AIRCRAFT DRAWINGS

BY

MANI RATHINAM RAJAMANI

DRAWINGS

• Drawing :

– A method of conveying ideas concerning the construction / assembly of

objects.

– Link b/w Designer and Assembler

– Described by lines, notes, abbreviations, symbols ,..ETC.

• Modern Drawings:

– Computer Aided Design Drafting (CADD)

– Computer Aided Design (CAD) : Product Design.

– Computer Aided Manufacturing (CAM) : Product Manufacturing.

– Computer Aided Engineering (CAE) : Product Engineering / Analysis /

Simulation & PLC.

Do’s & Dont’s

• Care and Use of Drawings :

– Drawings are both expensive and valuable.

– Handle with Care.

– Do smooth out the fold lines instead of bending back.

– lay them on a flat surface.

– Hands free of oil, grease, etc. that soil / smudge prints.

– Never make notes or marks on a print to avoid confusions.

– Authorized personnel changes Only permitted with sign and date any

changes they make.

DRAWING TYPES

• Information as size and shape of the object and all of its parts,

• Specifications for material to be used,

• how the material is to be finished,

• how the parts are to be assembled,

• Types of Drawings:

– (1) Detail,

– (2) Assembly,

– (3) Installation.

DRAWING TYPES • DETAIL DRAWING:

– A description of a single part,

– described by lines, notes, and symbols the

specifications for size, shape, material, and

methods of manufacture.

– several detail drawings may be shown on the

same sheet or print.

• ASSEMBLY DRAWING:

– A description of an object made up of two or

more parts.

– to show the relationship of the various parts

assembled.

– An assembly drawing is usually more complex

than detail drawing and accompanied by detail

drawings.

DRAWING TYPES

• INSTALLATION DRAWING :

– all necessary info for a part or an

assembly in the final installed

position in the aircraft.

– shows dimensions necessary for

location of parts with relation to

the other parts

– reference dimensions that are

helpful in later work in the shop.

SECTIONAL VIEW DRAWINGS

• Section / Sectional view is obtained by cutting away part of an object to

show the shape and construction at the cutting plane.

• Parts cut away are shown by use of section (crosshatching) lines.

• Types of sections are.

– Full Section

– Half Section

– Revolved Section

– Removed Section

SECTIONAL VIEW TYPES

• FULL SECTION :

– used when interior construction or hidden

features of an object cannot be shown

clearly by exterior views.

• HALF SECTION :

– the cutting plane extends only halfway

across the object,

– leaving the other half of the object as an

exterior view.

– used to advantage with symmetrical objects

to show both the interior and exterior.

SECTIONAL VIEW TYPES

• REVOLVED SECTION

– drawn directly on exterior view

– shows the shape of the cross

section of a part.

• REMOVED SECTION

– Illustrates particular parts of an

object.

– drawn like revolved sections,

– placed at one side.

– to bring out pertinent details.

– often drawn to a larger scale than

view indicated.

TITLE BLOCK

• TITLE BLOCKS:

– means of identification.

– consists of data concerning the

drawing

1. A drawing number.

2. The name of Part or Assembly.

3. Scale.

4. Date of Release.

5. Name of firm.

6. Name of draftsmen, checker, and

the approver.

– Position: lower right-hand corner.

DRAWING NUMBER

• Drawing or Print Numbers:

• All prints are identified by a number

• appears in a number block in lower right-hand corner of title block.

• may be also shown in other places

– near the top border line,

– in the upper right-hand corner,

– on the reverse side of the print at both ends.

• Purpose : quick identification of a print.

• sheet number and number of sheets in series.

REFERENCE AND DASH NUMBERS

• Ref No’s appear in title blocks

• refers to numbers of other prints.

• When more than one detail is shown, Dash numbers are used.

• Both parts would have same drawing number with an individual dash

number.

• Also appear on face of drawing near parts they identify.

• Also used to identify right-hand and left-hand parts which are mirror

images.

• Thumb rule : odd numbers for left-hand parts and even numbers for right-

hand parts.

BILL OF MATERIAL (BOM)

• A list of materials and parts necessary for fabrication / assembly of a

component / system.

• usually in ruled columns in which are listed

– Part number,

– name of the part,

– material from which part is to be made,

– quantity required,

– Source of part or material.

• On assembly drawings, each item is identified by a number in a circle or

square.

• An arrow connecting number with item assists in locating it in bill of

material.

OTHER DRAWING DATA

• REVISION BLOCK:

• Revisions are necessitated by changes in

dimensions, design, or materials.

• changes are listed in ruled columns

– either adjacent to the title block

– or at one corner of the drawing.

• All changes must be carefully noted on

all existing prints of drawing.

• When drawings contain such corrections,

attention is directed to changes by

lettering or numbering them.

• Changes are listed against a symbol in a

revision block.

REVISION BLOCK contains:

• identification symbol,

• Revised dates

• nature of revision

• Authority Name for

change

• Name of draftsman who

made change.

OTHER DRAWING DATA

• NOTES:

• refer to methods / alternate applicable methods of attachment or

construction.

• used only when information cannot be conveyed in conventional manner

• Used to avoid crowding the drawing.

• When the note refers to a specific part, a light line with an arrowhead leads

from the note to the part.

• If it applies to more than one part, note is worded to eliminate ambiguity as

to the parts to which it pertains.

• If there are several notes, they are generally grouped together and

numbered consecutively.

OTHER DRAWING DATA

• ZONE NUMBERS:

– are similar to numbers and letters printed on borders of a map.

– Help to locate a particular point.

– To find a point, mentally draw horizontal and vertical lines from the

letters and numerals specified;

– point where these lines intersect is the area sought.

– Used to locate parts, sections, and views on large drawings, particularly

assembly drawings.

– Parts numbered can be located on drawings by finding numbers in

squares along the lower border.

– Zone numbers read from right to left.

OTHER DRAWING DATA

• Finish Marks :

– used to indicate surface finish required

– better appearance and allow a closer fit with adjoining parts.

– Standard limits and tolerances must be observed.

– Do not confuse machined finishes with paint, enamel, chromium plating.

• Scale :

• exactly same size as drawn part; a scale of 1:1.

• Application:

• When shown near title block, application may refer to aircraft, assembly, sub-assembly or next installation on which part would be used.

LOCATION IDENTIFICATION • STATION NUMBERS :

– A numbering system is used on large assemblies for aircraft to locate stations

such as fuselage stations.

– Fuselage station value indicates a location value of inches from the datum of

the aircraft.

– Measurement is taken from nose or zero station or A point chosen by

manufacturer.

– Fuselage stations (FS), Wing stations (WS), Stabilizer Stations (SS).

• Measurement taken from centerline / zero station / ground level of aircraft.

LOCATION IDENTIFICATION

• WATERLINE :

– Vertical locations on an airplane are made in reference to the waterline.

LOCATION IDENTIFICATION

• BUTT LINES:

– locations left and right of

aircraft’s longitudinal axis

– Locations made by reference to

buttock line / butt stations.

– Left Buttock Line (LBL) and

Right Butt Line (RBL).

TOLERANCES & ALLOWANCES

• TOLERANCE:

– a given dimension with an allowable variation,

– plus (+) indicates maximum, and minus (−) minimum allowable variation.

– sum of plus and minus allowance figures is called tolerance.

– If the plus and minus allowances are the same, presented as value ± tolerance.

• ALLOWANCE:

– indicated in either fractional or decimal form.

– Used for very accurate dimensions,

– decimal allowances are used.

– Fractional allowances are sufficient when precise tolerances are not required.

– Standard tolerances may be given in title block to apply throughout drawing.

METHODS OF ILLUSTRATION

• DRAWINGS:

– Orthographic Projection Drawings

– Detail View

– Pictorial Drawings

– Perspective Drawings..

– Isometric Drawings

– Oblique Drawings

– Exploded View Drawings

ORTHOGRAPHIC PROJECTION

DRAWINGS

• six possible views of an object.

• front, top, bottom, rear, right side, and left side.

• One-, two-, and three-view drawings.

• ONE VIEW DRAWINGS:

– One-view drawings : commonly used for objects of uniform thickness such as gaskets, shims, and plates.

– used for cylindrical, spherical, or square parts if all dimensions shown in one view.

• TWO VIEW DRAWINGS:

– When space is limited and two views must be shown,

– symmetrical objects are often represented by half views.

DETAIL VIEW

• shows only a part of object but in greater

detail.

• shows to a larger scale than the principal

view.

• parts shown in detail on drawing is

encircled by a heavy line on principal view.

PICTORIAL DRAWINGS

• is similar to a photograph.

• shows an object as it appears to the eye.

• useful in showing general appearance of an object

• used extensively with orthographic projection drawings.

• used in maintenance, overhaul, and part numbers.

• Three types of pictorial drawings are used

1. Perspective,

2. Isometric,

3. Oblique,

4. Exploded View drawings.

PICTORIAL DRAWINGS • Perspective Drawings:

– shows an object as it appears to an observer.

– Resembles an object as in a photograph.

– lines of an object are not parallel

– actual angles and dimensions are not accurate.

• Isometric Drawings:

– uses a combination of views of an orthographic projection

– Tilts the object forward so that portions 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

– dimensioned as they are in an orthographic projection.

PICTORIAL DRAWINGS

• Oblique Drawings

– similar to an isometric view.

– except for one distinct difference.

– Two of three drawing axes are always at

right angles to each other.

• Exploded View Drawings

– a pictorial drawing of two or more parts that

fit together as an assembly.

– View shows individual parts and their

relative position to other parts before they

are assembled.

DIAGRAMS

• a graphic representation of an assembly /

system

• indicates various parts and expresses

methods or principles of operation.

• Four Types of diagrams

1. installation,

2. schematic,

3. block,

4. wiring diagrams.

INSTALLATION DRAWINGS

• a diagram of installation of the flight

components of an aircraft.

• Identifies each of the components in the

systems and shows their location in the

aircraft.

• used extensively in aircraft maintenance

and repair manuals,

• Are invaluable in identifying and locating

components and understanding the

operation of various systems.

SCHEMATIC DIAGRAMS

• do not indicate the location of

individual components in the aircraft,

• Used to locate components with respect

to each other within the system.

• used mainly in troubleshooting.

• each line is coded for ease of reading

and tracing the flow.

• Each component is identified by name,

and its location within the system

• Line notes indicate in and out flow of

the unit.

• used extensively in aircraft manuals.

BLOCK DIAGRAMS

• used to show a simplified relationship of a

more complex system of components.

• Individual components are drawn as a

rectangle (block) with lines connecting it to

other components (blocks) that it interfaces

with during operation.

WIRING DIAGRAMS

• shows electrical wiring and circuitry,

• coded for identification, of all the electrical

appliances and devices used on aircraft.

• Complicated structure.

• Thorough knowledge of wiring and electrical

schematics is essential.

FLOWCHARTS • used to illustrate a particular sequence, or flow of events.

• Types are

– Troubleshooting Flowchart:

• used for detection of faulty components.

• consist of a series of yes or no questions.

• If yes, one course of action is followed.

• If no, a different course of action is followed.

• a logical solution to a particular problem may be achieved.

– Logic Flowchart

• analysis of digitally controlled components and systems.

• uses standardized symbols to indicate specific types of logic gates

• relationship to other digital devices in a system.

• consist of individual components that take an input

• and provide an output.

• By analyzing inputs, it is possible to determine digital output.

LINES AND THEIR MEANINGS

• Lines mark boundaries, edges, and

intersection of surfaces.

• used to show dimensions and hidden

surfaces and to indicate centers.

• Types:

– Centerlines

– Dimension Line.

– Extension Lines.

– Sectioning Lines.

– Phantom Lines.

– Break Lines.

– Leader Lines.

– Hidden Lines.

– Outline / Visible Lines

– Stitch Lines.

– Cutting Plane and Viewing

Plane Lines.

LINES AND THEIR MEANINGS

DRAWING SYMBOLS

• represent shape and material.

• short hands of drawing.

• graphically portray characteristics

of a component with a minimal

amount of drawing space.

• Types:

– Material Symbols

– Shape Symbols

– Electrical Symbols

INTERPRETING DRAWINGS

• read drawing number and description.

• check model affected, latest change

letter, the next assembly listed.

• read illustrations.

• For multi-view drawing,

• get a general idea of shape of object

• select one view for a more careful

study.

• referring back and forth to adjacent

view.

GRAPHS & CHARTS

• Frequently used to convey

information graphically.

• Projection of values on x-y axes.

• all notes and legends be carefully

understood in order.

• Types of Graphs used:

– Nomograms:

• a graph of three sets of data.

• Input of any two sets of data

enables interpreter to obtain

value for third unknown.

QUESTIONS>?

THANK YOU