84.—(1) Subject to paragraph (3), an aircraft registered in the United Kingdom must not fly in Required Navigation Performance airspace unless it is equipped with area navigation equipment which enables the aircraft to maintain the navigation performance capability notified, prescribed or otherwise designated for that airspace.
(2) The equipment required by paragraph (1) must—
(a)be approved by EASA or the CAA;
(b)be installed in a manner approved by the CAA;
(c)be maintained in a manner approved by the CAA; and
(d)while the aircraft is flying in that airspace, be operated in accordance with procedures approved by the CAA.
(3) An aircraft need not comply with the requirements of this article if—
(a)the appropriate air traffic control unit, having been made aware of the lack of compliance, authorises the flight; and
(b)the aircraft complies with any instructions the air traffic control unit may give.