Cabin heat and Rotax Powered Aircraft

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drseti
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Re: Cabin heat and Rotax Powered Aircraft

Post by drseti »

Nomore767 wrote: Rotax have an S/B out whereby they differentiate CHT from coolant temp. CHTs, the actual temp of the cylinder head are hotter than the coolant.
True. This SB was motivated by a change in CHT sensor design. One version is immersed in coolant, and actually reads coolant temperature. Another type just reads the temperature of the head. Both types are approved for Rotax 912 engines. It is necessary to calibrate the colored arcs properly on your CHT gauges or EMS, so as to be compatible with the particular sensor your engine uses. Since a sensor replacement may result in a different type installed, it may become necessary to re-calibrate the readout if your mechanic changes sensors.
The other day with temps nearly 62F the oil temps were getting high and so a narrower band of tape is needed. It's a question of finding the sweet spot for the right size of tape in the winter months.
One possible solution here is to install the optional oil thermostat. It bypasses the oil cooler until the oil comes up to operating temperature. Designrs has one installed on his plane now; perhaps he'll post his results here.
One point to mention is that a couple of Rotax guys have said it's good to get the oil temp above the magic 212F at least once per day to 'boil off' condensation which can cause damage over time.
I agree. The oil thermostat helps to accomplish this. Of course, if your RV-12 didn't come with one, and it's an SLSA, you'll need to get an LoA from Van's to install it.
The opinions posted are those of one CFI, and do not necessarily represent the FAA or its lawyers.
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Nomore767
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Re: Cabin heat and Rotax Powered Aircraft

Post by Nomore767 »

drseti wrote:
Nomore767 wrote: Rotax have an S/B out whereby they differentiate CHT from coolant temp. CHTs, the actual temp of the cylinder head are hotter than the coolant.
True. This SB was motivated by a change in CHT sensor design. One version is immersed in coolant, and actually reads coolant temperature. Another type just reads the temperature of the head. Both types are approved for Rotax 912 engines. It is necessary to calibrate the colored arcs properly on your CHT gauges or EMS, so as to be compatible with the particular sensor your engine uses. Since a sensor replacement may result in a different type installed, it may become necessary to re-calibrate the readout if your mechanic changes sensors.
The other day with temps nearly 62F the oil temps were getting high and so a narrower band of tape is needed. It's a question of finding the sweet spot for the right size of tape in the winter months.
One possible solution here is to install the optional oil thermostat. It bypasses the oil cooler until the oil comes up to operating temperature. Designrs has one installed on his plane now; perhaps he'll post his results here.
One point to mention is that a couple of Rotax guys have said it's good to get the oil temp above the magic 212F at least once per day to 'boil off' condensation which can cause damage over time.
I agree. The oil thermostat helps to accomplish this. Of course, if your RV-12 didn't come with one, and it's an SLSA, you'll need to get an LoA from Van's to install it.
My Rotax 912 ULS has the new temp sensors and so measures coolant temp. I'm trying to get info from Vans regarding having to recalibrate the temp bands on Skyview's EMS. Looks like the max temp is reduced and coolant temps seem to run quite low.

There is some discussion about thermostats. Some say they work well, some not so much. Vans appears to be working on approving a shutter for the RV-12 which is controllable from the cockpit and can vary the amount of 'blockage' to the radiator to improve cabin heat in the cold months. The Experimental guys have a variety of different options. For my SLSA I have to go with what Vans says.
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Re: Cabin heat and Rotax Powered Aircraft

Post by 3Dreaming »

It is a change in the design of the cylinder head rather than the sensor.
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Re: Cabin heat and Rotax Powered Aircraft

Post by drseti »

Oh, right. I learned that a couple of weeks ago in my Rotax renewal course - and then had a senior moment. :(
The opinions posted are those of one CFI, and do not necessarily represent the FAA or its lawyers.
Prof H Paul Shuch
PhD CFII DPE LSRM-A/GL/WS/PPC iRMT
AvSport LLC, KLHV
[email protected]
AvSport.org
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Nomore767
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Re: Cabin heat and Rotax Powered Aircraft

Post by Nomore767 »

3Dreaming wrote:It is a change in the design of the cylinder head rather than the sensor.
True. When communicating with Vans they talk about the 'new' sensors because in the new head they point upwards (in my plane anyway) as opposed to the 'old' ones which don't. I don't think the sensors are 'new' as much as they're doing something 'new' as in measuring coolant temp as opposed to CHT.
Jim Lee
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Re: Cabin heat and Rotax Powered Aircraft

Post by Jim Lee »

The Phoenix motorglider has a cowl flap which regulates the amount of air into both radiators. With the cowl flap open, the Rotax engine has very good cooling in the hot Florida summers. With the cowl flap completely closed, the oil temp, and cyl head temp can be kept in the green no matter how cold it is outside, even during descent over the Colorado mountains in the winter. The only negative is that the pilot cannot forget to open the cowl flap on take off or during any climb or the engine can be overtemped quickly. Like most other LSA's, the cabin heat comes from a shroud around the muffler, and works quite well. Since the exhaust gas temps are always between 1300 and 1450 degrees no matter what the cowl flap setting, or the oil or coolant temp is, the heater always works well. It also helps that the cabin is well sealed and the canopy is open to the sun.
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