PRINCIPLES OF NAVAL ENGINEERING 



FRICTION BRAKE 



HANDWHEEL 



(WEATHER DECK) 



ANCHOR 

 CHAIN 



GEAR CASING 



MOTOR BRAKE- 



3.224X 

 Figure 21-11.— Vertical-shaft anchor windlass. 



time and without excessive effort on the part 

 of operating personnel, 



CARRIER CATAPULTS 



The efficiency of an aircraft carrier depends 

 upon the speed of its airplane launching opera- 

 tions. Therefore, a compact and efficient device 

 for getting all airplanes into the air within a short 

 time is needed. This requirement is met by the 

 modern carrier catapult. The catapult permits 

 controlled application of a predetermined amount 

 of power at any desired instant. Through the 

 controlled power of the catapult, the plane on the 

 catapult is safely accelerated from a standstill 

 to flying speed within the limited space available 

 on the flight deck of a carrier. 



The type of catapults used during World War 

 II and through the Korean incident were of the 

 pneumatic-hydraulic type. Catapults of this type 

 adequately met launching requirements, but the 

 gradual increase in the weight of newly designed 



aircraft and the attendant higher launching 

 speeds continually necessitated the develop- 

 ment of larger and heavier catapults. By 1950, 

 the size and weight of the pneumatic-hydraulic 

 type catapult had increased to a point where 

 any further increase would be impracticable. 

 British investigation of steam as the source 

 of power for catapults attracted the attention 

 of U. S. Navy officials; the Navy's powerful 

 steam catapult of today is the result of basic 

 British research.^ The present discussion deals 

 only with the steam catapult. 



The major components of a steam catapult 

 are shown schematically in figure 21-12. 



During the operational cycle of the steam 

 catapult, the plane is first spotted astride the 

 catapult slot slightly aft of the shuttle. The 

 airplane is coupled with the shuttle by means 

 of the bridle which slips over the shuttle hook 

 and over the hooks mounted on the underside 

 of the airplane frame. The airplane is anchored 

 to the deck by means of the holdback device 

 which is released at the moment of launch. 

 The grab, attached to the shuttle, pushes for- 

 ward after the bridle is attached so that the 

 shuttle puts tension on the bridle. 



When the airplane is ready to be launched, 

 with its engines running at full power, the 

 launching valves are opened and steam is ad- 

 mitted to the after side of each piston. The 

 resulting accelerating force combined with the 

 engine thrust causes a calibrated "breaking" 

 link in the holdback to part and the grab re- 

 leases the shuttle. The sliuttle and airplane are 

 free to be moved forward by the accelerating 

 force. 



At the end of the launching run, the plane 

 is airborne and the bridle is automatically 

 released from the hook. The brake stops the 

 piston-shuttle assembly. The grab, driven 

 by the retracting engine, now moves along the 

 track, hooks the shuttle, and returns it to the 

 launching or battery position. 



The principal component of the steam catapult 

 is a cylinder-piston assembly— two power cyl- 

 inders and two pistons per catapult. The 

 spear-tipped pistons, which in the launching 



For greater detail on the history and operation of 

 the steam catapult, see The Steam Catapult, NavAer 

 00-80T-69. 



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