17.—(1) Every flying machine and glider in respect of which a certificate of airworthiness issued or rendered valid under this Order is in force shall be weighed, and the position of its centre of gravity determined, at such times and in such manner as the Authority may require or approve in the case of that aircraft.
(2) Upon the aircraft being weighed as aforesaid the operator of the aircraft shall prepare a weight schedule showing:
(a)either the basic weight of the aircraft, that is to say, the weight of the aircraft empty together with the weight of unusable fuel and unusable oil in the aircraft and of such items of equipment as are indicated in the weight schedule, or such other weight as may be approved by the Authority in the case of that aircraft; and
(b)either the position of the centre of gravity of the aircraft when the aircraft contains only the items included in the basic weight or such other position of the centre of gravity as may be approved by the Authority in the case of that aircraft.
(3) Subject to the provisions of article 65 of this Order the weight schedule shall be preserved by the operator of the aircraft until the expiration of a period of 6 months following the next occasion on which the aircraft is weighed for the purposes of this article.