CHAPTER-XI

LIFT ESTIMATION

11.1. LIFT

Component of aerodynamic force generated on aircraft perpendicular to

flight direction

11.2. LIFT COEFFICIENT (CL)

Amount of lift generated depends on:

Planform area (S), air density (p), flight speed (V), lift coefficient (CL)

L = ½ x ρ x V2 x S x CL (11.1)

CL is a measure of lifting effectiveness and mainly depends upon:

_ Section shape, platform geometry, angle of attack (α), compressibility

effect

(mach number), viscous effects (Reynolds number)

11.3 CALCULATION

CL cruise = (2WAve) / ρ x v2 x s (11.2)

where, ρ = 0.287 (at 12496 m)

CL cruise = (2 x 10297.13 x 9.81) / (0.29 x 236.112 x 42.5)

CL cruise = 0.29 (11.3)

11.4. LIFT AT TAKE-OFF

CL Take off = CL cruise + ∆CL flap (11.4)

where, Take off flap at 200 is 0.5

CL Take off = 0.29 + 0.5 = 0.79 (11.5)

VR = 1.1 Vstall (11.6)

VR = 1.1x 54.75

VR = 60.23 m/s (11.7)

LTake off = ½ x ρ x V2 x S x CL Take off (11.8)

where, ρ = 1.225 (at sea level)

LTake off = 74601.54 N (11.9)

11.5. LIFT AT LANDING

CL Landing = CL cruise + ∆CL flap (11.10)

CL Landing = 0.29 + 0.9

CL Landing = 1.19 (11.11)

VR = 0.7 Vstall (11.12)

VR = 0.7x 54.75

VR = 38.33 m/s (11.13)

L Landing = ½ x ρ x V2 x S x CL Landing (11.14)

where, ρ = 1.225 (at sea level)

L Landing = 45511.34 N (11.15)

CHAPTER- XII

DRAG ESTIMATION

12.1. DRAG:

Drag is the resolved component of the complete aerodynamic force which

is parallel

to the flight direction (or relative oncoming airflow).

It always acts to oppose the direction of motion.

It is the undesirable component of the aerodynamic force while lift is the

desirable

component.

12.2. Drag Coefficient (CD)

Amount of drag generated depends on:

Planform area (S), air density, flight speed (V), drag coefficient (CD)

CD is a measure of aerodynamic efficiency and mainly depends

upon:

Section shape, planform geometry, angle of attack, compressibility

effects (Mach

number), viscous effects (Reynolds’ number).

12.3. Drag Components

Skin Friction.

Due to shear stresses produced in boundary layer.

Significantly more for turbulent than laminar types of boundary

layers.

12.4. Form (Pressure) Drag

Due to static pressure distribution around body - Drag is the

resolved Component of the complete aerodynamic force which is parallel

to the flight direction or relative oncoming airflow.

It always acts to oppose the direction of motion.

It is the undesirable component of the aerodynamic force while lift

is the desirable

component.

Amount of drag generated depends on:

Planform area (S), air density, flight speed (V), drag

coefficient(CD)

CD is a measure of aerodynamic efficiency and mainly depends

upon:

Section shape, planform geometry, angle of attack, compressibility

effects (Mach number),viscous effects (Reynolds’ number).

Skin Friction.

Due to shear stresses produced in boundary layer.

Significantly more for turbulent than laminar types of boundary

layers.

Due to static pressure distribution around body.

Component resolved in direction of motion.

Sometimes considered separately as forebody and rear (base) drag

components.

12.5 DRAG CALCULATION

12.5.1 Drag at Take-Off

CD Take-off = CD0 + K CL Take-off 2 (12.1)

where CD0 = 0.03 and apply eq (11.5) in 12.1

CD Take-off = 0.07 (12.2)

DTake off = ½ x ρ x V2 x S x CD Take off (12.3)

DTake off = 6610.26 N (12.4)

12.5.2 Drag at Landing

CD Landing = CD0 + K CL Landing 2 (12.5)

where CD0 = 0.03 and apply eq.(11.11) in (12.5)

CD Landing = 0.11 (12.6)

D Landing = ½ x ρ x V2 x S x CD Landing (12.7)

D Landing = ½ x 1.225 x 38.332 x 42.5 x 0.11 (12.8)

D Landing = 4206.32 N (12.9)