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 4.  Blocker Doors and Drag Links (Fig. 4)
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 A.  The inner wall of each translating sleeve holds a circumferential array of six trapezoid shaped blocker doors aligned flush with the inner wall of the translating sleeve. The blocker doors can be made of aluminum honeycomb, or they can be made of composite materials. Each blocker door is hinged near its wide, forward end to the translating sleeve so that its smaller, aft end can move radially inward approximately 90 degrees. A radial drag link connected at one end to the inner wall of the fan duct and at its other end to the center of each blocker door, pulls each blocker inward as the translating sleeve is moved rearward. The blocker doors thus make a radial wall to stop the fan flow.
 B.  The blocker door extends only to the rear of its hinge line and is contained in the cavity behind the front frame of the translating sleeve. In the reverse thrust position, the front frame of the translating sleeve is the aft entry ramp to the cascades.
 C.  You can get access to the blocker doors when the translating sleeve is moved rearward; you can get acces to the blocker door hinges from the aft side. You can get access to the drag links when you open the thrust reverser.
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SEE  A  DRAG LINK (1 EACH BLOCKER DOOR) 
BLOCKER DOOR (6 PER THRUST REVERSER HALF) SEE B 
CASCADE SEGEMENTS (EXPOSED) 
THRUST REVERSER DEPLOYED 
A 

SEE C DRAG LINK BLOCKER DOOR  SLEEVE HINGE FITTING  DRAG LINK 
B 
BLOCKER DOOR 
BLOCKER DOOR OPEN, LOOKING FORWARD C
Blocker Doors and Drag Links Figure 4 

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////////////////////////A / PW4000 SERIES /747-400 / ENGINES/MAINTENANCE MANUAL ////////////////////////
D.  The drag link connection at the duct inner wall is a pinned clevis joint. At the other end, the link goes through the center of the blocker door and is attached to a slotted clevis fitting on the back of the blocker door. A coil spring installed on a rod in the clevis fitting bears on the drag link attachment pin to preload the blocker door and linkage during cruise. The slot in the door clevis and the spring load supply the necessary overcentering action between the blocker door and drag link during operation. The hinge joints and drag link joints at the blocker door clamped spherical bearings.
 5.  Cascade Vane Segments (Fig. 5)
_____________________
 A.  Each reverser half contains nine cast magnesium cascade vane segments of
 approximately 20" x 14" x 2" (50.8 cm x 35.6 cm x 5.1 cm) in size. Each
 segment contains no more than 19 flow turning vanes (cascades) of
 different arrangements to flow the reverser fan exhaust into the desired
 external flow pattern. Each cascade vane segment can be individually
 removed for replacement or for access into the inner side of the duct.

 B.  The cascade vane segments are covered by the translating sleeves when the thrust reverser is stowed. During thrust reverser operation, the translating sleeves move to the rear, and shows the cascade vanes. The fan bypass air is blocked by the blocker doors, and sent through the cascade vanes to supply reverse thrust.

RADIAL SECTION EXAMPLE

1 CASCADE VANE SEGMENT POSITIONS 1 THROUGH 18 ARE ON THE ENGINES 1 AND 2; POSITIONS 19 THROUGH 36 ARE ON THE ENGINES 3 AND 4.
Positions of the Cascade Vane Segments Figure 5
E00067
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C.  The cascades vanes are arranged to flow air away from the aircraft structure or engine air inlet during thrust reverser operation. The cascades arrangement is different for the right and left halves, on the right and left engines. When the cascade vanes are replaced, it is important to make sure that the correct arrangement for correct exhaust flow pattern is installed.
　
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