S.I.S ??

Thank you Air Ministry, appreciate the feedback as with others who replied, gives a better understanding of the use of the drawings.

The definition of S.I.S. is Standard Instruction Sheet, as found in a volume of Standardisation Design Memoranda.

The SDM initiative seems to have been an ongoing attempt to produce a definitive list of standardised equipment, to be incorporated in all new and future designs, i.e. to eliminate a profusion of different bits of equipment, all capable of doing much the same job.

Whether the S.I.S. is part of this initiative or whether it pre-dated it I cannot say.

Service Installation Schedule? They look like lists of items required for service installation of modifications or alterations. I note that they include the mod number & approval by committee date. I’ve not come across that before as I was usually involved in Alteration leaflets, which have the items listed and/or drawings required. SRIMs (I think Service Radio Installation Modification) would be similar to alteration leaflets, but a ‘full blown’ modification could need that type of listing.
Keith

Ok thanks, sounds reasonable.

I was thinking along the lines of “specification info/index? sheet” ?

This is a guess – assuming that every piece of equipment would have needed at least one or a series of technical drawings to be made prior to being produced and that all of those would have been centrally stored, it would be logical that each piece of equipment/set would be allocated an Index number and that all equipment drawings would be found via reference to a card or filing cabinet index. So perhaps S.I.S. refers to ‘Sheet Indexing System’?