A hairdryer poking into the engine cowling for half an hour works a treat for me (and I'm starting from -20C).

A quick google....

Here

4. COLD WEATHER STARTING. During extreme cold weather, it may be necessary to preheat the engine
and oil before starting. [no values given]

This famous Lyco flyer says (page 15 of the PDF)

For most Lycoming models, preheat should be applied anytime temperatures are at 10˚ F or lower. The exception to this rule is the 76 series models that include the O-320-H, and the O/LO-360-E. These engines should be preheated when temperatures are below 20˚ F.

and uses the word "guideline". 10F is -12C and 20F is -6C.

Then you have piles of "urban knowledge" e.g.

here

Never attempt a start below freezing without pre-heating

Assuming they mean freezing point of water, that is 0C.

If somebody finds a current Lyco document speaking of mandatory preheating below +6C I will eat my EDM700 :)

This is an interesting product.

Ignorant? I spend plenty of time in EASA-land, as well as numerous other jurisdictions, too. You're correct: my maintenance qualifications are FAA certification, and I'm quite content to operate within those bounds.

You do not require a field approval, however, to operate a combustion heater, which will easily fit in the trunk (or "boot") of your car.

There's more than one way to skin a cat, more than one way to wet a duck (and it's backside), and more than one way to preheat an engine. The manufacturer recommended method involves a heated hangar. In lieu thereof, other methods are available.
Reiff makes an excellent product.

This may not be directly applicable to most engines people are flying these days, but as a matter of academic interest, let's not forget two more techniques fairly popular in the past:
- If the engine has an easily accessible drain cock, drain the oil while it's still warm, come back next morning with a pail of preheated (+50...60C) oil.
- At the time of shutdown, dilute the oil with avgas. While you are starting the cold engine, this will reduce the oil viscosity; as the engine warms up, the fuel will evaporate and the oil will return to its normal viscosity. Radial engines are often equipped with an oil dilution valve directly in the fuel system. Many winters ago, when it suddenly got as cold as -30C, I used this technique on my UAZ. With undiluted oil, the starter would barely crank the engine even with a warm battery, so it had to be towed for a few minutes to get started. A cupful of petrol into the oil in the evening would allow me to start in the morning without any problems. (Once again, this should not be construed as an endorsement of this method unless allowed by the manufacturer; Lycoming explicitly discourages it).

Draining the oil overnight, and oil dilution have already been addressed. Draining oil is a start and addresses the oil, but doesn't address the need for preheat, with or without having prepared the oil.

Oil dilution is a function of mixing a lubricant and a solvent and does result in chemical changes to the oil, as previously discussed.

Radials have used oil dilution in some cases, but so have horizontally opposed recip engines. With good reason, this option is no longer offered in airplanes such as the Cessna 206 (where it was once a common option), and oil dilution has been removed or deactivated in nearly all light airplanes.

Well, it will obviosly vary from engine to engine, but a bucketful of hot oil + some careful cranking may be enough to bring the engine to its starting temperature if it isn't very cold outside.

BTW, speaking of external combustion heaters... Just a couple of weeks ago, a Mi-8 helicopter in Russia was destroyed by fire after an explosion of the ground-based heater. If you use one, always have a fire extinguisher within easy reach.

IO540

Something we find useful in the North country, especially for automobile doors, is WD 40 spray. We open the doors and spray it on the latch and inside door jam. This prevents doors from sticking/freezing.

hope this helps

Always have a fire extinguisher handy during any engine start.

Dry lube silicon spray does the same thing. It doesn't attract dust or leave residue that can attractdust or dirt.

Took me five attempts at getting logged on this site..think I am unwelcome.

Why not just stick to the Lycoming handbook. If you have to preheat take the machine where you can use a popane fired 230/110V space heater on the front end and do it that way.

Of course I realise a lot of people who own these machines are not artisans. It is going to cost you money what ever you do.

Preheaters which involve a lot of hot air work well, as long as they are properly used. If the hot air involves actual fire, it is obviously very undesireable in the engine compartment. I have ferried for repairs two aircraft which had wiring fires in the engine compartment, bacause of the over zealous use of "propane" heaters.

Unfortunately, one of the three areas of the engine, the crankshaft area, is also the deepest in the engine. Cylinders and oil sumps are relatively easy to preheat by various means, but it takes a long time for heat to warm the crankshaft.

I use the proper electric oil sump heater, and switch in on for at least three hours before I fly. The heat rises well from the oil sump up, and throughout the cowl, and warms the whole engine. Those who blast in a whole bunch of hot air (least effectively into the upper cylinder area) for a "short" duration (less than 30 minutes) are probably fooling themselves. That heat has had little effect on the crankshaft, which is the most expensive part of the engine to be turning over with ineffective lubrication.

Slow and easy does it best.... like so many things in aviation....

A blanket around the cowl, with the heat inserted under the engine using scat hoses, over the course of several hours, works well. I've seen people burn the paint off cowling on light airplanes by attempting to put too much heat in too fast, especially through the inlets at the top of the cylinders (where it doesn't do much good.

Heat rises, of course, and allowing the engine to warm from the bottom, up, means that the entire engine eventually gets warmed. Manufacturer recommendation is to allow at least 5 hours for proper preheat, when using forced air.

I have also seen pilots cause leaks or damage seals by starting in cold weather and cycling a propeller full of cold, congealed oil.

Pre-oilers are good investments for those operating in cold weather, but rearlly are a wise investment for those operating in any kind of weather. Interestingly, they're not seen very often, any more. A preoiler circulates oil before the engine start, throughout the engine, to prelubricate (and warm) the engine. They're also useful for post flight shutdown lubrication and cooling.

Hot air rises, and there is usually plenty of it on this forum. Heat radiates conductively via the path of least resistance.

Actually, heat transfer by conduction, convection, and radiation are entirely different processes.

In the case of preheating an engine by forced air (external combustion heater), one is initially using the convection process for heat transfer, then relying upon the conductive properties of the metal.

In a given medium, heat conductivity relates to the thermal resistance of the material. The second law of thermodynamics provides that heat transfer is from the point of highest temperature to the lowest. One will heat the engine the most thoroughly and the fastest by heating from beneath, rather than above the cylinders, and allowing convection and conduction to transfer the heat upward, rather than down.

Heat in oil rises, heated air rises, heat in the engine rises, and yes, when conducting heat through the engine, including the application of heat at the sump, heat rises. The lower portions of the engine will be the first to cool, and should be heated first. After shutdown, the lower portions of the engine cool first, or fastest. Even in operation, the upper portion of the cylinder and upper spark plug tend to receive the greater heat, which is part of the reason that airflow through the cowling is directed at the upper half of each cylinder in a horizontally opposed installation, with airflow generally being aft and downward from there, in a pressure cowl installation.

SNS

Yes. Basic physics education for blue collar kids was lost in the UK around 1968. We now have a whole generation of people who had the money but not the understanding. They did the couse but knew SFA once they had passed the exam. This is part of the issue with the UK. They make up their own rules then invent the reality to match. You are not alone.

DAR

Tell em as it IS! They need a heater. Happy Holidays!

Not unless you are melting it, it doesn't!

Complete tosh. The molecules of metal in the engine are not free to move about like air or water (or other fluids, e.g. molten metal) and change density.

Therefore there is no lowering of density, and no heat rising in the metal of the engine.

If you are able to show me bubbles of pistons rising through denser, cooler cylinder heads then I will believe that metals can heat via convection!

FBW

To be fair, by heating the bottom of the engine, the outside air around it will presumably receive some heat too and then rise, transferring some heat to the top of the engine by convection.

Whether the amount of heat transferred this way is significant, compared to the amount of heat transferred internally by conduction, is debatable, but could be enough to make bottom-up heating preferable to top-down.

If we're getting all scientific about this, does anyone know the heat capacity of engine oil. We always put a 1kW fan heater inside the cowling and under our 0-200 for 30 minutes before a very cold start but I would be surprised if it had much effect on oil temperature.

We use it to warm the carburettor and induction system so the petrol vapour stands some chance of getting up to the cylinders before condensing (no primer, just an accelerator pump). With sufficient sucking in it always starts immediately after being in an unheated hangar at about -5C. Sometimes it stops again just as the oil pressure is coming up and, although it restarts with a couple more primes, I've never understood why.

Don't know about yours but an IO540 is about 160kg total weight, excluding externally mounted accessories and the exhaust. Of this, the oil is only about 8kg.

The crankshaft is probably the heaviest single item, at about (I guess) 20kg. The rest is all the various bits; some are ally, some are brass, and probably most of the weight is steel.

Taking a very average specific heat capacity as 0.7 (kJ/kg/K) this means that 100W (actually transferred into the engine mass) would make its temperature rise by 3C per hour.

I hope I got that calculation right :) Obviously it ignores heat losses from the engine, which will start to occur as soon as its temperature rises above ambient.

That is quite slow, but it probably represents the top end of what can be achieved by poking a heated probe down the dipstick hole.

If the dipstick heaters damage the oil they must be of crap design. On my engine, with 9 qt of oil, the bottom 3"-4" of the dipstick is immersed. If the dipstick hole is in a large pool of oil, then convection will easily carry away 100W, with a temp rise of the order of 10C in the immediate vicinity of the heater. If the dipstick hole is tight around the dipstick then heat will be efficiently transferred into the crankcase by conduction through the layer of oil. The important thing would be for the heater to be temperature controlled (which I guess none of them are) and to heat only the fully immersed portion. The most worrying thing would be if the heater breaks off; the engine will then have to be dismantled to get the bits out :) :)

And 100W might be what actually ends up in the engine from a 1kW fan heater poked up the cowling.

So to do it effectively, from really low temps like -10C or colder, one needs a lot more than 100W.

Fly-by-wife

Exactly - I am afraid our friend Mr Guppy has always had a rather umm, colourful imagination.

Fly-by-Wife
 

"The molecules of metal in the engine are not free to move about like air or water"

As I said you can PAY for an education and still be ignorant. You are an arts graduate maybe? HS cert? GED maybe?

So tell me FBW what exactly DOES move inside the metal. You can use any model you want as an illustration. The one I use was draughted by Niels Bohr in 1911. It is graphic..it has a pic usually..so I guess you should be able to grasp the idea.:ugh:

I have a 60W greenhouse tubular heater resting inside the bottom cowling of my Moth (and switched on), which keeps my Gipsy engine warm enough to start no problem all Winter. Works for me!
WW

DERG I don't see a problem with Fly-by-Wife's statement. He is trying to explain why heat does not transfer by convection inside solid bodies and pretty much hit the nail on the head.

I have a MEng and a MSc, in case you wonder and never brag about it, unless somebody with that sort of condescending attitude of yours starts posting useless considerations about other people's education.

Wow, hot topic!

I did not realize how much I did not know about how heat gets from one place, to another. I have just done what works all these years!

Maybe one day, I'll prefect the understanding of physics, but for now, I'm happy to fly warm, well lubricated, and thermodynamically ignorant!

Personally I just test the igniters, press the start button and watch the ITT......
:):)

Personally I just test the igniters, press the start button and watch the ITT.....:D he, he, I like it.

There is a downside to this as it will heat the oil in the bottom of the engine. This will drive off any water or acid in the oil which will then condense on the top of the engine which is cold.

This then means that the top of the engine can corrode. Unfortunately this happens to be the camshaft on a Lycoming. Not sure on a Gypsy, but I think it might be the crankshaft.

Lycoming specifically advise against sump heaters being used continuously and only recommend using them just before starting.

I have heard about people who have sump heaters controlled from their mobile phones. This allows them to be switched on a few hrs before you get to the hangar. Does anyone know of any switches that can be controlled by mobile phone as this would allow a very simple remote controlled fan heater to be rigged up.

Cold Starts
 

One mans cold start is another's normal start so there is no one fix fits all.
As we are primarily thinking about our UK conditions (and whats more the average facilities) what is needed is a simple application that actually works.
On the basis that most UK airfields and clubs do not have facilities for preheat this leaves it to the owner to organise (what is possible) within the limitations of what the Airfield operator/Hangar owner will allow.
This will NOT include draining and refilling oil outside of a maintenance organisation or wandering around the Hangar/Parking lot with pails of warm oil.
This leaves it down to having the best oil available to cope with the conditions prevailing and if you can get some "safe" heat around the engine beforehand so much the better.
We are not talking about "heatsoaking" the block rather than taking the bite out of the "cold oil" and giving the induction system some help in starting the engine.
If this preparation can be done inside so much the better,if not you may have to make up some simple cowl cover that lets the available heat do some work before it escapes.
If an engine has not operated for some days then it will need more preparation than one flown daily.

Hmmm, I do not agree.... I think that in large measure here, the "men" involved is Mr. Lycoming, and/or Mr. Continental. Their requirements with respect to temperatures for starting have been clearly presented here, and are not in dispute.

As has also been said, conveinence, (or being on any particular island) does not absolve one of conforming as closely as possible to the manufacturer's recommended practices for preheating (or any other aspect of operation).

I agree that the UK does not have weather conditions which would ever make draining engine oil and taking it into your log cabin overnight necessary. but the temperature values below which effective preheat of the engine are required, are clear. It sounds like those do occur in the UK (I have certainly experienced them).

At a minimum, any owner can arrange for a plug in engine preheating system to be installed, buy a properly fitted engine blanket, and a 500W generator. Take the generator to the plane, fire it up, plug, in, come back a few hours later, and you'll be ready to go. I have done this many times, where electriciy was not available.

If this is too much trouble and expense, a much cheaper method is to preserve the engine properly, take the battery out, and fly it next spring. This is what I have done to my second aircraft, a Lycoming powered amphibian, which does not have cabin heat. It sits safely and attended to, but out of service for the season.

The manufacturers of aircraft expect you to take care of them with consideration to the recommended practices. If you choose otherwise, you are taking direct responsibility for the engine's condition in the long term.

If owners are going to develop their own practices with respect to care, operation and maintenance of aircraft, why do people like me go to all the effort to write flight manual supplements, and instructions for continued airworthiness for these aircraft?

Fuji Abound said:
There is oil in the sump, the bottom of the sump gets heated and this heats up the oil contained in it. The oil then helps to heat the rest of the engine using convection.....does it not? :confused:

I tend to agree but I think there are additional factors:

Lyco/Conti are under immense legal pressure to not change their operating recommendations, irrespective of how much "history" has passed by outside their dusted up windows. This is because many of their engines fail before TBO when they are put together right, and many more fail before TBO because they are not put together right. So they work hard to evade liabilities, and modifying their operating suggestions would be an admission they originally "got it wrong". Hence all the garbage they continue to write re LOP etc. This is probably why they say -12C (or whatever) without qualifying it according to oil type used, which makes the -12C (or whatever) an obvious farce if stated as a straight unconditional figure for a given engine type.

For each type of oil there will be a low temperature below which it doesn't flow well enough to get around a (particular design of) engine fast enough, before it gets a chance to warm up. This behaviour should have been studied (they have been making these things since the 1950s, essentially) and documented, but nothing has been done. It is possible there are owners out there who regularly start at low temps and regularly get trashed engines, but I have not heard of it. Maybe they all preheat, or maybe the problem is not as big as it appears, or is much more engine type specific.

The lowest I have started mine at was probably about -3C, and the oil pressure gauge was up in the green within a few seconds; same as it always is. I don't know (without looking in the engine MM) how far along the oil path that gauge comes off, but it is supposed to be right at the end, for obvious safety reasons. This kind of stuff should have been documented by now.

It is the arrogant unwillingness of the manufacturers to get stuck into some proper research and documentation (and I fully understand why they behave like this - the above legal reasons) which has given rise to countless theories on engine management. Deakin (etc) would have not had anything to say if Lyco/Conti did some proper bench research and were open about the results.

It is quite true that the Lycoming and Continental operating instructions are probably largely influenced bt liability, and who can blame them for that! Also true that there are many factors which affect the circumstances of a cold start. I am certainly guilty of cold starts for my O-200, and it went through it's last overhaul with no related damage at all.

That said, if owners who are only modestly informed of all of the factors, are thinking to repeatedly "do their own thing", which conflicts with the mfg's recommendations, simply for convenience sake, that's not something I would support. There are lots of "tricks" and half measures which will get a cold engine running, and I'm not relating them here. There's a proper way, and it's clear. If you can't do that, come as close as you can. If you regularly fly in conditions for which a preheat is obviously appropriate, arrangements should be made to provide the required heat. If it's an occasional, unexpected circumstance, then yes, the engine will probably tolerate it a few times.

I don't expect the engine manufactures to invest more effort to further clarify the information they have already presented, with respect to preheat. If they were to do all the research, and sell an STC for "this is how to really cold start your engine", would people pay for it, and happily return the manufacturer's investment in research?

I hold STC's for changed process only for aircraft, and people still try to do it for free!

What part of the convection process do you not comprehend, when putting two hot air scat hoses from a combustion heater in the bottom of the cowl, to warm the engine? That's convection.

Heating metal to metal is conduction, and one doesn't need "bubbles" to transfer heat by conduction.

When preheating via a sump heating pad, one invokes the principles of conduction, convection and also radiation.

In most circumstances in the real world, one method of heat transfer is not present without the other.

You'll find that during engine operation, the upper spark plug in the horizontally opposed recip engine tends to be the hotter plug, which is why the lower plugs tend to be more susceptible to fouling. You'll also find that most light airplane pressure cowl assemblies run cowl inlet air across the top of the cylinders first then exhuast it through the bottom of the cowl; hottest part on top, to lowest on the bottom. Conductive heating, convective cooling.

Shut down, and one doesn't vent the engine through the bottom. Fly your 206 to a desert location and expect to leave during the heat of the day, it's a good idea to vent that cowl. You won't find it in the aircraft handbook, but one can open the oil filler door and oil check door, to vent the cowl best, because heat rises, and the doors are on the side and top of the cowl; this helps vent heat, which makes the follow-on engine start a little easier on a hot day.

Probably? I'm always impressed by uneducated guesswork.

You have the manufacturer data before you. Elect to disregard it at your peril. What part of "required" escapes you? It it a difficult definition, or simply something not found in the UK lexicon?

[QUOTE]This kind of stuff should have been documented by now.[/QUOTE

It has been, ad nauseum. Hence manufacturer guidelines on operation.

On the contrary, it's your arrogant unwillingness to buy the company and change the procedures, as you seem to know so much better than the folks who designed, manufactured, and built the engines. With your expertise, you could easily replace the legal department, engineering department, and serve as customer service to tens of thousands of operators who hungrily await your counsel. That you've failed to do so can only be a testament to your arrogance, can it not?

No?

Interesting that it's a testament to the "arrogance" of the manufacturer, then.

More interesting is the fact that the manufacturer has the legal right and responsibility to make those guidelines, requirements, and recommendations whereas you...do not.
It works until a float sinks, the carb floods, and avgas drips on the light or fills the cowl with vapor. It works until the light finally blows, or a short occurs, or something else happens to cause a fire. It happens.

It has been done, actually, and is well known. Oil flow rates and viscosity is only a part of the picture, however. You'll note that the manufacturers (the ones who know less than you, remember) specify heating the entire engine. Not just the oil. It's an engine preheat. Not an oil preheat. Warming the oil is only part of the process, only one of the reasons for the preheat, as we've already discussed. Your disbelief lies in your ignorance of the matter, but doesn't change the fact.

Turbine cold weather starts: the biggest hazard with cold weather starts in a turbine is a low battery Two solutions are to use a battery heater, and to use external power for the start. Low battery causes hot starts, hung starts, and slow starts, all of which can cause burner can damage and other thermal injury. Even if they never show up as a high ITT. One can do severe damage to an engine and never have it exceed ITT start or takeoff limits, most commonly during a very slow start or a hung start. The high temperatures aren't reaching the ITT probes as the gasses aren't passing through the engine due to the low speed or stagnated airflow: the damage is done prior to the probes.

Some turbine engines do have cold weather limitations, which must be observed. Turbines do make cold weather starts easier, but also present additional hazards.

This thread reminds me of the Christmas present you really didnt want - how ever hard you try to give it away it just keeps on coming back. ;)

Maybe they don't have these in the US, but they are 60W electric oil filled and you can pick them up with your hand as the surface temp is way less than 100 degC.

They could probably be dowsed in petrol without any problem.

They do still cause condensation in the top of the engine.

Just looked at Mr Guppy's profile and the 4 threads he has started. In one of them he asks

Anybody at Kalitta or Atlas have a line on where one might pick up a copy of a book a pilot put together on the Classic 747, possibly referred to as the "blakely book?" I understand it has a blue cover...looking for someone who knows where one could be purchased. PM with details. Thanks.

A long time ago when I was doing my engineering degree, we were taught the basics of piston design with dissimilar metals. The clearances needed to be specified so that you didn't have blow-by at operating temperatures (and also not excessive gaps in the bearings) but this then resulted in small and potentially negative clearances at low temperatures. We had to specify a 'do not move below' temperature that ensured no combination of manufacturing tolerances would result in a nil or negative clearance. I don't recall ever having an issue specifying a suitable multiple-grade oil, but we always had issues with clearances at low temperaures.

I would be astounded if the manufacturer recommendation is based on anything other than metal to metal clearances (as they already specify oils for different temperatures and probably don't care if a cold soaked battery doesn't have the oomph to crank a cold piston engine to light). Grinding metal to metal that is impossible to lube due to no clearance will definitely be a problem they would reasonably be expected to tell customers to avoid!

Aaaarrrggghhh....

Can anyone from colder climates report on having found they could not move the prop by hand (at all) below a certain temperature?

It must be possible but I wonder what that temperature (loss of piston clearance) would be.

With the piston being aluminum and the more being steel would this not be an issue?

Is it Christmas or what - too much time on your hands?

Another thread gone west.

SD