightbulb method qualifies as "engine mounted" as it's sitting in the nacelle all the time while in use:

Do not leave an engine-mounted pre-heater system on for more than twenty- four hours prior to flight. Continuous operation of engine-mounted preheater systems may result in aggressive corrosive attack internal to the engine.

The rationale behind this may not seem intuitive to some. Corrosion in oil is largely promulgated by the washing of acids of crankcase walls, chiefly from condensation. Acids settle in the oil and attack bearing surfaces and other areas in the engine, leading to pitting and other corrosion. Additionally, the circulation of the oil around the engine circulates the acidified oil to all parts of the engine, where it can go to work on the components of the engine and propeller when the engine is at rest. Each time condensation forms, the water washes more acid into the oil, and the water itself suborns corrosion as well.

Depending on the nature of the heater in use, heating part of the engine can result in a continual supply of condensation to various parts of the engine. Additionally, continual heating in one part of the engine using electronic means can overheat oil locally, causing chemical changes in the oil in the same way that dipstick heaters tend to do. Another, obvious problem with leaving the heating system in use all the time is the fire hazard.

Regardless of the method of preheating, save for those in the UK who are exempt, we can see that both Lycoming and Continental strongly recommend and even require it: it is not a "fossil recommendation."

[Pilot DAR]

SNS and I agree. He has found the text to confirm what I have done for 25 years. Basic physics and operational requirements or given conditions, don't really change to suit the operator's convenience. You just gotta do it right!

I need add very little to SNS through disseratation. I have used the "100W Mechanic's light" with success under the limited conditions of: a; no alternative, and b; right after shut down to keep the engine warm (not get it warm), and c; with a fitted insulated engine blanket. This means is still quite risky from a fire prespective though, and a last resort.

It is known to carry a small generator in the plane for overnight trips, so it can be run to energize heaters hours preflight.

For all the other care we take, let's get this right too!

[Zulu Alpha]

I seem to remember that there was a problem with some of the multigrade/synthetic oils if you changed to them after running the engine on non multigrade for some time. IIRC it was caused by lead build up with the std oil. The lead was then removed by the multigrade which gave problems with oilways blocking as so much of it was dumped into the oil.

If you ran the engine on multigrade from day one, then the lead didn't build up and there wasn't a problem.

[IO540]

Another long pompous dissertation from James Bond who flies solid IFR while under small arms fire... he should set up his own pilot forum, where only holders of eight gold stripes can join up.

Pprune is mostly a UK/European forum. The UK is rarely -6C or -12C.

If it is, which is extremely rare, prob99 you cannot get to the airport.

The lowest temp I have ever seen since coming here in 1969 was -8C, and indeed EGKK is -8C right now

EGKK 260520Z 00000KT 7000 NSC M08/M09 Q1029 582900//

Somebody I know up north is apparently seeing -19C but there is no chance of anybody driving around up there anyway. The car door doesn't even open, I hear.

If I tried to open the door on the plane in these temps, there is a good chance the door seal will be stuck to the other half and will rip off.

If one was parking outdoors and had an engine heater out there, unattended, the engine heater would get stolen pretty quick (at all but the H24-secure airports, and most of the latter do not allow GA parking anyway).

Elsewhere in N Europe, things get colder and -20C is common, but they tend to have equipment to deal with it..... like hangars

I seem to remember that there was a problem with some of the multigrade/synthetic oils if you changed to them after running the engine on non multigrade for some time. IIRC it was caused by lead build up with the std oil. The lead was then removed by the multigrade which gave problems with oilways blocking as so much of it was dumped into the oil.

I made that change twice (1x when new and 1x after the Lyco crank swap job) and never saw this.

No idea where this story originates but it could be with the pre-1960s crankshafts which had what I vaguely recall were calles slush tubes and those had a history of getting bunged up anyway; somebody tried to sell me one of those in 2005... But I never saw any big lead % in the oil analysis anyway.

[SNS3Guppy]

I seem to remember that there was a problem with some of the multigrade/synthetic oils if you changed to them after running the engine on non multigrade for some time. IIRC it was caused by lead build up with the std oil. The lead was then removed by the multigrade which gave problems with oilways blocking as so much of it was dumped into the oil.

If you ran the engine on multigrade from day one, then the lead didn't build up and there wasn't a problem.

Lots of misconceptions on oil. The subject is preheat, of course, but let's tackle oil.

The standard misconception is that mineral oil leaves varnish, which is then removed by the use of synthetic oil. The varnish theoretically ends up potentially plugging galleys, etc. There's no lead buildup.

Another popular misconception is that there's mineral oil, AD oil, and multiweight oil. They're all mineral oil, and they're all compatible. That is to say, straight weight oil is mineral oil, as is multi weight.

There's no issue with running alternating straight weight and multigrade oil. Traditionally, straight weight oil has been used for the break-in with a new cylinder, top overhaul, overhaul, or new engine, followed by the operator's choice of oil (often multigrade). I've worked for a number of operators who preferred straight weight in the summer, and multi-grade in the winter.

A brief period of time involving a series of lawsuits against Phillips for their XC-II oil caused some disharmony in the community and displeasure regarding multigrade oil. Current XC oil works for both break-in, and regular every day ongoing operation. Switching between this and straight weight won't cause contamination or varnish issues.

Another common misconception regarding oil is the change interval. Some feel it should be based on hours alone, but it should be by calendar interval as well as hours. An airplane which doesn't fly all year still needs regular oil changes. An airplane which flies regularly needs regular oil changes, too. It's a whichever-comes-first proposition.

Pprune is mostly a UK/European forum. The UK is rarely -6C or -12C.

If it is, which is extremely rare, prob99 you cannot get to the airport.

The lowest temp I have ever seen since coming here in 1969 was -8C, and indeed EGKK is -8C right now

The service instruction from both Lycoming and Continental states that preheating is required by minus seven to minus 12 degrees. It doesn't say it shouldn't be used at higher temperatures, or that it's not a good idea. Anytime the temperatures are freezing or lower, preheating is a very good idea.

However, as you noted temperatures presently are minus eight, then you're a degree colder than the required preheating temperature for Continental powerplants.

No idea where this story originates but it could be with the pre-1960s crankshafts which had what I vaguely recall were calles slush tubes and those had a history of getting bunged up anyway;

Actually, modern, current crankshafts applied to constant speed propellers use sludge tubes, and they do require cleaning at overhaul, as they do contain sludge. Hence, the name.

Somebody I know up north is apparently seeing -19C but there is no chance of anybody driving around up there anyway. The car door doesn't even open, I hear.

If I tried to open the door on the plane in these temps, there is a good chance the door seal will be stuck to the other half and will rip off.

This really makes you wonder how the rest of the world manages to get along in cold weather, doesn't it? Operations in much lower temperatures than that are common in some places...without ripping off door seals...and yes, preheating is standard fare. You might even be shocked to know that in many locales, preheating automobiles is common.

If one was parking outdoors and had an engine heater out there, unattended, the engine heater would get stolen pretty quick (at all but the H24-secure airports, and most of the latter do not allow GA parking anyway).

The intelligent person would put the preheater in their car, or leave a lockbox in the tie-down spot, like many owners do. Perhaps that's too much progressive thinking for the UK, though.

[A and C]

Oil & UK issues

As has been said above there is no problem with mixing Multi grade and other aviation piston engine oils, however I would not bother if the engine is more that 50% through it's life as the advantages of the Muilt-grade are unlikely to be of any benifit for the increased cost and the multi grades do have a habit of "cleaning" the engine so you have to inspect the filters more regularly over the first 100 hours or so when changing to multi grade.

The lead thing is a red herring. lead build up in the oil ways was as a result of using a pure synthetic oil in engines running leaded fuel, synthetic oils can't hold in suspension the lead that has blown by the piston rings and so the lead is centrifuged out of the oil in the rotating parts of the engine hence the lead build up in the sludge traps and eventualy the crankshaft oilways. The major oil company that was marketing FULLY synthetic oil should have known better!

Semi-synthetics are OK as the mineral part of the oil can hold the lead in suspension untill the oil change at 50 hours, I would not run a semi-synthetic oil past 50 hours as the ability of the mineral part of the oil to hold the lead in suspension is limited.

Mr Guppy seems to be unable to understand that the climate in the UK at the moment is unusual in and so it is highly understandable that we are about at prepaired for it at Hawaii would be for snow. the other thing that he forgets is that the VOLUME of the water content of the presipitation and could air is much higher than the "dry cold" of the mid continental USA and brings different problems.

We also have a bunch of reguators who are (in EASA) just pen pushers and so don't understand the first thing about aviation and so the cost of fitting a pre heat system to an aircraft is not viable for the few days when you might need it. That is always provided the runway has been cleared of snow!

We may have to review these things over the next few years in view of climate change, IO540 is on the south coast and had -8C last night I am only about 70NM inland from him (EGTB) and had -14C last night so I think things are changing.

[DERG]

Use A Preheater

Got the answer from my oracle person. You cannot start this engine unless you preheated. If ambient is below 6C DO NOT START the engine.
Reason:tolerances are too tight. Consequences: bore scratching.
Has FA to do with the oil apparently..all to do with this Lycoming Alu design.

[A and C]

DERG

I take it that 6C is a typo and you mean -6c.

[Malcom]

Mr Guppy is unbelievably ignorant of just how lucky he is in FAAland. If I want to fit a Tanis heater to my UK engine - totally independent of any aircraft systems - I have to submit a mod including the the full spec of the ins and outs of a ducks backside, a blank cheque and an open-ended completion date expectation to EASA for a total benefit of perhaps 14 days extra flying days per year, 13 of which I cant get to the airfield which wont be open anyway. We dont bother with winter prep like preheating or airfield clearing because its just not cost effective or worth the bother to anybody in the UK. Only just a couple of years ago the run-up to Xmas was T-shirt weather - what use a preheater then?

BTW, interesting reading - manufacturers recommendations & SBs etc suddenly becoming gospel when previous recitations on various subjects made us believe he knew far more than Messrs Lycoming & Continental.

Also BTW, my hovercraft has heated windows and a squiffy heater unit, so I'm fully prepared. The eels can stay outside.

[IO540]

If we had -8C for weeks every winter, UK GA would grind to a halt, because in most places hangarage is scarce (and costs say £500/month when you can get it) and one cannot usually park the car close enough to the plane to unload heavy equipment.

We would have to get seriously sorted, but most owners would still be grounded because they simply don't have a solution to pre-heating the whole plane.

The Americans have it easy. At most places, they can drive right up to their plane, unload stuff, etc. They have fantastic FBO facilities, with warm rooms, showers even, and even courtesy cars which are sometimes free.

[Saab Dastard]

This is another thread degenerating into sarcasm and personal animosity.

I don't particularly want to spend my holiday having to keep a lid on your puerile behaviour.

Any more (and you know who you are) and you will be banned from this thread and / or PF forum.

SD

[DERG]

A and C

Nope, plus 6 centigrade. As per the book.