The most recent Sport Aviation has an article on make up hoses. The
author states that 'you must use 37 degree fittings' and as is typical,
gives no reason why. Is there a reason for this that involves the laws
of nature, vs the "laws of the FAA"?


Veedube...

No, the law of common sense. The fittings for hoses and tubing are 37 degrees,
whereas those made for air conditioning are another value and those for
plumbing are....and those for autos are....another.

If you want leak-free fittings, you have to use parts which mate with the
correct and matching angles.

Neal