14 C.F.R. § 29.1021
Oil system drains
A drain (or drains) must be provided to allow safe drainage of the oil system. Each drain must—
(a) Be accessible; and
(b) Have manual or automatic means for positive locking in the closed position.
A drain (or drains) must be provided to allow safe drainage of the oil system. Each drain must—
(a) Be accessible; and
(b) Have manual or automatic means for positive locking in the closed position.