Q400
Flight Crew Air Transport Pilot (ATP)
Distraction; Troubleshooting
Aircraft Equipment Problem Critical
General Maintenance Action
Aircraft; Procedure
After arriving we wrote up the aircraft for being misrigged and a slight 'bump' or catch while doing the roll control check. I later checked with Maintenance and saw a photo of what had happened. The aileron control cable was frayed to one strand of wire and left a large 'bird's nest' of wire was built up on the cable. If the strand of wire had snapped there would be no aileron control and no checklist for the emergency. The ailerons most likely would have floated to the up position and acted like spoilers deployed in flight - a grave emergency.   I spoke to the Mechanic about the write up and asked if Bombardier was informed and he said they were. I later spoke to the Captain who did the test flight and he asked if Bombardier was informed and Maintenance said no it was normal (wink; wink). The purpose of this report is to make sure Bombardier and the FAA know about the write up and can conduct an investigation or inspections as needed. It could be poor maintenance; poor design; damage; etc.
A Q400 flight crew felt an abnormal aileron bump or catch which was recorded in the maintenance log. Maintenance subsequently discovered a frayed wire bundle with single aileron control cable strand remaining.