The practice of recording drawings, parts catalogs, and maintenance and overhaul manuals on microfilms was introduced in recent years. Microfilm is regular 16 mm or 35 mm film. Since 35 mm film is larger, it provides a better reproduction of drawings.

Depending on the size of the drawing to be reproduced, a varying number of drawings can be photographed on one reel of 35 mm film. To view or read drawings or manuals on a reel of film, you need either a portable 35 mm film projector or a microfilm reader or viewer.

The advantage of microfilm is that several reels, which represent perhaps hundreds of drawings, require only a small amount of storage space. Too, a person working on an aircraft may need to refer to a specific dimension. He can place the reel of microfilm in a projector, locate the drawing or desired information, and read the dimension. If he has to study a detail of the drawing, or work with the drawing for a long period of time, an enlarged photographic reproduction can be made, using the microfilm as a negative.

Microfilm of drawings has many other uses and advantages. However, microfilm is not intended to replace the need for original drawings, especially where the originals are modified and kept current over a long period of time.

When drawings are filmed on continuous reels, corrections can be made by cutting out superseded drawings and splicing in the revised ones. When these corrections become numerous, the procedure becomes impractical and is discarded in favor of again filming all the related drawings.

A method that allows corrections to be made easily is to photograph the drawings and then cut up the film into individual slides. This has one disadvantage; it requires considerable time to convert the film into slides, insert them into transparent protective envelopes, and arrange them in sequence so that desired drawings can be located quickly. A 70 mm microfilm has become available very recently. With it, larger size drawings can be reproduced as individual frames or slides, and these can be inserted in regular paper envelopes and kept in an ordinary file. When held to the light, this large microfilm can be read with the naked eye.