Orval Fairbairn wrote:
The operative word here is "unimproved." Usually, a dedicated grass
runway is an "improved" runway; therefore, it falls outside the
restriction. Improved runways include turf, pavement -- even graded
dirt, for that matter.

"Improved" at our flight school, and at other flight schools/FBOs at
this municipal airport and two others within a 15 nm radius means PAVED,
period. Grass, turf, graded dirt and any other *non-paved* surface is
considered unimproved ... as verified by FBO/flight school owners
whenever questioned by students/renters as they sign the aircraft rental
agreement. This applies to EVERYONE flying the aircraft - students,
licensed pilots, CFIs, examiners. That's not to say some don't land
elsewhere, but as with any "rule", there will always be some that think
it doesn't apply to them!