TM 1-1500-204-23-4 4 Friction stop and jump test.  The altimeter  shall  be  tested  for  friction  in  both  ascending and descending directions at the test points specified in table   4-8.      With   the   internal   vibrator   energized,   the pressure   to   the   static   port   of   the   altimeter   shall   be applied at the rates indicated for the test points in table 4-8.  The change in the indicating position of the pointer, due to apparent stopping and jumping as the counter is turning  or  at  any  other  place  around  the  dial,  shall  be recorded as friction and shall not exceed the tolerances specified  in  table  4-8,  column  C.    This  test  shall  be repeated  with  all  electrical  power  off.    The  stop  and jump  friction  for  the  test  as  specified  shall  not  exceed the tolerances in specified table 4-8, column D. 5 Static     friction     test.          At    the completion of the friction stop and jump test paragraph 4, and with all electrical power off, the altimeter shall be subjected to a constant rate of decreasing pressure not exceeding  3,000  feet  per  minute  until  the  pressure  is within  100  feet  of  the  tolerance  listed  in  table  4-9  for each   test   point.      At   this   time,   the   rate   of   pressure change  shall  be  gradually  decreased  until  the  desired test point is obtained.  The pressure shall then be held constant  while  two  readings  of  the  altimeter  are  taken, the  first  without  the  integral  vibrator  operating  and  the second   with   the   vibrator   operating.      The   difference between  the  two  readings  shall  be  recorded  as  static friction   and   shall   not   exceed   the   tolerances   listed   in table 4-9. 6 Case leak test.  The leakage of the     altimeter     case,     when     the     pressure     within     it corresponds   to   an   altitude   of   30,000   feet,   shall   not change the altimeter reading by more than the tolerance shown in table 4-7 during an interval of one minute. 7 Barometric  scale  error  test.    At constant atmospheric pressure, the barometric pressure scale shall be set at each of the pressures (falling within its range of adjustment) that are listed in table 4-10 and shall cause the pointer to indicate the equivalent altitude difference  shown  in  table  4-10  within  a  tolerance  of  25 feet. 8 Internal  lighting  test.    Red  and white   internal   lighting   shall   be   functionally   tested   in accordance with applicable maintenance manual. (c) Replacement criteria. After completion   of   tests,   a   tamper   seal   shall   cover   the baroset locking screw.  An inspection sticker with date of completed bench test shall be placed on the outside of the case.  Compute reinspection date from date on the inspection sticker. h.  Direct Reading Pressure Indicators.  Principles of    operation,    types,    and    testing    of    direct    reading pressure indicators are described in following paragraphs. (1) Principles of operation and types indicators.        Direct    reading    pressure    indicators    are connected   directly   to   pressure   source   by   tubing   or flexible  hose.    Typical  of  the  direct  reading  pressure indicators  are  the  fuel  pressure,  oil  pressure,  hydraulic pressure, manifold pressure, and vacuum pressure. (2)    Testing.        The    following    paragraphs describe tests and replacement criteria for direct reading pressure indicators. (a)   Pressure   pointer   oscillation   test. When  pressure  indicator  pointers  oscillate  excessively (more Table 4-8.  Friction Stop and Jump Error (Counter Drum Pointer) Column A Column B Column C Column D test point rate of ascent tolerance tolerance altitude or descent vibrator vibrator (feet) (feet per minute) operative (feet) inoperative (feet) 0 500 25 300 1,000 500 25 120 3,000 500 25 120 5,000 500 25 120 10,000 500 25 350 20,000 3,000 25 350 30,000 3,000 25 350 35,000 3,000 50 600 40,000 3,000 50 600 Change 1  4-19