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The clamshell door system is a pneumatically operated system. When the pilot activates the reverse thrust system, the clamshell doors rotate to uncover the ducts and close the inner fan airflow. Therefore, when the direction of flow is changed, the thrust created by the fans of the engine will be less. However, this will not affect normal engine operation. The thrust created by the primary airflow will be same. Since 80 % of the full thrust is generated by the fan airflow, we should only affect that airflow.
2
The bucket target system is a hydraulically operated system that uses bucket type doors to reverse the hot gas stream( exhaust airflow). The thrust reverse doors are operated by a conventional hydraulic powered pushrod system. The actuator incorporates a mechanical lock in the extended position. In the forward thrust mode the bucket doors form the convergent-divergent final nozzle for the engine.
3
The cold stream reverse system is controlled by an air motor. The output is converted into mechanical movement by a series of flexible drives, gearboxes and screw jacks. During normal operation, the reverse thrust cascade vanes are covered by the blocker doors. On selection of reverse thrust, the actuation system folds the blocker doors to blank off the cold stream final nozzle, thus diverting the airflow through the cascade vanes.
In passenger aircraft, reverse thrust is only used when on the ground. There are typically interlocks in the system that prevent the thrust reversers from deploying if the aircraft does not sense that it is on the ground. Once the aircraft touches down, the pilot will deploy the reverse thrust. But in military aircraft, thrust reversers can be used in the air. As it will enable them to perform very steep descents.
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