by Goodflight777 » Mon Feb 17, 2014 9:52 am
I would like to offer a perspective somewhat different from most appearing here.
Experimental aviation needs as much engine choice as possible. So any viable engine should be welcome. The most important characteristic of an aircraft engine is reliability. Everything else is a distant second, at least if you value your life. So a good question is, what is the reliability of the Viking engine? It is a bit early to fully answer that question, but early indications are encouraging. I haven't read or heard of any accidents or catastrophic failures so far. Of course the Viking engine is based on the Honda Fit engine, itself an excellent engine.
I went up in Cody Lyon's Viking powered Sonex at a fly in, and it was a good experience. The thrust really pushed me back in the seat during the takeoff roll. Although I didn't evaluate the plane in any systematic way, there did not seem to be any serious problems with CG or trim. IMO, these discussions make more of this than warranted. The available power of the engine can overcome wing loading issues with a few more knots of airspeed for example. Jan's re- rigging the wing was probably unnecessary, and a mistake. But that is the nature of experimental development. Surely simpler solutions are possible.
Liquid cooled engines have great potential for reliability because they run MUCH cooler- often 200F cooler. That makes an enormous difference in engine reliability and longevity. That is why the Rotax 912 series is very reliable (and has fully certified versions). That is true, despite squeezing 100hp out of only 82 cu in. Try that with an air cooled engine. That is 1.2hp/cu in. A Jabiru 3300 gets 120hp out of 202cu in. That is only 0.6 hp/cu in. The VW engines get about the same. Yet it still takes heroic efforts at baffling to keep them from overheating. Now, the Viking engine has approximately the same power/cu in as the Rotax. It is liquid cooled completely, with a full water jacket, not just the heads, as with the Rotax. So the thermal stresses and gradients are even less than the Rotax.
An often heard objection to liquid cooling is the extra complexity of radiators, hoses, etc. But I think that is a fallacy: Was the Rolls Royce Merlin unreliable? The Rotax? No. But sure, if you ignore your car engine for 5 years, a hose may break. However, unlike car engines, we inspect aircraft engines constantly, with periodic & preflight inspections, and mandatory maintenance. So any leak or hose issues would be detected long before any serious problem arises. The big advantage of liquid cooling can hardly be overstated. Head warping, burnt valves, glazed cylinders, detonation, damaged rings and blow-by, etc. are virtually eliminated. Many of the air cooled engines constantly have these problems, needing top end work after only a couple hundred hours, or less.
Despite Jan's eccentricities, I think he may have a good product with the Viking engine. But I am afraid so much negative piling-on might prevent the engine from being successful. If we want more engine choices, we should allow the engine to be evaluated on it''s own merits, not on excessive emphasis on personalities. I have no financial interests or personal relationship to Jan, his employees or Viking, but only would like to see this engine succeed and be an option in our experimental aircraft.