Thanks, Joe. I asked due to my few experiences. I wasn't going out flying when it was raining, but got caught in a brief (and light) shower 2 times years ago while under power from the Rotax 503. I was immediately concerned for several reasons:
1. Possibility of water induction into engine through the two individual air filters.
2. Possible damage to both prop & rotorblades leading edges from impact of raindrops. I suspected flight in heavy, sustained rain would be far more of a worry than the light & brief rain-encounter would.
3. Reduced efficiency of wings, being flown into water vapor, possibly reducing lift due to changed air molecules as well as distortion of rotorblade airflow by water.
It turned out I had to slightly increase throttle to counter a slight altitude sinking upon entering the light rain squall. Maybe 100-150 engine rpms to stop the very gentle sink from cruising speed, level flight.
This was about the same as encountering a down draft. I've never encountered a violent downdraft while flying a gyro, only a gentle pressure downward, like a giant hand pushing down on the rotorblade disc. If I wished to maintain the altitude I was at, I added slight throttle to stop that gentle sink, which everytime was extremely brief.
I have encountered many updrafts that take my breath away because of the rapid, sudden elevator ride up. Usually combined w/ sudden, hard yaw changes left, and then right, or right, and then left, w/out any rudder pedal inputs by me. I believe those hard yaws are a result of entering a thermal's spinning in whichever direction it happens to be turning, and then exiting out it's other side.