This part of ISO 8267 specifies the interface requirements for tow bar attachment fittings on the nose gear (when towing operations are performed from the nose gear) in conventional tricycle type landing gears of commercial civil transport passenger and freight aircraft. Its purpose is to achieve tow bar attachment fittings interface standardization by aircraft mass category (which determines tow bar forces) in order to ensure that a single type of tow bar with a standard connection can be used for all aircraft types within or near that mass category, so as to assist operators and airport handling companies in reducing the number of different tow bar types used. This part of ISO 8267 is applicable to all new models of main line aircraft within the specified maximum ramp mass range, entering service or designed after its date of publication. This part of ISO 8267 is applicable to main line commercial transport aircraft of airworthiness certified under FAR/JAR Parts 25 with a maximum ramp mass of > 50 000 kg (110 000 Ib). It does not apply to aircraft of airworthiness certified under FAR/JAR Parts 25 but with a maximum ramp mass of ≤ 50 000 kg (110 000 Ib), which are covered by ISO 8267-2. Where a family of existing or contemplated aircraft types bridges two mass categories, use a single tow bar attachment fitting interface for all of them, and consider the use of the standard dimensions for the higher mass category throughout the family. NOTE As far as practical, this part of ISO 8267 was defined in order to be compatible with as many existing aircraft types as possible in the mass category concerned.