For the sake of argument
When one is building it is easy to focus on ultimate performance but when that phase is done it seems to me the emphasis shifts to safety and reliability and a little compromise in performance is acceptable to get them. I read in Jack Cox's Sportsman Pilot (Winter 2005 - the current issue) some very interesting information about Lightspeed ignition systems in the article about Paul Lipps and his contribution to it (as well as his amazing propellers). I wanted maximum performance when I built our RV-6A but not at the expense of giving up the "stand alone keep the engine going if everything else fails" single mission reliability of mags (if it starts it will not be the cause of you not completing the mission). That is why I compromised and chose to use the LASAR system. Because Lycoming didn't time it propertly at the factory, it almost caused me to burn up my cowling but I got my own LASAR timing box from Van's, correctly set the timing, repaired the cowl (significant repair by the way) and since them everything seems fine. I am carying around a heavy box on the firewall of an airplane that is already the heaviest RV-6A I have ever read about (please don't ask). My cruise speeds are in the low to mid 170 knot range at 2450 rpm and a standard Hartzell constant speed prop (blended units were not available when I bought mine). Since speed is directly dependent on the blade angle and RPM of the engine (the plane can't fly faster than the prop would pull it through the air with 100% efficiency - I don't think a 74 inch pitch propeller cannot move the airplane 75 inches in one revolution) you have to have a constant speed prop or go to a higher pitch fixed prop to take advantage of a more efficient ignition system's ability to produce more power. Since I am getting very good speed with my constant speed prop I assume that the LASAR system is performing better than straight mags in power generation but I do not know that for a fact. Based on weight alone our airplane should be 1 to 2 knots slower than everyone else but the wing span is 18 inches longer so the baseline is not identical - and quite honestly I am not sensitive enough to detect 1 or 2 knots. If I were racing, always maintained my airplane in absolute peak condition and never asked it to carry me someplace when I wanted to go even if it was worn and tired, I am pretty sure I would go with the Lightspeed system but for my application the LASAR system which reverts to straight mag function in the event of electronic/electrical failure seems to be the better way to go. I have no good objective data that show the LASAR system is any better than straight mags. It is heavier than a straight mag system, it is more complex and once you shut it down on the ground you cannot restart it if the LASAR box fails, so a good argument can be made for the straight mag system's advantages for normal operations as well.
Bob Axsom
RV-6A, N710BJ