Customs exemption for aircraft parts limits basic duty to three percent ad valorem and waives additional duty. Exempts parts of aeroplanes, helicopters and simulators of aircraft falling in the First Schedule and required for manufacture or servicing from so much of the basic customs duty as exceeds 3 per cent ad valorem and from the whole of the additional duty leviable under section 3, excluding rubber tyres and tubes; 'parts' expressly includes engines, engine parts, wireless apparatus, washers, screws, bearings and other First Schedule items.