Slope testing
Shawn's statement is a bit too all-inclusive.
" Sloping ground testing is done on carefully calibrated concrete slopes (Pax River and Boscombe Down)."
Not Always so, and for good reasons.
The Not Always so: UH-60 and S-92 were done on dirt ( and since we only had dirt, the 76 must have been done that way-just can't recall doing them. Nick will remember.)
The 53K will be done on a new slope landing complex they built at the West Palm facility after I retired. Grass Slopes 3 to 15 degrees with a concrete sub-strata.
Reason why is not only replication of the real world, but that replication is also important from getting the mechanical stability part of the equation correct, or at least highly representative. More important for an articulated rotor, to be sure.
NAS PXT built a 9 degree 50' x 50' concrete slope for the SH-60B, but that was for doing the 12 ft/sec hard landings. At the time, that was all they had.
Thanks,
John