Hi Mark,

I'm no Pro (that is I'm not sponsored by anyone), but I have been flying pattern for 7 or 8 years now... I don't know which engine to pick, but I guess I would go for the lightest and most powerful option. I have no experience with either the SM30 or ZDZ40, but based on the specs the SM30 seems to be the petrol option, which is most likely to come in under 5 kg's in the Impact.

In my years in pattern I have used the following engines:

OS-61SF
Webra Racing 61LS
YS-120SC
YS-140FZ
OS-140RX (with and without the Mintor dual plug head)
Mintor 3M-170
OS-140RX-FI

In my opinion the absolutely most reliable pattern engine on the market today is the OS-140RX equipped with the sealed rear bearing from the OS-140RX-FI. The engine is light, powerful, economical to run using 10% nitro fuel, and in my mind OS has some of the most reliable engines on the market. The small parts count compared to a 4 stroke also means that it's much cheaper to maintain. Based on my own experiences and the above I would recommend the OS-140RX as the best choice.

I know this doesn't help you in regard to the choice of petrol engines, but let's face it, you really need to build a light airframe in order to keep the current 5kg limit in F3A, and even more so when using a petrol engine...