Several of the local RV builders, including myself intend to make a joint

purchase

of an aircraft double flaring tool. Split between half a dozen builders,

this is

cheap insurance.
 The DOT mandates that ALL brake lines on your car be double flared. Why?

Because

it's a "critical" system. Personally, I feel that EVERY fuel and oil line

on my

aircraft is "critical". This is a situation that reminds me of the great

1980s Bell

Helmet advertisement, which asked:
"Got a $10 head?. Buy a $10 helmet!"

Charlie Kuss

Bill Freeman wrote:

While I agree whole heartedly with the premise of "safety", and also
I do not claim to be an expert on double flares, altho I have made them for my
brake lines on Fords which use wierd non-standard unobtainable fittings on the
proportioning valve.  It appears to me that double flaring is used to bring the
wall thickness of the flare up to a reasonable level and form a smooth well
shaped surface to seal against, both necessitated by the extreme thin walls
in steel brake line tube.   OTOH, relatively thick walled aluminum tube used
in aircraft fuel systems does not seem to need double flares (which are a pain
in the butt -big time, and frequently fail to work mandating cutting and
rework).
I also question whether the AN series of fittings were intended to be used with
double flares and whether double flares might actually cause problems.
As far as I know, AN fittings are generally reliable and safe, and I can see
no reason to got to the trouble, expense and doubtful effectiveness of
double flares for A/C fuel systems

Bill

 
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