Engine preheat
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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!
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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.
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.
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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!
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!
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Personally I just test the igniters, press the start button and watch the ITT.....
he, he, I like it.
Personally I just test the igniters, press the start button and watch the ITT......
he, he, I like it.
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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!
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.
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.
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One mans cold start is another's normal start so there is no one fix fits all
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?
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Fuji Abound said:
Fly-by-wife
Exactly - I am afraid our friend Mr Guppy has always had a rather umm, colourful imagination.
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? 
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!
Exactly - I am afraid our friend Mr Guppy has always had a rather umm, colourful imagination.
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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?
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.
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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!
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!
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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!
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.
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.
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.
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.
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.
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!
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.
Personally I just test the igniters, press the start button and watch the ITT......
Some turbine engines do have cold weather limitations, which must be observed. Turbines do make cold weather starts easier, but also present additional hazards.
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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. 
Last edited by Fuji Abound; 28th Dec 2010 at 20:36.
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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!
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 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
They could probably be dowsed in petrol without any problem.
They do still cause condensation in the top of the engine.
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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.
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.
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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!
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!
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I would be astounded if the manufacturer recommendation is based on anything other than metal to metal clearances
It must be possible but I wonder what that temperature (loss of piston clearance) would be.
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It must be possible but I wonder what that temperature (loss of piston clearance) would be.
