CH 701 912 ULS Cooling

Now that summer is here in Idaho and I want to fly on the really hot days - sadistic - I wonder what those of you out there have done to increase the cooling air through the cowl by adding a "lip' at the rear bottom edge.

I have molded a ram air scoop for the water radiator inlet and also built a scoop for the NACA duct. There was a little imrpvement - about five to eight degree drop -but wondering how the "lip".

on the cowl bottom works.

Any thoughts on this would be appreciated.  Attached a pic showing both of my scoops..

ttfn

Phil Smith

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Permalink Reply by François Balaux on June 6, 2016 at 9:27am

Hi Phil

From past experience I think you will have more improvement by working on getting the air out of the cowling. If if can't get out the pressure will raise and fresh air won't get in.

Did you trim the cowling around the gear leg?

Regards,

Francois

Permalink Reply by Phil Smith on June 6, 2016 at 9:53am

I haven't done anything to the bottom of the cowl.  Do you or anyone else have experience with modifying the outlet area.  The setup is a Zenith FWF with a rotax 912ULS as supplied from the factory.  I have seen mention of the lip idea...in fact it has a service kit for some older 172s.

The problem is not a show stopper just an aggravation on 95 plus degree days.  The oil and the head temp creep into the yellow - thought if there was an easy fix I'd try it.  All I'm looking for is about five to ten more degree reduction.

tnx

Phil

Permalink Reply by François Balaux on June 6, 2016 at 10:27am

I have not modified my 701. As I live in Quebec City, Canada I have to block about half of the radiator with a plate most of the time to have correct temperature.

However in the assembly guide, cowl section, there is a note : "NOTE: Wait to trim outlet till flight testing. Trim away the bottom cowl as required for proper cooling."

I had to fix a few cooling issues on industrial electronic/mechanic stuff and it is always easier to work on the air exhaust than the intake. 

Regards,

Francois

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