This SAE Aerospace Standard (AS) specifies the interface requirements for towbar 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 with a maximum ramp weight between 8600 kg (19 000 lb) and 50 000 kg (110 000 lb), commonly designated as "regional aircraft". Its purpose is to achieve towbar attachment fittings interface standardization by aircraft weight category (which determines towbar forces) in order to ensure that one single type of towbar with a standard connection can be used for all aircraft types within or near that weight category, so as to assist operators and airport handling companies in reducing the number of different towbar types used. This Aerospace Standard is intended to be applicable to all new models of regional aircraft within the specified maximum ramp weight range, entering service or designed after its date of publication. See Section 3, Effectivity, hereafter. It is not its intent to apply to previously in service regional aircraft models, which present a considerable variety of towbar attachment fittings, However, where deemed appropriate in order to facilitate operation of such aircraft types at airports, simple retrofit modifications are described that may be considered to bring certain in service fittings to be compatible with a towbar head meeting this Aerospace Standard.