AD/CA21/5 - Wing Strut Carry Through Structure
COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY
SCHEDULE OF AIRWORTHINESS DIRECTIVES
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Skyfox Aviation (Calair/Hedaro) CA21 and CA22A Series Aeroplanes
AD/CA21/5 Wing Strut Carry Through Structure 2/96
Applicability: All CA21 and CA22A aircraft, including CALAIR CA21 aircraft.
Note: For CA22A/25, CA25 and CA25N models see AD/CA25/2.
Requirement: 1. Remove the 3/32" blind type sealing rivet from the wing strut carry through tube oiling hole. Check that corrosion preventive fluid is present in the tube, using a small diameter wire as a dipstick. Refill the tube with up to 100 ml of Shell ENSIS fluid, or similar corrosion preventive fluid. Refit a 3/32" blind type sealing rivet in the oiling hole.
Note: Skyfox Aviation Service Bulletin No 10 also refers to oiling of the wing strut carry through tube. Addition of a colour contrast dye to the preventive fluid may assist inspection with Requirement 2. Check before use to ensure the dye has no adverse effects on either the corrosion inhibitor properties of the fluid or on the tube material.
- Visually inspect the wing strut carry through tube and adjacent fabric in the area shown in the figure below. Inspect for cracks, evidence of fluid seepage from the tube or for any corrosion damage. The cause of any fluid seepage is to be determined and rectified before returning the aircraft to service. Repair cracks and corrosion before returning the aircraft to service.
3.a. Gain access to the wing lift strut mount cross tube structure inboard of the lower lift strut attachments. Remove the paint from the wing lift strut mount cross tube, using a non abrasive method, in the area shown in the diagram below.
Note: Gaining access to the wing lift strut mount cross tube for inspection in accordance with Requirement 3 may require cutting a hole in the fabric covering. A hole 50 mm in diameter should be sufficient.
3.b. Inspect, using the dye penetrant method as per CAO 108.10, the wing lift strut mount cross tube inboard of the strut attachment lugs for signs of cracks. Inspect both port and starboard fittings. Pay particular attention to the inboard end of the strut attachment lug weld as indicated in the diagram below. Repair cracks found before further flight. Repaint the cross tube before returning aircraft to service.
COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY
SCHEDULE OF AIRWORTHINESS DIRECTIVES
View image in the official source
Compliance: 1. Action in accordance with Requirement 1 before 500 hours aircraft time in service or 50 hours time in service after 1 February 1996, whichever occurs later. Re- inspect at intervals not to exceed 100 hours time in service.
2. Inspect in accordance with Requirement 2 before 500 hours aircraft time in service or 50 hours time in service after 1 February 1996, whichever occurs later. Re- inspect at intervals not to exceed 100 hours time in service.
3. Inspect in accordance with Requirement 3 before further flight if no fluid is found in the tube as a result of Requirement 1.
Background: A CA22 Skyfox aircraft registered to the Australian Ultralight Federation experienced on inflight failure of the wing lift strut mount cross tube. The aircraft had previously been involved a landing accident and repaired. Failure occurred at a time well below the retirement life. The area of the failure is subject to a combination of tensile and bending stress.
A once off dye penetrant inspection of the wing lift strut mount cross tube was required by the issue of Directive AD/CA25/2. A laboratory examination of the failed tube has indicated that failure had resulted from fatigue initiating at the toe of the weld. The examination indicated that there was no eivdence of crack initiation from the earlier accident.
This Directive, specifically for the CA21 and CA22A aircraft, sets a threshold for inspection and requires repeat visual inspections to be made. The dye penetrant inspection is conditional on the findings of the visual inspections.
This Directive does not remove the life limitation of the wing lift strut mount cross tube in AD/CA21/6.