With a pusher, a fan is pretty much a necessity for cooling on the ground.  On my Velocity I found that the negative pressure from the prop did result in some airflow through the rad in the cowl; which did OK on cool days, but fan made a significant difference, and now taxing and waiting for takeoff clearance on not an issue even on hot days.

 

I have found that the fan makes no noticeable difference on cooling when at flight speeds whether on or off; and the cooling in flight is not reduced since installing the fan.  I think if you had waited a bit longer in flight the temp would have come down without the fan on; other wise I would not expect it to stay stable at 180 without the fan.

 

Al

 

The new cooling system also has a cooling fan which I was able to integrate into the plenum holding the radiator.  At 95 F degrees OAT, and turning the fan on at about 190 F degrees coolant temperature, The fan maintained 180 F for 20 minutes of ground operation, including some high power testing.

 

This morning OAT was about 78 F, which is very good for North Carolina in August,  I wanted something less than 95 F for the first test of the new cooling system.  I did not use the cooling fan for taxi or takeoff, as I wanted to see what the cooling was without the fan.  I took of and climbed up to about 1200’ AGL.  The coolant was up to about 205, and oil at 185.  I leveled off and reduced the throttle to normal cruise power.  I watched the coolant temperature for a little while (maybe 15-20 seconds), and it seemed to stay at the 205 F reading.  I wish now that I’d been a little more patient, but I kicked on the cooling fan, and the temperature came down pretty quickly to slightly above 180 F.  I turned the fan off again and the temperature stayed right there.  I did power up and climb another 300 feet or so, but really didn’t push it too hard on the first flight.  The temperature didn’t really move too much during the brief climb.  All other systems ran perfectly and it was a very nice flight.  I did stay within gliding distance of the runway the whole flight, but based on zero squawks on this flight, the next one will be longer.

 

While I would like to have seen a little better performance, I was happy with the improved cooling over the old system.  Climbing to pattern altitude old the old system at today’s temperature would have been 215 – 220F.  On the next flight, I’ll take off using the cooling fan, and see what kind of numbers I get with it.  I hope to see something more in the 185-190 range, but I’ll have to see what the real number are.

 

 

Steve Brooks

Cozy MKIV N75CZ

Turbo rotary