Fixed Wing

Question 1

Equation for Cl and Cd?

Answer 1

Cl = L/(0.5rhoS*V^2)

Same for Cd but replace L for D

Question 2

Induced Drag Coefficient equation?

Answer 2

K/(pi*A)
where e = Oswald efficiency factor
K = 1/e
and A is the aspect ratio = span^2 / area

Question 3

What are the equations for the coefficents a, b, A and B?

Answer 3

a = Cdo
b = K/(pi*A)

Used for Climb:
A = a0.5rhoS
B = (bW^2) / (0.5rhoS)

Question 4

Relationship between TAS and EAS

Answer 4

Ve = Sqrt(sigma)*V
where :
Ve = EAS
V = TAS
sigma = density ratio = rho/rho,o

Question 5

What is wetted area?

Answer 5

Area of a/c or component that is exposed to airflow

Question 6

Wing Characteristics?

Answer 6

Aspect ratio = A = span^2 / area
Wing sweep = ‘triangle without base’
Taper = gamma

Question 7

Lift Coefficient conventions

Answer 7

CL with capital L is for 3D lift coefficient

Cl with lower case l is for 2D lift coefficient

Question 8

Difference between Endurance and Range?

Answer 8

Endurance is time in the air for a given amount of fuel

Range is distance flown for a given amount of fuel

Question 9

What does c represent is equations?

Answer 9

c = Specific fuel consumption measured in N/N/s

often W1 and W2 is seen in range and endurance calcs as chnage in weight due to fuel burn.

Question 10

Explain GSAR

Answer 10

GSAR = Gross Still Air Range
is an idealised concept that ignores wind and fuel used to climb to and from cruise altitude

For Jet
To maximise GSAR need to maximise sqrt(CL)/CD (max range on formula sheet)

For Prop
To maximise GSAR need to maximise CL^(3/2) / CD (min drag)

Question 11

What is Specific Air Range (SAR) and Specific Endurance (SE)?

Answer 11

SAR - Distance flown per unit weight of fuel

SE – Time flown per unit weight of fuel

Question 12

How high can an aircraft fly?

Answer 12

Thrust falls faster, so climb rate falls with altitude. The maximum altitude or ceiling is defined by:
Absolute Ceiling – rate of climb is zero
Service Ceiling – altitude at which a useful rate of climb is still available (100 feet per minute)
Zoom Ceiling – aircraft converts kinetic energy to potential energy to temporarily exceed absolute ceiling

Question 13

Distance needed to take-off may change due to what factors?

Answer 13

Weight may not be precisely known
Forecast atmospheric conditions may be different from values assumed during flight planning
Wind effects
Engine thrust/aircraft drag change with age
Pilot technique

Question 14

Required Take-off distances

Answer 14

Take Off Run Required (TORR) =
[(DISTANCE FROM START TO LIFT OFF) +⅓ (DISTANCE FROM LIFT OFF TO SCREEN)] x 1.15

Emergency Distance Required (EDR) =
(DISTANCE FROM START TO SPEED AT WHICH CRITICAL ENGINE FAILS) + (DISTANCE TO COME TO A STOP THROUGH BRAKING)

Take Off Distance Required (TORD) =
(DISTANCE FROM START TO AN ALTITUDE OF 35 FEET) x 1.15

Unfactored Take-off distance required = Sg +St + Sc

Question 15

Typical Speeds during take-off relations

Answer 15

𝑽lof ≥ 𝟏.𝟏𝑽𝒔 and 𝑽𝟐 ≥ 𝟏.𝟐𝑽s

𝑽trans= 𝟏.𝟏𝑽s

Question 16

How do landing calculations vary in comparison to take-off ones?

Answer 16

Are the same just the opposite.
For flare and descent use transition and climb equations from previous take off analysis
But Sg term is slightly different

Made up of :
Approach distance
Flare
Ground roll = free roll + braking distance

Question 17

What is the aerodynamic centre?

Answer 17

The aerodynamic centre is a fixed point for which the pitching moment is invariant with incidence (i.e. aircraft attitude)

Question 18

When can the pilot fly hands off?

Answer 18

M = 0

where M is total pitching moment