582 winter operations

[109jb 181]

So I finally had a chance to fly again today and the OAT was about 25 deg F.

My radiator has cockpit controlled Venetian blind shutters on the back side to block airflow through the radiator in cold weather and these were closed but the gray head 582 still took quite a while to warm up to the 140 deg F minimum.  During takeoff, climb, and cruise the engine coolant temperature was OK and got to about 160 deg F with the cabin heat turned off. When the cabin heat was turned on the temp started dropping and I turned the cabin heaters off when it had dropped to 140. My airplane has 2 of the hot water heater cores with the large PC type fans plumbed as in the attached picture. Even with the heater fans turned off I couldn't keep the temperature up during reduced power descent. Part of the problem was that I had to reduce power enough to keep from exceeding the EGT limit due to the unloaded prop. I flew my descent and into the pattern without advancing the throttle to keep EGT in check and the coolant temp had dropped to about 120. It dropped even further after I made my final power reduction to land dropping to about 110 before I came to a stop on the runway. I felt it prudent to let it warm up again before I taxied in.

Based on the above I have to change something on the setup, or I have to learn the proper winter operation procedures for the 582.  So here is what I'm thinking and I would like to hear from more experienced 582 pilots to see if there is agreement or not about my plan.

1. I first will get richer main jets so that I can perform descents without having to pull the power off so far.

2. I plan to install a fan speed control on my heater fans to I can modulate them

3. I don't know if the engine has a thermostat installed at all. I have read that the gray heads didn't come with one standard. First I will make sure that a working standard Rotax thermostat is installed in the head.

4. I am also thinking that I will do what my father did on his UTV and install an inline thermostat with bypass at point A in the cooling system diagram. He did it for better heat in the cab, which is part of my reasoning, but also because I think it would help keep the heat in the engine in cold weather. The one he used and I would use also is this one http://coupersproducts.com/ice-crusher-maxstat-inline-coolant-bypass-thermostat-for-utv-heaters/  What it does is it has a second thermostat that when closed directs the coolant flow only through the heater cores. When the thermostat opens the coolant flows through both the radiator and the heater cores. My thinking is that this is perfect because it would eliminate the need for the radiator shutters because the second thermostat essentially provides the same function. I realize that a failure of the second thermostat could result in coolant not getting to the radiator, but it would still have coolant running through the heater cores and in the event of a failure, even in summer, I could turn on the heater fans to cool the engine at least some.

So, what do all you experienced 582 fliers think of the above and do you have any specific winter flying tips for me.

Thanks,

John Brannen

[1avidflyer 1983]

It is even more crucial to have a thermostat installed for cold/cooler weather as you are finding out.  If you for some reason had to go around, at the last minute, you could very well have a cold seizure because of rapid heating of the pistons, and not as fast expansion of the cylinders, and that's not a good thing.   May not even notice an issue till you pull back the power a bit, and then the friction of the expanded pistons against the to cool cylinders makes the engine stop.   Then you get to consider the so called impossible turn, or landing straight ahead.   Also, you have described why I'm more in favor of a muffler shroud for heat then using the hot coolant.  With the coolant, when you really want heat, there's less of it to spare.  Muffler can give you exhaust fumes perhaps, and that's not so good either, but if your system is good, it should be less of an issue.  Besides, on the Kitfox with the huge hole in the front of the cowl, there should be lots of air going through to get rid of any exhaust leaks.   On the raised IGTs,  I also always went with larger main jets and raised the jet needle in the winter when I was flying a two stroke.  I have pictures of my last muffler shroud somewhere on the site, and others do as well.  JImChuk

PS  did a search and found these pics of my muffler shroud heater.  

avidfoxflyers.com/index.php?/topic/4584-heater-thoughts/#comment-38386
 

[109jb 181]

Yep. I was thankful that I keep the airplane at my friends grass strip right now with very little traffic to worry about.  I made my approach knowing that if I had to add power I could risk a cold seize. fortunately I planned the approach well and never had to add power except to taxi in which I did after letting it warm up again.

I figured it was a stuck open thermostat. It never even occurred to me that the engine might not have a thermostat installed and I only found out this evening that they shipped without them. I didn't have a drain bucket to drain the coolant or I would have checked it. 

As for the cabin heat, I think the secondary thermostat will solve the problem of keeping enough heat in the engine. I went ahead and ordered one, and I ordered a new thermostat for the cylinder head. Once installed, if the secondary thermostat is closed and the engine is still cooling off with the heater fans running I may have to shut the cabin heat off for a descent or something but I don't mind turning off heat for short periods anyway. I take the approach that when I fly I dress for the outside conditions just in case I wind up in those outside conditions.  I don't think that will be the case though. Time will tell. 

If the above doesn't work then I will consider a heat muff approach, but I'm not real fond of them from almost being killed by one in a 1969 VW Beetle when I was a kid. Over the years I've also worked several accidents with NTSB that were CO related. I'm not totally against heat muff type heaters, but if I can avoid I will.  If I do go that route I will definitely have a CO detector in the airplane..

The larger jets are ordered. The stock 165 jets with needle raised full up works in all regimes except power on descents. I ordered 170 and 175 mains. The chart says 170's will work down to -4 deg F which should be enough but I got the 175's too.

Hopefully my plan will work out. 

[109jb 181]

Looked at your heat muff build and it looks good. Would be really easy for inspections.

[1avidflyer 1983]

Looked at your heat muff build and it looks good. Would be really easy for inspections.

Made it from 6" thick wall stove pipe.  JImChuk

[akflyer 1427]

I run 2 jets.  165 in the summer 170 in the winter.  Only once or twice did I wish I had 175 jets but I doubt you will be flying at -40 like my dumb butt was.

If you want to loose altitude and keep the engine RPM up, pull back on the stick, don't push forward.  Slow the plane down and trust me, it will come down.  use your power to keep the sink rate where you want it.

First and foremost, check the thermostat.  Are you running a 120, or 160 deg thermostat?  I run the marine (OMC) thermostats and they are 160 and work juuuust fine in the cold weather.

With the shutters on the back side you still have cold air hitting the radiators.  Put a strip of aluminum foil tape on the FRONT of the radiator and see what that does for you.

I have had the water cabin heater and the heat muff.  I have always gotten more heat off the heat muff and at less weight.

 

 

[marcusofcotton 52]

I believe you are setting yourself up for a cold seizure. You need to block off the front of the radiator like Lenny says and forget about shutting off flow to it with a separate thermostat. If the radiator liquid gets too cold, then when you go for more power the thermostat will sense heat at the head and open. When it opens it will allow for a cold slug of coolant from your radiator to hit the bottom of the engine and there is your cold seizure. And yes, you do want the 160 degree thermostat for sure.

 

[109jb 181]

I believe you are setting yourself up for a cold seizure. You need to block off the front of the radiator like Lenny says and forget about shutting off flow to it with a separate thermostat. If the radiator liquid gets too cold, then when you go for more power the thermostat will sense heat at the head and open. When it opens it will allow for a cold slug of coolant from your radiator to hit the bottom of the engine and there is your cold seizure. And yes, you do want the 160 degree thermostat for sure.

 

I don't see how the secondary thermostat could do any different than the primary thermostat.. If there were  only the primary thermostat in the system and the scenario you describe happens where the radiator liquid gets too cold, even the primary opening would allow for your "slug" of cold water.  Since it doesn't happen with a single thermostat system, I fail to see how it would be any different with the second thermostat in there.  

Additionally, the flow through the heater cores  is unobstructed and when the secondary thermostat opens, it opens in response to the heat of the coolant around the thermostat pill.  In other words, it doesn't go from closed to full open like a light switch. This behavior would tend to modulate the flow through the radiator and it would mix with the coolant from the heater cores on the opposite side moderating the temp of the coolant going back to the engine.  Quickly thinking about it seems that this would be even better than without the secondary thermostat since without it, most of the coolant flow is going through the radiator due to the fact that it has larger hoses, and has a straight path rather than having to run through tees. The radiator is the path of least resistance. That right there sets it up so that it cools faster than wanted.

All that said, lets assume what you describe is possible. Again quickly thinking about it I think it can easily be countered by installing the secondary thermostat in place of the return tee rather than the supply tee. Facing the thermostat pill so it faces the engine means that once again the flow through the heater cores is unobstructed and the thermostat pill would be in the continuous flow through the heater cores and would open if the returning coolant got too hot. Conversely, it would close if the coolant got too cold. The problem I see with this is selecting the right temp thermostat.  On the supply side the primary and the secondary thermostats would only be a few inches apart in my installation and therefore I could use a 160 deg thermostat for both the primary and secondary.  With the secondary on the return side, its thermostat should be a lower temp one since the coolant has lost heat running through the heater cores/radiator. But what temp??  

I run 2 jets.  165 in the summer 170 in the winter.  Only once or twice did I wish I had 175 jets but I doubt you will be flying at -40 like my dumb butt was.

If you want to loose altitude and keep the engine RPM up, pull back on the stick, don't push forward.  Slow the plane down and trust me, it will come down.  use your power to keep the sink rate where you want it.

First and foremost, check the thermostat.  Are you running a 120, or 160 deg thermostat?  I run the marine (OMC) thermostats and they are 160 and work juuuust fine in the cold weather.

With the shutters on the back side you still have cold air hitting the radiators.  Put a strip of aluminum foil tape on the FRONT of the radiator and see what that does for you.

I have had the water cabin heater and the heat muff.  I have always gotten more heat off the heat muff and at less weight.

I got the 175 jets just in case. The shipping is a killer and I decided to play  it safe. I agree that I will probably never use them but if I do need them I have them.

When I was descending I was at about 45 mph indicated and I was keeping as much power as I could in , but with just me on board it took very little power before I wasn't descending anymore.  I'm sure I could have slowed it down more but since I have so few hours in the airplane I was not comfortable doing that just yet.

I'm not sure I even have a thermostat in it right now, but I ordered the OMC 160 degree stat for the engine. If I do wind up using the secondary thermostat I will use a 160 there if its on the same side as the engine thermostat.

I'm not opposed to blocking off the radiator if that's what it takes.  I am even thinking that what I may do next year is put the fiberglass radiator duct that Kitfox sells on my airplane and put a door on the inlet like a carburetor butterfly. I don't think it will come to it but if I have to I'll block the radiator.

I think the reason that the hot water heaters aren't working up to snuff is precisely because of the reduced flow through the cores. With flow going through the radiator as the path of least resistance, there isn't much of the engine heat making it to the heater cores. The secondary thermostat would solve that and should make the heaters work much better. I know it worked on my father's UTV.

 

Thanks for the responses. Don't think I am totally discounting them. Your responses allow me to think through the situation so I can make a better informed decision which way to go. Nothing is carved in stone so to speak yet.

[akflyer 1427]

I think you will find that with a thermostat you will be fine.  I dislike adding additional failure points to the life blood system on my plane.  I too installed a heater on my side x side including a 12v pump that stratos manufactures to give circulation through the heater core.  The pump body failed in short order.  I was able to bypass it on the side of the trail and dump in some drinking water I had and saved the ride.  This would have been a forced emergency in the airplane.  Do what you wish as it is your airplane, I just like to keep things as simple as possible when it comes to my plane.

 

[1avidflyer 1983]

Speaking of thermostats, it has been recommended to drill an 1/8" hole in the thermostat, so there is always some limited amount of hot water going through.  That supposedly will reduce the very hot verses very cold water issue.  I might have read that in one of Mike Stratman's proper care and feeding of the rotax engine articles.  I did it, and it didn't seem to hurt anything.  YMMV.  JImChuk

[109jb 181]

I think you will find that with a thermostat you will be fine.  I dislike adding additional failure points to the life blood system on my plane.  I too installed a heater on my side x side including a 12v pump that stratos manufactures to give circulation through the heater core.  The pump body failed in short order.  I was able to bypass it on the side of the trail and dump in some drinking water I had and saved the ride.  This would have been a forced emergency in the airplane.  Do what you wish as it is your airplane, I just like to keep things as simple as possible when it comes to my plane.

I'm sure you are right about the engine thermostat making things work for the engine as you have a lot more experience with the 582 than I do.  However, I'm not just thinking about the engine staying warm but also myself staying warm. Like you, I also like to keep things as simple as possible unless there is a clear benefit for doing otherwise.  In the case of the secondary thermostat I see the potential benefits and disadvantages as follows:

Benefits:
1. Controlled flow of heated coolant through heater cores (ie: Better heat output)
2. Isolation of the radiator will help maintain heat within the engine. 

Disadvantages:
1. If the secondary thermostat fails closed, the radiator will be isolated and unable to cool the coolant.

The only disadvantage I see is the potential failure of the secondary thermostat in the closed position.  Failure in the open position wouldn't be a problem and the only other issue would be a leak. I'm not worried about it leaking, so that leaves the closed failure. The most common failure mode for a thermostat is to fail open, so this mode would be essentially no different that not having a secondary thermostat.  If it fails closed, then the flow to the radiator will be blocked. While not as common a failure mode, it has to be considered. In my case, with 2 fairly large heater cores would still be in the flow even with a stuck closed secondary thermostat. Although I can't prove it, I feel that the heater cores with the fans running would be large enough to allow the engine to be operated at a power setting that would allow sustained flight.  This airplane doesn't need a lot of power to stay aloft. 

Basically, at this point I still see enough potential benefit and not enough disadvantage that I'm still leaning toward including the secondary thermostat.

 

[109jb 181]

Speaking of thermostats, it has been recommended to drill an 1/8" hole in the thermostat, so there is always some limited amount of hot water going through.  That supposedly will reduce the very hot verses very cold water issue.  I might have read that in one of Mike Stratman's proper care and feeding of the rotax engine articles.  I did it, and it didn't seem to hurt anything.  YMMV.  JImChuk

Drilling a small hole in the thermostat has nothing to do with flow. It is to allow air to escape when filling the system.

[marcusofcotton 52]

 

 

 

The hole also lets a small amount of coolant to flow  (my factory original hole was smaller iirc). I no longer have all my Rotax manuals but I recall a minimum coolant return to engine temperature specification. Give it serious respect. In the picture below you can barely see behind my head a pink 2" wide velcro strap wrapped around my radiator. I had two of these I'd install depending on ambient temp as needed to keep radiator temp up.

My heater left a little to be desired when below 0F, no carbonmonoxide worries though.

 

Edited 11 Jan 2020 by marcusofcotton

[1avidflyer 1983]

Looks nice Mark,  what fly in was that?  Somehow those rear skis look familiar.... :-)  JImChuk

[marcusofcotton 52]

Jackson Ski Plane 2018 McGregor, MN. Those rear skis are slowly getting closer to becoming Avid skis. I'll add that the Jabiru heat muff while being modest in the Avid is definitely better than the heat in the trike was.

[109jb 181]

The hole also lets a small amount of coolant to flow  (my factory original hole was smaller iirc).

I disagree with the thought that the small hole in the thermostat is for flow. Sure, the fact that it is there means that even with a closed thermostat there will be a tiny amount of flow but that ain't why its there. It is an old wives tale that it is for flow, and it is really only to prevent an air pocket forming around the pill of the thermostat. If an air pocket forms, the thermostat will not open at the correct time. As a matter of fact many thermostats come with a "jiggle valve" in that hole. The purpose of that valve is to let air escape, but not allow water flow during operation.  Also, in the case of my airplane with the cylinder head facing up I have the 3/16" vent line connected to the top of the head which provides a flow path for the coolant bypassing the thermostat anyway. This line is also really only to purge air.

I recall a minimum coolant return to engine temperature specification. Give it serious respect.

If I wasn't respecting it I wouldn't have posted about being concerned about it in the first place. My concern about the water temperature is the whole point of starting this thread.

I found the spec for the inlet vs outlet temp in the Rotax install manual. Optimum is pump inlet temp 5 to 9 deg below the head outlet temp with an 11 deg maximum differential. The manual refers to it as a radiator inlet to radiator outlet temperature, but what really matters is what the engine sees. So with this information I could put the secondary thermostat on the water pump side with a 155 thermostat and a 160 degree stat in the head giving the optimum differential. The secondary valve would operate like a mixing valve blending the hotter water flowing through the heater cores with the colder water flowing through the radiator. 

 

[Allen Sutphin 705]

Must be a thousand 582's out there flying with the standard cooling system setup in all kinds of weather and temps with no issues. I would check that the cooling system is functioning properly prior to improving it! 

[marcusofcotton 52]

John, I didn't disagree with you on the primary design purpose of the hole. I'm glad you know the coolant temperature differential spec, I wish you well in achieving it and cabin heat. Let us know how it works out for you for the benefit of all of us and those who follow. Don't forget the sage advise also regarding holding accessories out at shoulder height and letting go of them to see if they go up or down.

Blue skies and happy flying.

Edited 12 Jan 2020 by marcusofcotton

[109jb 181]

Must be a thousand 582's out there flying with the standard cooling system setup in all kinds of weather and temps with no issues. I would check that the cooling system is functioning properly prior to improving it! 

That is absolutely going to happen. As I said before I suspect that the engine doesn't have a thermostat.  If it doesn't then that would explain what happened during my cold weather flight. I couldn't check because at the airport I'm keeping it at I didn't have tools or a catch pan to drain coolant to check. I haven't been back out there since that flight. That place (a friends strip) is 30 minutes away but the good news is that the airport 5 minutes away called Friday and had a hangar open up.  I will first put the new one I have on my counter in  and as soon as I get a good day weather wise I will head down and move the plane to its new apartment. Any mods will happen after it gets to its new home.  I had always planned on re-doing the cooling system because although it works and doesn't leak, the workmanship isn't the best.

[marcusofcotton 52]

I believe you are setting yourself up for a cold seizure. You need to block off the front of the radiator like Lenny says and forget about shutting off flow to it with a separate thermostat. If the radiator liquid gets too cold, then when you go for more power the thermostat will sense heat at the head and open. When it opens it will allow for a cold slug of coolant from your radiator to hit the bottom of the engine and there is your cold seizure. And yes, you do want the 160 degree thermostat for sure.

 

I don't see how the secondary thermostat could do any different than the primary thermostat.. If there were  only the primary thermostat in the system and the scenario you describe happens where the radiator liquid gets too cold, even the primary opening would allow for your "slug" of cold water.  Since it doesn't happen with a single thermostat system, I fail to see how it would be any different with the second thermostat in there.  

 

Just reviewing a bit and feel I should respond to the portion of your reply that I underlined. Beware, cold seizures definitely do happen on these engines (gray head or blue head) with however many thermostats one might or might not have!

Congrats on securing the airport spot!

[109jb 181]

John, I didn't disagree with you on the primary design purpose of the hole. I'm glad you know the coolant temperature differential spec, I wish you well in achieving it and cabin heat. Let us know how it works out for you for the benefit of all of us and those who follow. Don't forget the sage advise also regarding holding accessories out at shoulder height and letting go of them to see if they go up or down.

Blue skies and happy flying.

No worries.  I know a lot of people would just go with what is known to work, which in this case would be insuring a thermostat is installed and blocking off the radiator as required.  I tend to overdo but it is at least always a fun trip. Since I'm getting a close by hangar soon I should be able to finally start whittling away at the list of changes I want to make to the plane. I'll be sure to post my results with this.

[109jb 181]

I believe you are setting yourself up for a cold seizure. You need to block off the front of the radiator like Lenny says and forget about shutting off flow to it with a separate thermostat. If the radiator liquid gets too cold, then when you go for more power the thermostat will sense heat at the head and open. When it opens it will allow for a cold slug of coolant from your radiator to hit the bottom of the engine and there is your cold seizure. And yes, you do want the 160 degree thermostat for sure.

 

I don't see how the secondary thermostat could do any different than the primary thermostat.. If there were  only the primary thermostat in the system and the scenario you describe happens where the radiator liquid gets too cold, even the primary opening would allow for your "slug" of cold water.  Since it doesn't happen with a single thermostat system, I fail to see how it would be any different with the second thermostat in there.  

 

Just reviewing a bit and feel I should respond to the portion of your reply that I underlined. Beware, cold seizures definitely do happen on these engines (gray head or blue head) with however many thermostats one might or might not have!

Congrats on securing the airport spot!

I am aware.  To be clear, my intention was not that it doesn't or can't happen, just that putting a secondary thermostat in will not change that scenario. I obviously worded it incorrectly.