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Replacement Interval - Exhaust Springs

in 912 / 914 Technical Questions 10 years ago
Is there a recommended replacement interval for exhaust springs on the 912/914 series aircraft engines? I checked the line maintenance manual but couldn't find this information.

  • Re: Replacement Interval - Exhaust Springs

    by » 10 years ago

    Hi Ian,

    There is no interval. It is on condition. Check the spring loops each 100 hr/annual and look for wear on the spring hook and look at the exhaust loop. If you have bad vibrations your springs could wear in 300 hrs and if you have a smooth running engine and take care of it they may last 1000 hrs.
    Just keep an eye on them and if they are wearing replace them. Make sure they are safety wired and make sure you have high temp silicone on the outside of the spring coil. Make the silicone bead wide enough and thick enough to give it a little body and strength. This helps keep down the harmonic vibration wear. Do not fill the springs with silicone as these are heat treated springs and filling them full of silicone keeps the heat in the spring and can lead to premature failure. Whereas if it is left open in the center and the silicone is on the outside it has some air circulation and can dump the heat.

    There are a few that fill the springs and does not safety wire the springs. They put a dab of silicone on the spring hook. This doesn't keep the spring secure if it breaks and the silicone hides the spring and loop so it can not be inspected. If the springs are not safety wired they can break and then fall out on the taxiway, runway or over a populated area.

    Here is an old picture that may help.




    20150219_173748.jpg (You do not have access to download this file.)
    Exhaustspring1-Copy.jpg (You do not have access to download this file.)

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell

      
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