..."IF the single flare is done correctly" is the key statement.
Not to mention that in AC 43-13, double flare is recommended for "soft aluminum tubing 3/8" or less." Soft aluminum tubing includes 3003 and 5052.
You will find those references in the hydraulic tubing section of the AC.
The single flare has worked fine on many aircraft over the years...as long as it is done correctly.
The double flare is less likely to form cracks, forms a more robust flare, and the tool makes it very easy to create consistent flares.
There isn't a "wrong" choice, I just chose the double flare...either way, make sure you are creating the flare correctly. If you don't, it WILL leak, and typically, tightening the B nut further will actually make the leak worse...
Aerospace Engineer '88
Dues+ Paid 2020,...Thanks DR+