Atpl Saron - Theory Of Flight

Front 1

Lift equation

Back 1

Lift = 1/2p × V2 x S x Cl

p = air density

V = true airspeed

S = size of wing (surface area)

Cl = lift coefficient

i) shape of wing

ii) AoA

Front 2

Cambered aerofoil

Back 2

- produce more lift than symmetrical aerofoil

- will produce lift at zero AoA

- stall at lower AoA than uncambered

Flaps inc camber

Front 3

Parasite drag

Back 3

a) Skin friction - friction over surface

b) Form drag - air over shape

c) Interference - of flow as 2 objects joined

Proportional to:

1. Air density

2. Surface area

3. Velocity squared

*unchanged w/ weight & AoA

Front 4

Induced drag

Back 4

- pressure difference (top/bottom of wing) = downward force = reaction (lift) = reduction in horiz velocity

Inc w/ factors that inc leakage around wing tip (& AoA):

1. Weight

2. Dec air density (inc AoA)

3. Dec TAS (inc AoA)

- *inv proportional to V2

Design features that reduce:

1. High aspect ration

2. Winglets (inc effective aspect ratio)

- most effective t/o, climb, hight alt cruise

- *inc form drag

Front 5

Total drag

Back 5

Acts in same direction as relative airflow

- induced drag high at low speeds

- parasite drag high at high speeds

Min drag speed - lift/drag ratio max

Front 6

Range

Back 6

TW - slow down to reduce fuel consumption

HW - speed up to minimize time exposed

Range inc:

- Red weight (= less induced drag)

- Inc alt (up to Vmd or slightly ab for jet a/c)

- better fuel economy

To achieve - Max velocity / fuel flow

**to maint, as weight reduced,

1. a/s must be reduced

2. red thrust to maint AoA

Front 7

Speed for max range

Back 7

Speed where ratio of power/thrust to TAS is lowest- 1.32 x Vmd

- not stable & difficult to maintain

- LRC higher but reduces trip duration

Front 8

Stall

Back 8

AoA at which Cl starts to dec

Design features:

1. Washout - root higher AoI to ensure it stalls 1st

2. Higher camber at root

3. Stall strips at root create early separation of airflow

4. Vortex generators - reenergize boundary layer delaying separation

Front 9

Surface contamination and stall

Back 9

Reduce critical AoA

Thin layer:

-Dec lift up to 30%

-Inc drag up to 40%

Front 10

Mach number

Back 10

= TAS / LSS

Front 11

Speed of sound

Back 11

= 39 x (sq rt temp K)

Temp in K = C + 273

Front 12

Sub/Trans/Supersonic

Back 12

Subsonic: airflow over entire airframe < LSS (~ <M0.75)

Transonic: airflow over some of a/c lower/higher than LSS (M0.75~1.2)

Supersonic: airflow over entire airframe > LSS

Front 13

Shockwave formation

Back 13

- As speed of a/c app LSS disturbance of airfoil not communicated forward

- collision of air molecules on LE causes rise of pressure, density, and temp & dec in velocity

= turbulence/separation aft of shockwave

Front 14

Mmo

Back 14

Max operating mach number

mach number- indicated by barber pole

Beyond will = control and stability problems

- caused by shockwaves (mach buffet)

- lower altitudes more limiting

Limiting mach number

- max operating speed in relation to speed of sound

Front 15

Mcrit

Back 15

- speed at which shockwave 1st appears on wing

- separation not yet occured

- airflow at speed of sound but not exceed

Where speed > Mcrit

- as air passes through shockwave

- temp inc, press inc, density inc, speed dec (= drag rise/diversion)

Front 16

Mach tuck

Back 16

If speed > Mmo

Shockwave also caused rearward movement of CofL = less total lift

= nose down pitch

Also, disturbed airflow dec horizontal stab (TDF) effectiveness

Design:

- pitch trim compensator

- stick puller

Front 17

Design to delay shockwave formation

Back 17

1. Supercritical aerofoil;

- thin flat topped wing

- reduce acceleration of airflow

2. Vortex generators

- mix airflow ab wing w/ boundary layer, reducing speed, delay boundary layer separation

3. Sweepback

- longer effective chord to oncoming airflow, wing thinner reducing acceleration of air

*inc Mcrit

- shockwave 1st form at root

Front 18

Sweepback

Back 18

*Secondary advantage of yaw/directional stability

- less sweep = more drag on upwind wing - corecting yaw

Disadvantage:

- dec thickness/lower camber = dec lift & higher TO/landing speeds

- dutch roll ( combined roll & yaw)

- correct w/ rate gyro + yaw damp

Front 19

Angle of bank for rate one turn

Back 19

= (TAS kts / 10) + 7

= (TAS mph / 10) + 5

360° in 2mins OR

3° / sec

Front 20

Stall speed in a turn

Back 20

= normal stall speed x sq rt load factor in turn

45° AoB = 1.41 LF

60° AoB = 2 LF

Front 21

Longitudinal stability improved

Back 21

Moving CoG forward of CoP

Front 22

Laminar flow wing vs conventional wing

Back 22

Laminar flow max thickness

- 40% chord

Conventional wing max thickness

- 30% chord

Front 23

*Canards

Back 23

- reduce main wing loading

- better controls main wing AoA & airflow

- inc maneuverability at high AoA

- reduces stall speed

Front 24

Buffet boundary

Back 24

Factors that affect AoA

- g loading

- AoB- weight

- pressure/density alt

Narrow margin of protection btwn low and high speed buffet

Front 25

Buffet boundary

Back 25

Buffeting (due airflow separation)

Low speed - conventional stall (AoA)

High speed - shock wave (AoA & TAS)

- choose buffet margin to account for inc 'g' loading (ex due turn or CAT)

Front 26

Coffin corner

Back 26

Push down - descend

Lower altitude will give wider safety margin

Front 27

Dihedral

Back 27

Lateral stability

- in bank, low wing flying higher AoA, produces more lift, tendency to return wings level

- desirable response to small disturbances

- ac must first develop a sideslip towards the 'dropped' wing before can return wings level

Front 28

Low energy regime during landing

Back 28

A/c not certified to successfully complete go around (w/out ground contact) once entered

1. Flaps/gear landing config

2. A/c in descent

3. Thrust stabilized in idle range

4. A/s dec

5. A/c close to ground (50' in some cases)

Front 29

State of equilibrium - forces opposing weight/drag in climb

Back 29

Resultant of

1. Thrust

2. Lift

Front 30

State of equilibrium - forces opposing weight in descent

Back 30

Resultant of lift and drag

Front 31

Critical engine on 4-engine a/c

Back 31

#1 or #4 depending on prop rotation