Back in April 2018 I published an item covering the issue of an Aeroprakt Safety Alert concerning inspections and possible replacement of the rudder cables on A22LS aircraft. You can read the article by clicking here: Rudder Cable Safety Alert or the Bulletin itself here: Aeroprakt SB A22LS-17
Following the issue of the Alert, we submitted a pair of the broken cables and a length of new cable to the ATSB for testing and examination. You can view a copy of their report by clicking here: ATSB Report Rudder Cable Analysis Results
The ATSB Report reaches the following conclusions:
- The primary cause of the RH cable fracture was fatigue, resulting in overstress of the remaining wires.
- The LH cable was unserviceable (based on manufacturer requirements) due to deformation and wire fractures that were already apparent.
- The cables and pulleys provided to the ATSB were compliant with the manufacturer’s specifications (pending chemical analysis results).
- Most of the fatigue would have occurred prior to the accident flight, and it is likely that some would have been present at the last 200-hourly cable inspection (1600 hours).
- Fatigue in both cables may have been accelerated by the cable running around a smaller diameter pulley than is recommended.
In Summary – please ensure your rudder cables are correctly inspected every 200 hours per the Safety Alert and Maintenance Manual. This does NOT mean a quick glance and a ‘twang’ of the cables behind the seats! At any sign of wear or broken cable strands, both rudder cables must be replaced.
Finally, please note that the incident aircraft was registered 24-7930 – not, as erroneously stated in the report, 24-7390.