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paulyg123

APU Question - Starting it up.

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On a cold dark cockpit, (default cold dark set up), I first switch the Bus Transfer to auto. Then I hit the APU switch to ON. Nothing happens for 3 minutes, the EGT needle is at "0". I then hit the START APU switch again and I finally get the EGT needle to 4 then I flick down the two APU Gen switches and I have APU power and all is OK.Is 3 minutes too long to wait? Do I need to hitthe APU switch twice? or am I dong something wrong. How long does it takefor the APU EGT needle to move upon startingthe APU?

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Why did you wait? Just cycle from OFF -> START then it springs to ON, then just wait for the APU to complete the start cycle and energize the buses when the APU is ready.

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The right procedure is to put to on for a second or 2, 3 seconds is better (the fadec will do a self test, door will be opened, dc fuel pump will start, apu shut off valve will open) then put to Start and release it. Only on Start the APU will be started.Bus transfer switch must be left on AUTO in all conditions, except for failures of automatic transfer.From cold and dark, Battery alone is sufficient to start the APU.

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