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-   -   Maintenance Issue / Tailpipe hanger strap (http://www.powerflowsystems.com/forum/showthread.php?t=72)

siriusjim 01-21-2009 07:37 PM

Maintenance Issue / Tailpipe hanger strap
 
There have been isolated (3 out of 370+ installations) reports of the tailpipe support hanger strap cracking or tearing on Tuned Exhaust Systems installed on the DA40.

The cause for this problem has been identified as too much tension being put on the hanger material by using a hanger strap that is too short in length.

The tailpipe should be positioned evenly between the bottom of the firewall and the lower cowling. Some of the failed straps had been trimmed shorter than the original strap provided by PFS.

Fortunately, the fix is extremely simple: the strap in question is actually fiber-reinforced neoprene baffle material as found in every maintenance shop. It is not a unique or PFS specific part.

Simply have your shop replace the torn strap with one made from this material (approximately 3.5" by 1.75") and you're "Good to Go"!

meyerflyr 08-12-2009 02:14 PM

Re: Maintenance Issue / Tailpipe hanger strap
 
I oversee the maintenance (Quality Control Manager) of a fleet of 20 DA-40 ACFT, at a flight training center. We started flight operations in FEB of this year, and in six months we have now had 14 of the exhaust straps broken at the flange attaching point. Other A&P/IAs agree that when the neoprene gets warm and experiences a sudden jolt (a not so soft landing) that this is what is causing the problem. These ACFT are new and so wear and tear can be ruled out. Even some of the ones that we have replaced have broken. (We manufactured them with the material and dimensions as suggested before, in other words just like the ones from the factory).
Any ideas for a fix?

dtilman 10-23-2010 02:33 PM

Re: Maintenance Issue / Tailpipe hanger strap
 
Further investigation and testing into the higher incidence of exhaust straps breaking has revealed the following:

1) Diamond factory installed Power Flow Exhausts were using a silicone material supplied by Diamond that testing has now shown to not have the same longevity as Power Flow supplied fiberglass reinforced neoprene rubber (sent out to aftermarket customers.) Specifically, the silicone material would stretch but then not completely return to its original position, whereas the neoprene rubber material did not stretch as much and returned to its original position. Over time, this stretching would weaken the silicone strap and it would rub against the edge of the washer. At some point, the strap would fail along this edge.

2) Diamond and Power Flow have developed a replacement washer that has a beveled and curled edge to prevent a sharp edge against the strap. This kit is available from Diamond, and is being included in all new production and aftermarket kits as of September 2010.

3) A possible contributing factor is the spring tension at the muffler ball joint. Some customers have reported that the springs were compressed more than Power Flow's specifications (.435-.475) creating a higher tension on the muffler joint. Maintainers should verify that the spring height is set per Power Flow latest set of installation instructions.

The most current set of instructions can always be found at:
http://www.powerflowsystems.com/imag...S-15250-00.pdf


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