Target or Clamshell Reverser Cascade Reverser Figure 15-19.  Thrust reversers. On most installations, reverse thrust is obtained with the  thrust lever at idle by pulling up the reverse lever to a detent.  Doing so positions the reversing mechanisms for operation  but leaves the engine at idle rpm. Further upward and  backward movement of the reverse lever increases engine  power. Reverse is cancelled by closing the reverse lever  to the idle reverse position, then dropping it fully back to  the forward idle position. This last movement operates the  reverser back to the forward thrust position. reversers are simple clamshell doors that swivel from the  stowed position at the engine tailpipe to block all of the  outflow and redirect some component of the thrust forward. Cascade reversers are more complex. They are normally  found on turbofan engines and are often designed to reverse  only the fan air portion. Blocking doors in the shroud  obstructs forward fan thrust and redirects it through cascade  vanes for some reverse component. Cascades are generally  less effective than target reversers, particularly those that  reverse only fan air, because they do not affect the engine  core, which continues to produce forward thrust. Reverse thrust is much more effective at high airplane speed  than at low airplane speeds for two reasons: the net amount of  15-16