Mach tuck the speed of sound and control authority both increase. To prevent Mach stall from progressing, the pilot should keep the airspeed below the type's critical Mach number by reducing throttle, extending speed brakes, and if possible, extending the landing gear. A number of design techniques are used to counter the effects of Mach tuck. On both conventional tailplane and canard foreplane configurations, the horizontal stabiliser may be made large and powerful enough to correct the large trim changes associated with Mach tuck. In place of the conventional elevator control surface, the whole stabiliser may be made moveable or "all-flying", sometimes
Mach (kernel) as well. Mach 2.5 was also selected for the NeXTSTEP system and a number of commercial multiprocessor vendors. Mach 3 led to a number of efforts to port other operating systems parts for the microkernel, including IBM's Workplace OS and several efforts by Apple to build a cross-platform version of the classic Mac OS. Mach was originally intended to be a replacement for classical monolithic UNIX, and for this reason contained many UNIX-like ideas. For instance, Mach used a permissioning and security system patterned on UNIX's file system. Since the kernel was privileged (running in "kernel-space") over other OS servers