Further to my recent information about checking the cardan rings on the A22LS BEFORE THE NEXT FLIGHT – here is a very short video clip showing what needs to be done:
Some cracks have recently been found in the Cardan rings on an Australian operated A22LS Foxbat. Although there have been no other reports of similar cracks in the worldwide fleet, because it affects part of the primary flight control system, the factory will be issuing a mandatory inspection requirement and an amendment to the Aircraft Maintenance Manual (AMM). RA-Aus and CASA have been informed.
There are two Cardan rings on the aircraft – these are a type of universal joint – connecting the flaperon control torque tube and the flaperon. They are located just outside the fuselage where the control tube exits the cabin at the rear of the wing – see picture above (click photo for a bigger version).
The cracking is caused by over-tightening the long vertical connecting bolt, possibly made worse by allowing the control surfaces to bang up and down in the wind when the aircraft is parked outside with the controls unrestrained.
Here’s what you need to do BEFORE THE NEXT FLIGHT:
– lower the flaps to their full extent;
– remove the safety pin and loosen and remove the long bolt which runs vertically through the Cardan ring;
– inspect top and bottom lugs of the ring for any cracks;
– if no cracks are found, lubricate and replace the bolt and tighten to 2Nm of torque; don’t forget to replace the safety pin!
– if cracks are found, please contact me at Foxbat Australia on email@example.com with clear, in focus pictures of the cracks.
On completion of the inspection, either (a) if no problems are found, record a statement to that effect in the aircraft maintenance log, or (b) if cracks are found, complete an RA-Aus incident report (click this link to get to the form on the RA-Aus website) and send it to the RA-Aus National safety Manager.
If you have any questions about this advisory, please call me, Peter, on 0413 900 892.
Sharp eyed Foxbat owners have noticed that the flaperon hinges have small holes drilled in the spindles which run through the centres of the hinge bearings. One or two owners have even added washers and inserted safety pins in these holes, assuming that this will add to the security of the flaperon hinge.
The factory has confirmed it is absolutely not necessary to fit safety pins – the geometry of the flaperon controls and hinges means that the flaperon just cannot come off its hinges. In fact adding safety pins may actually be detrimental to the wear of the hinges. As the wing and airframe flexes under flight loads, it is important that the flaperon is free to move on the spindles, not just up and down but also laterally.
It is also important to ensure the hinge bearings are kept lubricated, even between services if needed, to ensure they are free to slide. If you have installed washers and safety pins – please remove them now.