TM 1-1510-225-10 8A-12 CAUTION Never connect an external power source to the  aircraft  unless  a  battery  indicating  a charge of at least 20 volts is in the aircraft and  in  the  ON  position.     If   the   battery voltage  is  less  than  20  volts,  the  battery must   be   recharged,   or   replaced   with   a battery  indicating  at  least  20  volts  before connecting  external  power.    Use  only  an external  power  source  fitted  with  an  AN- type plug. The    battery    should    be    on    to    absorb transients present in some auxiliary power units. An  EXT  PWR  annunciator  alerts  the  crew  when an   external   power   plug   is   connected   to   the aircraft. NOTE If  the  battery  is  partially  discharged,  the BATTERY  CHG  annunciator  will  illuminate approximately   6   seconds   after   external power  is  on  line.    If  the  annunciator  does not  extinguish  within  5  minutes,  refer  to the  Battery  Chg  Annunciator  Illuminated procedure in Chapter 9. 1.  BATT switch – ON. 2.  GPU – Connect. 3.  EXTERNAL POWER advisory light – ON. 4.  Exterior LIGHTS switches – As required. 5.  Propeller area – Clear. 6.  Engine – Start. CAUTION If ignition does not occur within 10 seconds   after   moving   the   condition lever to LOW IDLE, initiate Engine Clearing procedure,  Paragraph  8A-25.    If  for  any reason the starting attempt is discontinued, the  entire  starting  sequence must be repeated after allowing the engine to   come   to   a   complete   stop   (1-minute minimum). a.  IGNITION  AND  ENGINE  START  switch  – ON.        IGN    ON    light    illuminated    and associated FUEL PRESS light extinguished. b.  CONDITION lever (after N₁ stabilizes at or above 12% for 5 seconds) – LOW IDLE. CAUTION Monitor ITT to avoid a hot start.  If there is a rapid rise in ITT, be prepared to abort the start  before  limits  are  exceeded.    During engine start, the maximum allowable ITT is 1000  °C  for  5  seconds.    If  this  limit  is exceeded,    use    Abort    Start    procedure, Paragraph   8A-24,   and   discontinue   start. Record the peak temperature and duration on DA Form 2408-13-1. c.   ITT   and   N₁   –   Monitor.      ITT   1000   °C maximum.  N₁ minimum 58%. d.  Oil pressure – Check (60 psi minimum). e.  IGNITION  AND  ENGINE  START  switch  – OFF after 50% N₁. 7.  Engine and systems instruments – Check. 8.  CONDITION lever – HIGH IDLE.  Monitor ITT as the condition lever is advanced. 9.  GPU – Disconnect. CAUTION Do   not   turn   on   generators   with   GPU connected. 10.  GEN    switch    (after    GPU    disconnected)    – RESET then ON. NOTE After  starting  the  first  engine  with  a  GPU, the   second   engine   is   normally   started using  a  battery  start.    If  a  GPU  start  is required  or  desired  for  the  second  engine start, follow the Second Engine Start (GPU Start) procedure, Paragraph 8A-27. Otherwise,   follow   Second   Engine   Start (Battery Start) procedure, Paragraph 8A-23. 11.  BATTERY CHG annunciator – Monitor. * 8A-27.  SECOND ENGINE START (GPU START). 1.  Propeller area – Clear. 2.  Engine – Start. a.  IGNITION  AND  ENGINE  START  switch  – ON.      IGN   ON   light   illuminated   and   the associated FUEL PRESS light extinguished.