Maintenance of stock exhaust

[Tosh]

Hi,

I am in the market looking for DA40 and found a nice 2005 model with the stock exhaust at local airport. My IA who is maintaining the plane told me she is in a good shape, but one snag is serial number of Hartzell prop which PowerFlow exhaust doesn't support. If I will want to install PF, I need to replace the prop too.

Actually, I don't have plan to get PF installed in near future, but my concern is what the IA said about the stock exhaust. He said the DA40's stock exhaust is poorly designed and prone to maintenance, and if it failed (I guess it means crack), it has to be shipped to Diamond factory in Canada for repair.

If this is the case, sooner or later I will want to replace the faulty exhaust with PF. This makes me more concerned in long run and I am wondering if I should find the other airplane which already has PF exhaust installed, or at least with Hartzell prop with higher S/N which meets PF's requirements.

I searched this forum and looks like quite a few people had some problems with the stock exhaust, but couldn't find the potential repair is a show-stopper issue involving Diamond factory.

Any thoughts?

-Tosh

[Tim H]

My IA uses www.dawleyaviation.com and is very pleased with their work.

Tim

[Steve]

Initially, the stock exhaust was prone to cracks in the tubing at the exhaust flange. A Service Bulletin came out in 2003 (I think) to install a muffler brace which seemed to resolve the issue. My stock exhaust was replaced under warranty in 2003 due to two cracked exhaust risers, and since the brace was installed after that, no issues.

If a repair is required, any good exhaust shop can do it.

Steve

[Tosh]

Thanks Tim and Steve. I will check the muffler SB.

[DA40 pilot]

I got almost 2000 hours out of my exhaust before it had a crack in it and had to be replaced. The added 4-5 knots is not worth the $12k to upgrade to the new prop and Powerflow in my opinion. The Hartzell metal prop is bulletproof.

[Rich]

I got almost 2000 hours out of my exhaust before it had a crack in it and had to be replaced. The added 4-5 knots is not worth the $12k to upgrade to the new prop and Powerflow in my opinion. The Hartzell metal prop is bulletproof.

No propeller is "bulletproof". That's a bit of hyperbole. I wrecked an aluminum fixed-pitch prop by picking up large gravel from a tie-down spot. And metal blades are subject to fatigue and have been known to depart the aircraft in flight, very often with fatal consequences. Note, for another example, that the PF upgrade could not be done with the older Hartzell prop because the Hartzell folks wouldn't approve it. They needed to come up with a different prop to support the added power.

More important than the few knots of additional airspeed is the substantially improved climb rate with the Powerflow. It's a harder choice economically when you have to replace the prop along with it. Easier when, like me, a prop change is not required.

[N503TS DA42]

I had my DA40 exhaust replaced by Acorn Welding.
http://www.acornwelding.com/pdf/Diamond ... 20Star.pdf
They sent me what looks like to have been a brand new exhaust but I think officially they need to call it an overhaul of your existing exhaust. The build quality was far superior to the stock model. I think it was just over $2k including shipping.

[BlackMammoth]

Note, for another example, that the PF upgrade could not be done with the older Hartzell prop because the Hartzell folks wouldn't approve it. They needed to come up with a different prop to support the added power.

It wasn't actually about power, it was about vibration. The original Hartzell prop did not pass the FAA vibration testing when used with the Powerflow system. The later "Powerflow approved" prop has slightly thicker tips and this added mass at the tips lowered the vibration to acceptable levels. - Source: Spoke with engineer who ran the DA40 Powerflow Top Prop program at Hartzell before I bought my Powerflow / new prop.