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Question 257-1 : What is the stagnation point ? [ Explanation maintenance ]
The point where the velocity of the relative airflow is reduced to zero.
Question 257-2 : What is the effect on induced drag of mass and speed changes all other factors of importance remaining constant ?
Decreases with increasing speed and decreasing mass.
We know that induced drag is proportional to the angle of attack , so..if you reduce speed, you must increase your angle of attack to maintain the same lift assuming we want to stay in level flight. if we increase speed, you must decrease your angle of attack, thus induced drag will decrease...it's basicaly the same for the mass.at a given speed and altitude, to maintain level flight with a lighter aircraft, less angle of attack is required, thus induced drag will decrease.
Question 257-3 : What increases the critical angle of attack use of ?
Slats.
Question 257-4 : When considering a swept back wing, with no corrective design features, at the stall ?
Tip stall will occur first, which produces a nose up pitching moment.
Question 257-5 : Which boundary layer, when considering its velocity profile perpendicular to the flow, has the greatest change in velocity close to the surface ?
Turbulent boundary layer.
The boundary layer extends from the surface to near freestream speed. think of the surface layer as molecules bouncing slowly along. in the turbulent layer they are ripped smartly up to high speed very soon after you leave the surface and then slowly speed up toward freestream over the rest of the layer.
Question 257-6 : The si unit of measurement for pressure is ?
N/m².
.icao annex 5 units of measurement attachment b. 2. mass, force and weight.2.1 the principal departure of si from the gravimetric system of metric engineering units is the use of explicitly distinct units from mass and force. in si, the name kilogram is restricted to the unit of mass, and the kilogram force from which the suffix force was in practice often erroneously dropped is not to be used. in its place the si unit of force, the newton, is used. likewise, the newton rather than the kilogram force is used to form derived units which include force, for example, pressure or stress n/m² = pa , energy nm = j , and power nm/s = w.
Question 257-7 : The polar curve of an aerofoil section is a graphic relationship between ?
Lift coefficient cl and drag coefficient cd.
Question 257-8 : The speed for minimum glide angle occurs at an angle of attack that corresponds to assume zero thrust ?
Cl/cd max.
Question 257-9 : The value of the induced drag of an aeroplane in straight and level flight at constant mass varies linearly with ?
1/v².
Induced drag comes from the air's reaction to the aerofoil, or is induced from the creation of lift, when air at different pressures mixes at the trailing edge, so it comes from lift producing surfaces wings and varies with angle of attack, so the slower the aerofoil is moving, the more induced drag you will get, because you have to shift more air in a shorter distance however, if no lift is induced, there is no induced drag. similary, the more lift there is, the more induced drag there is. it may comes from tip vortices, for example, and is inversely proportional to the square of the velocity.
Question 257-10 : Upon extension of fowler flaps whilst maintaining the same angle of attack ?
Cl and cd increase.
Question 257-11 : True airspeed tas is ?
Lower than the indicated airspeed ias at altitudes below sea level, under isa conditions.
.true air speed tas is obtained from indicated air speed ias by correcting for the following errors instrument, position, compressibility and density..so, tas is greater than ias with increasing altitude as density reduces...for this question, they state at altitudes below sea level , so it is reverse tas will be lower than ias density is higher for altitude below mean sea level...keep in mind that.ias is proportional to 1/2 rho tas².. rho = density.
Question 257-12 : The span wise flow on an unswept wing is from the ?
Lower to the upper surface via the wing tip.
Img /com en/com080 459.jpg.the boundary layer flow is back over the wing, and once past the point of maximum camber is moving to an area of higher pressure, an adverse pressure gradient.
Question 257-13 : Total pressure is rho = density ?
Static pressure plus dynamic pressure.
Question 257-14 : The terms q and s in the lift formula are ?
Dynamic pressure and the area of the wing.
Lift formula = 1/2 rho cl x v² x s..where. q or 1/2 rho v² is dynamic pressure rho = density, v = speed in m/s... cl is coefficient of lift... s is wing area.
Question 257-15 : The stall speed ?
Increases with an increased weight.
Question 257-16 : Trailing edge flaps once extended ?
Degrade the best angle of glide.
Question 257-17 : Which statement concerning the local flow pattern around a wing is correct ?
By fitting winglets to the wing tip, the strength of the wing tip vortices is reduced which in turn reduces induced drag.
Question 257-18 : Which statement is correct ?
Flap extension causes a reduction in stall speed and the maximum glide distance.
Extension of flaps causes a reduction of the stall speed, the maximum glide distance also reduces...stalls occur at the critical angle of attack, at which point the airflow over the wing becomes chaotic and the wings can no longer produce sufficient lift to counteract weight..the extension of flaps has the effect of increasing the relative angle of attack of the airfoil, but induced drag is also increased..more drag = less gliding distance.
Question 257-19 : While flying under icing conditions, the largest ice build up will occur, principally, on ?
The frontal areas of the aircraft.
Question 257-20 : Which statement is correct ?
Spoiler extension increases the stallspeed, the minimum rate of descent and the minimum angle of descent.
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.
Question 257-21 : Which statement is correct ?
As the angle of attack increases, the stagnation point on the wing's profile moves downwards.
Img /com en/com080 23.jpg.in red, the stagnation point will move down compare to the chord line..in blue, the point of lowest pressure will move forward.
Question 257-22 : During a climbing turn to the right the ?
Angle of attack of the left wing is larger than the angle of attack of the right wing.
.when the airplane is established in climb, in a right coordinated turn, the left wing is faster than the right one..also, if a stall occurs while climbing in the same condition, the left wing will reach first his max angle of attack, the airplane will roll to the left... chikarelly.if the speed of the left wing is higher, the angle of attack will be lower....for the left wing, to be higher it must generate more lift. the down going aileron on the left wing increases angle of attack.
Question 257-23 : Dividing lift by weight gives ?
Load factor.
Question 257-24 : Dangerous stall characteristics, in large transport aeroplanes that require stick pushers to be installed, include ?
Excessive wing drop and deep stall.
The stick pusher inhibits excessive wing drop and deep stall..at approximately one knot above stall speed, pre programmed stick forces automatically move the stick forward, preventing the stall from developing.
Question 257-25 : Bernoulli's law states. note rho is the mean sea level density under isa conditions. pstat is static pressure. pdyn is dynamic pressure. ptot is total pressure ?
Pstat + 1/2rhov² = constant.
Pt total pressure.ps static pressure.pd dynamic pressure 1/2 x density x tas²..bernoulli's theorem is.pt = ps + pd
Question 257-26 : Assuming zero wing twist, the wing planform that gives the highest local lift coefficient at the wing root is ?
Question 257-27 : Given the following aeroplane configurations.1. clean wing..2. slats only extended..3. flaps only extended..place these configurations in order of increasing critical angle of attack ?
3, 1, 2.
.the angle at which the stall occurs is called the critical angle of attack...3 trailing edge flap decrease the critical angle of attack and increase the value of clmax..1 critical angle of attack of a clean wing is higher than a wing with flaps only extended, but generate less lift..2 the slat re directs the airflow at the front of the wing, allowing it to flow more smoothly over the upper surface while at a high angle of attack. this allows the wing to be operated effectively at the higher angles required to produce more lift.
Question 257-28 : Floating due to ground effect during an approach to land will occur ?
When the height is less than halve of the length of the wing span above the surface.
Question 257-29 : An aeroplane climbs to cruising level with a constant pitch attitude and maximum climb thrust, assume no supercharger. how do the following variables change during the climb gamma = flight path angle ?
Gamma decreases, angle of attack increases, ias decreases.
Your flight path angle gamma will decrease because as you climb, the thrust will decrease.. 682.if you maintain the same pitch angle, angle of attack will increase..and an increase in angle of attack means an increase in drag ias will decrease since we do not have an excess of thrust to counteract this additional drag.
Question 257-30 : An aerofoil is cambered when ?
The line, which connects the centres of all inscribed circles, is curved.
. /com en/com080 520.png.the green line is the chord the direct line from leading edge to trailing edge..in red, the line which connects the centres of all inscribed circles. this line is curved when the aerofoil is cambered.
Question 257-31 : An aeroplane, being manually flown in the speed unstable region, experiences a disturbance that causes a speed reduction. if the altitude is maintained and thrust remains constant, the aeroplane speed will ?
Further decrease.
The speed unstable region means the backside of the drag or power curve also called the region of reversed command..in this speed unstable region , you control airpseed with elevator and altitude with throttle. if a disturbance causes a speed reduction, in order to maintain altitude and without ay action on thrust, you have to increase lift by increasing angle of attack by pulling the stick or the control column.
Question 257-32 : A slat will ?
Prolongs the stall to a higher angle of attack.
The deployment of a slat increases the maximum coefficient of lift by more than 70%, and the stalling angle of attack from 15° to 22°.. /com en/com080 524.jpg.a deployed slat will increase the boundary layer energy and increase the suction peak on the fixed part of the wing, so that the stall is postponed to higher angles of attack. a slat goes not significantly affect the camber of a wing.
Question 257-33 : A flat plate, when positioned in the airflow at a small angle of attack, will produce ?
Both lift and drag.
Question 257-34 : An aeroplane has the following flap positions 0°, 15°, 30°, 45°. slats can also be selected. generally speaking, which selection provides the highest positive contribution to the clmax ?
The slats from the retracted to the take off position.
Question 257-35 : An increase in wing loading will ?
Increase the stall speed.
Anything that causes an increase in wing loading will also cause an increase in stall speed such as pulling gs, turn or flying a loaded aircraft.
Question 257-36 : The difference between the effects of slat and flap asymmetry is that. 'large' in the context of this question means not or hardly controllable by normal use of controls ?
Flap asymmetry causes a large rolling moment at any speed whereas slat asymmetry causes a large difference in clmax.
At high speed the angle of attack will be small and with an asymmetric leading edge slat deployment, there will be little change in cl but cd would increase on the deployed slat turbulent boundary layer. this causes yaw which can be controlled by rudder...however at lower speeds and high angle of attack, a 'large' change in clmax will occur between the wings with a flap asymmetry. this would then lead to a strong rolling moment.
Question 257-37 : The airload on the horizontal tailplane tailload of an aeroplane in straight and level cruise flight ?
Is in general directed downwards and will become less negative when the c.g. moves aft.
.when the cg is ahead of the center of pressure, the balance of lift and weight will be pushing the nose down. to keep level you need a tail moment pushing the tail down.. /com en/com080 560.jpg.with an aft cg, the downward force on the horizontal tailplane can be reduced, the lift is also reduced to keep the balance of lift and total weight constant.
Question 257-38 : The boundary layer of a wing is ?
A layer on the wing in which the stream velocity is lower than the free stream velocity.
.the boundary layer thickness describes the distance above the wing where the velocity of the airflow goes from zero at the surface to near 99% free stream velocity..free stream velocity is the airflow far away from the influences of the airfoil it's the undisturbed airflow..the boundary layer can be either laminar or turbulent.
Question 257-39 : If the aspect ratio of a wing increases whilst all other relevant factors remain constant, the critical angle of attack will ?
Decrease.
.the aspect ratio of a wing is the relationship between its length and width, or span and chord actually the square of the span divided by the wing 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...but the wing's aspect ratio ar also affects the overall lift coefficient of the wing. /com en/com080 570.jpg.for a given reynolds number, the 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.
Question 257-40 : On a large transport aeroplane, the auto slat system ?
Extends the slats automatically when a certain value of angle of attack is exceeded.
The autoslat system is designed to enhance airplane stall characteristics at high angles of attack during takeoff or approach to landing..as the airplane approaches.the stall angle, the slats automatically begin driving to the full extended position prior to stick shaker activation. the slats return to the up or extend position when the pitch angle is sufficiently reduced below the stall critical attitude.
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