46-06-04 CONVAIR: (Was Service Note 3 of AD-2-571-2.) Applies Only to BT-13 Series Airplanes Equipped With a Propeller Spinner.
Inspect the propeller spinner attaching lugs after each 25 hours of operation for cracks or signs of impending failure. If cracks are found, the lugs should be reinforced or the spinner should be removed entirely.