TM  55-2835-209-23 Preventive  Maintenance  Checks  and  Services Interval Task Item 250 250 Hrs/ 500 1000 Item To Be No. Hrs 12 Mos Hrs Hrs Inspected AVUM AVIM Remarks 1 2 3 4 5 6 7 8 x Hot Section In- spection x Fuel Filter Element x Orifice  Fitting x Fuel Nozzle As- sembly x Igniter Plug Assembly x Magnetic  Drain Plug  Assembly x Lubricating Oil x Oil  Filter Element 3-14 4-11 4-17 4-19.1 5-11 6-2 6-2 6-12 Inspect hot section. Remove and replace fuel filter element. Inspect  orifice fitting. Inspect fuel nozzle assembly. Inspect igniter plug assembly. Inspect  magnetic drain  plug  assembly for  debris. Drain and refill. Remove  and  replace oil filter element. Section  VII  TROUBLESHOOTING 1-27  TROUBLESHOOTING  GENERAL Troubleshooting  (Fault  Isolation)  is performed  with  the  APU  installed  in  the aircraft. Refer to TM 55-1520-237-T. Change 1 1-21