Thrust reversal - Clamshell door system

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Thrust reversal - PRINCIPLES OF OPERATION

Clamshell door system

Fig. 15-3 A typical thrust reverser system using clamshell doors.

9. The clamshell door system is a pneumatically operated system, as shown in detail in fig. 15-3. Normal engine operation is not affected by the system,  because  the  ducts  through  which  the exhaust gases are deflected remain closed by the doors until reverse thrust is selected by the pilot. 10. On the selection of reverse thrust, the doors rotate to uncover the ducts and close the normal gas stream exit. Cascade vanes then direct the gas stream in a forward direction so that the jet thrust opposes the aircraft motion.
11. The clamshell doors are operated by pneumatic rams through levers that give the maximum load to the doors in the forward thrust position; this ensures effective sealing at the door edges, so preventing gas  leakage.  The  door  bearings  and  operating linkage operate without lubrication at temperatures of up to 600 deg. C.