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Franz Thermostat


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Here's my informal sense. My German is not fluent by any means. I have one of the devices and intend to install it this winter, so I can see it as I discuss it.


Take the six-sided aluminum block with the threaded hole and all the tapped holes off the thermostat. Put some Loctite 243 on the threads and screw it down on the radiator, leaving at least 1 mm between it and the radiator. The picture # 1 is confusing on this. It shows that gap but does not label it. It only labels the gap above it.


Look at picture number 2. Put a little ring of Loctite 5910 around the outside edge of the port on the thermostat. As you can see by looking closely at picture number 2, you don't use much.


Put a flat washer part number 10709 in each of the ports as shown in picture 3. Put some more 5910 around the outside edge as you can see in picture 4.


Set the thermostat down on the aluminum block that you screwed onto the radiator and fasten it down with the 4 screws. Tighten them evenly to 8 Newton meters.


Connect the hoses (I guess you have to come up with the hoses) to each end of the thermostat. When you fasten the hoses, use a torque value of 25 Nm.

ATTENTION: Be sure to hold the thermostat while you are tightening the hose connection (I guess this is so you don't twist or cant the thermostat and damage it's connection to the radiator).

Be sure that the hoses are not mounted so that they are taut - there needs to be some flexibility in the hose.


NOTICE: Be sure to have a minimum diameter of 9.5mm for the hoses.


Don't mount the thermostat directly to the engine. (It was not tested that way.)


After the installation the oil system has air in it. Purge the system per the Rotax S.B.

After the installation, conduct a thorough examination and test to be sure it functions properly.



This thermostat kit is not tested in your airplane, and therefore we don't accept responsibility for any consequences.

It is possible that the engine could stutter (I am probably not rendering this accurately - I suspect it is a common term that I'm not familiar with).


Installation of this thermostat means you aircraft no longer meets certification criteria (my loose rendering of the intent - I have no idea if it affects U.S. SLSA or not [mine is an ELSA so that is not an issue for me]).


NOTICE: Only work on the oil system when it is cool.


Again, I make no guarantees that this is accurate. Better get a German technical translator to be sure.

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