Chapter 03 - Aircraft Components and Terminology

8/13/2019 Chapter 03 - Aircraft Components and Terminology

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WILJAM FLIGHT TRAINING

Chapter 3.

Ai rcraf t Components and Terminology

Wing Position Terminology

Wings are attached to an aircrafts fuselage in either a low, high or mid position (Fig. 3.1).

LOW WING

HIGH WING

MID WING

FIG. 3.1

The actual wing position is determined by the following design parameters:

Engine Positioning/Propeller Blade Length

Undercarriage Positioning

Short Take-Off and Landing Capability

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The wings are inclined above, or below the horizontal. Wing inclination above the horizontal isknown as dihedral, and inclination below the horizontal is known as anhedral (Fig. 3.2).

DIHEDRAL

WINGSPAN

ANHEDRAL

WINGSPAN

FIG. 3.2

Wing Planform Terminology

The following terminology is associated with wing planform:

Gross Wing Area (S). The plan view area of the wing including the portion of thewing normally cut out to accommodate the fuselage (Fig. 3.3)

GROSS WING AREA (S)

FIG. 3.3

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Net Wing Area. The area of the wing excluding the fuselage portion (Fig. 3.4).

NET WING AREA

FIG. 3.4

Wing Span (b). The straight-line distance between wing tips (Fig. 3.5).

AVERAGECHORD

WING-TIP

WING-SPAN

FIG. 3.5

Average Chord (CAV ). The Mean chord (Fig. 3.5). The product of the span andaverage chord gives the gross wing area (i.e. b x CAV= S).

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Aspect Ratio (AR). The ratio of wing span to average chord. Long thin wings areof high aspect ratio, whilst short stubby wings are of low aspect ratio (Fig. 3.6).

Aspect Ratio =AreaWingGross

2Span)(Wingor

2Chord)(Average

AreaWingGrossor

ChordAverage

SpanWing

HIGH ASPECT RATIO LOW ASPECT RATIO

FIG. 3.6

Taper Ratio (TR). The ratio of tip chord (Ct) to root chord (Cr) (Fig. 3.7).

TIPCHORD ROOT CHORD

FUSELAGE

TAPERED WING

FIG. 3.7

The Angle of Sweepback. The angle between the line of 25% chord and aperpendicular to the root chord (Fig. 3.8).

ANGLE OF SWEEPBACK

25% TIPCHORD

25% ROOTCHORD

C

FIG. 3.8


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Mean Aerodynamic Chord (MAC). The chord drawn through the centroid (centreof area) of the halfspan area. It must be noted that the MAC and CAVare not thesame (Fig. 3.9).

MAC

MAC = MEAN AERODYNAMIC CHORD

FIG. 3.9

Aspect ratio, taper ratio, and sweepback are some of the main factors that determine theaerodynamic characteristics of a wing.

Wing Section Terminology

For an aircraft to have acceptable aerodynamic characteristics, various wing or aerofoil sectionsare used. Reference Fig. 3.10 the terminology associated with aerofoil sections is as follows:-

MAXIMUM THICKNESS

UPPER SURFACE

MEAN CAMBERLINE

MAXIMUMCAMBER

CHORD LINE

LOWER SURFACE TRAILINEDGE

CHORD

LEADINGEDGE

FIG. 3.10

The Chord l ine. A straight line joining the leading and trailing edges of a wing.

The Chord. The length of the chord line that is used as a reference for all otherdimensions relating to a wing.

The Mean Camber Line. The line drawn equidistant between the upper and lowersurfaces of an aerofoil.

Maximum Camber. The maximum distance between the mean camber line and thechord line. This is one of the variables that determines the aerodynamic characteristicsof a wing.

Maximum Thickness. The maximum distance between the upper and lower surfaces.

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Maximum Thickness Chord Ratio. The ratio of maximum thickness to chordexpressed as a percentage. For subsonic wings the ratio is normally 12 - 14%.

Aerofoi l Cross-sectional Shapes

A thick well-cambered wing will produce high lift at slow speeds, whereas a thin wing with thesame camber will produce good high-speed characteristics (Fig. 3.11).

The above are both examples of asymmetrical aerofoils. If the mean camber line is coincidentwith the chord line the wing camber is reduced to zero, and this is known as a symmetricalaerofoil (Fig. 3.12).

HIGH LIFT AT SLOW SPEEDS TYPICAL HIGH SPEED AEROFOIL

FIG. 3.11

FIG. 3.12

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Chapter 03 - Aircraft Components and Terminology