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Aircra& Drawings

Chapter 2

Drawings •  Drawings and prints are the link between the design engineers and the mechanics

•  To accomplish their job, mechanics must be able to read and understand manufacturer's drawings and documenta?on

•  A mechanic must be able to create a drawing to describe a replacement part

•  FAA requires a mechanic to have the up-‐to-‐date documenta?on !  Annual subscrip?on for small aircra& is about $20,000

Computer Graphics •  Most new drawings are created on a computer •  CAD – Computer Aided Design

!  CADD -‐ Computer Aided Design Dra&ing

!  CAE – Computer Aided Engineering

•  CAM – Computer Aided Manufacturing

•  CNC – Computer Numerical Control

Type of Drawings •  Detail Drawing

!  The informa?on needed to fabricate a part

•  Assembly Drawing !  Descrip?on of an object made up of two or more parts

!  Instruc?ons on how to create an assembly from a collec?on of smaller parts

•  Installa?on Drawing !  Informa?on for a part or an assembly in the final installed posi?on in the aircra&

!  Shows the dimensions necessary for the loca?on of specific parts with rela?on to the other parts

Detail Drawing

Assembly Drawing

Assembly drawing of an aircra& alternator.

Assembly Drawing

Part numbers of all components of the aircra& alternator.

Installa?on Drawing

Installa?on Drawing

Installa?on drawing of a baQery sump jar.

Sec?onal View Drawing •  A sec?on or sec?onal view is obtained by cuSng away part of an object to show the shape and construc?on at the cuSng plane

•  Part or parts cut away are shown by the use of sec?on (crosshatching) lines.

•  Types !  Full Sec?on !  Half Sec?on !  Revolved Sec?on

!  Removed Sec?on

Full Sec?on •  Full cutaway that shows the interior construc?on or hidden features of an object not shown by an exterior view

Full Sec?on

Half Sec?on •  Cut plane extends only halfway across the object •  Half of the object’s exterior is visible

Half Sec?on

Some Where Between Half and Whole Sec?on

Cutaway Drawing •  Similar to a Half Sec?on but only part of the object is “cutaway”

•  “Cutaway Drawing” some?mes used to mean Full or Half Sec?on

Cutaway Drawing

Revolved Sec?on •  Shows the shape of a cross sec?on of a part

Revolved Sec?on

Removed Sec?on •  Illustrates par?cular parts of an object •  Like a revolved sec?on, except details are placed to one side of main object

•  Sec?ons are o&en larger scale to show more detail

Removed Sec?on

Exploded-‐View •  A diagram that shows the rela?onship or order of assembly of various parts

•  O&en used in illustrated parts manuals

Exploded-‐View

Exploded view of a hydraulic restrictor.

Exploded-‐View

Figure 5-‐7. Exploded view of a hydraulic restrictor.

What kind of Sec?on?

PT-‐6

Piaggio P-‐180 Avan? II

King Air 250

Detail View •  Shows only a part of an object in great detail •  Details in larger scale

Detail View

Diagrams •  Graphic representa?on of an assembly or system, indica?ng the various parts and expressing the methods or principles of opera?on

•  4 types: !  Installa?on !  Schema?c !  Block

!  Wiring diagrams

Installa?on Diagram •  Iden?fies each of the components in the systems and shows their loca?on in the aircra&

Installa?on Diagram

Schema?c Diagrams •  Locate components with respect to each other within the system

•  Doesn’t indicate the loca?on of individual components in the aircra&

•  Used in troubleshoo5ng

Schema?c Diagrams

Notice: Details on flow direction but not exact pressures

Block Diagrams •  Shows a simplified rela?onship of a more complex system of components

•  Individual components are drawn as a rectangle (block) with lines connec?ng it to other components

•  Shows component interfaces and how they operate

Block Diagrams

Wiring Diagrams •  Shows the electrical wiring and circuitry •  O&en shows the wire size and type •  Coded for iden?fica?on

Wiring Diagrams

Flowcharts •  Troubleshoo?ng Flowcharts -‐ frequently used for the detec?on of faulty components !  A logical solu?on to a par?cular problem

•  Logic Flowchart -‐ Standardized symbols to indicate specific types of logic gates and their rela?onship to other digital devices in a system

Troubleshoo?ng Flowchart

Logic Flowchart

Pictorial Diagram •  Pictorial diagrams show the components as they actually appear, rather than using conven?onal symbols

Pictorial Diagram

Figure 5-‐12. Pictorial diagram of a light airplane electrical system.

Perspec?ve Drawings •  Shows an object as it appears to an observer •  It most closely resembles the way an object would look in a photograph

•  Because of perspec?ve, some of the lines of an object are not parallel and therefore the actual angles and dimensions are not accurate

Perspec?ve Drawings

In a perspec?ve view, parallel lines converge at a vanishing point off the drawing.

Isometric Drawings •  A combina?on of the views of an orthographic projec?on (2D view) and ?lts the object forward so that por?ons of all three views can be seen in one view

•  Provides the observer with a three-‐dimensional view of the object

•  Lines in an isometric drawing are parallel and dimensioned as they are in an orthographic projec?on

Isometric Drawings

Three surfaces of an isometric view are visible, and all lines in this drawing are true length except A and B.

Orthographic Projec?on Drawings •  Most drawing are a 2-‐D view of an object •  A single view of an object may not convey enough informa?on !  Mul?ple views are provided

Orthographic Projec?on Drawings

Orthographic Projec?on Drawings •  Possible views

!  Total of six

!  Front !  Top !  BoQom

!  Rear !  Right side !  Le& side


Auxiliary views are used when the orthographic views do not convey the needed informa?on.

Lines •  Lines are more than just a method to connect two objects

•  The way a line is drawn helps define its use

Centerlines •  Indicate the center of an object or part of an object

•  Alternate long and short dashes

Dimension Lines •  Shows the dimension (measurement) of an object

•  Light solid line •  Broken at the midpoint for inser?on of measurement indica?ons

•  Opposite poin?ng arrowheads at each end to show origin and termina?on of a measurement

Dimension Lines •  Dimension of an angle is indicated by placing the degree of the angle in its arc

•  Dimensions of circular parts are by default given in terms of the diameter of the circle

•  Dimension of an arc is given in terms of its radius

•  Dimensioning distances between holes in an object, dimensions are usually given from center to center

Dimension Lines •  Countersunk holes -‐ the angle of countersinking and the diameters are given

Dimension Lines

Extension Lines •  Extend the line showing the side or edge of a figure for the purpose of placing a dimension to that side or edge

•  Very narrow and have a short break where they extend from the object and extend a short distance past the arrow of the dimensioning line

Extension Lines

CuSng Plane/Viewing Plane Lines •  CuSng plane/viewing plane lines indicate the plane in which a sec?onal view of the object is taken

•  Arrows on the cuSng plane/viewing plane lines indicate the direc?on the part is viewed

CuSng Plane/Viewing Plane Lines

Sec?oning Lines •  Indicate the exposed surfaces of an object in sec?onal view

Phantom Lines •  One long and two short evenly spaced dashes •  Indicate the alternate posi?on of parts of the object or the rela?ve posi?on of a missing part

Break Lines •  Indicate that a por?on of the object is not shown on the drawing

•  Used for sha&s, rods, tubes, and other such parts which have a por?on of their length broken out

•  Short breaks -‐ solid, freehand lines •  Long breaks -‐ solid ruled lines with zigzags

Leader Lines •  Indicate a part or por?on to which a note, number, or other reference applies

•  Solid lines with one arrowhead

Hidden Lines •  Indicate invisible edges or contours •  Short dashes evenly spaced and are frequently referred to as dash lines

Drawing Symbols •  Material Symbols

!  Line symbols show the kind of material from which the part is to be constructed

!  Cast Iron is the generic material •  Easy to draw •  Material specifica?on is listed in the bill of materials or indicated in a note

•  Shape Symbols

•  Electrical Symbols

Material Symbols

Shape Symbols

Title Block •  Title block provides a means of iden?fying a drawing

•  O&en found in the lower right-‐hand corner of a drawing

Title Block Essen?als •  A drawing number

!  Some ?me the part number

•  Name of part or assembly

•  Drawing Scale •  Date of drawing •  Name of firm

•  Name of dra&sman, checker or person a approving the drawing

•  Drawing revision

Title Block

Drawing Numbers •  Drawing or print number

!  Iden?fies the drawing

!  Some?mes the part number

•  Reference number !  Refers/sends you to another drawings

•  Dash number !  Iden?fies versions of a part !  Odd – le&, Even – right

Drawing Sizes •  A-‐size: 8 1/2” X 11” •  B-‐size: 11” X 17” •  C-‐size: 17” X 22” •  D-‐size: 22” X 34” •  E-‐size: 34” X 44”

Revision Block •  Revisions to a drawing are necessitated by changes in: !  Dimension !  Design !  Material

!  Sub-‐parts !  Product update

•  Changes are usually listed in a ruled columns either adjacent to the ?tle bock or at one corner of the drawing

•  All changes must be approved and noted

Revision Block

Notes •  Notes are added to drawings to convey informa?on that is not shown in the drawing

•  Notes maybe in a special sec?on of drawing !  Some?mes called a note block

•  Notes maybe scaQered throughout the drawing !  Usually next to the item that needs clarifica?on

Zone Numbers •  Zone numbers on drawings are similar to the numbers and leQers printed on the borders of a map

•  Locates a par?cular point •  Draw horizontal and ver?cal lines from the leQers and numerals specified; the point where these lines intersect is the area sought

Zone Numbers

Sta?on Numbers and Loca?on Iden?fica?on •  Fuselage Sta?ons – numbered in inches from a reference or zero point know as the reference datum. (length wise)

•  BuQock Line (buQ line) – width measurement le& or right of, and parallel to, the ver?cal center line. (width wise)

•  Water Line – the measurement of height in inches perpendicular from a horizontal plane located at fixed number of inches below the boQom of the aircra& fuselage (high wise)

Sta?on Numbers and Loca?on Iden?fica?on

Allowance and Tolerances •  The more precise a part is made, the more expensive it is !  An engineer will give a manufacturer a range of measurements that are acceptable for a part to reduce costs

!  This is called varia?on

!  The wider the varia?on the lower the part cost

Allowance and Tolerances •  Parts are assigned a varia?on

!  Next to the dimension

!  Default for a drawing •  In the notes •  In the ?tle block

•  An object is given a base dimension plus a varia?on !  The varia?on is called the tolerance

Allowance and Tolerances •  Tolerance

!  Plus allowance – indicated by a “+” •  How much greater than the base dimension

!  Minus allowance – indicated by a “-‐” •  How much less than the base dimension

!  Tolerance is the total of the plus and minus allowance

!  e.g. 0.250 ± 0.010 •  Base is 0.250 •  Plus allowance is 0.010 •  Minus allowance is 0.010 •  Tolerance is 0.010 + 0.010 = 0.020 •  Range from 0.240 to 0.260

Allowance and Tolerances •  Tolerance

!  e.g. 0.250 + 0.010 – 0.005 •  Plus and minus variance don’t have to be the same •  Range from 0.245 to 0.260

•  Tolerance is 0.010 + 0.005 = 0.015 !  e.g. 0.250 + 0.010 – 0.000

•  Range from 0.250 to 0.260 •  Tolerance is 0.010 + 0.000 = 0.010

!  e.g. 0.250 + 0.010 •  Range from 0.250 to 0.260

•  Tolerance is 0.010 + 0.000 = 0.010

Finish Marks •  Finish Marks indicate how the surface must be machine finished

•  Each part must have a (machining) finish !  Rough (cheaper to make or beQer oil coverage) !  Smooth

!  Close fit !  Flat (beQer seal)

•  Final coa?ng (different than machining finish) !  Paint

!  Pla?ng !  Nothing

Only use Dimensions •  When measuring an object, use only the listed dimensions

•  Never measure off a drawing !  Assume the drawing is a communica?on tool, not an exact image of the object

!  Drawings can change size when they are reproduced

Drawing Scale •  It is imprac?cal to make a single drawing that is the same size as a plane

•  Drawings are made to scale !  e.g. ½” = 1’ – every ½ inch on the drawing represent 1 foot on an airplane

•  The drawing scale is usually include in the Title Block

Charts •  A “drawing” of informa?on in the form of a table, graph, or diagram

•  Where to find informa?on: !  Horizontal axis (x-‐axis) !  Ver?cal axis (y-‐axis)

!  Chart’s lines or bars

Charts •  How to find the informa?on:

1.  Determine the informa?on you know

2.  Determine the informa?on to find 3.  Locate the known informa?on on the x-‐axis, y-‐axis

or chart lines

4.  Draw lines connec?ng the informa?on you know 5.  Find the intersec?on of the lines 6.  Draw a line to the x-‐axis, y-‐axis or chart line to find

the informa?on you are looking for

Problem •  The proper tension for a 3/l6-‐inch extra-‐flexible (7 x 19) control cable rigged at 87°F is pounds.

•  Known informa?on: !  3/l6-‐inch extra-‐flexible (7 x 19) control cable

!  87°F

•  Informa?on to find: !  Tension

3/16 7 X 19 Cable

87°

X

Answer: 125 pounds

Make Your Own Drawings •  For 337’s and geSng parts made •  Start with graph paper or CAD program

•  Steps: 1.  Block in the space and basic shape used for the

sketch. 2.  Add details to the basic block. 3.  Darken the lines that are to show up as visible lines

in the finished sketch.

4.  Add dimensions and any other informa?on that will make the sketch more usable.

Make Your Own Drawings

Figure 5-‐13. Sequence of steps used for making a sketch.

Find Center of Circle

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