A drain (or drains) must be provided to allow safe drainage of the oil system. Each drain must—
(b)
Have drain valves, or other closures, employing manual or automatic shut-off means for positive locking in the closed position; and
(c)
Be located or protected to prevent inadvertent operation.
Code of Federal Regulations
[Amdt. 23-29, 49 FR 6847, Feb. 23, 1984, as amended by Amdt. 23-43, 58 FR 18973, Apr. 9, 1993]