As we work ever creatively towards using the Zenith STOL aircraft in practical applications, in the heat of the tropics, we are currently working towards a concept for improved cooling.  It has taken us a long time, but we are close to test flying the 'nose job' on the 701 with a Rotax 912iS up front.

The fun part is the new nose shape and the radiator arrangement (do note that in this picture there are lots of Clecos, which get replaced with rivets BEFORE test flights!).  We have lowered the cowling lip considerably, to reduce pressure behind the cowl, and also for improved efficiency when we fly with our belly pod, and hope to see at least 10-15C (50 - 60F) overall improvement in our temps - CHT and Oil.  The challenge has been the development of a suitable radiator gantry - and until we get 50 or more hours on the design, we will keep that bit under wraps.  The engine is the pretty green Rotax 912iS, and we have a lot of specialist adaptations on our 701, so please do not think that it is a 'standard' (although I doubt that there are many of them out there anyway!) 701!

The majority of the new shape is achieved using two rolled pieces of 6061 T6 - the stock and trade of Zenith aircraft.  Then we have a little bit of fibreglass work (it would have been less without the previous attempts).  We have removed considerable amounts of the original fibreglass cowling and we actually hope that our finished design will be a little lighter than we started with!  

We are ready to give up some aerodynamics (what is a little drag between friends) for better cooling, especially with our full load long flights at low level in air on temps over 40C (104F).    You may note that we take the air in from the outside to the air filter - it really helps for performance!  Of course, the oil rad is now at the front, so we remove the NACA duct completely - lots of changes and factors!

If the weather is in our favour, we will test fly this week, and let you know the results... 

Then our plan is to use the same configuration on the CH750 - which we still hope to build and fly to Europe in April next year !

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