RA 4266 refers to the use of self locking nuts, but as in the case of a lot of RA's it referes to the MAP-01 Chapter 6.15:
https://www.gov.uk/government/upload...tial_Issue.pdf
https://www.gov.uk/government/upload...ablemap-01.pdf
Extract from Chapter 6.15:
General Rules
As a general rule, the male threaded portion and nut may be removed from the assembly and re-used more than once, the nut must meet the minimum run-down torque criteria detailed in each platform Aircraft Maintenance Manual (AMM) Topic 1 on each application and must achieve a minimum of 1.5 threads protruding beyond the nut when the final locking torque is achieved. For small stiffnuts of 6mm O/D and below, the run-down torque must be greater than that which can be applied with finger pressure.
Further generic instructions on the procedures that must be used for checking aircraft self-locking fasteners is included in AP 119A-0428-1 Chap 3 paragraph 7. An entry referring to these generic procedures must be included in each AMM.