being conducted under JBD panels. The panel supports attache to the JBD operating linkage arm assembly, with a quick release pin and fit into an indentation in the depressed deck area (JBD pit) at the forward end. The panel supports are used to lock panels in the raised position for maintenance purposes or emergencies. A panel support is provided for each set of operating gear, three supports for Mk 7 Mod 0/2 and two for Mk7 Mod 1 JBDs. The emergency lowering device connects to a tow tractor on one end and fits against the operating linkage arm assembly at the other end. This allows the tractor to push   the   operating   linkage   “over-center”.   With   the emergency bypass valves open, the weight of the panels will then force fluid from the raise end of the hydraulic cylinders through the emergency bypass valve permitting the panels to slowly lower. Preparation for Use When  the  JBDs  are  put  in  operation  for  the  first time or after being idle, use the following procedures: 1. Perform the preoperational inspection accord- ing to the applicable maintenance requirement card (MRC). 2. Ensure that personnel, aircraft, and flight deck equipment  are  clear  of  the  panel  area  before attempting to raise the JBDs. CAUTION Damage by excessive heat can result from jet   engine   exhaust   if   cooling   water   is   not flowing at the correct pressure. 3. Check  to  ensure  salt  water  supplied  from  the ship's    fire    main    is    flowing    through    the water-cooled panels. 4. Functionally    test    the    JBD    hydraulic    and electrical   system   for   proper   operation   and leaks. EMERGENCY OPERATION PROCEDURES In the event of an emergency or a malfunction, the procedures discussed in the following paragraphs must be  followed.  The  emergency  lowering  of  a  JBD  will require a minimum of eight personnel:   Topside Safety Petty Officer (overall in charge)   Topside JBD phone talker   Below decks phone talker/Valve operator   Two  personnel  to  install  emergency  lowering device   Two  safety  observers  (stationed  at  the  port  and starboard sides of the JBD panels)   Tractor driver Electrical Control Failure Should   the   chestpack,   deckedge,   and   auxiliary control panels become affected by an electrical power failure and the hydraulic system is functional, proceed as follows: 1. Station a crewperson to act as a valve operator at the stack valves. The valve operator shall be equipped with a sound-powered phone set. The chestpack   or   JBD   deckedge   operator   shall remain    at    his    or    her    station    and    relay instructions  to  the  valve  operator.  The  JBD deckedge or auxiliary panel operator shall also monitor the pressure gauges. 2. The  valve  operator,  when  instructed  by  the chestpack   or   JBD   deckedge   operator,   shall raise  or  lower  the  JBD  panels  by  the  manual push pins of the A and B solenoids of the stack valves. The B solenoid controls the raising of the  panels,  and  the  A  solenoid  controls  the lowering. Hydraulic Control Failure Should  the  JBD  hydraulic  system  fail  with  the JBDs    in    the    FULL-UP    position,    the    following procedures must be used to lower the panels: 1. Establish  sound-powered  phone  communica- tion   between   the   valve   operator   and   the chestpack or deckedge operator. WARNING Ensure all tag-out procedures are according to current shipboard instructions. 2. Close the main supply valve and attach a safety tag. 3. Open the applicable emergency bypass valves one-quarter turn or as necessary to control the lowering speed of the panel. 4. Using  the  panel  emergency-lowering  device, place  the  fitted  end  against  the  panel  linkage 5-12