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Question 232-1 : The high lift device shown in the figure below is a . err a 081 182 ? [ Formation assignment ]

Krueger flap

. /com en/com080 182 jpg. exemple 332 Krueger flap.

Question 232-2 : A plain flap will increase clmax by ?

Increasing the camber of the aerofoil

exemple 336 Increasing the camber of the aerofoil.

Question 232-3 : The frontal area of a body placed in a certain airstream is increased by a factor 3 the shape will not alter the aerodynamic drag will increase with a factor ?

3

. drag formula .d = 1/2 x rho x v² x s x cd.if s frontal area = surface is increased by a factor 3 drag d will increase with a factor 3 exemple 340 3.

Question 232-4 : The aerodynamic drag of a body placed in a certain airstream depends amongst others on ?

The airstream velocity

.the drag formula is drag = cd 1/2 rho v² s.where cd = drag coefficient.rho = density.v = tas airstream velocity in m/s .s = surface.there is no reference to the cg location the weight or the specific mass of the body exemple 344 The airstream velocity.

Question 232-5 : A body is placed in a certain airstream the airstream velocity increases by a factor 4 the aerodynamic drag will increase with a factor ?

16

.the drag d formula is d = cd 1/2 rho v² s.where cd = drag coefficient.rho = density.v = tas in m/s .s = surface.if v is increases by a factor 4 drag will increase with a factor 16 4² exemple 348 16.

Question 232-6 : A body is placed in a certain airstream the density of the airstream decreases to half of the original value the aerodynamic drag will decrease with a factor ?

2

.the drag d formula is d = cd 1/2 rho v² s.where cd = drag coefficient.rho = density.v = tas in m/s .s = surface.if rho is divide by 2 drag will decrease with a factor 2 exemple 352 2.

Question 232-7 : The point where the aerodynamic lift acts on a wing is ?

The centre of pressure

.the pressure created by an aerofoil at any point may be represented by a vector at right angles to its surface whose length is proportional to the difference between absolute pressure at the point and the free stream static pressure .all of them can be represented by a single vector acting at a particular point called the centre of pressure . 669.the centre of pressure is a theoretical point on the chord line through which the resultant of all forces the total reaction is said to act .its position is usually around 25% of the way from the leading edge simply because more lift is generated there but it moves steadily forward as the angle of attack is increased until just before the stalling angle when it moves rapidly backwards the centre of pressure's most forward point is just before the stalling angle this is why an aeroplane's nose drops when the wings stall and the centre of pressure moves behind the cg .thus when speed is increased in straight and level flight on a positively cambered aerofoil you have to decrease the angle of attack to keep the the total lift force constant and the point where the resultant of all forces are acting the centre of pressure moves aft exemple 356 The centre of pressure.

Question 232-8 : The location of the centre of pressure of a positively cambered aerofoil section at increasing angle of attack will ?

Shift forward

.the pressure created by an aerofoil at any point may be represented by a vector at right angles to its surface whose length is proportional to the difference between absolute pressure at the point and the free stream static pressure .all of them can be represented by a single vector acting at a particular point called the centre of pressure . 669.the centre of pressure is a theoretical point on the chord line through which the resultant of all forces the total reaction is said to act .its position is usually around 25% of the way from the leading edge simply because more lift is generated there but it moves steadily forward as the angle of attack is increased until just before the stalling angle when it moves rapidly backwards the centre of pressure's most forward point is just before the stalling angle this is why an aeroplane's nose drops when the wings stall and the centre of pressure moves behind the cg .thus when speed is increased in straight and level flight on a positively cambered aerofoil you have to decrease the angle of attack to keep the the total lift force constant and the point where the resultant of all forces are acting the centre of pressure moves aft exemple 360 Shift forward.

Question 232-9 : The si unit of measurement for density is ?

Kg/m³

exemple 364 Kg/m³.

Question 232-10 : The unit of measurement of pressure is ?

Psi

exemple 368 Psi

Question 232-11 : A laminar boundary layer is a layer in which ?

No velocity components exist normal to the surface

. vertical axis is also call normal axis by normal they mean perpendicular to the wing surface .the airflow in the laminar boundary layer is parallel to the wing surface in a horizontal direction and hence there are no flows perpendicular to the surface exemple 372 No velocity components exist, normal to the surface.

Question 232-12 : The subsonic static pressure ?

Decreases in a flow in a tube when the diameter decreases

. /com en/com080 815 jpg.the static pressure decreases in a venturi a tube where the diameter decreases and the airflow speed increases exemple 376 Decreases in a flow in a tube when the diameter decreases.

Question 232-13 : The lift and drag forces acting on a wing cross section ?

Depend on the pressure distribution about the wing cross section

.the distribution of velocities with resulting pressure distribution is determined by the shape or profile of the surface and the angle of attack cl or cd .the aerodynamic force of lift results from the pressure differential between the top and bottom surfaces of the wing .drag is the product of dynamic pressure drag coefficient and surface area exemple 380 Depend on the pressure distribution about the wing cross section.

Question 232-14 : The lift force acting on an aerofoil no flow separation ?

Is mainly caused by suction on the upperside of the aerofoil

exemple 384 Is mainly caused by suction on the upperside of the aerofoil.

Question 232-15 : The relative thickness of an aerofoil is expressed in ?

% chord

exemple 388 % chord.

Question 232-16 : The aerofoil polar is ?

A graph of the relation between the lift coefficient and the drag coefficient

. /com en/com080 1264 jpg.airfoil and aircraft polars have been used for a long time in aeronautics the correct german term is lilienthal'sches polardiagramm indicating that this method of graphing results of airfoil tests has been used first by otto lilienthal he plotted the lift and drag forces of his experimental results as lift versus drag as we still use it today using coefficients instead of the actual forces exemple 392 A graph of the relation between the lift coefficient and the drag coefficient.

Question 232-17 : Aspect ratio of a wing is the ratio between ?

Wing span squared and wing area

.aspect ratio is the ratio of the square of the wing span to the total wing.planform area .you could have two aerofoils of equal surface area but different aspect ratios depending on what they were designed for the higher the aspect ratio of length to width the more lift you get with less induced drag at the tips .a wing with higher aspect ratio with long wingspan and small chord reaches higher lift coefficient but stalls at a lower angle of attack than the wing with low aspect ratio exemple 396 Wing span squared and wing area.

Question 232-18 : Dihedral of the wing is ?

The angle between the 0 25 chord line of the wing and the lateral axis

.the dihedral is the angle between the wings and the horizontal looked at from the front where the wingtips are higher than the roots .it is an angle that raises the centerline of the wing tip above the centreline of the root . /com en/com080 208 jpg.notice horizon isn't a plane neither an axis .the angle between the 0 25 chord line of the wing and the lateral axis is the correct answer exemple 400 The angle between the 0.25 chord line of the wing and the lateral axis.

Question 232-19 : The induced drag ?

Increases as the lift coefficient increases

exemple 404 Increases as the lift coefficient increases.

Question 232-20 : Flap extension at constant ias whilst maintaining straight and level flight will increase the ?

Maximum lift coefficient clmax and the drag

.lift = cl x 1/2 rho v² x s.cl = lift coefficient.rho = density.v = tas in m/s .s = surface.clmax available increases with all types of flap so will drag the pilot adjusts attitude and power to maintain speed and straight and level flight exemple 408 Maximum lift coefficient (clmax) and the drag.

Question 232-21 : When trailing edge flaps are extended whilst maintaining straight and level flight at constant ias ?

The centre of pressure moves aft

.to maintain straight and level flight at constant ias while deploying trailing edge flaps you have to lower the nose decreasing angle of attack so your lift coefficient will remain constant .the centre of pressure moves backward when the angle of attack decreases exemple 412 The centre of pressure moves aft.

Question 232-22 : Which of the following situations leads to a decreasing stall speed ias ?

Decreasing weight

exemple 416 Decreasing weight.

Question 232-23 : The difference between ias and tas will ?

Decrease with decreasing altitude

.true air speed tas is obtained from indicated air speed ias by correcting for instrument position compressibility and density errors .use the very simple ertm diagram ertm for e as/ r as rectified air speed or cas / t as/ m ach . /com en/com080 103a jpg.if altitude increases difference between ias and tas increases inversely if altitude decreases difference between ias and tas decreases .for rapid calculation .tas = ias + 2% per 1000 ft altitude exemple 420 Decrease with decreasing altitude.

Question 232-24 : Compared with stalling airspeed vs in a given configuration the airspeed at which stick shaker will be triggered is ?

Greater than vs

.a stick shaker is a mechanical device to rapidly and noisily vibrate the control yoke the 'stick' of an aircraft to warn the pilot of an imminent stall it is connected to the control column of most business jets airliners and military aircraft .when the angle of attack alpha approaches a critical value the stick is made to shake as a warning .example stalling airspeed vs is 100 kt stick shaker activation is at 110 kt the airspeed at which stick shaker will be triggered is greater than vs to give enough time to the pilot to react by increasing speed and/or reducing the angle of attack exemple 424 Greater than vs.

Question 232-25 : The term angle of attack in a two dimensional flow is defined as ?

The angle between the wing chord line and the direction of the relative wind/airflow

exemple 428 The angle between the wing chord line and the direction of the relative wind/airflow.

Question 232-26 : The critical angle of attack ?

Remains unchanged regardless of gross weight

.the angle at which the stall occurs is called the critical angle of attack .a fixed wing aircraft by definition is stalled at or above the critical angle of attack rather than at or below a particular airspeed the airspeed at which the aircraft stalls varies with the weight of the aircraft the load factor bank angle the center of gravity of the aircraft and other factors however the aircraft always stalls at the same critical angle of attack exemple 432 Remains unchanged regardless of gross weight.

Question 232-27 : Comparing the lift coefficient and drag coefficient at normal angle of attack ?

Cl is much greater than cd

.for maximum aerodynamic efficiency it is necessary to generate enough lift to balance the weight while at the same time generate as little drag as possible the higher the lift/drag ratio the greater the aerodynamic efficiency therefore at normal angles of attack cl is much higher than cd between 10 and 20 times greater exemple 436 Cl is much greater than cd.

Question 232-28 : Which statement is correct regarding cl coefficient of lift and the angle of attack ?

For a symmetrical aerofoil section if the alpha is zero cl is zero

. /com en/com080 878 jpg.a symmetrical aerofoil need to have a positive angle of attack to produce lift it the pitching moment is zero the lift is zero . /com en/com080 687 jpg.a positively cambered aerofoil asymmetrical aerofoil section with positive camber produces lift with a zero angle of attack exemple 440 For a symmetrical aerofoil section, if the alpha is zero, cl is zero.

Question 232-29 : The mean aerodynamic chord mac for a given wing of any planform is ?

The chord of a rectangular wing with same moment and lift

.for a rectangular wing of constant aerofoil dimensions and constant chord the mac is just the chord . same moment and lift means equilibrium on a rectangular wing mac permits to define a point where the lift forces acting this single point is about half way out along the wing and at about 25% back from the leading edge exemple 444 The chord of a rectangular wing with same moment and lift.

Question 232-30 : Induced drag may be reduced by ?

An increase in aspect ratio

.induced drag varies with lift speed and aspect ratio is inversely proportional to aspect ratio and v² so multiply by 1/v² and directly proportional to lift²/cl²/weight² . /com en/com080 38 jpg.aspect ratio is defined as the square of the wingspan divided by the area of the wing planform exemple 448 An increase in aspect ratio.

Question 232-31 : The relationship between induced drag and the aspect ratio is ?

A decrease in the aspect ratio increases the induced drag

.it is reduced because the effect of wing tip vortices is reduced .coefficient of induced drag cdi = cl² / pi x aspect ratio .aspect ratio is defined as the square of the wingspan divided by the area of the wing planform . /com en/com080 38 jpg.induced drag varies with lift speed and aspect ratio is inversely proportional to aspect ratio and v² so multiply by 1/v² and directly proportional to lift²/cl²/weight² exemple 452 A decrease in the aspect ratio increases the induced drag.

Question 232-32 : A high aspect ratio wing produces ?

A decrease in induced drag

.it is reduced because the effect of wing tip vortices is reduced .coefficient of induced drag cdi = cl² / pi x aspect ratio .aspect ratio is defined as the square of the wingspan divided by the area of the wing planform . /com en/com080 38 jpg.induced drag varies with lift speed and aspect ratio is inversely proportional to aspect ratio and v² so multiply by 1/v² and directly proportional to lift²/cl²/weight² exemple 456 A decrease in induced drag.

Question 232-33 : What will happen in ground effect ?

The induced angle of attack and induced drag decreases

.ground effect changes airflow . /com en/com080 821 jpg.when entering the ground effect it requires a decrease in angle of attack to maintain the same cl the induced angle decreases exemple 460 The induced angle of attack and induced drag decreases.

Question 232-34 : Which statement is correct about the laminar and turbulent boundary layer ?

Friction drag is lower in the laminar layer

exemple 464 Friction drag is lower in the laminar layer

Question 232-35 : Behind the transition point in a boundary layer ?

The mean speed and friction drag increases

. /com en/com080 247 jpg.the laminar boundary layer the one at the front of the wing is smooth and thin inside it the speed of the air reduces smoothly from the free stream value to near zero at the surface because of this regular reduction in speed the average speed inside the layer is about half the free stream value and this fact and the fact that the layer is very thin mean that the total kinetic energy inside the layer is relatively small .the turbulent layer is thicker and the turbulence pulls down free stream air deep into the layer this has two results one is that the turbulent layer has more kinetic energy and the other is that near the surface the airflow slows down very rapidly causing more drag drag is bad but kinetic energy is good for the turbulent layer punches through problems and keeps the airflow attached to the wing as you get nearer the stall .in summary the turbulent layer is thicker has a higher mean speed within the layer more drag but more internal energy

Question 232-36 : When trailing edge flaps are extended in level flight the change in pitching moment ignoring any effects on the tailplane will be ?

Nose down

.pitch behaviour depends on flap type wing position and horizontal tail location the increased camber from flap deflection produces lift primarily on the rear portion of the wing this produces a nosedown pitching moment . /com en/com080 253 jpg exemple 472 Nose down.

Question 232-37 : Extension of leading edge flaps will ?

Increase critical angle of attack

exemple 476 Increase critical angle of attack.

Question 232-38 : Slat extension will ?

Increase the critical angle of attack

exemple 480 Increase the critical angle of attack.

Question 232-39 : What factors determine the distance travelled over the ground of an aeroplane in a glide ?

The wind and the lift/drag ratio which changes with angle of attack

.a headwind will decrease the distance travelled over the ground .a tailwind will increase the distance travelled over the ground .the angle of attack for the best ratio varies with the design of the wing but is around a third to a quarter of the size of the stalling angle flying at the best lift/drag ratio is flying at the maximum range speed most lift for the least drag for the most economy and the most distance for altitude lost .the wind and lift/drag ratio determine the distance travelled over the ground of an aeroplane in a glide exemple 484 The wind and the lift/drag ratio, which changes with angle of attack.

Question 232-40 : The following unit of measurement kgm/s² is expressed in the si system as ?

Newton

.si unit kg = mass and m/s² = acceleration .mass x acceleration = force and si unit for force is newton exemple 488 Newton.


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