Drag

Question 1

Drag acts parallel to and in the ____________ as the relative airflow (in the ____________ to the flight path)

Answer 1

Drag acts parallel to and in the same direction as the relative airflow (in the opposite direction to the flight path)

Question 2

PARASITE DRAG - __________
INDUCED DRAG - ______________.
Parasite drag is further sub-divided into:
 __________ Drag
 ____________________ Drag, and
 _____________________________ Drag
NOTE: Skin Friction and Form Drag are together known as _______________–.

Answer 2

PARASITE DRAG - independent of lift generation, and
INDUCED DRAG - the result of lift generation.
Parasite drag is further sub-divided into:
 Skin Friction Drag
 Form (Pressure) Drag, and
 Interference Drag
NOTE: Skin Friction and Form Drag are together known as PROFILE DRAG.

Question 3

The layer of air extending from the surface to the point where __________ is known as the boundary layer. In flight, the nature of the boundary layer will determine the _________, the ______, the value of ______, and to some extent the high speed characteristics of an aircraft.

Answer 3

The layer of air extending from the surface to the point where no viscous effect is detectable is known as the boundary layer. In flight, the nature of the boundary layer will determine the maximum lift coefficient, the stalling characteristics, the value of form drag, and to some extent the high speed characteristics of an aircraft.

Question 4

The increased rate of change in velocity at the surface in the turbulent flow will give _____ skin friction than the laminar flow. A turbulent boundary layer also has a ________ of kinetic energy than a
laminar layer.

Answer 4

The increased rate of change in velocity at the surface in the turbulent flow will give more skin friction than the laminar flow. A turbulent boundary layer also has a higher level of kinetic energy than a
laminar layer.

Question 5

Forward movement of the transition point will increase skin friction because there will be a
greater area of turbulent flow. The position of the transition point is dependent upon:

Answer 5

—Surface condition - The thin laminar layer is extremely sensitive to surface irregularities. Any roughness on the skin of a leading portion of an aircraft will cause transition to turbulence at that point and the thickening, turbulent boundary layer will spread out fanwise down-stream causing a marked increase in skin friction drag.
—Adverse pressure gradient (Figure 6.3) - A laminar layer cannot exist when pressure is rising in the direction of flow. On a curved surface, such as an aerofoil, the transition point is usually at, or near to the point of maximum thickness. Because of the adverse pressure gradient existing on a curved surface the transition point will be further forward than if the surface was flat.

Question 6

FORM (PRESSURE) DRAG: Results from ____________ ___________.Because of separation there will be a ____ pressure at the trailing edge than the leading edge. An aerodynamic force will act in the direction of the lower pressure - form drag. Separation will occur when the boundary layer _________________________

Answer 6

FORM (PRESSURE) DRAG: Results from the pressure at the leading edge of a body being greater than the pressure at the trailing edge.Because of separation there will be a lower pressure at the trailing edge than the leading edge. An aerodynamic force will act in the direction of the lower pressure - form drag.Separation will occur when the boundary layer does not have sufficient kinetic energy in the
presence of a given adverse pressure gradient.

Question 7

Loss of kinetic energy in the boundary layer can be caused by various factors

Answer 7

–As angle of attack increases, the transition point moves closer to the leading edge and the adverse pressure gradient becomes stronger. This causes the separation point to move forward. Eventually, boundary layer separation will occur so close to the leading edge that there will be insufficient wing area to provide the required lift force, C L will decrease and stall occurs.
–When a shock wave forms on the upper surface, the increase of static pressure through the shock wave will create an extreme adverse pressure gradient. If the shock wave is sufficiently strong, separation will occur immediately behind the shock wave.

Question 8

Laminar and Turbulent Separation: Separation has been shown to be caused by the airflow meeting an adverse pressure gradient, but it is found that a turbulent boundary layer is _______ to separation than a laminar one when meeting the same pressure gradient. In this respect the turbulent boundary layer is preferable to the laminar one, but from the point of view of _____ the laminar flow is preferable.

Answer 8

Laminar and Turbulent Separation: Separation has been shown to be caused by the airflow meeting an adverse pressure gradient, but it is found that a turbulent boundary layer is more resistant to separation than a laminar one when meeting the same pressure gradient. In this respect the turbulent boundary layer is preferable to the laminar one, but from the point of view of drag the laminar flow is preferable.

Question 9

Streamlining: Each part of an aircraft will be subject to form (pressure) drag. To reduce form drag it is necessary to ___________________. Streamlining increases the ratio between the _________________, reducing the curvature of the surfaces and thus the _______________. Fineness ratio is the measure of streamlining. It has been found that the ideal fineness ratio is ________.

Answer 9

Streamlining: Each part of an aircraft will be subject to form (pressure) drag. To reduce form drag it is necessary to delay separation to a point as close to the trailing edge as possible. Streamlining increases the ratio between the length and depth of a body, reducing the curvature of the surfaces and thus the adverse pressure gradient. Fineness ratio is the measure of streamlining. It has been found that the ideal fineness ratio is 3:1.

Question 10

Profile Drag: __________________________. It can be considered that these drags result from the ______________ of the aircraft presented to the relative airflow.

Answer 10

Profile Drag: The combination of skin friction and form drag is known as profile drag. It can be considered that these drags result from the “profile” (or cross-sectional area) of the aircraft presented to the relative airflow.

Question 11

INTERFERENCE DRAG: When considering a complete aircraft, parasite drag ___________. Additional drag results from ____________. ________________ is necessary to minimise interference drag.

Answer 11

INTERFERENCE DRAG: When considering a complete aircraft, parasite drag will be greater than the sum of the parts. Additional drag results from boundary layer ‘interference’ at wing/ fuselage, wing/engine nacelle and other such junctions. Filleting is necessary to minimise interference drag.

Question 12

FACTORS AFFECTING PARASITE DRAG
If IAS is doubled the Parasite Drag will be _________ - if IAS is halved the Parasite Drag will be _______ of its previous value.

Answer 12

FACTORS AFFECTING PARASITE DRAG
– Indicated Air Speed
Parasite Drag varies directly with the square of the Indicated Air Speed (IAS).
– Configuration
Parasite Drag varies directly in proportion to the frontal area presented to the airflow; this is known as ‘Parasite Area’. If flaps are deployed, the undercarriage lowered, speed brakes selected or roll control spoilers operated, ‘Parasite Area’ is increased and Parasite drag will increase.
–Airframe Contamination
Contamination by ice, frost, snow, mud or slush will increase the Parasite Drag Coefficient, and
in the case of severe airframe icing, the area.

Question 13

The lower the IAS, the _____ the angle of attack - the _______ the vortices.
The stronger the vortices - the greater the induced drag.

Answer 13

The lower the IAS, the higher the angle of attack - the stronger the vortices.
The stronger the vortices - the greater the induced drag.

Question 14

An aircraft is viewed from the rear. An __________ vortex will be induced at the right wing-tip and a ___________ vortex at the left wing-tip. At higher angles of attack (Lower IAS) the _____ chordwise vector will increase the resultant spanwise flow, making the vortices stronger.

Answer 14

An aircraft is viewed from the rear. An anti-clockwise vortex will be induced at the right wing-tip and a clock-wise vortex at the left wing-tip, Figure 6.6. At higher angles of attack (Lower IAS) the decreased chordwise vector will increase the resultant spanwise flow, making the vortices stronger.

Question 15

Induced Downwash: Wingtip vortices create certain vertical velocity components in the airflow in the vicinity of the wing, both in front of and behind it. These vertical velocities ______ upwash and downwash which ________ the effective angle of attack. The stronger the vortices, the ______ ______________.

Answer 15

Induced Downwash: Wingtip vortices create certain vertical velocity components in the airflow in the vicinity of the wing, both in front of and behind it. These vertical velocities strengthen upwash and downwash which reduces the effective angle of attack. The stronger the vortices, the greater the reduction in effective angle of attack.

Question 16

To replace the lift lost by the increased upwash and downwash the wing must be flown at a
higher angle of attack, than would otherwise be necessary. This increases drag. This extra drag
is called ______________

Answer 16

To replace the lift lost by the increased upwash and downwash the wing must be flown at a
higher angle of attack, than would otherwise be necessary. This increases drag. This extra drag
is called Induced drag

Question 17

Factors that Affect Induced Drag:

Answer 17

–The size of the lift force -lift is greater than weight during a steady turn so induced drag will be higher during a steady turn than in straight and level flight. Therefore, induced drag also increases as the Load Factor increases. Induced drag will increase in proportion to the square of the lift force.
–The speed of the aircraft-Induced drag decreases with increasing speed (for a constant lift force). This is because as speed increases the downwash caused by the tip vortices becomes less significant, the rearward inclination of the lift is less, and therefore induced drag is less. Induced drag varies inversely as the square of the speed.
–The aspect ratio of the wing - The tip vortices of a high aspect ratio wing affect a smaller proportion of the span so the overall change in downwash will be less, giving a smaller rearward tilt to the lift force. Induced drag therefore decreases as aspect ratio increases (for a given lift force). The induced drag coefficient is inversely proportional to the aspect ratio.

Question 18

Higher aspect ratio wings are ______ sensitive to changes in angle of attack, but require a ______ angles of attack for maximum lift.

Answer 18

Higher aspect ratio wings are more sensitive to changes in angle of attack, but require a smaller angles of attack for maximum lift.

Question 19

The Disadvantage of Very high aspect ratio wings are :

Answer 19

–Excessive wing bending moments: which can be reduced by carrying fuel in the wings and mounting the engines in pods beneath the wing.
—Reduced rate of roll (particularly at low airspeed): This is caused by the down-going wing (only while it is actually moving down) experiencing an increased effective angle of attack. The increased effective angle of attack is due to the resultant of the forward TAS of the wing and the angular TAS of the tip. The higher the aspect ratio, the greater the vertical TAS of the tip for a given roll rate, leading to a greater increase in effective angle of attack. The higher the effective angle of attack at the tip, the greater the resistance to roll. This phenomena is called aerodynamic damping
– Reduced ground clearance in roll during take-off and landing.

Question 20

If speed is doubled in level flight: dynamic pressure will be ___ times greater, CL must be decreased to ___ of its previous value, CDi will be ___ of its previous value and Di will be reduced to ___ of its previous value.
If speed is halved in level flight: dynamic pressure will be __ of its previous value, CL will need to be four times greater, CDi will be 16 times greater, giving four times more Di

Answer 20

If speed is doubled in level flight: dynamic pressure will be four times greater, CL must be decreased to ¼ of its previous value, CDi will be 1/16 of its previous value and Di will be reduced to ¼ of its previous value.
If speed is halved in level flight: dynamic pressure will be ¼ of its previous value, CL will need to be four times greater, CDi will be 16 times greater, giving four times more Di

Question 21

METHODS OF REDUCING INDUCED DRAG

Answer 21

Wing End-plates: A flat plate placed at the wing tip will restrict the tip vortices and
have a similar effect to an increased aspect ratio, but without the extra bending loads.
However, the plate itself will cause parasite drag, and at higher speeds there may be no
overall saving in drag.
 Tip Tanks: Fuel tanks placed at the wing tips will have a similar beneficial effect to an
end plate, will reduce the induced drag, and will also reduce the wing root bending
moment.
 Winglets: Small vertical aerofoils which form part of the wing tip (Figure 6.12). Shaped
and angled to the induced airflow, they generate a small forward force (i.e. “negative
drag”, or thrust). Winglets partly block the air flowing from the bottom to the top
surface of the wing, reducing the strength of the tip vortex. In addition, the small vortex
generated by the winglet interacts with and further reduces the strength of the main
wingtip vortex.
 Wing tip shape: The shape of the wing tip can affect the strength of the tip vortices, and
designs such as turned down or turned up wing tips have been used to reduce induced
drag.

Question 22

While parasite drag is not directly associated with the production of lift, in reality it does vary with lift. True / False

Answer 22

True.

Question 23

Factors Affecting Parasite Drag are :

Answer 23

–Effect of Configuration: Parasite drag, D p , is unaffected by lift, but is variable with dynamic
pressure and area. If all other factors are held constant, parasite drag varies significantly with
frontal area. As an example, lowering the landing gear and flaps might increase the parasite
area by as much as 80%. At any given IAS this aeroplane would experience an 80% increase in
parasite drag.
–Effect of Altitude: In most phases of flight the aircraft will be flown at a constant IAS, the
dynamic pressure and, thus parasite drag will not vary. The TAS would be higher at altitude to
provide the same IAS.
–Effect of Speed: The effect of speed alone on parasite drag is the most important. If all other
factors are held constant, doubling the speed will give four times the dynamic pressure and
hence, four times the parasite drag, (or one quarter as much parasite drag at half the original
speed). This variation of parasite drag with speed points out that parasite drag will be of greatest
importance at high IAS and of much lower significance at low dynamic pressures. To illustrate
this fact, an aeroplane in flight just above the stall speed could have a parasite drag which
is only 25% of the total drag. However, this same aeroplane at maximum level flight speed
would have a parasite drag which is very nearly 100% of the total drag. The predominance of
parasite drag at high flight speeds emphasises the necessity for great aerodynamic cleanliness
(streamlining) to obtain high speed performance.

Question 24

–Parasite and induced drags vary with speed the speed at which total drag is a minimum (Vmd) occurs when the _____________________________
–It is important to remember that L/D max is obtained at a specific angle of attack and also that the
maximum Lift/Drag ratio is a measure of ____________________-.

Answer 24

–Parasite and induced drags vary with speed the speed at which total drag is a minimum (Vmd) occurs when the induced and parasite drag are equal.
–It is important to remember that L/D max is obtained at a specific angle of attack and also that the
maximum Lift/Drag ratio is a measure of aerodynamic efficiency.–If an aircraft is operated at the L/D max angle of attack, drag will be a minimum while generating
the required lift force. Any angle of attack lower or higher than that for L/D max increases the drag for a
given lift force; greater drag requires more thrust, which would be inefficient, and expensive. It must also
be noted that if IAS is varied, L/D will vary.

Question 25

Lift/Drag ratio may be found from the drag polar by drawing the _________ to the curve from the origin.

Answer 25

Lift/Drag ratio may be found from the drag polar by drawing the tangent to the curve from the origin.

Question 26

As fuel is consumed gross weight will decrease. As the aircraft weight decreases less lift is required (lower C L) which will reduce induced drag. Total drag will be less and V md _________. However, the AOA to maintain the same L/D ratio will __________

Answer 26

As fuel is consumed gross weight will decrease. As the aircraft weight decreases less lift is required (lower C L) which will reduce induced drag. Total drag will be less and V md will occur at a lower IAS.However, the AOA to maintain the same L/D ratio will remain same.

Question 27

If an aircraft is operated at a higher gross weight, more lift will be required. If more lift is generated, induced drag will be higher. Total drag will be greater and V md will ________. If an aircraft is manoeuvred so that the load factor is increased, the result will be ___________________.

Answer 27

If an aircraft is operated at a higher gross weight, more lift will be required. If more lift is generated, induced drag will be higher. Total drag will be greater and V md will occur at a higher IAS. If an aircraft is manoeuvred so that the load factor is increased, the result will be similar to that caused by an increase in gross weight. i.e. induced drag will increase.

Question 28

If an aircraft is flown at a constant IAS, dynamic pressure will be _____. As density decreases with increasing altitude, TAS must be _______ to maintain the constant IAS (Q = ½ ρ V 2 ). If the aircraft is flown at a constant IAS, drag will ____________.

Answer 28

If an aircraft is flown at a constant IAS, dynamic pressure will be constant. As density decreases with increasing altitude, TAS must be increased to maintain the constant IAS (Q = ½ ρ V 2 ). If the aircraft is flown at a constant IAS, drag will not vary with altitude.

Question 29

Extension of the landing gear, airbrakes, or flaps will increase parasite drag, but will not substantially affect ________. The effect of increasing parasite drag is to increase total drag at any IAS but to ___________ the speed Vmd compared to the clean aircraft.

Answer 29

Extension of the landing gear, airbrakes, or flaps will increase parasite drag, but will not substantially affect induced drag. The effect of increasing parasite drag is to increase total drag at any IAS but to decrease the speed Vmd compared to the clean aircraft.

Question 30

--Steady flight at speeds greater than V md is characterised by a relatively strong tendency of the aircraft to maintain the trim speed quite naturally; the aircraft is speed stable. --Speed stability is an important consideration, particularly at speeds at and below ____________ --Steady flight at speeds ____ than V md is characterised by a tendency for the aircraft to _________ the aircraft is speed unstable. If a disturbance reduces speed it will _____. If a disturbance increases speed it will continue to drift up to V md.

Answer 30

--Steady flight at speeds greater than V md is characterised by a relatively strong tendency of the aircraft to maintain the trim speed quite naturally; the aircraft is speed stable. --Speed stability is an important consideration, particularly at speeds at and below V md, most often encountered during the approach to landing phase of flight. --Steady flight at speeds less than V md is characterised by a tendency for the aircraft to drift away from the trim speed and the aircraft is speed unstable. If a disturbance reduces speed it will naturally continue to reduce. If a disturbance increases speed it will continue to drift up to V md.

Question 31

--If an aircraft maintains a constant IAS in the speed unstable region, the addition of parasite drag by selecting undercarriage down or by deploying flaps has _____________ speed stable region to the left. --At speeds very close to V md an aircraft usually exhibits __________________

Answer 31

--If an aircraft maintains a constant IAS in the speed unstable region, the addition of parasite drag by selecting undercarriage down or by deploying flaps has the benefit of reducing V md which can improve speed stability by moving the speed stable region to the left. --At speeds very close to V md an aircraft usually exhibits no tendency towards either speed stability or speed instability - the neutral IAS region.

Question 32

POWER REQUIRED = ____________ --If an aircraft climbs at a constant IAS, Drag will ___________, but TAS _________ - so Power Required will ________.

Answer 32

POWER REQUIRED = DRAG x TAS --If an aircraft climbs at a constant IAS, Drag will remain constant, but TAS must be increased - so Power Required will increase.

Question 33

The speed corresponding to minimum Power Required (VMP), is _____ than the speed for minimum drag (VMD). -- Effect of Altitude: An aircraft flying at VMD will experience ____ drag at any altitude because VMD is an ____. -- At altitude the TAS for a given IAS is higher, but the power required also increases by the amount (Power Required = Drag x TAS). So the ratio of TAS to Power Required is unaffected and VMP will remain slower than VMD.

Answer 33

The speed corresponding to minimum Power Required (VMP), is slower than the speed for minimum drag (VMD). -- Effect of Altitude: An aircraft flying at VMD will experience constant drag at any altitude because VMD is an IAS/ EAS. -- At altitude the TAS for a given IAS is higher, but the power required also increases by the amount (Power Required = Drag x TAS). So the ratio of TAS to Power Required is unaffected and VMP will remain slower than VMD.

Question 34

Parasite Drag varies directly as the _____ of the Indicated Air Speed (IAS) - Double the speed_______ times the parasite drag. Halve the speed, ______ the parasite drag.The designer can minimise Parasite Drag by:-

Answer 34

Parasite Drag varies directly as the square of the Indicated Air Speed (IAS) - Double the speed, four times the parasite drag. Halve the speed, one quarter the parasite drag. Streamlining. Filleting and The use of laminar flow wing sections.

Question 35

Induced Drag varies ________ of the Indicated Air Speed (IAS) - Halve the speed, ________ the induced drag coefficient (CDi) and ___________ the induced drag (Di). Double the speed, _______ and __________ the Di.

Answer 35

Induced Drag varies inversely as the square of the Indicated Air Speed (IAS) - Halve the speed, 16 times the induced drag coefficient (CDi) and four times the induced drag (Di). Double the speed, one sixteenth the CDi and one quarter the Di.

Question 36

Reason for induced Drag

Answer 36

Spanwise airflow generates wingtip vortices. The higher the C L (the lower the IAS) the stronger the wingtip vortices. Wingtip vortices strengthen downwash. Strengthened downwash inclines wing lift rearwards. The greater the rearward inclination of wing lift the greater the Induced Drag.

Question 37

The designer can minimise Induced Drag by:-

Answer 37

Using a high aspect ratio wing planform. A tapered wing planform with wing twist and/or spanwise camber variation, or (Incorporation of wing end-plates, tip tanks, winglets or various wing tip shapes.

Question 38

Total drag is a minimum when ___________. At low IAS _______ drag is dominant. At high IAS _____________ drag dominates. The IAS at which Parasite and Induced drag are equal is called _________ (V md).

Answer 38

Total drag is a minimum when Parasite and Induced drag are equal. At low IAS Induced drag is dominant. At high IAS Parasite drag dominates. The IAS at which Parasite and Induced drag are equal is called minimum drag speed (V md).

Question 39

At a constant IAS, altitude has ______ on Total drag, but TAS will ________ as density ___________ with increasing altitude. Configuration changes which increase the “Parasite Area”, such as undercarriage, flaps or speed brakes, increases Parasite drag, increases Total drag and __________ V md.

Answer 39

At a constant IAS, altitude has no affect on Total drag, but TAS will increase as density decreases with increasing altitude. Configuration changes which increase the “Parasite Area”, such as undercarriage, flaps or speed brakes, increases Parasite drag, increases Total drag and decreases V md.

Question 40

Speed stability.

Answer 40

--An aircraft flying at a steady IAS higher than V md with a fixed throttle setting will have speed stability. --An aircraft flying at a steady IAS at V md or slower with a fixed throttle setting will usually NOT have speed stability. --If an aircraft flying at a steady IAS and a fixed throttle setting within the non-stable IAS region encounters a disturbance which slow the aircraft, the aircraft will tend to slow further; IAS will tend to continue to decrease and Total drag increase.

Question 41

VMP the Indicated Air Speed for minimum ‘Power Required’ is _____- than the minimum drag speed (VMD). Maximum TAS/Power ratio _________ occurs at _____________ .

Answer 41

VMP the Indicated Air Speed for minimum ‘Power Required’ is slower than the minimum drag speed (VMD). Maximum TAS/Power ratio (1.32 VMP) occurs at VMD .

Question 42

What is the effect on total drag of an aircraft if the airspeed decreases in level flight below that speed for maximum L/D? a. Drag increases because of increased induced drag. b. Drag decreases because of lower induced drag. c. Drag increases because of increased parasite drag. d. Drag decreases because of lower parasite drag.

Answer 42

A

Question 43

By changing the angle of attack of a wing, the pilot can control the airplane’s: a. lift and airspeed, but not drag. b. lift, gross weight, and drag. c. lift, airspeed, and drag. d. lift and drag, but not airspeed.

Answer 43

C

Question 44

What is the relationship between induced and parasite drag when the gross weight is increased? a. Parasite drag increases more than induced drag. b. Induced drag increases more than parasite drag. c. Both parasite and induced drag are equally increased. d. Both parasite and induced drag are equally decreased.

Answer 44

B

Question 45

In theory, if the airspeed of an airplane is doubled while in level flight, parasite drag will become: a. twice as great. b. half as great. c. four times greater. d. one quarter as much.

Answer 45

C

Question 46

As airspeed decreases in level flight below that speed for maximum lift/drag ratio, total drag of an aeroplane: a. decreases because of lower parasite drag. b. increases because of increased parasite drag. c. increases because of increased induced drag. d. decreases because of lower induced drag.

Answer 46

C

Question 47

Which statement is true relative to changing angle of attack? a. A decrease in angle of attack will increase pressure below the wing, and decrease drag. b. An increase in angle of attack will decrease pressure below the wing, and increase drag. c. An increase in angle of attack will increase drag. d. A decrease in angle of attack will decrease pressure below the wing and increase drag.

Answer 47

C

Question 48

On a wing, the force of lift acts perpendicular to, and the force of drag acts parallel to the: a. flightpath. b. longitudinal axis. c. chord line. d. longitudinal datum

Answer 48

A

Question 49

That portion of the aircraft’s total drag created by the production of lift is called: a. induced drag, and is greatly affected by changes in airspeed. b. induced drag, and is not affected by changes in airspeed. c. parasite drag, and is greatly affected by changes in airspeed. d. parasite drag, which is inversely proportional to the square of the airspeed

Answer 49

A

Question 50

The best L/D ratio of an aircraft occurs when parasite drag is: a. a minimum. b. less than induced drag. c. greater than induced drag. d. equal to induced drag.

Answer 50

D

Question 51

An aircraft has a L/D ratio of 15:1 at 50 kts in calm air. What would the L/D ratio be with a direct headwind of 25 kts? a. 30 : 1 b. 15 : 1 c. 25 : 1 d. 7.5 : 1

Answer 51

B

Question 52

Which is true regarding aerodynamic drag? a. Induced drag is a by‑product of lift and is greatly affected by changes in airspeed. b. All aerodynamic drag is created entirely by the production of lift. c. Induced drag is created entirely by air resistance. d. Parasite drag is a by-product of lift.

Answer 52

A

Question 53

At a given True Air Speed, what effect will increased air density have on the lift and drag of an aircraft? a. Lift will increase but drag will decrease. b. Lift and drag will increase. c. Lift and drag will decrease. d. Lift and drag will remain the same.

Answer 53

B

Question 54

If the Indicated Air Speed of an aircraft is increased from 50 kts to 100 kts, parasite drag will be: a. four times greater. b. six times greater. c. two times greater. d. one quarter as much.

Answer 54

A

Question 55

If the Indicated Air Speed of an aircraft is decreased from 100 kts to 50 kts, induced drag will be: a. two times greater. b. four times greater. c. half as much. d. one quarter as much.

Answer 55

B

Question 56

The best L/D ratio of an aircraft in a given configuration is a value that: a. varies with Indicated Air Speed. b. varies depending upon the weight being carried. c. varies with air density. d. remains constant regardless of Indicated Air Speed changes.

Answer 56

D

Question 57

The tendency of an aircraft to develop forces which restore it to its original condition, when disturbed from a condition of steady flight, is known as: a. manoeuvrability. b. controllability. c. stability. d. instability.

Answer 57

C

Question 58

As Indicated Air Speed increases in level flight, the total drag of an aircraft becomes greater than the total drag produced at the maximum lift/drag speed because of the: a. decrease in induced drag only. b. increase in induced drag. c. increase in parasite drag. d. decrease in parasite drag only.

Answer 58

C

Question 59

The resistance, or skin friction, due to the viscosity of the air as it passes along the surface of a wing is a type of: a. induced drag. b. form drag. c. parasite drag. d. interference drag.

Answer 59

C

Question 60

Which relationship is correct when comparing drag and airspeed? a. Parasite drag varies inversely as the square of the airspeed. b. Induced drag increases as the square of the airspeed. c. Parasite drag increases as the square of the lift coefficient divided by the aspect ratio. d. Induced drag varies inversely as the square of the airspeed.

Answer 60

D

Question 61

If the same angle of attack is maintained in ground effect as when out of ground effect, lift will: a. decrease, and parasite drag will decrease. b. increase, and induced drag will decrease. c. decrease, and parasite drag will increase. d. increase and induced drag will increase.

Answer 61

B

Question 62

Which statement is true regarding aeroplane flight at L/Dmax? a. Any angle of attack other than that for L/Dmax increases parasite drag. b. Any angle of attack other than that for L/Dmax increases the lift/drag ratio. c. Any angle of attack other than that for L/Dmax increases total drag for a given aeroplane’s lift. d. Any angle of attack other than that for L/Dmax increases the lift and reduces the drag.

Answer 62

C

Question 63

Aspect ratio of a wing is defined as the ratio of the: a. square of the chord to the wingspan. b. wingspan to the wing root. c. area squared to the chord. d. wingspan to the mean chord.

Answer 63

D

Question 64

A wing with a very high aspect ratio (in comparison with a low aspect ratio wing) will have: a. poor control qualities at low airspeeds. b. increased drag at high angles of attack. c. a low stall speed. d. reduced bending moment on its attachment points.

Answer 64

A

Question 65

At a constant velocity in airflow, a high aspect ratio wing will have (in comparison with a low aspect ratio wing): a. increased drag, especially at a low angle of attack. b. decreased drag, especially at a high angle of attack. c. increased drag, especially at a high angle of attack. d. decreased drag, especially at low angles of attack.

Answer 65

B

Question 66

What happens to total drag when accelerating from CLmax to maximum speed? a. Increases. b. Increases then decreases. c. Decreases. d. Decreases then increases.

Answer 66

D

Question 67

If the Indicated Air Speed of an aircraft in level flight is increased from 100 kt to 200 kt, what change will occur in (i) TAS (ii) CDi (iii) Di ? (i) (ii) (iii) a. 2 1/4 1/16 b. 0 4 16 c. 4 1/16 1/4 d. 2 1/16 1/4

Answer 67

D