This standard specifies the characteristics of flat washers,in FE-PA4901,used to protect thin wall during reveting operation in aerospace applications.
AECMA PREN 4502-2000 history
2000AECMA PREN 4502-2000 Aerospace Series Washers, Flat, for Riveting, in Heat Resisting Steel FE-PA4901 (Multimet), Inch Based Series Edition P 1
1998AECMA PREN 4502-1998 Aerospace Series Washers, Flat, for Riveting, in Heat Resisting Steel FE-PA91HT (Multimet) Edition P 1