Experiencing a bug with the altimeter. The altimeter will always fire when it goes below ~10000m. This only happens while on kerbin while my second stage is falling back to Kerbin. They are falling above water so i'm not sure if the terrain thing works above water? the altitude reads as -1 bellow 10,000. quickly had a look at the code and guess the problem lies on this line in KM_Altimeter: this.currentAlt = (double) this.currentAlt < 10000.0 ? (float) (double) this.get_vessel().heightFromTerrain : this.currentAlt; dont have any idea about KSP mods though i just had a peek at the decomplied dll seems very likely that it would be something to do with this though!