steve342 Posted June 19, 2017 Share Posted June 19, 2017 My enjoyment of an early evening flight yesterday was interrupted by the sound and feel of my rough running Top 80 engine. Was at 800ft on a very hot & humid Hampshire day c.28C, had just come off 8-10mins of full power throttle on full speedbar, down to 60% throttle for a min or so before applying full throttle and speedbar again only to encounter rough running/vibration and no throttle response beyond 75%. Yikes, so......trims to normal, back on brakes, turn back to t/o point 5 miles away, look for a suitable field for a likely forced landing. Tried full throttle again, no joy, eased back to 60% to maintain level flight, seemed a little bit smoother. Shall I continue and risk damaging engine (possible fuel contamination/blown head gasket/holed piston??) or make a precautionary landing miles away from t/o field? Thought crossed my mind it may be carb icing, had a similar prob on microlights a few times in the past, was maintaining level flight so opted to fly a little longer. Sure enough, a few minutes later I got back throttle response, vibration stopped, all seemed normal again. Took it easy getting back to field and when overhead, gunned the engine up and down the throttle range for a while and all was well, was relieved to land safely after the unexpected bit of excitement. Conclusion? Most likely carb icing I guess due the venturi cooling effect in the carb particularly after a period of high revs - very humid air, happened during a flight transition when light aircraft would normally apply carb heat to counter carb ice risk, alas the Top 80 doesn't have that luxury . Next time I'll blip the throttle a bit more during wind down. Last thing I was expecting on a boiling hot day, useful lesson learnt though! Quote Link to comment Share on other sites More sharing options...
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