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Question 259-1 : Which statement, about the effects on drag of removing external tip tanks from the wings of an aeroplane, is correct.i. parasite drag decreases..ii. induced drag increases. ? [ Explanation maintenance ]
I is correct, ii is correct.
.the external wing tip tanks act like winglets, they reduce the wing tip vortices induced drag decreases , but they increase the parasite drag form drag + skin friction drag.. /com en/com080 1125.jpg. siai marchetti sf 260 with tip tanks.
Question 259-2 : Which statement about an aeroplane leaving ground effect is correct.i. the downwash angle increases..ii. the induced angle of attack increases. ?
I is correct, ii is correct.
Ground effect changes airflow. /com en/com080 821.jpg.when leaving the ground effect, it requires an increase in angle of attack to maintain the same cl. the induced angle increases.
Question 259-3 : Regarding deep stall characteristics, identify whether the following statements are correct or incorrect.i. the combination of a wing with sweepback and a t tail make an aeroplane prone to deep stall..ii. a stick shaker system is fitted to an aeroplane that exhibits abnormal stall characteristics. ?
I is correct, ii is incorrect.
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...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.. /com en/com080 810.jpg.the stick pusher and not the stick shaker inhibits this type of stall..at approximately one knot above stall speed, pre programmed stick forces automatically move the stick forward, preventing the stall from developing.
Question 259-4 : Which statement about an aeroplane entering ground effect is correct.i. the downwash angle decreases..ii. the induced angle of attack remains constant. ?
I is correct, ii is incorrect.
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.
Question 259-5 : Which statement about an aeroplane entering ground effect is correct.i. the downwash angle decreases..ii. the induced angle of attack increases. ?
I is correct, ii is incorrect.
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.
Question 259-6 : Which statement about an aeroplane leaving ground effect is correct.i. the downwash angle increases..ii. the induced angle of attack decreases. ?
I is correct, ii is incorrect.
Ground effect changes airflow. /com en/com080 821.jpg.when leaving the ground effect, it requires an increase in angle of attack to maintain the same cl. the induced angle increases.
Question 259-7 : Regarding deep stall characteristics, identify whether the following statements are correct or incorrect.i. a wing with forward sweep and a low horizontal tail makes an aeroplane prone to deep stall..ii. a stick shaker system is fitted to an aeroplane that exhibits abnormal stall characteristics. ?
I is incorrect, ii is incorrect.
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..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.. but on a wing with forward sweep, the stall occurs at the wing root.example of a aircraft with a wing with forward sweep. /com en/com080 824.jpg.hfb 320 hansa jet...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 is not the case for a low horizontal tail.. /com en/com080 810.jpg.the stick pusher and not the stick shaker inhibits this type of stall..at approximately one knot above stall speed, pre programmed stick forces automatically move the stick forward, preventing the stall from developing.
Question 259-8 : Which statement is correct.i. a stick pusher activates at a lower angle of attack than a stick shaker..ii. a stick shaker prevents the pilot from increasing the angle of attack further. ?
I is incorrect, ii is incorrect.
A stick pusher activates at a higher angle of attack than a stick shaker..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..vdo927.you can see that first the stick shaker is activated, and if the pilot do not reacts and the angle of attack continues to increase, the stick pusher is activated...a stick shaker is a mechanical device to rapidly and noisily vibrate the control yoke the 'stick' of an aircraft to warn the pilot that the speed is close to the stall speed. a stick shaker do not prevent the pilot from increasing the angle of attack further, it just warns the pilot.
Question 259-9 : Which of these statements about the strength of wing tip vortices are correct or incorrect.i. assuming no flow separation, the strength of wing tip vortices is not affected by angle of attack..ii. the strength of wing tip vortices decreases as the aspect ratio decreases. ?
I is incorrect, ii is incorrect.
.formation of vortices.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. since air always moves from high pressure toward low pressure, and the path of least resistance is toward the airfoil's tips, there is a spanwise movement of air from the bottom of the airfoil outward from the fuselage around the tips. this flow of air results in 'spillage' over the tips, thereby setting up a whirlpool of air called a 'vortex'...just as lift increases with an increase in aoa, induced drag also increases. this occurs because as the aoa is increased , there is a greater pressure difference between the top and bottom of the airfoil, and a greater lateral flow of air consequently, this causes more violent vortices to be set up, resulting in more turbulence and more induced drag...the strength of the wingtip vortices is determined by the magnitude of the pressure difference between the upper and lower wing surfaces, and by the time during which this pressure difference acts to drive the air into the vortices. the greater the pressure difference or the longer the time available, the stronger the vortices will be...the time during which the pressure difference acts upon the air is proportional to the time it takes the air to pass from the leading edge to the trailing edge of the wing. so for any given airspeed, the length of the wing chord determines the time taken. this means that decreasing the chord length will decrease the vortex strength, which will decrease the stalling angle and the drag...the intensity or strength of the vortices is directly proportional to the weight of the aircraft and inversely proportional to the wingspan and speed of the aircraft...good answers for this kind of questions.assuming no flow separation, the strength of wing tip vortices increases as the angle of attack increases..assuming no flow separation, the strength of wing tip vortices decreases as the angle of attack decreases..the strength of wing tip vortices decreases as the aspect ratio increases..the strength of wing tip vortices increases as the aspect ratio decreases.
Question 259-10 : Which of these statements about the effect of wing sweep on centre of pressure location are correct or incorrect.i. the centre of pressure on a straight wing moves aft as the angle of attack approaches and exceeds the critical angle of attack..ii. the centre of pressure on a strongly swept back wing ?
I is correct, ii is correct.
.straight wing.the centre of pressure moves forward as 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 pressure of the wing in a forward direction relative to the center of gravity of the airplane, causing the nose to pitch up.
Question 259-11 : Considering subsonic incompressible airflow through a venturi, which statement is correct.i. the static pressure in the throat is lower than in the undisturbed airflow..ii. the speed of the airflow in the throat is higher than in the undisturbed airflow. ?
I is correct, ii is correct.
Img /com en/com080 815.jpg..static pressure decreases in a venturi, and airflow speed increases.
Question 259-12 : Which statement, about an aeroplane leaving ground effect at constant angle of attack, is correct.i. the lift coefficient cl decreases..ii. the induced drag coefficient cdi increases. ?
I is correct, ii is correct.
Ground effect changes airflow. /com en/com080 821.jpg..when leaving the ground effect, the lift coefficient cl decreases, it requires an increase in angle of attack to maintain the same cl..the induced angle increases, so the induced drag coefficient cdi increases.
Question 259-13 : Which statement about an aeroplane entering ground effect is correct.i. the downwash angle decreases..ii. the induced angle of attack decreases. ?
I is correct, ii is correct.
.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, thus, if the angle of attack is maintain constant the question states entering ground effect at constant angle of attack , the lift coefficient cl increases..when entering ground effect induce flow reduces and the induced angle of attack decreases, thus the induced drag coefficient cdi decreases.
Question 259-14 : Which of these statements about induced drag are correct or incorrect.i. induced drag decreases as angle of attack decreases..ii. at constant load factor, induced drag decreases with decreasing aeroplane mass. ?
I is correct, ii is correct.
.induced drag increases as angle of attack increases since induced drag is induced by lift, as you increase lift by increasing the angle of attack cl increases , the induced drag will increase...induced drag decreases with decreasing aeroplane mass if less lift has to be produced, less induced drag will be generated.
Question 259-15 : The parameters that can be read from the aeroplane parabolic polar curve are the ?
Minimum glide angle and the parasite drag coefficient.
.the polar curve of an aerofoil section is a graphic relationship between lift coefficient cl and drag coefficient cd.. /com en/com080 1264.jpg.where the line crosses the cl=0 axis there is no lift, and therefore no induced drag, so cd at that point is from parasite drag only..angle of glide is cl/cd, the lift/drag ratio. if the lift/drag ratio is 10 1 then the glide angle is 1 in 10. the tangent to the curve from the cl/cd origin shows the best cl/cd ratio, and thus the best glide angle you can get. rate of descent would depend on what speed you were doing down the hill and that is not shown on the polar diagram...the polar diagram shows coefficients only. to get real world data you have to add in all the other bits of the lift and drag equations like s and rho and v squared.
Question 259-16 : For most jet transport aeroplanes, slat extension has ?
A greater effect on stall speed than flap extension.
Question 259-17 : One advantage of mounting the horizontal tailplane on top of the vertical fin is ?
To improve the aerodynamic efficiency of the vertical fin.
Question 259-18 : Which drag components make up parasite drag.1 pressure drag.2 friction drag.3 induced drag.4 interference drag.the combination that regroups all of the correct statements is ?
1, 2, 4.
Question 259-19 : The transition point is where the boundary layer changes from ?
Laminar into turbulent.
Question 259-20 : As angle of attack is increased on a conventional low speed aerofoil at low subsonic speeds, flow separation normally starts on the ?
Upper surface near the trailing edge.
Question 259-21 : Assuming no flow separation, when speed is decreased in straight and level flight on a positively cambered aerofoil, what happens to the.1. centre of pressure.and.2. the magnitude of the total lift force ?
1 moves forward and 2 remains constant.
.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.
Question 259-22 : Given the following characteristic points on a jet engine aeroplane's polar curve..1 clmax.2 long range cruise zero wind.3 maximum lift to drag ratio.4 minimum rate of descent assume zero thrust.5 maximum range cruise zero wind.arrange these points in order of increasing angle of attack ?
2, 5, 3, 4, 1.
.the aerofoil polar is a graph of the relation between the lift coefficient and the drag coefficient.. /com en/com080 918.jpg
Question 259-23 : Assuming standard atmospheric conditions, in order to generate the same amount of lift as altitude is increased, an aeroplane must be flown at ?
A higher tas for any given angle of attack.
Question 259-24 : In comparison to a conventional aerofoil section, typical shape characteristics of a supercritical aerofoil section are ?
A larger nose radius, flatter upper surface and negative as well as positive camber.
. /com en/com080 958.jpg..
Question 259-25 : Induced drag is the result of ?
Downwash generated by tip vortices.
Question 259-26 : Given an aeroplane in steady, straight and level flight at low speed and considering the effects of cg location and thrust, the highest value of wing lift occurs at ?
Forward cg and idle thrust.
Img683.with a forward cg, the horizontal stabiliser produces a down force. the force of lift must balance weight and the tail downward force. at high angle of attack we are in steady flight at low speed any thrust from the engines would tend to produce a vector force upwards, this would help lift. thus, at idle thrust, the wing lift force would be at it highest value...this question also appears with the opposite statement at the exam.'...the lowest value of wing lift occurs at aft cg and take off thrust.'. 684
Question 259-27 : The main function of a trailing edge flap is to ?
Increase the maximum lift coefficient of the wing.
Question 259-28 : Stall speed ias varies with ?
Weight.
Question 259-29 : What will happen if a large transport aeroplane slowly decelerates in level flight from its cruise speed in still air at high altitude ?
Stick shaker activation or low speed buffeting.
.the only way to maintain altitude as the aeroplane is slowly decelerated is to slowly and gently increase the angle of attack thereby maintaining 1g flight. eventually the aeroplane will either begin to low speed buffet or the stick shaker stall warning device will activate...high speed buffet is related to shock induced airflow separation as the aeroplane is accelerated above mcrit...shock stall is also related to shock induced airflow separation as the aeroplane is accelerated above mcrit...an accelerated stall is when the aeroplane is stalled with a load factor greater than 1.
Question 259-30 : Which of the following increases the maximum duration of a glide ?
A decrease in mass.
.a headwind will always reduce the glide range and a tailwind will always increase the glide range...as mass increases, the best glide ratio is achieved at higher speeds. to increase the speed, you must increase the descent angle. the glide duration will be reduced..a decrease in mass will permit to increase the duration of the glide.
Question 259-31 : Wing spoilers are deflected symmetrically in flight in order to ?
Decelerate the aeroplane and/or increase its rate of descent.
.a spoiler is a device intended to reduce lift in an aircraft. spoilers are plates on the top surface of a wing which can be extended upward into the airflow and spoil it. by doing so, the spoiler creates a carefully controlled stall over the portion of the wing behind it, greatly reducing the lift of that wing section. spoilers differ from airbrakes in that airbrakes are designed to increase drag making little change to lift, while spoilers reduce lift as well as increasing drag...if in flight, spoilers are deployed while maintaining level flight, they decelerate the aeroplane..if in flight, spoilers are deployed while descending and maintaining speed, they increase its rate of descent.. /com en/com080 977.jpg..
Question 259-32 : A positively cambered aerofoil will generate zero lift ?
At a negative angle of attack.
Img /com en/com080 878.jpg..a symmetrical aerofoil need to have a positive pitch to produce lift. if the pitching moment is zero, the lift is zero.. a positively cambered aerofoil produces lift with a zero pitching moment, thus, not to produce lift, it need a negative pitching moment.
Question 259-33 : The lift coefficient cl versus angle of attack curve of a negatively cambered aerofoil section intersects the horizontal axis of the graph ?
To the right of the origin.
. /com en/com080 984.jpg..a negatively cambered aerofoil section produces lift at positive angle of attack only in our example, at approximately 3° angle of attack... stanley.hi there was no graph with the question... best regards....this is normal, there is no graph with this question at the exam. you need to know the shape of the cl/aoa curve.
Question 259-34 : Regarding the lift formula, if density doubles, lift will ?
Also double.
Lift formula.lift = 1/2 rho cl x v² x s...where..'1/2 rho' is dynamic pressure...'cl' is coefficient of lift...'v' is speed in m/s...'s' is wing area....if density is double, lift will also double.
Question 259-35 : Assuming all bodies have the same cross sectional area and are in motion, which body will have the highest pressure drag.. err a 081 986 ?
Body b.
. /com en/com080 986.jpg..
Question 259-36 : When a wing spoiler is extended at constant angle of attack ?
Drag increases but lift decreases.
.when you deploy the spoilers, you will need to increase angle of attack to restore the coefficient of lift to that required at the lower speed the aircraft will be traveling..however if the angle of attack is unchanged, the aircraft will no longer produce sufficient lift to oppose the weight, and therefore the aircraft will descend..right answer drag increases but lift decreases.
Question 259-37 : The point, where the single resultant aerodynamic force acts on an aerofoil, is called ?
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.
Question 259-38 : Wing loading is the ratio between ?
Aeroplane weight and wing area.
. /com en/com080 992.jpg.wing loading is the number of kilos of aircraft weight supported by each square foot of wing area. wing loading is usually expressed as the value when the airplane is at its maximum certified weight, so the actual wing loading will vary depending on fuel and payload onboard the airplane at any point..wing loading = 'aircraft weight' divided by 'wing area'.
Question 259-39 : Increasing the aspect ratio of a wing ?
Decreases induced drag.
Question 259-40 : What may happen if the 'ultimate load factor' is exceeded ?
Structural failure.
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