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) of conventional tricycle type landing gears of commercial civil transport 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 regional aircraft within the specified maximum ramp mass range which enter service or are designed after its date of publication. It does not apply to previously in service regional aircraft models, which present a considerable variety of tow bar attachment fittings. However, a simple retrofit modification is described that may make certain in-service fittings compatible with a tow bar head in conformity with this part of ISO 8267, where deemed appropriate in order to facilitate operation of such aircraft types at airports. This part of ISO 8267 is applicable to regional commercial transport aircraft 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 airworthiness certified under FAR/JAR Parts 23 as commuter category aeroplanes; — aircraft 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 8267-1. 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, be it part of this part of ISO 8267 or ISO 8267-1, 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.