Most countries are member of the International Civil Aviation Organization (ICAO) and as such have signed the "Chicago Convention 1944" (111 pages, 2 Mb). Aviation rules and regulations in member countries are based on the recommendations of the ICAO.
The United Kingdom CAA has published an emergency mandatory permit directive regarding a washer near the magneto ring flywheel hub in some Rotax Aircraft Engines.
Excerpt from the document:
During a production process review, a deviation in hardening of certain Part Number (P/N) 944072 washers has been detected, which exceeds the hardness of the design specification.
Reason: The affected washers are part of the magneto ring flywheel hub installation and have been installed on a limited number of engines. No defective washers have been shipped as spare parts, so washers P/N 944072 delivered as spares are not affected.
This condition, if not corrected, could lead to cracks in the washer, loosening of the magneto flywheel hub and consequent ignition failure, in-flight engine shutdown and forced landing.
To continue reading see the pdf below:
Experimental Aircraft Info