Posted for Mike Wills <willsm@spawar.navy.mil>:

Tommy,

  The accident aircraft was a Velocity with a Powersport engine. Everything was high quality - no mickey mouse stuff. Exhaust system all 321 stainless. Dont remember exactly how many hours of operation but I think it happened at somewhere around 20 hours (including ground runs). The failure occured at the "Y" where a gap of maybe 1/4" opened up and also at the header flange. Theory is that the hot exhaust in the cowl caused a vapor lock. Aircraft tried to make a field and came up a little short causing a lot of damage. I think there were no injuries.

  I say that it was due in part because the header was wrapped with fiberglass header wrap tape. This may have contributed by trapping the heat in the pipe. Also made the exhaust system difficult to inspect for damage which may have been (probably was) going on for some time before the accident.

  Lot of conjecture, but I put slip couplings in my primaries to allow for differential expansion. Tracy uses the flex couplings. I'd strongly recommend a change to your system.

  Pictures and more info on the Powersport website.  http://www.powersportaviation.com/n214kw_incident_report.htm

Mike Wills