For the most part, flying through rain is a non-event. If the NexRad or Radar is showing light green or dark green, usually there aren’t that many bumps and your plane just gets a wash. Sometimes the visibility drops down a little bit making us IFR pilots have to transition to our instruments.
It get’s a little more exciting when the precipitation on your screen turns to yellow. This means there is a lot more precipitation echoes either in the clouds or coming out of the clouds, meaning harder rain. I usually tend to stay away from yellow unless it’s absolutely necessary to go through it.
I had a situation a few weeks ago where I deemed it necessary to fly through some yellow NexRad returns. I was flying a G1000 Columbia into Monroe, Louisiana, KMLU. The winds were mostly light, but slightly favoring runway 04, which was the runway in use. As I got closer, a decent size rain shower with mostly yellow returns was sitting over the final approach fix for runway 04 and slowly tracking to the northeast.
I didn’t particularly want to spend the entire approach getting beat on with rain, so I decided to fly the RNAV 14 approach at MLU and circle to land on runway 04. The rain hadn’t quite reached the airport yet, so I decided that circling to 04 should be no problem.
I started the RNAV 14 at the FLESH IAF. Since I was approaching from the west, I did not need to do the procedure turn, so I joined the Final Approach Course (FAC) after crossing FLESH.
In the meantime, that rain shower was inching closer to the FAC for the RNAV 14. I wasn’t concerned about my safety if I flew through some of it and I didn’t have passengers on board who would get nervous, so I elected to continue. I wasn’t seeing any lightning coming out of the clouds, so it appeared to only be moderate rain.
Just before I got to JIVEY, the FAF, I entered the clouds and the rain. About 20 seconds later, my altimeter and airspeed started bouncing around a lot. Now, based on all I’ve said so far, what would cause that, and what would you do?
(Jeopardy theme song playing while contestants ponder questions)
The answers? Due to the moderate precipitation, water had gotten into my static port and caused the unusual readings on my altimeter and airspeed indicators on the G1000.
I had experienced this before, so I knew what to do. I reached down and turned the static source from primary to alternate, which starts taking static pressure from inside the cabin in the Columbia. Instantly, everything went normal.
The other time I had experienced this was also in a Columbia, so I’m under the impression that the way the Columbia static ports are designed, they are a little bit more susceptible to water creeping into them than other airplanes.
Moral of the story? If your pitot/static instruments start jumping around, the first thing you do is turn your alternate static source on.