mooniac15u Posted November 21, 2018 Report Posted November 21, 2018 11 hours ago, Marauder said: I was wondering about that correlation. I think adding a desiccator to the system would pull the moisture out. The question comes down to Larry’s findings that at a 25% humidity level, no corrosion would occur. I also wonder if the humidity remains constant throughout the engine area. I think that is why Mike B speaks about really insulating the entire engine and prop. Any cold areas would be a magnet for condensation. Sent from my iPhone using Tapatalk Pro Those are really good questions. Water is an important factor but so is the oxygen in the air. In lab we would remove moisture and oxygen from reaction vessels by replacing it with dry nitrogen. I don't know how practical that would be for an engine and what it would look like when you tried to start it with nitrogen in the cylinders. 1 Quote
jetdriven Posted November 21, 2018 Report Posted November 21, 2018 On 11/11/2018 at 4:22 PM, larryb said: I leave mine on year-round, with one additional detail. A thermostat set at 90 degrees. I figure 90 is not too hot to deteriorate anything long-term. I know it's a lot hotter during flight, but not 24/7. The main detail is that warm air holds more water in suspension than cool air. So, for a given quantity of water in the engine, a warmer engine will have a lower RH. I did some experiments with a humidity meter and found significant reduction in RH keeping the engine at 90. Larry It’s not really RH that corrodes engines. Total water per cubic meter is what does. More water.. more corrosion. Warmer air holds more water so it’s more corrosion espcoecially if the air gets near the dew point. Hwiever, no corrosion happens below 32f. Let it sit cold. Preheat. 3 Quote
carusoam Posted November 21, 2018 Report Posted November 21, 2018 1) presence of oxygen is required for oxidation/rust... 2) presence of moisture is the catalyst for the oxidation/rust... 3) temperature effects the rate of oxidation/rust... 4) Lab data rules! control moisture or oxygen controls oxidation/rust... Losing control of RH in a lab turned metal surfaces rusty over a weekend...set point 50%, actual 90%... instead of delivering dry desiccated air, a dry nitrogen blanket would work... build a tent around the cowling and exhaust.... 5) Thoughts and ideas make great sense... facts and experience are better... 6) cold temps make available moisture really low... 7) heating an engine with captured moisture could really go wrong... 8) I don’t think I would want to be the guy to go first... who would pickle an engine if heating works? 9) many people in NJ leave their planes in a hangar without heat or pickling... What is the chance that good ideas that make sense go wrong? The only way to know would be put your rh meter inside the engine, then monitor the data... Otherwise, there are too many variables, to know that you are doing the same thing as the other guy with the meter... PP thoughts only, not a mechanic... Best regards, -a- Quote
aviatoreb Posted November 21, 2018 Report Posted November 21, 2018 (edited) 5 hours ago, jetdriven said: It’s not really RH that corrodes engines. Total water per cubic meter is what does. More water.. more corrosion. Warmer air holds more water so it’s more corrosion espcoecially if the air gets near the dew point. Hwiever, no corrosion happens below 32f. Let it sit cold. Preheat. Throwing my hat into the ring: The last thing you said is the first time anything related to the following was said - chemical reactions are faster as temperature rises. So that would be an argument against continuous heating. I realize that you were describing a reduction in corrosion by water in an environment of only frozen water which must also be a faster. That said - I do pre-heat continuously in the winter. With a full wrap (Bruces) cowl-blanket-cover . It is very toasty and dry inside the cowl. I have measured relative humidity in the cowl during the winter sometime in the past with a borrowed lab grad humidity sensor, which I found to be something very low - much lower than the already low ambient environment, but I forget the numbers... One thing I notice is that when I land there are dabbles of water on the dipstick for reasons we already know but after a day of continuous preheating that dip still is dry as a stone - other than oil of course. I crack the dip stick open to allow a path for air to pass through the crank case and I am presuming that air is continuously passing through the crank case as convective air current rises through the system as heat rises thus sucking in cold air from below. Edited November 21, 2018 by aviatoreb Quote
mooniac15u Posted November 21, 2018 Report Posted November 21, 2018 Liquid water and water vapor are in equilibrium, meaning that water is constantly condensing and evaporating. Above the dewpoint the rate of evaporation is higher and below the dewpoint the rate of condensation is higher. At the dewpoint the rates are equal. The dewpoint will be governed by the actual water content in the air. It is the temperature at which the existing water content is 100% RH. The RH dictates the balance of the equilibrium and therefore the amount of available liquid water. So, it is the predominant factor in determining how the water will impact corrosion rates. Of course water itself is not a good conductor so the presence of ions is relevant as well. Chloride ion seems to be the biggest contributor to corrosion. Quote
carusoam Posted November 21, 2018 Report Posted November 21, 2018 Who are you gonna believe... 1) Pro pilot with endless mechanical skills... 2) Chemical engineer, with moderate typing skills... 3) Math professor, with expertise in related rates... 4) Our chemist, who has supplied a few excellent chemistry answers in the past... 5) Mike Bush, an excellent aviation writer... It looks like everyone is somewhat in agreement with each other with a few caveats like making sure you follow all of the advice given by any one resource... Selectively choosing some advice, can leave you holding the bag... Missing a detail can be pretty important as well... Great input from some great MSers... Best regards, -a- 2 Quote
Marauder Posted November 21, 2018 Report Posted November 21, 2018 Who are you gonna believe... 1) Pro pilot with endless mechanical skills... 2) Chemical engineer, with moderate typing skills... 3) Math professor, with expertise in related rates... 4) Our chemist, who has supplied a few excellent chemistry answers in the past... 5) Mike Bush, an excellent aviation writer... It looks like everyone is somewhat in agreement with each other with a few caveats like making sure you follow all of the advice given by any one resource... Selectively choosing some advice, can leave you holding the bag... Missing a detail can be pretty important as well... Great input from some great MSers... Best regards, -a- Hence my request for evidence in controlled studies... Toss in variables like “evolving” metallurgy, engine usage, maintenance (how frequently the oil is changed), temperatures & humidity of the environment, etc., I don’t think there is a straightforward recommendation. Sent from my iPad using Tapatalk Pro Quote
aviatoreb Posted November 21, 2018 Report Posted November 21, 2018 3 hours ago, Marauder said: Hence my request for evidence in controlled studies... Toss in variables like “evolving” metallurgy, engine usage, maintenance (how frequently the oil is changed), temperatures & humidity of the environment, etc., I don’t think there is a straightforward recommendation. Sent from my iPad using Tapatalk Pro Note - I came to my current practice years ago by thinking about the mechanism at play as I already described. It is gratifying to hear of the many people with other backgrounds who have similar practice each with their own arguments as to why.... But anyway, I am convinced enough for my own sake that this is what I do with my own airplane (hence my own checkbook). But I very much doubt there will ever be a study sufficiently robust to decide this issue once and for all since the issue is simply not that important. GA airplanes are not that numerous to justify a would be multi-million dollar study across many engines tested in the various environments with various treatments, over a long time, in a controlled manner. This is not going to happen. Sure I bet there are related scientific studies - eg slabs of metal in short studies in treated environments, but then we keyboard warriors will debate how close to realistic such a study is. Until then - my airplane is in the hangar, wrapped in my Bruce's, and plugged in. For the next 4 or 5 months - in between flying. 2 Quote
mooneyflyer Posted November 21, 2018 Report Posted November 21, 2018 Mike Busch says: There has been considerable controversy about whether or not it's a good idea to leave an electric preheating system plugged in continuously when the airplane isn't flying. Both TCM and Shell have published warnings against leaving engine-mounted electric preheaters on for more than 24 hours prior to flight. However, these cautions are really applicable primarily to single-point heaters such as oil pan heaters. The concern of TCM and Shell is that heating the oil pan will cause moisture to evaporate from the oil sump and then condense on cool engine components such as the camshaft, crankshaft or cylinder walls, resulting in accelerated corrosion of those parts. However, if the entire engine is heated uniformly by means of a multipoint heating system, or because the engine and propeller are covered with insulated engine and prop covers, such condensation is very unlikely to occur. In fact, using an insulated cover and a multipoint preheating system that is plugged in continuously is one of the most effective methods of eliminating internal engine corrosion, particularly if the aircraft is kept in an unheated hangar rather than outdoors. If the entire engine is maintained above the dewpoint, condensation simply cannot occur. 1 Quote
INA201 Posted November 22, 2018 Report Posted November 22, 2018 https://www.aopa.org/news-and-media/all-news/2014/march/10/aircraft-maintenance-proper-engine-preheating Quote
warren.huisman Posted December 2, 2018 Report Posted December 2, 2018 (edited) I went out to the hangar today and what I found made me wonder if the question is not to leave the heat on all the time or not but other circumstances that we may or may not have control over. Last week and this weekend has been cold and wet. Rain, snow, rain,..... Today, it started to warm up. When I opened the cabin door, it was very humid in the cabin. Moisture on the inside of the windows. Of course the cabin is "sealed" up with the door closed so what moisture that was in there was basically trapped. It is my habit, in the winter, to install the engine cover and propeller cover just before I leave. The engine is usually still warm. This is potentially bad for the engine I think. The amount of moisture contained in the warm air is probably "trapped" under the thermal blanket and therefore will simply condense. What are your guys thoughts on this? I think I will leave the thermal blanket off now until I start the pre-heat so the engine can acclimate to the environment. I may even leave the window open in the cabin to get some ventilation. Thoughts? Edited December 2, 2018 by warren.huisman Quote
amillet Posted December 2, 2018 Report Posted December 2, 2018 I put this on the cabin floor in the winter. I leave the door cracked open enough for the cord https://www.amazon.com/GoldenRod-inch-Dehumidifier-5D-24-Dehumidifiers/dp/B005FRG03O Quote
aviatoreb Posted December 2, 2018 Report Posted December 2, 2018 3 hours ago, warren.huisman said: I went out to the hangar today and what I found made me wonder if the question is not to leave the heat on all the time or not but other circumstances that we may or may not have control over. Last week and this weekend has been cold and wet. Rain, snow, rain,..... Today, it started to warm up. When I opened the cabin door, it was very humid in the cabin. Moisture on the inside of the windows. Of course the cabin is "sealed" up with the door closed so what moisture that was in there was basically trapped. It is my habit, in the winter, to install the engine cover and propeller cover just before I leave. The engine is usually still warm. This is potentially bad for the engine I think. The amount of moisture contained in the warm air is probably "trapped" under the thermal blanket and therefore will simply condense. What are your guys thoughts on this? I think I will leave the thermal blanket off now until I start the pre-heat so the engine can acclimate to the environment. I may even leave the window open in the cabin to get some ventilation. Thoughts? My thought is the the heat cannot be trapped under the blanket as long as it is warmer under the blanket than outside in the rest of the hangar. Because heat rises, even if slowly through a blanket. So that rising air must be sucking air from below. The heater then is working like a slow engine moving air. Quote
warren.huisman Posted December 3, 2018 Report Posted December 3, 2018 6 hours ago, amillet said: I put this on the cabin floor in the winter. I leave the door cracked open enough for the cord https://www.amazon.com/GoldenRod-inch-Dehumidifier-5D-24-Dehumidifiers/dp/B005FRG03O Is this really a dehumidifier of simply a heater? Looks interesting. Quote
amillet Posted December 3, 2018 Report Posted December 3, 2018 Just a heater but seems to work well to circulate air Quote
DualRatedFlyer Posted December 3, 2018 Report Posted December 3, 2018 10 hours ago, amillet said: Just a heater but seems to work well to circulate air I have a home built engine heater which is just a little space heater with a dryer vent that I plug into the cowl flaps to heat the engine. I usually activate it wirelessly from home to preheat the engine, then when I get to the hanger I pull the dryer vent out of the cowl flaps and put it in the window to warm up the cabin. Does this thing put out enough heat to knock the chill out of the cabin? Would be nice to activate it wirelessly as well and get a thorough preheat of the cabin. Interested in hearing your experience/feedback. Quote
carusoam Posted December 3, 2018 Report Posted December 3, 2018 A small heater circulating air around inside the cabin can work really well... something with tip-over and temperature protection.... No need to keep heating cold outside air to put that into the airplane... that would be Dad’s idea of heating the great outdoors... PP thoughts only... Best regards, -a- Quote
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