Dutch roll inducement and Mach Tuck
Does the 727 wing dihedral additional to sweep have a combinatorial causal effect? Reduced aerodynamic damping at high altitude might also be influential I reckon.
What could cause a Dutch Roll apart from YD failure..Turbulence?
"Handling the Big Jets, D.P.Davis" has an exhaustive and best technical explaination of how to deal with Dutch Roll.It also explains series dampers and Roll dampers.
Does 727 suffer from significant Mach Tuck.Is there a Mach Trim indicator on the 727?