Whenever required for the protection of public money and property, the Secretary of the Air Force may lend arms and their accouterments, and issue ammunition, to a department or independent agency of the United States, upon request of its head. Property lent or issued under this subsection may be delivered to an officer of the department or agency designated by the head thereof, and that officer shall account for the property to the Secretary of the Air Force. Property lent or issued under this subsection and not properly expended shall be returned when it is no longer needed.