kontiki
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- May 30, 2011
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Kontiki
All,
I was under my airplane working (Grumman Tiger) and just happened to aim my light up the exhaust to have a curiosity look.
Ref. the photos, What you are looking at is the muffler inside the exhaust system. I called PFS and their after-hours support was excellent. I have a new muffler coming. This system was installed about 500 hours ago. I've flown the airplane for maybe the last 5.
Per the PFS rep, I probably could temporarily operate without the muffler, but that is not the certified configuration. He said I would lose about 1.5 HP. Getting it out wasn't difficult.
Sometime in 2010 they increased the thickness of the perforated liner from .022 to .048. He said deformation is usually associated with some type of over-temp event.
I haven't asked the previous owner about it, it's moot for me at this point.
Apparently there is a basalt fiber winding around a perforated steel tube. The fiber compacts down and gradually disintegrates over time. The rep didn't think the perforated steel liner should distort like this when operated normally. He also suggested operators take a look up there on preflight.
1 - There should be zero deformation.
2 - If nothing is visible behind the perforations, the fiber is used up and the liner needs to be replaced.
No one could miss this on an inspection if they accomplished the detailed instructions in the STC ICAW report as they are written. PowerFlow lets you download this portion of the package from their site. I recommend every owner ensure their AMT has a copy of the Instructions for Continued Airworthiness (ICAW) in the PowerFlow Systems STC package for that mod when doing an Annual on their airplane.
I was under my airplane working (Grumman Tiger) and just happened to aim my light up the exhaust to have a curiosity look.
Ref. the photos, What you are looking at is the muffler inside the exhaust system. I called PFS and their after-hours support was excellent. I have a new muffler coming. This system was installed about 500 hours ago. I've flown the airplane for maybe the last 5.
Per the PFS rep, I probably could temporarily operate without the muffler, but that is not the certified configuration. He said I would lose about 1.5 HP. Getting it out wasn't difficult.
Sometime in 2010 they increased the thickness of the perforated liner from .022 to .048. He said deformation is usually associated with some type of over-temp event.
I haven't asked the previous owner about it, it's moot for me at this point.
Apparently there is a basalt fiber winding around a perforated steel tube. The fiber compacts down and gradually disintegrates over time. The rep didn't think the perforated steel liner should distort like this when operated normally. He also suggested operators take a look up there on preflight.
1 - There should be zero deformation.
2 - If nothing is visible behind the perforations, the fiber is used up and the liner needs to be replaced.
No one could miss this on an inspection if they accomplished the detailed instructions in the STC ICAW report as they are written. PowerFlow lets you download this portion of the package from their site. I recommend every owner ensure their AMT has a copy of the Instructions for Continued Airworthiness (ICAW) in the PowerFlow Systems STC package for that mod when doing an Annual on their airplane.
