TM 1-1510-218-10 5-10 20 minute  time  groupings.    It  is  suggested  the  cycle rate  should  not  exceed  10  cycles  equally  spaced  in 1 hour.    This  rate  is  to  keep  the  power  pack  motor operations within an intermittent duty class. b.   Brake   Deice   Limitations.      The   following limitations apply to the brake deice system. (1)  The   brake   deice   system   shall   not   be operated at ambient temperatures above 15 °C. (2)  The   brake   deice   system   shall   not   be operated longer than 10 minutes, one timer cycle, with the   landing   gear   retracted.      If   operation   does   not automatically terminate approximately 10 minutes after gear retraction, turn BRAKE DEICE switch off. (3)  Maintain     85%     N₁     or     higher     during simultaneous operation of the brake deice and surface deice    systems.        If    adequate    pneumatic    pressure cannot  be  provided  for  simultaneous  operation  of  the brake  deice  and  surface  deice  systems,  turn  BRAKE DEICE switch off. (4)  BRAKE DEICE switch shall be turned off during single engine operation, in order to maintain an adequate supply of systems pneumatic bleed air. 5-13.  PNEUMATIC SURFACE DEICE BOOTS LIMITATIONS. The pneumatic surface deice system shall not be operated    when    ambient    temperatures    are    below -40 C.  Permanent   damage  to   the   deice   boots   can occur. Section III.  POWER LIMITS 5-14.  ENGINE LIMITATIONS. Operation    of    the    engines    is    monitored    by instruments,  with  the  operating  limits  marked  on  the face of each instrument. CAUTION Engine   operation   using   only   the   engine– driven  fuel  pump  without  boost  pump  fuel pressure is limited to 10 cumulative hours. All time in this category shall be entered on DA   Form   2408-13-1   for   the   attention   of maintenance personnel. Use  of  aviation  gasoline  is  time  limited  to 150  hours  of  operation  during  any  Time– Between–Overhaul (TBO) period.  It may be used    in    any    quantity    with    primary    or alternate fuel. NOTE Aviation gasoline (AVGAS) contains a form of  lead  that  has  an  accumulative  adverse effect on gas turbine  engines.    The  lowest octane AVGAS available (less lead content) should be used.  If any AVGAS is used the total operating time must be entered on DA Form 2408-13-1. 5-15.  OVERTEMPERATURE AND OVERSPEED LIMITATIONS. a.   Whenever  limiting  temperatures,  listed  in  the Engine Operating Limitations, Table 5-1, are exceeded and   cannot   be   controlled   by   retarding   the   power levers,   shutdown   the   engine   and   land   as   soon   as possible. b.  During engine starting, the temperatures and time  limits,  listed  in  the  Engine  Operating  Limitations, Table 5–1, must be observed.  When these limits are exceeded,  the  incident  will  be  entered  as  an  engine discrepancy in the appropriate maintenance forms.  It is   particularly   important   to   record   the   amount   and duration of overtemperature. c.   Whenever  the  prescribed  engine  overspeed limit  or  engine  RPM  operating  limit  is  exceeded,  the incident must be reported as an engine discrepancy in the  appropriate  maintenance  forms.    It  is  particularly important   to   record   the   maximum   percent   of   RPM registered   by   the   tachometer,   and   the   duration   of overspeed. d.  Continued   engine   operation   above   725   °C   C D  (770 °C  T ), TGT will reduce engine life.