Before my First Flight this week in N737G, I flew a bunch of circuits and bumps in Tony's airplane N477RV. He has the OEM strong springs - I immediately noticed the trouble I was having keeping the power at Idle, even after cranking down the friction lock. On each final approach, I was mostly controlling the airplane with one hand and pulling like the dickens on the throttle with the other.
I also flew the Vans Demonstrator extensively last summer, and I believe it has the OEM strong springs. I remember pulling on it a lot too, but not as much as Tony's. Still, I do remember a few hot, long landings where it turns out I had substantial power on that I was not aware of.
I installed the McFarlane 5 lb springs prior to my First Flight. These are described as "less than half the Rotax OEM spring force." They also offer a set of 3.5 lb springs. Granted, my experience with these springs is limited, but I noticed immediately that my fighting with the throttle was much diminished - maybe even gone away.
This subject has been hashed and re-hashed endlessly on this Forum, but I personally do NOT like the Rotax schema, and don't really understand it. Fighting the throttle during landing is a major distraction, and going uncommanded to full throttle is reminiscent of the (supposed) Toyota problem of throttles going wide open and causing car crashes. It's hard to imagine the Vans supplied throttle cables, which are pretty doggone stout, failing and requiring the throttles to go full open. It looks to me much more likely that those springs will fail before the cable.
And, if that really happened, and the engine went to wide open - THEN what would you do??? How would you shoot an approach? Blip it like the rotary engine in a WW I fighter?
Bob Bogash
N737G
Flying