From the Boeing 757/767 FCTM:
"The airplane exhibits excellent stability throughout the high altitude/ high Mach range. Mach buffet is not normally encountered at high Mach cruise.The airplane does not have a Mach tuck tendency.
With Mach trim inoperative, the airplane exhibits a neutral trim change when accelerating to speeds approaching MMO. When the Mach trim system is operative, the airplane exhibits a nose up trim change that increases steadily as the airplane accelerates to speeds approaching MMO. The stabilizer motion associated with this nose up trim change is imperceptible without careful scrutiny of the aisle stand indicator.
As speed nears MMO, drag increases rapidly. At high weights, sufficient thrust may not be available to accelerate to MMO in level flight at normal cruising altitudes."
Last edited by 763 jock; 15th Jun 2007 at 16:28.