This sounds like a case for rerouting the line so it just isn't in
such proximity to the exhaust pipe. For U.S. builders, firesleeve is
in effect required under 23.1183. While Part 23 doesn't technically
apply to homebuilts, there's a good chance an FAA inspector will
include something appearing on most all production aircraft within
his/her definition of airworthiness. Post-certification, a case can
be made that you're stuck with it in lieu of FAA notification (else
insurance is voided).
Although not its purpose, I suspect the firesleeve accomplishes a bit
of heat shielding. If the line is hardening and cracking now, might
removal of the firesleeve nullify the effect of swapping one with a
higher temp rating?
Regards,
Fred F., A063
Nigel Charles wrote:
>
> Message text written by INTERNET:MJKTuck@cs.com
> >I'm doing my 75 hour check and noticed that the oil return line was
> actually
> touching one of the exhaust stubs burning through the firesleeve. Further
> examination revealed a very localized area of hardening and surface
> cracking
> of the rubber oil return line.
>
> I know there was some word recently in the factory newsletter about hose
> marked 'Conti' (not the redline stuff which is prone to heat degradation)
> and
> that you can get some from the factory but often it is quicker for me to
> just
> get something like this from Aircraft Spruce. Can anyone recommend a
> particular type which is heat resistant and OK to use for 912UL oil return
> line use?
> <
>
> Two of us have gone for the silicone hose with the oil resistant inner
> liner. This is good for about 300C. It also curves without kinking. My
> inspector suggested that as it has such high temperature resistance there
> was no need for the firesleeve making inspection during servicing easier.
> It is available from most specialist automobile parts suppliers. It is not
> cheap (35 per metre in the UK although on that basis it is probably $35
> per metre in the USA).
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