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On a swept wing aeroplane at low airspeed the 'pitch up' phenomenon ? [ Formation assignment ]

Question 231-1 : Is caused by wingtip stall never occurs since a swept wing is a 'remedy' to pitch up is caused by extension of trailing edge lift augmentation devices is caused by boundary layer fences mounted on the wings

.flying at low speed means flying at high angle of attack there is a tendency for the swept wing to develop a strong spanwise flow towards the wingtip when the.wing is at high angles of attack . /com en/com080 27 jpg.stall occurs at the wingtips first resulting in a shift of the center of lift of the wing in a forward direction relative to the center of gravity of the airplane causing the nose to pitch up exemple 331 Is caused by wingtip stall.Is caused by wingtip stall.

The lift of an aeroplane of weight w in a constant linear climb with a climb ?

Question 231-2 : W cos gamma w 1 sin gamma w 1 tan gamma w/cos gamma

Lift = weight x cos climb angle. 1526 exemple 335 W.cos.gammaW.cos.gamma

Which one of the following statements about the lift to drag ratio in straight ?

Question 231-3 : At the highest value of the lift/drag ratio the total drag is lowest the highest value of the lift/drag ratio is reached when the lift is zero the lift/drag ratio always increases as the lift decreases the highest value of the lift/drag ratio is reached when the lift is equal to the aircraft weight

.lift/drag ratio is maximum at the speed for minimum total drag exemple 339 At the highest value of the lift/drag ratio the total drag is lowest.At the highest value of the lift/drag ratio the total drag is lowest.

At a load factor of 1 and the aeroplane's minimum drag speed what is the ratio ?

Question 231-4 : Di/dp = 1 it varies between aeroplane types di/dp = 2 di/dp = 1/2

.the minimum drag speed occurs at the speed where the induced drag is equal to the parasitic drag this is the speed at which the best gradient of climb is achieved exemple 343 Di/dp = 1.Di/dp = 1.

The correct drag d formula is ?

Question 231-5 : D= cd 1/2 rho v² s d= cd 2 rho v² s d= cd 1/2 rho v s d= cd 1/2 1/rho v² s

.where cd = drag coefficient.rho = density.v = tas in m/s .s = surface.drag is the force that opposes the forward motion of a body through the air it's an aerodynamic force on a body acting parallel and opposite to the relative wind exemple 347 D= cd 1/2 rho v² sD= cd 1/2 rho v² s

The value of the parasite drag in straight and level flight at constant weight ?

Question 231-6 : Square of the speed speed angle of attack square of the angle of attack

.parasite drag only varies with speed and is directly proportional to v² . /com en/com032 209 jpg. exemple 351 Square of the speed.Square of the speed.

An aeroplane accelerates from 80 kt to 160 kt at a load factor equal to 1 the ?

Question 231-7 : I 1/16 ii 1/4 i 1/4 ii 2 i 1/2 ii 1/16 i 4 ii 1/2

.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 .we know that speed is double 80 kt to 160 kt so 1/2 x rho x v² is multiplicate by 4 to maintain lift l constant you have to divide the lift coefficient cl by 4 lift formula = 1/2 x rho x v² x s x cl .if cl is divide by 4 thus the coefficient of induced drag cdi from cdi = cl² / pi x aspect ratio will be divide by 16 .using now the induced drag formula = 1/2 x rho x v² x s x cdi knowing that cdi is divide by 16 and 1/2x rho x v² is multiplicate par 4 it result that induced drag will be divide by 4 exemple 355 (i) 1/16 (ii) 1/4(i) 1/16 (ii) 1/4

What is the effect of high aspect ratio of an aeroplane's wing on induced drag ?

Question 231-8 : It is reduced because the effect of wing tip vortices is reduced it is increased because high aspect ratio has greater frontal area it is unaffected because there is no relation between aspect ratio and induced drag it is increased because high aspect ratio produces greater downwash

.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 359 It is reduced because the effect of wing-tip vortices is reduced.It is reduced because the effect of wing-tip vortices is reduced.

The most important problem of ice accretion on a transport aeroplane during ?

Question 231-9 : Reduction in clmax increase in weight increase in drag blocking of control surfaces

For a transport aeroplane increasing in weight is not the most important problem only frontal areas are covered by ice not all of the airplane surfaces .increase in drag can be one of the most important problem but you can counteract drag by increasing the angle of attack until you reach clmax which will be reduces because the airflow separation will occur earlier .clmax reduction is the most important problem . /com en/com080 51 jpg. exemple 363 Reduction in clmax.Reduction in clmax.

The effects of very heavy rain tropical rain on the aerodynamic characteristics ?

Question 231-10 : Decrease of clmax and increase of drag decrease of clmax and decrease of drag increase of clmax and increase of drag increase of clmax and decrease of drag

exemple 367 Decrease of clmax and increase of drag.Decrease of clmax and increase of drag.

In what way do 1 induced drag and 2 parasite drag alter with increasing speed ?

Question 231-11 : 1 decreases and 2 increases 1 increases and 2 increases 1 decreases and 2 decreases 1 increases and 2 decreases

.parasite drag only varies with speed and is directly proportional to v² . /com en/com032 209 jpg.the induced drag decreases as the lift coefficient decreases if you increase speed in straight and level flight you must reduce the angle of attack it means a reduction of cl coefficient of lift exemple 371 (1) decreases and (2) increases.(1) decreases and (2) increases.

Which of the following wing planforms produces the lowest induced drag all ?

Question 231-12 : Elliptical rectangular tapered circular

.both lift distribution and load distribution are of great importance in the wing design process .to give minimum induced drag the span wise efficiency factor e should be as close to 1 as possible this is the case of an elliptic span wise lift distribution a number of methods are available to modify the span wise distribution of lift they include 1 planform taper to obtain an elliptic planform used for the spitfire wing which was remarkably elliptic 2 a geometric twist and/or aerodynamic twist to obtain elliptic lift distribution or 3 a combination of all of these methods .in the past 1930s it was thought that for an elliptic lift distribution the chord must vary elliptically along the span the direct result of such logic was that the wing planform must be elliptical for this reason several aircraft wing planforms such as supermarine spitfire a famous british world war ii fighter were made elliptic but today we know that there are various parameters that make the lift distribution elliptic thus there is no need for the wing planform to be planform an elliptical planform is hard to manufacture and is costly from the point of view of construction the best type of wing is the un tapered untwisted wing exemple 375 Elliptical.Elliptical.

If flaps are deployed at constant ias in straight and level flight the ?

Question 231-13 : Decrease remain the same increase or decrease depending on the initial angle of attack increase

.the action of the airfoil that gives an aircraft lift also causes induced drag when an airfoil is flown at a positive aoa a pressure differential exists between the upper and lower surfaces of the airfoil the pressure above the wing is less than atmospheric pressure and the pressure below the wing is equal to or greater than atmospheric pressure .if flaps are deployed at constant ias we must reduce the aoa to stay in a level flight thus pressure difference between the top and the bottome of the airfoil is reduced the magnitude of tip vortices will decrease exemple 379 Decrease.Decrease.

Induced drag at constant ias is affected by ?

Question 231-14 : Aeroplane weight aeroplane wing location angle between wing chord and fuselage centre line engine thrust

exemple 383 Aeroplane weight.Aeroplane weight.

Induced drag is created by the ?

Question 231-15 : Spanwise flow pattern resulting in the tip vortices interference of the air stream between wing and fuselage separation of the boundary layer over the wing propeller wash blowing across the wing

exemple 387 Spanwise flow pattern resulting in the tip vortices.Spanwise flow pattern resulting in the tip vortices.

Vortex generators ?

Question 231-16 : Transfer energy from the free airflow into the boundary layer change the turbulent boundary layer into a laminar boundary layer reduce the spanwise flow on swept wing take kinetic energy out of the boundary layer to reduce separation

.vortex generators are rows of small thin blades which project vertically about 2 5 cm into the airstream they each generate a small vortex which causes the free stream flow of high energy air to mix with and add kinetic energy to the boundary layer this re energises the boundary layer and delays separation exemple 391 Transfer energy from the free airflow into the boundary layer.Transfer energy from the free airflow into the boundary layer.

Compared with level flight prior to the stall the lift 1 and drag 2 in the ?

Question 231-17 : 1 decreases 2 increases 1 decreases 2 decreases 1 increases 2 increases 1 increases 2 decreases

.at the stall the lift coefficient begins to fall but it is still high the angle of attack is still high and therefore induced drag is still high profile drag is rising as the airflow separates and breaks down overall there is a small drop in lift coefficient and a continuing rapid rise in drag coefficient exemple 395 (1) decreases (2) increases.(1) decreases (2) increases.

Entering the stall the centre of pressure of a straight 1 wing and of a ?

Question 231-18 : 1 move aft 2 move forward 1 move aft 2 move aft 1 not move 2 move forward 1 move aft 2 not move

.straight wing .the centre of pressure moves forward when the angle of attack increases until it approaches and exceeds the critical angle of attack then it moves aft at the stall .swept back wing .there is a tendency for the swept wing to develop a strong spanwise flow towards the wingtip when the wing is at high angles of attack . /com en/com080 27 jpg.stall occurs at the wingtips first resulting in a shift of the center of lift of the wing in a forward direction relative to the center of gravity of the airplane causing the nose to pitch up exemple 399 (1) move aft, (2) move forward.(1) move aft, (2) move forward.

Which of the following statements about the spin is correct ?

Question 231-19 : During spin recovery the ailerons should be kept in the neutral position an aeroplane is prone to spin when the stall starts at the wing root in the spin airspeed continuously increases every aeroplane should be designed such that it can never enter a spin

exemple 403 During spin recovery the ailerons should be kept in the neutral position.During spin recovery the ailerons should be kept in the neutral position.

During an normal spin recovery ?

Question 231-20 : The ailerons are held in the neutral position the control stick is moved side ways against the angle of bank the control stick is moved side ways in the direction of the angle of bank the control stick is pulled to the most aft position

exemple 407 The ailerons are held in the neutral position.The ailerons are held in the neutral position.

Which of the following statements about the stall of a straight wing aeroplane ?

Question 231-21 : Just before the stall the aeroplane will be have an increased nose down tendency buffeting is the result of tailplane flow separation the nose down effect is the result of increasing downwash due to flow separation the horizontal tail will stall at a higher speed than the wing

.straight wing .the centre of pressure moves forward when the angle of attack increases until it approaches and exceeds the critical angle of attack then it moves aft just before the stall or at the stall . /com en/com080 111 png.loss of lift is felt ahead of the centre of gravity of the aircraft and the centre of pressure moves rearwards so the nose drops and angle of attack is reduced exemple 411 Just before the stall the aeroplane will be have an increased nose down tendency.Just before the stall the aeroplane will be have an increased nose down tendency.

Which of the following are used as stall warning devices ?

Question 231-22 : Stick shaker and stallstrip angle of attack indicator and speed indicator angle of attack sensor and stallstrip stick shaker and angle of attack indicator

.we are talking about warning devices so 'angle of attack sensor' or 'angle of attack indicator' are not regarded as stall warning devices as they dont give you a warning .if you dont have an eye on the angle of attack indicator you won't know that you are approaching the stall . /com en/com080 112 jpg.stallstrips exemple 415 Stick shaker and stallstrip.Stick shaker and stallstrip.

Which combination of design features is known to be responsible for deep stall ?

Question 231-23 : Swept back wings and a t tail straight wings and a t tail swept back wings and wing mounted engines straight wings and aft fuselage mounted engines

There is a tendency for the swept wing to develop a strong spanwise flow towards the wingtip when the wing is at high angles of attack . /com en/com080 27 jpg.stall occurs at the wingtips first resulting in a shift of the center of lift of the wing in a forward direction relative to the center of gravity of the airplane causing the nose to pitch up . /com en/com080 810 jpg.it is a characteristic of t tail aircraft to pitch up viciously when stalled in extreme nose high attitudes making recovery difficult or violent .the tailplane and elevator are in the path of the separated airflow from the wing .it must be emphasised that 'pitch up' is the primary cause of deep stall and a t tail is a contributory factor exemple 419 Swept back wings and a t-tail.Swept back wings and a t-tail.

When a strongly swept back wing stalls and the wake of the wing contacts the ?

Question 231-24 : Nose up tendency and/or lack of elevator response tendency to increase speed after initial stall nose down tendency increase sensitivity of elevator inputs

exemple 423 Nose up tendency and/or lack of elevator response.Nose up tendency and/or lack of elevator response.

The function of the stick pusher is ?

Question 231-25 : To activate and push the stick forward at or beyond a certain value of angle of attack to activate and push the stick forward prior to stick shaker to vibrate the controls to pull the stick to avoid a high speed stall

.a stick pusher prevents the pilot from increasing the angle of attack further .a stick pusher is a device installed in some fixed wing aircraft to prevent the aircraft from entering an aerodynamic stall some large fixed wing aircraft display poor post stall handling characteristics or are vulnerable to deep stall to prevent such an aircraft approaching the stall the aircraft designer may install a hydraulic or electro mechanical device that pushes forward on the elevator control system whenever the aircraft's angle of attack reaches the pre determined value and then ceases to push when the angle of attack falls sufficiently exemple 427 To activate and push the stick forward at or beyond a certain value of angle of attack.To activate and push the stick forward at or beyond a certain value of angle of attack.

On a wing fitted with a 'fowler' type trailing edge flap the 'full extended' ?

Question 231-26 : An increase in wing area and camber an unaffected wing area and increase in camber an unaffected cd at a given angle of attack an increase in wing area only

exemple 431 An increase in wing area and camber.An increase in wing area and camber.

When flaps are extended whilst maintaining straight and level flight at ?

Question 231-27 : Remain the same increase decrease first increase and then decrease

Lift coefficient can be changed either by changing angle of attack or by changing the camber as the question states maintaining straight and level flight at constant ias then you have to generate the same lift so lift coefficient must stay constant .lowering the flaps will increase the camber and for fowler flaps the wing area as well so the lift coefficient will increase .to maintain lift coefficient constant you will have to reduce the angle of attack exemple 435 Remain the same.Remain the same.

When flaps are deployed at constant angle of attack the lift coefficient will ?

Question 231-28 : Increase decrease remain the same vary as the square of ias

.the angle of attack is the angle between the relative airflow and the wing chord when you deploy flaps it will increase camber and the local angle of attack both of which would increase the lift for the same value of dynamic pressure cl will increase exemple 439 Increase.Increase.

Trailing edge flap extension will ?

Question 231-29 : Decrease the critical angle of attack and increase the value of clmax increase the critical angle of attack and increase the value of clmax decrease the critical angle of attack and decrease the value of clmax increase the critical angle of attack and decrease the value of clmax

.trailing edge flap extension increases the camber of a wing and increases the coefficient of lift air flow on the upper surface must follow this increased cambered profil thus airflow separation on the upper surface of the wing will occur earlier the airflow separation will start at a lower angle of attack than for a clean wing .example when the critical angle of attack was 15° for the wing without trailing edge flaps deployed it is now at 10° .and as the coefficient of lift is increased you can fly at a lower speed by producing the same lift since 's' wing surface increases in the lift formula = 1/2 rho s v² cl exemple 443 Decrease the critical angle of attack and increase the value of clmax.Decrease the critical angle of attack and increase the value of clmax.

Which of the following statements about the difference between krueger flaps ?

Question 231-30 : Deploying a slat will form a slot deploying a krueger flap does not deploying a krueger flap will form a slot deploying a slat does not deploying a slat will increase critical angle of attack deploying a krueger flap does not deploying a krueger flap will increase critical angle of attack deploying a slat does not

Img /com en/com080 123 jpg. exemple 447 Deploying a slat will form a slot, deploying a krueger flap does not.Deploying a slat will form a slot, deploying a krueger flap does not.

What is the most effective flap system ?

Question 231-31 : Fowler flap split flap plain flap single slotted flap

. /com en/com080 124 jpg.a fowler flap move aft then turn down it significantly increases the camber and the wing area exemple 451 Fowler flap.Fowler flap.

Deploying a fowler flap the flap will ?

Question 231-32 : Move aft then turn down turn down then move aft just move aft just turn down

. /com en/com080 125 gif. exemple 455 Move aft, then turn down.Move aft, then turn down.

A slotted flap will increase the clmax by ?

Question 231-33 : Increasing the camber of the aerofoil and re energising the airflow decreasing the skin friction increasing only the camber of the aerofoil increasing the critical angle of attack

exemple 459 Increasing the camber of the aerofoil and re-energising the airflow.Increasing the camber of the aerofoil and re-energising the airflow.

In order to maintain straight and level flight at a constant airspeed whilst ?

Question 231-34 : Increased held constant increased or decreased depending on type of flap decreased

.when you retract the flaps surface wing is reduced .in order to maintain straight and level flight at a constant airspeed you must increase the coefficient of lift cl in the lift formula .lift = cl x 1/2 rho v² x s..cl = lift coefficient.rho = density.v = tas in m/s .s = surface.to increase cl you must increase the angle of attack exemple 463 Increased.Increased.

The function of the slot between an extended slat and the leading edge of the ?

Question 231-35 : Cause a venturi effect which energizes the boundary layer allow space for vibration of the slat reduce the wing loading slow the air flow in the slot so that more pressure is created under the wing

.the function of the slot is to accelerate the flow close to the upper skin retarding the de attachment along the chord . /com en/com080 993 jpg.it is kind of a nozzle that works with the rest of the wing when deployed exemple 467 Cause a venturi effect which energizes the boundary layer.Cause a venturi effect which energizes the boundary layer.

An aeroplane has the following flap settings 0° 15° 30° and 45° slats can ?

Question 231-36 : Flaps from 30° to 45° the slats flaps from 0° to 15° flaps from 15° to 30°

.lowering flap increases both the lift and the drag but not in the same proportion although the lift is the larger force the proportional increase in the drag is greater and so the maximum obtainable lift/drag ratio decreases .the flaps angle from 30° to 45° regarding to the free airflow offers a larger surface thus the parasite drag will be more increased exemple 471 Flaps from 30° to 45°.Flaps from 30° to 45°.

After take off the slats when installed are always retracted later than the ?

Question 231-37 : Because slats extended gives a large decrease in stall speed with relatively less drag because slats extended provides a better view from the cockpit than flaps extended because vmca with slats extended is more favourable compared with the flaps extended situation because flaps extended gives a large decrease in stall speed with relatively less drag

Upon extension of a spoiler on a wing ?

Question 231-38 : Cd is increased and cl is decreased only cl is decreased cd remains unaffected both cl and cd are increased cd is increased while cl remains unaffected

.spoilers creates a burbling flow over the wing to destroy lift when you extend a spoiler the coefficient of drag cd is increased and the coefficient of lift cl is decreased .take care if the question states speed and load factor remain constant and the aircraft remains in straight and level flight it means that the reduction in lift is recovered by increasing the angle of attack and thrust thus in this case cl remains unaffected exemple 479 Cd is increased and cl is decreased.Cd is increased and cl is decreased.

When 'spoilers' are used as speed brakes ?

Question 231-39 : At same angle of attack cd is increased and cl is decreased clmax of the polar curve is not affected they do not affect wheel braking action during landing at same angle of attack cl remains unaffected

exemple 483 At same angle of attack, cd is increased and cl is decreased.At same angle of attack, cd is increased and cl is decreased.

How does stall speed ias vary with altitude ?

Question 231-40 : It remains constant at lower altitudes but increases at higher altitudes due to compressibility effects it remains constant it increases with increasing altitude because the density decreases it remains constant at lower altitudes but decreases at higher altitudes due to compressibility effects

.the ias stall speed is considered constant at low altitudes because of the tas stall speed increases due to the decreasing altitude but the ias is almost constant this is because the factor increasing the tas stall speed density also affects the ias speed in the same amount .however at higuer altitudes we consider another factor the compresibility that affects the anemometer and hence increases the reading of ias .resuming the ias stall speed is considered constant at lower altitudes below 10000 ft and increases with altitude at higuer altitudes due to compresibility effects exemple 487 It remains constant at lower altitudes but increases at higher altitudes due to compressibility effects.It remains constant at lower altitudes but increases at higher altitudes due to compressibility effects.

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