Airplanes and Aerodynamics

Summary

1.1 Flaps

Main functions : During approach and landing, increase angle of attack. causes the wing to produce the same amount of lift at a slower airspeed.

1.2 Airplane Wings

Spoilers
many mordern turbojets have, top of the wing can be deployed automatically or PIC to disrupt airflow and destroy lift
just after landing, spoiliers allow the brakes to be more effective.

Rectangular wings
generally are designed. root stalls first with the stall progression toward the wingtip.

change in the angle of attack of the wing, lift, drag, airspeed changed.

angle of attack of wing directly controls the distribution of positive and negative pressure acting on the wing.

Frost on the upper wing disrupts the smooth airflow => increases drag
and causes the airplane to stall at higher airspeed and lower angle of attack than normal => stall speed incareses

1.3 Stalls

Angle of attack remains constant regardlees of [ Weight / Dynamic pressure / Bank angle / Pitch attitude ]

Stall speed is Affected by [ Wiehgt / Load factor / Power setting ]

Tubulence can increases stall speed due to increased load factors.

 

 

1.4 Spins

Recover from spin, may become difficult when the CG is too far rearward.

Rotation of aa spin is always around the C.G

 

1.5 Lift and Drag

wing produces lift, Higher pressure below the wing, lower pressure above the wing

Lift is force acting perpendicular to the relative wind.

increase in the angle of attack wll increase drag. ( drag acts paraleel to the flight path)

In all staday state flight, Sum is same(forward = rearward, upward=downward)

 

Angle of bank increase => vertical compnent of lift decreases and the hoizontal lift increases.

 

airspeed increase => lift, parasite drag increase, as suare of the increase in airspeed

 

induced drag is byproduct fo lift, also greatly affected by changes in airspeed

 

* drag diagram

As Airspeed increase, total drag increases due to the increased parasite drag.

As airspeed decrease, total drag increase due to increased inducred drag

 L/D Max is the minimum point of the total drag curve.

 

1.6 Ground Effect

due to the interference of the ground surface with the airflow patterns

within distance of its wingspans to the surface.

change alters the wing's upwash, downwach, and wingtip vortices.

 

leaving ground effect zone, increase in induced grag and requires more thrust.

in ground effect needs a lower angle of attack to producxe the same lift as when out of ground effect. 

 

1.7 Airplane Stability

inherent ability of an objet

return to its original potsition.

ex ) in turbulent air

 

Stactic stability : Positive - Neutral - Negative

Poitive : return to original position

Neutral : no tendency

Negative : continue to move directionof the force

 

Dynamic stability

Positive : oscillation become smaller and smaller, settles down

Neutral : oscillationss remain unchanged

Negative : oscillatiions tend to increase.

 

in airplane

Longitudinal stability about lateral axis

Lateral stability about ongitudinal axis

Directional stability about the vertical axis

 

rear of CG range, will tend to be unstable about lateral axis

 

1.8 Turns

increase ins airspeed in turn, increase in the radius, decrease rate of turn.

 

contant bank angle, load factor will be constant ergardless of

rate of turn / airpseed / weight

 

as bank increased => additional vertiacl lift convert to horizontal lift, decreasing vertical lift

=> need increasing angle of attack

 

standard rate of turn : 2min. for 360 degree. 3degree / sec.

 

 

1.9 Load Factor

ratio between the total airload on the wing, gross weight of the airplane

 

increase load factor will cause an airplane to stall at higher airspeed

 

as bank angle increase, load factor will increase. 

 

Load factor is multipe of the weight x gravity

 

60 degreee bank has load factor of 2.0

 

1.10 Transonic and Supersonic Flight

ratio of ture airspeed in kts to the speed of sound in kts.
=> Mach number

subsonic : below 0.75

transonic : 0.75 - 1.20 

super sonic : 1.2 - 5

hyper sonic : above 5