COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES British Aerospace (Hawker Siddeley) HS 748 Series Aeroplanes AD/HS 748/13 Engine Mount Structure "W" Frame Socket Fittings Inspection Hole Applicability: All HS748 aircraft. 5/95 Requirement: 1. Perform a detailed visual inspection of the "W" frame socket fitting inspection holes to determine if fasteners have been installed or the inspection holes reworked. Inspect in accordance with Jetstream Preliminary Technical Leaflet (PTL) 501 Issue 2, Para 2.1 Part One. 2. With the "W" frame removed, perform a detailed visual inspection of all "W" frame socket fitting inspection holes to determine if fasteners have been installed or the inspection holes reworked. Inspect in accordance with Jetstream PTL 501 Issue 2, Para 2.2 Part Two. 3. Magnetic Particle inspect all inspection holes and rework as necessary. Inspect and rework as required in accordance with Jetstream PTL 501 Issue 2, Para 2.3 Part Three. Note: CAA(UK) AD 002-09-94 refers. Compliance: 1. Inspect in accordance with Requirement 1 before 27 April 1996. 2. Inspect in accordance with Requirement 2 before initial installation on an aircraft or at the next "W" frame removal. 3. Inspect and rework, if fasteners or reworked inspection holes are found, in accordance with Requirement 3, at next "W" frame removal or before 27 April 1996, whichever occurs first. Note: Jetstream PTL 501 Issue 2 is the actioning document for Jetstream Service Bulletin HS748-71-33. Background: Jetstream Customer Bulletin No241C inserted drive screws in the inspection holes. The drive screws form sharp grooves in the inspection holes in a highly stressed area. Cracks have been reported in "W" frames and some holes have been reworked in excess of their original diameter.