snubber  holds  the  hook  down  and  prevents  it  from bouncing when it strikes the carrier deck. CATAPULT EQUIPMENT Carrier aircraft have built-in equipment for catapulting  off  the  aircraft  carrier.  Older  aircraft  had hooks on the airframe that attached to the cable bridle. The  bridle  hooks  the  aircraft  to  the  ship's  catapult. Newer  aircraft  have  a  launch  bar  built  into  the  nose landing gear assembly. See figure 4-16. The holdback assembly allows the aircraft to be secured to the carrier deck   for   full-power   turnup   of   the   engine   prior   to takeoff. For nose gear equipment, a track attaches to the deck to guide the nosewheel into position. The track has provisions  for  attaching  the  nose  gear  to  the  catapult shuttle and for holdback. NOTE:   The holdback tension bar separates when the catapult is fired, allowing the aircraft to be launched with the engine at full power. Q4-9. In  fuselage  construction,  what  are  the  three classes of monocoque design? Q4-10. Points  on  the  fuselage  are  located  by  what method? Q4-11. In  an  aircraft,  what  are  the  main  structural members of the wing? Q4-12. What does the term “wet wing” mean? Q4-13. The stabilizing surfaces of an aircraft consist of what two airfoils? Q4-14. What  are  the  three  groups  of  flight  control surfaces? Q4-15. What  is  the  purpose  of  speed  brakes  on  an aircraft? Q4-16. Most present-day Navy aircraft are equipped with what type of landing gear? ROTARY-WING AIRCRAFT LEARNING    OBJECTIVE: Identify    the construction features of the rotary-wing aircraft and recognize the fundamental differences between rotary-wing and fixed-wing aircraft. Within the past 20 years, helicopters have become a reality,   and   are   found   throughout   the   world.   They perform countless tasks suited to their unique capabilities. A    helicopter    has    one    or    more    power-driven horizontal    airscrews    (rotors)    to    develop    lift    and propulsion. If a single main rotor is used, it is necessary to employ a means to counteract torque. If more than one main rotor (or tandem) is used, torque is eliminated by turning each main rotor in opposite directions. The fundamental advantage the helicopter has over fixed-wing     aircraft     is     that     lift     and     control     are independent  of  forward  speed.  A  helicopter  can  fly forward,  backward,  or  sideways,  or  it  can  remain  in stationary flight (hover) above the ground. No runway is  required  for  a  helicopter  to  take  off  or  land.  For example, the roof of an office building is an adequate landing area. The helicopter is considered a safe aircraft because the takeoff and landing speed is zero, and it has autorotational  capabilities. This  allows  a  controlled descent with rotors turning   in case of engine failure in flight. FUSELAGE Like   the   fuselage   of   a   fixed-wing   aircraft,   the helicopter fuselage may be welded truss or some form of monocoque construction. Many Navy helicopters are of the monocoque design. 4-13 ANf0415 Figure 4-15.—Arresting gear installation.