Joe Hull

Cozy Mk-IV #991 (In Phase1 Flight Test - 10.9 hrs flown)

Redmond (Seattle), Washington

 

Good News:  Velocity N755V received FAA airworthiness certification yesterday.  Also survived an intensive 4-hr inspection by a factory authorized insurance inspector with a small list of minor items to attend to.

 

Not So Good News:  Main issue now seems to be cooling during ground operations, particularly oil cooling, and the secondary temporary issue of mixture reprogramming (again, after software update).  With the wing root cooler in a pusher configuration there is almost no oil cooling when standing still.  So running at significant power to adjust mixture allows little time to do anything before reaching temp limits. Then, with cowl on, it takes hours for it to cool down.

 

My expectation was for enough natural convection cooling on the ground to handle low power taxi operations.  Earlier static running suggested that there would be sufficient time, but I’m finding that; a) taxi maneuvering with brake steering takes more power than anticipated, and b) the 3” thick, 16 fins/in. oil cooler core has almost no natural-convection cooling. Have no good ideas at the moment how to improve this situation.  Haven’t gotten to high speed taxi yet to see if temps stabilize.

 

Tracy; can you tell me the basics of your water spray system?

 

The in-cowl coolant rad gets reasonable air flow because of negative pressure generated by the prop aft of the cowl.

 

More later,

 

Al