Rotax 503 rapid descent-- best throttle setting?

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Active Member
Mar 3, 2021
Caldwell, ID
So the other day I found myself with a lot of excess altitude coming off the Boise hills in my Sky Raider and needing to get down under the Boise Class Charlie shelf (or go way around it). How to descend a thousand feet or more in just a few minutes, without entering the dreaded "lean zone" on the tachometer? I've seen in these forums that you want to avoid the range between 4,000RPM and 5,000RPM for extended runs. I've also read that you don't want to unload the prop too much in a long diving descent, as this also causes a lean run.

So, do I go straight to full idle, and keep the airspeed down to avoid shock cooling the cylinders? This is an induction-air cooled Rotax 503DCDI without the fan.

What do you guys do?