Engineering Drawings, Diagrams and Standards
Read the drawing, do not guess it
Engineering drawings are a controlled language. Understand the title block (part number, nomenclature, drawing number, revision status, scale, units, projection symbol), the difference between first-angle and third-angle orthographic projection and how the truncated-cone symbol tells you which is used, the view types (front, plan, end, section, detail, auxiliary, isometric) and line conventions (visible, hidden, centre, dimension, break, cutting plane).
Know how dimensions and tolerances are stated: nominal size, limits, bilateral and unilateral tolerance, general tolerance notes, geometric tolerancing symbols (flatness, straightness, concentricity, position, perpendicularity), surface finish symbols, and notes on heat treatment and finish. Dimensions are in millimetres unless stated, and a drawing must never be scaled to obtain a dimension that is not given.
Know the standard document structure in aviation: ATA 100 chapter numbering, aircraft station numbering (fuselage stations, waterlines, buttock lines), zone numbers, the illustrated parts catalogue, the structural repair manual and the standard wiring practices manual. Distinguish a schematic (function) from an interconnection or wiring diagram (physical routing) and from a block diagram.
Traps: working from a superseded revision, reading a first-angle view as third-angle, assuming a sectional view shows everything behind the cutting plane, and confusing a part number with a drawing number.
Rule of thumb: check the revision block and the effectivity before you read a single dimension.