Question for mountain flyers

[Vlad]

I went to an airport the other day where wind of 20 kts is considered calm. High elevations, a tunnel, I planned to visit for over a year. I am flying a fixed pitch carbureted O-320 RV9A only 400 hours on a perfectly running engine. Spent some time there, departed around noon it was gusting near 30 according to ASOS all along the runway. Nice short lift off and then at a hundred feet suddenly engine rapidly reduced power ( I would estimate a 20% or more) for a couple of seconds then surged passed the takeoff RPM. Takes your attention for sure. Turbulence followed which actually was a relief thinking it's likely the gusts not the power plant.

Anyone had anything similar? Any explanations?

 

[Toobuilder]

Yep. Very common occurrence in my parts. Rolling gusts/wind shear can feel like engine problems, but most of the time you are just powering through a “surf” of air. With a fixed pitch, a sudden tailwind will make the RPM sag and the airplane will settle.

 

[PhatRV]

I first experienced something like this now that I am flying in higher wind with my FP airplane. I suspected the gusty wind was causing the irregular RPM especially at the slightly higher than idle. Someone said it could be due to vapor lock but nice to know it wasn't the case.