Originally Posted by
zzuf
..... I note that FAR 23 directional static stability test require that the aircraft recover from a "skid", rudder free. There is no requirement to recover from a "slip" - very strange......
Strange indeed: FAR 23.177 talks about lateral stability with tendency to raise the lower wing in a sideslip and directional stability with tendency to recover from a wings level sideslip. AC23-8c has this clarifying note: "... the determination of "appropriate" wings level sideslip (previously referred to as skid) angles will depend on sound judgment ....".
So, playing instructor, I'll use the term skid per Rich Stowell. I try to keep my engineering life separate.