During the 8th flight of my
RV8 with 13B Turbo, I experienced an exhaust leak at the turbo exhaust flange.
I mistakenly used brass exhaust nuts which are twice as tall as regular
nuts. They work great on most engines. I should have know better, as the
temperature at the turbo outlet, under the insulation is much
higher.
The brass nuts softened and deformed into a flange face at the washer!
Once the tension was gone, the heat & vibration did the rest.
The exhaust gasket blew where the gap was widest, at the top.
The escaping heat burned thru the insulating jacket and the stick on
reflective aluminum. Then the fiberglass cowl charred, I smelled that!
I was close to my destination, and high, so I was able to pull off the
power, put down the nosed and get on the ground without incident.
I'm disassembling it now, looks like I need 4 high temperature lock nuts
and a TO-4 exhaust flange gasket. I should review and improve the insulation
over the turbine housing. Also I need to repair the charred area of the cowl,
which might be in the form of an aluminum access
hatch.