COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Douglas DC4 Series Aeroplanes AD/DC4/1 Vacuum System - Modification NK Applicability: All models. Requirement: Rework the vacuum system in accordance with either of the following modifications: 1. Replace the present oil separator with a Genesco No. 40081 separator. The new separator incorporates a pressure relief valve and can be dismantled for cleaning; or 2. Install a fusible plug in the side of the vacuum pump discharge port at right angles to the axis of the discharge port boss. Note: Some pumps incorporate a plugged hole in the discharge port which may be enlarged to a 3/8 in. NPT tapped hole to accommodate the fusible plug. This plug should employ an AN-840-8D fitting with a binary eutectic mixture of 68 per cent tin and 32 per cent cadmium which has a melting point of 351oF (See Figure 1). The 3/8 in. fusible plug is intended for pumps model 3P211 and 3P485. For smaller pumps a modified AN-840-6D fitting should be used. or FAA AD 49-46-1; or ANO 105.1.16.0.1.1.