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Question 246-1 : The gust load factor due to a vertical upgust increases when ? [ Question security ]
The gradient of the cl alpha graph increases.
.an increase of angle of attack increases lift, thus when you fly at high angle of attack, a gust will have more effect the gust load factor increases...wing area decreases > aspect ratio decreases hence gust load factor decreases...speed increases > gust load factor increases..aspect ratio increases > gust load factor increases....altitude increases > gust load factor decreases due to less dynamic pressure..weight increases > gust load factor decreases due to more mass to accelerate.
Question 246-2 : All gust lines in the v n graph originate from a point where the ?
Speed = 0, load factor = +1
. 2763.the aircraft envelope starts from the origin, so v = 0 and n = 0, but the gust envelope starts at v = 0 and n = 1 because we have n = 1 in straight and level flight..the gust envelope is superimposed over the aircraft envelope to give reference points.
Question 246-3 : An aeroplane in straight and level flight is subjected to a strong vertical gust. the point on the wing, where the instantaneous variation in wing lift effectively acts is known as the ?
Aerodynamic centre of the wing.
Question 246-4 : How does va eas alter when the aeroplane's mass decreases by 19% ?
10% reduction.
.mass decreases by 19%..100% 19% = 81%..sqrt 0.81 = 0.9..va decreases by 10%.
Question 246-5 : How can wing flutter be prevented ?
By locating mass in front of the torsion axis of the wing.
.flutter is a dangerous phenomenon encountered in flexible structures subjected to aerodynamic forces. as the airspeed increases, there may be a point at which the structural damping is insufficient to damp out the motions which are increasing due to aerodynamic energy being added to the airfoil. this vibration can cause structural failure and therefore considering flutter characteristics is an essential part of designing an aircraft.. 813.to counteract this phenomenon, the control surface's cg must be as close as possible of the hinge the torsion axis.
Question 246-6 : The lift coefficient cl of an aeroplane in steady horizontal flight is 0.35. an increase in angle of attack of 1 degree would increase cl by 0.079. if a vertical gust instantly changes the angle of attack by 2 degrees, the load factor will be ?
Question 246-7 : The lift coefficient cl of an aeroplane in steady horizontal flight is 0.4. an increase in angle of attack of 1 degree will increase cl by 0.09. a vertical up gust instantly changes the angle of attack by 5 degrees. the load factor will be ?
2.13
.1° will increase cl by 0.09...5° will increase cl by 5 x 0.09 = 0.45... 0.45 + 0.4 /0.4 = 2.125.
Question 246-8 : Vra is ?
The recommended turbulence penetration airspeed.
.vra is defined as rough airspeed or turbulent air penetration speed...cs 25.1517 rough air speed, vra. a a rough air speed vra for use as the recommended turbulence penetration air speed, and a rough air mach number mra, for use as the recommended turbulence penetration mach number, must be established to ensure that likely speed variation during rough air encounters will not cause the overspeed warning to operate too frequently... b at altitudes where vmo is not limited by mach number, in the absence of a rational investigation substantiating the use of other values, vra must be less than vmo 35 ktas... c at altitudes where vmo is limited by mach number, mra may be chosen to provide an optimum margin between low and high speed buffet boundaries.
Question 246-9 : Which of the following statements is correct.i. a dorsal fin increases the contribution of the vertical tail plane to the static directional stability, in particular at large angles of sideslip..ii. a dorsal and a ventral fin both have a positive effect on static lateral stability. ?
I is correct, ii is incorrect.
.dorsal and ventral fins contribute in exactly the same way to directional static stability, a dorsal fin contributes positively to lateral static stability. 2764.if the aircraft is yawed to the left the dorsal and ventral fins will create a side force to the left. the line of action of this force is well aft of the aircraft cg, giving a yawing moment to the right a stabilising effect.. 2765..the ventral fin, being below the aircraft cg, has a negative influence on lateral static stability. 2766
Question 246-10 : The stall speed line in the manoeuvring load diagram runs through a point where the ?
Speed = va, load factor = limit load factor.
.the stall line starts at a point where load factor = 0 and airspeed = 0 , and runs through a point where the load factor reaches limit load factor for a large aeroplane +2.5g..this point is va design manoeuvring speed.. 2767
Question 246-11 : The stall speed line in the manoeuvring load diagram runs through a point where the ?
Speed = vs, load factor = +1.
.the stall line runs from n=0 airspeed=0, and 0g to +2.5g the normal limit load factor at the speed of va. 2767.the stall speed line runs through the point speed = vs, load factor = +1... joangoris.there's another question where it asks the same and the correct answer is va, not vs..i don't understand, any help thanks.. .you are talking about the following question. the stall speed line in the manoeuvring load diagram runs through a point where the.right answer speed = va, load factor = limit load factor...the stall line starts at a point where load factor = 0 and airspeed = 0 , and runs through a point where the load factor reaches limit load factor for a large aeroplane +2.5g...this point is va design manoeuvring speed...here, since the answer speed = va, load factor = limit load factor is not offered, the only correct one is speed = vs, load factor = +1.
Question 246-12 : Which of these statements about flutter are correct or incorrect.i. moving the engines from the wing to the aft fuselage improves wing flutter suppression..ii. excessive free play or backlash increases the speed at which control surface flutter occurs. ?
I is incorrect, ii is incorrect.
.flutter is a dangerous phenomenon encountered in flexible structures subjected to aerodynamic forces. as the airspeed increases, there may be a point at which the structural damping is insufficient to damp out the motions which are increasing due to aerodynamic energy being added to the airfoil. this vibration can cause structural failure and therefore considering flutter characteristics is an essential part of designing an aircraft..if the cg is aft of the torsional axis, inertia causes the cg of the wing to lag behind any movement of the axis caused by changes in lift. this lag can cause still further changes in incidence and hence lift making the matter worse. by having the cg on or forward of the axis now uses the property of inertia to counter the effect..wing mounted engines extending ahead of the wing contribute, by moving the wing's cg forward, to wing flutter suppression..the risk of flutter increases as ias increases, and the speed at which control surface flutter occurs will be decreased with excessive free play or backlash of the control surface the phenomenon occurs earlier.
Question 246-13 : Which of these statements about flutter are correct or incorrect.i. aero elastic coupling affects flutter characteristics..ii. the risk of flutter increases as ias increases. ?
I is correct, ii is correct.
.flutter is a divergent oscillatory motion of a control surface caused by the interaction of aerodynamic forces, inertia forces and the stiffness of the structure it is a combination of bending and torsion of the structure... aero elastic coupling affects flutter characteristics.. the risk of flutter increases as ias increases.. if flutter occurs, ias should be reduced.. resistance to flutter increases with increasing wing stiffness.
Question 246-14 : Which of these statements about the gust load factor on an aeroplane are correct or incorrect.i. when the mass decreases, the gust load factor increases..ii. when the altitude decreases, the gust load factor increases. ?
I is correct, ii is correct.
.wing area decreases > aspect ratio decreases hence gust load factor decreases...speed increases > gust load factor increases.aspect ratio increases > gust load factor increases..altitude increases > gust load factor decreases due to less dynamic pressure.weight increases > gust load factor decreases due to more mass to accelerate.
Question 246-15 : Which of these statements about flutter are correct or incorrect.i. wing mounted engines extending ahead of the wing contribute to wing flutter suppression..ii. excessive free play or backlash reduces the speed at which control surface flutter occurs. ?
I is correct, ii is correct.
.flutter is a dangerous phenomenon encountered in flexible structures subjected to aerodynamic forces. as the airspeed increases, there may be a point at which the structural damping is insufficient to damp out the motions which are increasing due to aerodynamic energy being added to the airfoil. this vibration can cause structural failure and therefore considering flutter characteristics is an essential part of designing an aircraft..if the cg is aft of the torsional axis, inertia causes the cg of the wing to lag behind any movement of the axis caused by changes in lift. this lag can cause still further changes in incidence and hence lift making the matter worse. by having the cg on or forward of the axis now uses the property of inertia to counter the effect..wing mounted engines extending ahead of the wing contribute, by moving the wing's cg forward, to wing flutter suppression..the risk of flutter increases as ias increases, and the speed at which control surface flutter occurs will be decreased with excessive free play or backlash of the control surface the phenomenon occurs earlier.
Question 246-16 : Which of these statements about flutter are correct or incorrect.i. if flutter occurs, ias should be reduced..ii. resistance to flutter increases with increasing wing stiffness. ?
I is correct, ii is correct.
.flutter is a divergent oscillatory motion of a control surface caused by the interaction of aerodynamic forces, inertia forces and the stiffness of the structure it is a combination of bending and torsion of the structure... aero elastic coupling affects flutter characteristics.. the risk of flutter increases as ias increases.. if flutter occurs, ias should be reduced.. resistance to flutter increases with increasing wing stiffness.
Question 246-17 : Which of these statements about the gust load factor on an aeroplane are correct or incorrect.i. when the slope of the lift versus angle of attack curve decreases, the gust load factor decreases..ii. when the wing loading decreases, the gust load factor increases. ?
I is correct, ii is correct.
. when the slope of the lift versus angle of attack curve decreases, the gust load factor decreases means an decrease of angle of attack decreases lift, thus when you fly at small angle of attack, a gust will have less effect...wing area decreases > aspect ratio decreases hence gust load factor decreases...speed increases > gust load factor increases.aspect ratio increases > gust load factor increases..altitude increases > gust load factor decreases due to less dynamic pressure.weight increases > gust load factor decreases due to more mass to accelerate.
Question 246-18 : Which of these statements about the gust load factor on an aeroplane are correct or incorrect.i. when the wing area increases, the gust load factor increases..ii. when the eas increases, the gust load factor increases. ?
I is correct, ii is correct.
.wing area decreases > aspect ratio decreases hence gust load factor decreases...speed increases > gust load factor increases.aspect ratio increases > gust load factor increases..altitude increases > gust load factor decreases due to less dynamic pressure.weight increases > gust load factor decreases due to more mass to accelerate.
Question 246-19 : Which of these statements concerning flight in turbulence is correct ?
Vra is the recommended turbulence penetration air speed.
.vra is defined as 'rough airspeed' or 'turbulent air penetration speed'...cs 25.1517 rough air speed, vra. a a rough air speed vra for use as the recommended turbulence penetration air speed, and a rough air mach number mra, for use as the recommended turbulence penetration mach number, must be established to ensure that likely speed variation during rough air encounters will not cause the overspeed warning to operate too frequently... b at altitudes where vmo is not limited by mach number, in the absence of a rational investigation substantiating the use of other values, vra must be less than vmo 35 ktas... c at altitudes where vmo is limited by mach number, mra may be chosen to provide an optimum margin between low and high speed buffet boundaries.
Question 246-20 : Flutter sensitivity of an aeroplane wing is reduced by ?
Locating the engine ahead of the torsional axis of the wing.
.flutter is a dangerous phenomenon encountered in flexible structures subjected to aerodynamic forces. as the airspeed increases, there may be a point at which the structural damping is insufficient to damp out the motions which are increasing due to aerodynamic energy being added to the airfoil. this vibration can cause structural failure and therefore considering flutter characteristics is an essential part of designing an aircraft..if the cg is aft of the torsional axis, inertia causes the cg of the wing to lag behind any movement of the axis caused by changes in lift. this lag can cause still further changes in incidence and hence lift making the matter worse. by having the cg on or forward of the axis now uses the property of inertia to counter the effect..wing mounted engines extending ahead of the wing contribute, by moving the wing's cg forward, to wing flutter suppression.
Question 246-21 : Flutter of control surfaces is ?
A divergent oscillatory motion of a control surface caused by the interaction of aerodynamic forces, inertia forces and the stiffness of the structure.
.flutter is a divergent oscillatory motion of a control surface caused by the interaction of aerodynamic forces, inertia forces and the stiffness of the structure it is a combination of bending and torsion of the structure... aero elastic coupling affects flutter characteristics.. the risk of flutter increases as ias increases.. if flutter occurs, ias should be reduced.. resistance to flutter increases with increasing wing stiffness.
Question 246-22 : Which statement regarding the manoeuvre and gust load diagram in the clean configuration is correct. i. the gust load diagram has a symmetrical shape with respect to the n = 1 line for speeds above vb.. ii. the manoeuvre load diagram does not extend beyond the speed vc. ?
I is correct, ii is incorrect.
. 2386.the gust load diagram has a symmetrical shape with respect to the n = 1 line for speeds above vb... 2768.the manoeuvre load diagram extends beyond the speed vc.
Question 246-23 : The significance of va for jet transport aeroplanes is reduced at high cruising altitudes because ?
Buffet onset limitations normally become limiting.
.the manoeuvring speed va, expressed as indicated airspeed or mach number, of a transport aeroplane depends on aeroplane mass and pressure altitude. from the buffet onset boundary chart you will obtain the values of the mach number at which low speed and mach buffet occur at different weights and altitudes. va is reduced at high cruising altitudes because buffet onset limitations normally become limiting.
Question 246-24 : A fundamental difference between the manoeuvring limit load factor and the gust limit load factor is, that ?
The gust limit load factor can be higher than the manoeuvring limit load factor.
.an aircrafts flight envelope must consider the stength requirements of the structure in still and turbulent conditions...consider an aircraft manoeuvring at it normal limit of 2.5g in still air. if the aircraft were to experience a sudden upgust this would increase the angle of attack. increase lift and load factor. the aircraft must be able to withstand this increase hence the factor the gust limit can be higher than the normal limit.
Question 246-25 : Which of these statements concerning flight in turbulence is correct ?
Vb is the design speed for maximum gust intensity.
Question 246-26 : From the buffet onset graph of a given jet transport aeroplane it is determined that at fl 310 at a given mass buffet free flight is possible between m = 0.74 and m = 0.88. in what way would these numbers change if the aeroplane is suddenly pulled up e.g. in a traffic avoidance manoeuvre ?
The lower mach number increases and the higher mach number decreases.
.anytime that too great a lift demand is made on the wing, whether from too fast an airspeed or from too high an angle of attack near the mmo, the high speed buffet will occur...mach buffet occurs as a result of supersonic airflow on the wing. stall buffet occurs at angles of attack that produce airflow disturbances burbling over the upper surface of the wing which decreases lift. as density altitude increases, the angle of attack that is required to produce an airflow disturbance over the top of the wing is reduced until the density altitude is reached where mach buffet and stall buffet converge coffin corner..when this phenomenon is encountered, serious consequences may result causing loss of airplane control... 1075.this is purely the aerodynamics factors which define the buffet onset boundary graph...at low speed buffet you are near the conventional stall it occurs at higher speeds with altitude , in the other hand, high speed buffet occurs at lower speeds with altitude, so at some stage the buffets will merge. the margin between them called 'coffin corner' is reduced by g force caused by turning and turbulence it means that you have to avoid any manoeuvres that can result in an increase of the load factor.
Question 246-27 : For a fixed pitch propeller designed for cruise, the angle of attack of each blade, measured at the reference section... ?
Is optimum when the aircraft is in a stabilized cruising flight.
Question 246-28 : Why is a propeller blade twisted from root to tip ?
To maintain a constant angle of attack along the whole length of the propeller blade.
Question 246-29 : Constant speed propellers provide a better performance than fixed pitch propellers because they ?
Produce an almost maximum efficiency over a wider speed range.
Question 246-30 : Propeller efficiency may be defined as the ratio between ?
Usable power available power of the propeller and shaft power.
Question 246-31 : An engine failure can result in a windmilling 1 propeller and a feathered 2 propeller. which statement about propeller drag is correct ?
1 is larger than 2.
.a windmilling propeller produces drag roughly equivalent to that of a solid disk of the same diameter as the propeller itself.. drag from a windmilling propeller is high. it is being driven by the relative airflow, and is generating both drag and torque. a feathered propeller generates the least drag. there is no torque because it is not rotating and the parasite drag is a minimum because the blades are edge on to the relative airflow.
Question 246-32 : Increasing the number of propeller blades will ?
Increase the maximum absorption of power.
.efficiency is power out compared to power in, so you need an aerofoil design that has a good lift/drag ratio. a high aspect blade long and narrow will give you low induced drag and so it needs low engine power to overcome drag. as propellers operate at big angles of attack to produce thrust, a low induced drag will give you a good efficiency...if you look at your light aircraft that is exactly what they have. fairly long narrow blades high aspect ratio and good efficiency, so you dont need a big engine to drive them...unfortunately they don't move a lot of air backwards, so although they are fine if the aircraft weight is low, you need more disc solidity the ratio of the total blade area to the disc area , if you need more thrust. the minute you increase disc solidity with wider blades you are reducing aspect ratio and losing efficiency. you will need a stronger engine to overcome the higher drag...power absorbtion is the same as disc solidity in that it reduces efficiency...if you have a powerful engine you are wasting it if you put a high aspect ratio low disc solidity propeller on it, because you could drive it at idle. you might as well use the power available by increasing the disc solidity and produce more thrust...increasing disc solidity or absorbing more available power will always be contrary to efficiency.
Question 246-33 : Gyroscopic precession of the propeller is induced by ?
Pitching and yawing.
.gyroscopic effect works like this.if an up force is applied to the tail plane, causing nose pitch up, that would be the same as applying a forward force to the 6 o'clock position on the prop to cause the pitch up. if this was a right hand propeller clockwise when viewed from the rear , this force would then act at the 9 o'clock postion on the propeller in a forwards movement, causing a yaw to the right..in this image, try to imagine the forward force at any position, and the effect that it will have on the attitude of flight.. /com en/com080 607a.png.. clockwise propeller when viewed from the rear, with a force on the tail causing nose pitch down. /com en/com080 607.png..
Question 246-34 : Asymmetric propeller blade effect is mainly induced by ?
The inclination of the propeller axis to the relative airflow.
Question 246-35 : Does the pitch angle of a constant speed propeller alter in medium horizontal turbulence ?
Yes slightly.
Question 246-36 : Which of the following statements about a constant speed propeller is correct ?
The blade angle increases with increasing aeroplane speed.
.when it refers to blade angle it refers to the angle between the chord line and the direction of propeller rotation.. /com en/com080 636.jpg..for a fixed pitch propeller the pitch angle cannot be changed it varies from root to tip to maintain near constant angle of attack along the blade...the angle of attack as in the case of a aircraft wing is defined as the angle between the chord line and relative airflow. with a propeller however the relative airflow is the resultant of the airflow due to rotation and forward speed. change either of these values and the angle of attack will change.. /com en/com080 549.jpg.. for a constant speed propeller , the propeller system will maintain a constant angle of attack regardless to the speed of the aircraft or the rotational speed. it can only be achieved by increasing or decreasing the blade angle.the blade angle of a constant speed propeller increases with increasing aeroplane speed..the blade angle of a constant speed propeller decreases if rpm increases.
Question 246-37 : Which is one of the disadvantages of increasing the number of propeller blades ?
Decrease propeller efficiency.
.increased noise no, flown a 2 bladed cessna 172, noisy as, flown a 3 bladed c172, quieter..less power can be absorbed by the propeller no, it's the size that can absorb the power..higher tip speed no, more blades = slower rotation speed and then, less noise..decrease propeller efficiency yes, too many blades interfere with the airflow for the next blade.
Question 246-38 : If you decrease the propeller pitch during a glide with idle power at constant ias the lift to drag ratio will ?
Decrease and the rate of descent will increase.
.if you decrease the propeller pitch go from a coarse pitch to a fine pitch , you will then have more drag. drag to lift ratio is reduced an the rate of descent will increase.
Question 246-39 : If you increase the propeller pitch during a glide with idle power at constant ias the lift to drag ratio will ?
Increase and the rate of descent will decrease.
.if you increase the propeller pitch go from a fine pitch to a coarse pitch , you will then have less drag, which means a better lift to drag ratio, and at constant ias, a lower rate of descent.
Question 246-40 : The angle of attack for a propeller blade is the angle between the blade chord line and the ?
Local air speed vector.
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