30.—(1) This article applies to a flying machine or a glider for which a certificate of airworthiness issued by the Department or rendered valid under this Order is in force.
(2) An aircraft to which this article applies must be weighed, and the position of its centre of gravity determined, at such times and in such manner as the Department may require.
(3) When the aircraft is weighed its operator must prepare a mass schedule showing —
(a)either the basic mass, or such other mass as may be approved by the Department for that aircraft; and
(b)either the position of the centre of gravity at its basic mass or such other position of the centre of gravity as may be approved by the Department for that aircraft.
(4) Subject to article 90, the mass schedule must be preserved by the operator of the aircraft for at least six months after the next occasion on which the aircraft is weighed for the purposes of this article.
(5) In this article “basic mass” means the empty mass of the aircraft established in accordance with the type certification basis of the aircraft.