§ 61.51 Pilot logbooks.
[. . .]
(j)Aircraft requirements for logging flight time. For a person to log flight time, the time must be acquired in an aircraft that is identified as an aircraft under § 61.5(b), and is -
(1) An aircraft of U.S. registry with either a standard or special airworthiness certificate;
(2) An aircraft of foreign registry with an airworthiness certificate that is approved by the aviation authority of a foreign country that is a Member State to the Convention on International Civil Aviation Organization;
(3) A military aircraft under the direct operational control of the U.S. Armed Forces; or
(4) A public aircraft under the direct operational control of a Federal, State, county, or municipal law enforcement agency, if the flight time was acquired by the pilot while engaged on an official law enforcement flight for a Federal, State, County, or Municipal law enforcement agency.