schinus

My Feedback: (2)

I have a DA 85 with MTW can mounted in a 32% Aeroworks Extra 260. By the fifth flight of both plane and engine the weld of the exhaust header split right at the flange where it bolts to the cylinder head. Talked to Jeff at DA and he suggested weld may have been faulty as there hasn't been a slew of that problem being reported. I bought a new MTW header pipe and the same exact thing happend after 4 more flights. This time I looked at it under magnification and it was apparent, to me anyway, that the weld pulled apart from the flange. I could not see any evidence of weld penetration into the flange. I have had comments from IMAC guys I fly with that my engine was one of the smoother 85s they've heard. On the second header I made absolutely sure there was no stress on the header from misalignment etc. before I tightened the flange bolts. Could it be something I am missing in the set-up? I can't afford to replace this part every 4/5 flights @ $70 + a pop!!!. Just heard from Jeff that they will replace it free this time but if it goes a 3rd time it must be a set-up problem. Any suggestions from you guys would be GREATLY appreciated.
Thanks, Tom

Tony Hallo

A photo of the failure would be nice, I'm guessing fatigue caused by high frequency vibration. My friend has the same setup in a Aeroworks 260, I would brace the J bent as it sticks out quite a bit. An example of what I'm talking about, I your case I would get close to the flex joint.

murray44

I fly with a modeler who had the same thing happen to his header which was mounted on a DA 85. There appeared to be no weld penetration into the flange which bolts to the engine. The weld filet looked very nice, but did not hold onto the flange. Actually we believe it was assembled using brazing rods which did not hold to the bolt flange. We repaired it ourselves using silver solder rods obtained from AI and so far it's holding up under the vibrations. Be sure to support the header somewhere around the connector.

schinus

My Feedback: (2)

Tony....thanx for the input. In my set-up there is flxible tubing on the engine side of where your picture shows your brace attached to the FW. Then there is the teflon coupling from the flex to the can inlet....in the same spot as your picture shows the teflon. I would've thought the flex area would absorb much of the vibration but maybe where it is located it just isolates the fuselage. I like your brace application and will look at adapting the same. DA told me they haven't seen an influx of this issue but as I have posts on other sites I am getting reports that may indicate otherwise.

Murray44....Glad your friend noticed the lack of weld penetration like my failure. My fillet looks perfect but that was it. I knew I wasn't the only one!! DA said I could use silver solder like you did but I have no familiarity with brazing or welding of any kind. Fortunately I have friends who can assist. DA wanted this failed unit back anyway. Glad to hear it is holding up after repairs I'll probably end up doing the same. Thanx for your help.
Tom