I’ve flown C40 and kept up with the forums for several years. This class has generated a lot of excitement around the country for its simplicity and low cost. I find it disappointing the rules committee has decided to make the Evolution 46NX illegal, 7 weeks before the NATS. This is a move that has disgruntled many and will prevent the growth of C40 due to the lack of manufactures who actually produce a .40 size engine. Several people have spent their hard earn money on an engine deemed to be in compliance with other Silver class engines, only to be told at the last minute it was all a waste. Can someone tell me what happened that was so catastrophic to warrant this engine being deemed illegal? It appears this rule change was based on the results from the Georgetown, TX race; which took place last month. After reviewing the fast times for each pilot I don’t see any difference between these times and the 2015 NATS times. I have raced C40 planes with OS 46 engines against others with Thunder Tiger 40’s and have not seen a difference in speed that merited a concern. My opinion of C40 planes in a racing sense is it takes a lot to make them handle but once this is achieved a huge amount of speed can be gained. Anyone that’s flown a Q500 plane can attest to this. The better handling plane typically wins. What type of test needs to be performed to prove this engine is competitive with the others? I’ve tested and flown planes with .40 and .46 OS Max, Thunder Tiger, Evolution, ASP and Magnum engines. The propeller I use the most is an APC 9.5x6. These engines can all turn this prop between 15.9K – 16.2K on the ground; set rich so they’ll unload in the air. From what I and others have witnessed at C40 races there’s not much difference in speed between these sport engines. I hope the rules committee reverses their decision concerning this engine with the NATS just around the corner. If the decision isn’t reversed, I’d recommend everyone with the Evolution 46NX engine that’s thinking about racing C40 not go that route and instead move into 424 pylon racing.