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Question 266-1 : Static lateral stability will be decreased by ? [ Theoretical lift off ]
Reducing wing sweepback.
.sweepback angle is the angle at which the wing points backwards from the root to the tip.. /com en/com080 467.png.sweepback is used mainly on high speed aircraft and its primary purpose is to delay the formation of sonic shock waves which are produced at high speeds and cause a large increase in drag..the secondary effect of sweepback is to improve lateral stability. when a side slip occurs, the lower wing presents a larger span as seen from the direction of the approaching air, and as with dihedral, the effect is to roll the aircraft back towards the horizontal. if the sweepback angle is reduced, the static lateral stability decreases.
Question 266-2 : How can a pilot recognise static stick force stability in an aeroplane during flight ?
To maintain a speed above the trim speed requires a push force.
.when an aeroplane is properly trimmed, a push force is required to increase airspeed and a pull force is required to decrease airspeed. in this manner, the aeroplane would have positive stick force stability with a stable feel for airspeed...warning this question exists in the database, but with the other possible answer.to maintain a speed below the trim speed requires a pull force.
Question 266-3 : Which design features reduce static lateral stability.1. high wing.2. low wing.3. large and high vertical fin.4. ventral fin.the combination that regroups all of the correct statements is ?
2, 4.
.for static lateral stability to be present an aircraft must have stopped rolling and be side slipping..the design features that provide static lateral stability are. the dihedral effect increase in angle of attack on the lower wing compared to the upper wing.. high wing and low cg pendulous affect.. keel effect the keel/side surface above the centre of gravity will be presented to the relative airflow which will give a force to help in correcting the roll and a low cg...an aircraft can have one or a combination of the above to provide the required amount of static lateral stability although some aircraft may be too stable and methods such as anhedral wings are used to reduce static lateral stability...more information on vertical and ventral fin.dorsal and ventral fins contribute in exactly the same way to directional static stability, a dorsal fin contributes positively to lateral static stability. /com en/com080 618a.jpg.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.. /com en/com080 618b.jpg..the ventral fin, being below the aircraft cg, has a negative influence on lateral static stability. /com en/com080 618c.jpg..
Question 266-4 : Which of the following statements about static longitudinal stability is correct.i. a requirement for positive static longitudinal stability of an aeroplane is, that the neutral point is behind the centre of gravity..ii. a wing with positive camber provides a positive contribution to static ?
I is correct, ii is correct.
.aerodynamic center is a stationary point located at the 25% chord of the wing only when airflow is subsonic...a wing considered alone is statically unstable because the aerodynamic centre is in front of the centre of gravity. a vertical gust will momentarily increase the angle of attack and increase lift which when multiplied by the arm will generate a nose up pitching moment about the centre of gravity. this tends to increase the angle of attack further an unstable pitching moment...now lets look at a wing together with a tailplane.the tailplane is positioned to generate a stabilizing pitching moment about the centre of gravity. the same vertical gust will increase the angle of attack of the tailplane and increase tail plane lift, which when multiplied by the arm, will generate a negative nose down pitching moment about the centre of gravity...if the tail moment is greater than the wing moment the sum of the moments will not be zero, resulting in a nose down moment with an angular acceleration about the centre of gravity..nose down angular acceleration about the centre of gravity returns the aircraft to its original position of equilibrium. the greater the tail moment relative to the wing moment, the greater the rate of acceleration towards the original equilibrium position...the length of both arms wing and tailplane to centre of gravity is dependent on centre of gravity position if the centre of gravity is more forward the tail arm is larger and the wing arm smaller..a more forward cg position increases static longitudinal stability...if the nose down negative tail moment is greater than the nose up positive wing moment, the aircraft will have static longitudinal stability.
Question 266-5 : Which of these statements are correct or incorrect regarding a sideslip, with the relative airflow coming from the right, on an aeroplane that exhibits both directional and lateral stability.i. the initial tendency of the nose of the aeroplane is to move to the right..ii. the initial tendency of the ?
I is correct, ii is correct.
.a side slip with the relative airflow coming from the right, is the slip of the tail to the right. the nose goes left..if an aeroplane has static directional stability, the intial tendency is to come back in the flight pattern of the aircraft through the air the nose of the aeroplane is to move to the right.. /com en/com080 74.jpg..in a side slip to the right, the lower wing is the right one, and it presents a larger span as seen from the direction of the approaching air, and as with dihedral, the effect is to roll the aircraft back towards the horizontal the initial tendency of the left wing is to move down.
Question 266-6 : Which of these statements are correct or incorrect regarding a sideslip, with the relative airflow coming from the left, on an aeroplane that exhibits both directional and lateral stability.i. the initial tendency of the nose of the aeroplane is to move to the left..ii. the initial tendency of the ?
I is correct, ii is correct.
.a side slip with the relative airflow coming from the left, is the slip of the tail to the left. the nose goes right..if an aeroplane has static directional stability, the intial tendency is to come back in the flight pattern of the aircraft through the air the nose of the aeroplane is to move to the left.. /com en/com080 1085.jpg..in a side slip to the left, the lower wing is the left one, and it presents a larger span as seen from the direction of the approaching air, and as with dihedral, the effect is to roll the aircraft back towards the horizontal the initial tendency of the right wing is to move down.
Question 266-7 : During a take off roll with a strong crosswind from the left, a four engine jet aeroplane with wing mounted engines experiences an engine failure. the failure of which engine will cause the greatest control problem ?
The left outboard engine.
.in case of a failure of one engine, the aircraft will yaw on the side where the engine failure occurs...with wind, the yaw movement will see the aircraft nose coming into the wind the aircraft tends to face the wind due to the large surface area of his vertical fin...with a strong crosswind from the left, in order to counteract this tendency, you must apply rudder to the right. now if the left outboard engine fails, thrust from the right engines will combined and it might be impossible to counteract the turning moment.. /com en/com080 883.jpg
Question 266-8 : Static directional stability is mainly provided by ?
The fin.
Question 266-9 : Longitudinal stability is directly influenced by ?
Centre of gravity position.
Question 266-10 : An aeroplane, with a cg location behind the centre of pressure of the wing can only maintain a straight and level flight when the horizontal tail loading is ?
Upwards.
. /com en/com080 910.jpg.the force from the tailplane must be upwards to maintain a straight and level flight.
Question 266-11 : In a skidding turn the nose pointing inwards , compared with a co ordinated turn, the bank angle i and the ball or slip indicator ii are respectively ?
I too small, ii displaced towards the high wing.
.a skidding turn results from an excess of centrifugal force over the horizontal lift component, pulling the airplane toward the outside of the turn. the rate of turn is too great for the angle of bank. correction of a skidding turn thus involves a reduction in the rate of turn, an increase in bank, or a combination of the two changes.. /com en/com080 913.jpg
Question 266-12 : The most forward cg location may be limited by.1. insufficient flare capability..2. excessive in flight manoeuvrability..3. insufficient in flight manoeuvrability..the combination that regroups all of the correct statements is ?
1, 3.
Question 266-13 : Which statement concerning longitudinal stability and control is correct ?
A bob weight and a down spring have the same effect on the stick force stability.
.bob weights are sometimes known as counter weights. their purpose is to change the amount of control force required to deflect the control column under different g loadings. normally the amount of force the pilot must apply to the control column, assuming reversible controls, varies with airspeed only. however, by installing a bob weight the aeronautical engineer can make it more difficult to pull on the control column as g force increases. the purpose of the bob weight is to reduce the likely hood the pilot will overstress the aircraft.. /com en/com080 949.jpg..the down spring produces a mechanical load on the elevator, causing it to move toward the nosedown position if not otherwise balanced. /com en/com080 949a.jpg..they have the same effect on the stick force stability, the difference is that a bob weight increases stick force stability according to g while a down spring increases stick force stability according to stick displacement.
Question 266-14 : When a turn is initiated, adverse yaw is ?
The tendency of an aeroplane to yaw in the opposite direction of turn mainly due to the difference in induced drag on each wing.
.the solution is to use differential aileron deflection. the aileron linkage causes the up going aileron the move through a larger angle than the down going aileron. this increases the drag on the up aileron, and reduces it on the down aileron, and so reduces the difference in drag between the two wings.
Question 266-15 : During the take off roll, when the pilot raises the tail in a tail wheeled propeller driven aeroplane, the additional aeroplane yawing tendency is due to the effect of ?
Gyroscopic precession.
Question 266-16 : Assuming no pilot input the motion of the aeroplane in the diagram shows.. err a 081 1013 ?
Dynamic longitudinal stability.
Question 266-17 : Assuming no pilot input the motion of the aeroplane in the diagram shows.. err a 081 1014 ?
Neutral dynamic longitudinal stability.
.static stability is the initial tendency of the aircraft following removal of a disturbing force ~ dynamic stability is what happens after this initial reaction...if the aeroplane continues to oscillate about equilibrium with no reduction in amplitude, therefore the aeroplane in the diagram has neutral dynamic longitudinal stability.
Question 266-18 : Which of the following statements is correct.i. a high limit load factor enables the manufacturer to design for a lower stick force per g..ii. the stick force per g is a limitation on the use of an aeroplane, which the pilot should determine from the aeroplane flight manual. ?
I is correct and ii is incorrect.
.passenger aircraft are stressed to 2.5 g, the normal limit load factor. as you manoeuvre the aircraft from trim you will feel an increase in stick force up to the limit load factor. this is the stick force gradient stick for per g..the stick force limit is defined by cs23/25 so you cannot exceed the max value. if you were to increase the limit load factor the stick force per g would decrease. reduced stick force gradient..stick forces are specified in cs23/25 certification specifications not in the aeroplane flight manual.
Question 266-19 : What is the recommended action following failure of the yaw damper s of a jet aeroplane, flying at normal cruise altitude and speed prior to encountering dutch roll problems ?
Reduce altitude and mach number.
Question 266-20 : Where on the curve in the diagram does the aeroplane exhibit neutral static longitudinal stability.. err a 081 1261 ?
Point 2.
. positive static longitudinal stability means that a nose down moment occurs after encountering an up gust it is a stabilising effect since the airplane coming back to his previous position...regarding the angle of attack you have while flying, the response to a gust will varies..part 1 when angle of attack is increased, the response is a tendency to a nose down moment stability...point 2 at this point, when angle of attack is increased, the response is neutral when the airplane is flying at point 2's aoa, when it encounters an up gust, it will stop at the new angle of attack...part 3 when angle of attack is increased, the response is a tendency to a nose up moment instability.
Question 266-21 : Excessive static lateral stability is an undesirable characteristic for a transport aeroplane because ?
It would impose excessive demands on roll control during a sideslip.
.the illustration shows an aeroplane in a right sideslip. the right wing has an increased effective angle of attack and the left wing has a decreased effective angle of attack this generates a stabilising rolling moment to the left.. /com en/com080 1263.jpg..for the pilot to hold the aeroplane in this sideslip for a crosswind landing would require enough stick force to oppose the stabilising rolling moment. excessive static lateral stability is too large, it would impose excessive demands on roll control during a sideslip crosswind landing..during a co ordinated turn there is no sideslip, so static lateral stability is not a factor. and none of the other answers are correct.
Question 266-22 : Where on the curve in the diagram does the aeroplane exhibit static longitudinal stability.. err a 081 1266 ?
Part 1.
. positive static longitudinal stability means that a nose down moment occurs after encountering an up gust it is a stabilising effect since the airplane coming back to his previous position...regarding the angle of attack you have while flying, the response to a gust will varies..part 1 when angle of attack is increased, the response is a tendency to a nose down moment stability...point 2 at this point, when angle of attack is increased, the response is neutral when the airplane is flying at point 2's aoa, when it encounters an up gust, it will stop at the new angle of attack...part 3 when angle of attack is increased, the response is a tendency to a nose up moment instability.
Question 266-23 : Where on the curve in the diagram does the aeroplane exhibit static longitudinal instability.. err a 081 1267 ?
Part 3.
. positive static longitudinal stability means that a nose down moment occurs after encountering an up gust it is a stabilising effect since the airplane coming back to his previous position...regarding the angle of attack you have while flying, the response to a gust will varies..part 1 when angle of attack is increased, the response is a tendency to a nose down moment stability...point 2 at this point, when angle of attack is increased, the response is neutral when the airplane is flying at point 2's aoa, when it encounters an up gust, it will stop at the new angle of attack...part 3 when angle of attack is increased, the response is a tendency to a nose up moment instability.
Question 266-24 : Static lateral stability will be increased by ?
Increasing wing sweepback.
.sweepback angle is the angle at which the wing points backwards from the root to the tip.. /com en/com080 467.png.sweepback is used mainly on high speed aircraft and its primary purpose is to delay the formation of sonic shock waves which are produced at high speeds and cause a large increase in drag..the secondary effect of sweepback is to improve lateral stability. when a side slip occurs, the lower wing presents a larger span as seen from the direction of the approaching air, and as with dihedral, the effect is to roll the aircraft back towards the horizontal...in general, as the sweepback angle is increased the dihedral angle will be reduced.
Question 266-25 : Static lateral stability will be increased by ?
The use of a high, rather than low, wing mounting.
Question 266-26 : Turning motion in a steady, level co ordinated turn is created by ?
The centripetal force.
.for an aircraft to change direction, a force is required to deflect it towards the centre of the turn. this is called the centripetal force. banking the aircraft inclines the lift. it is the horizontal component of lift which causes the aircraft to turn.. /com en/com080 1276.jpg.as the angle of bank increases, the angle of attack must be increased to bring about a greater total lift. the vertical component must be large enough to maintain level flight, while the horizontal component is large enough to produce the required centripetal force.
Question 266-27 : During a short period oscillation, the altitude ?
Remains approximately constant, whereas during a phugoid it varies significantly.
Question 266-28 : The purpose of a dorsal fin is to ?
Maintain static directional stability at large sideslip angles.
Question 266-29 : Assuming no pilot input the motion of the aeroplane in the diagram shows.. err a 081 1292 ?
Static longitudinal stability and dynamic longitudinal instability.
Question 266-30 : The centre of gravity moving aft will ?
Increase the elevator up effectiveness.
.an aft shift of centre of gravity will increase maneuverability and also make the nose seem lighter so you would need less control input to change the pitch and therefore more effective.
Question 266-31 : When the cg position is moved forward, the elevator deflection for a manoeuvre with a given load factor greater than 1 will be ?
Larger.
.the question is about longitudinal stability. if your aircraft is less stable then smaller control deflections will get the response required aft cg. however, with a forward cg the aircraft is more stable, so to manoeuvre you have to make a bigger stick deflection resulting in a bigger elevator deflection.
Question 266-32 : Which of the following statements about a mach trimmer is correct ?
A mach trimmer corrects the change in stick force stability of a swept wing aeroplane above a certain mach number.
.a mach trim system provides speed stability at the higher mach numbers. mach trim is automatically accomplished above mach 0.6 by adjusting the elevators with respect to the stabilizer as speed increases. the flight control computers use mach information to compute a mach trim actuator position. the mach trim actuator repositions the elevator feel and centering unit which adjusts the control column neutral position.
Question 266-33 : During initiation of a turn with speedbrakes extended, the roll spoiler function induces a spoiler deflection ?
Downward on the upgoing wing and upward on the downgoing wing.
. /com en/com080 134.jpg.while turning, the outer wing has a higher speed, thus, it generates more lift. as for the differential aileron deflection we need to equals the drag of the right and left aileron , the speed brakes on the outer wing need to be deflect downward and upward for the inner wing.
Question 266-34 : Stick forces, provided by an elevator feel system, depend on ?
.to generate lift we have to move air downwards, and to roll into a banked attitude to turn we have to lift one wing while dropping the other. to lift a wing we have to generate more lift and so we lower the aileron on that side, we don't get something for nothing and so this extra lift increases the drag, meanwhile dropping the other wing by moving the aileron upwards reduces the drag. the increased drag generated by the down going aileron causes the nose to yaw in the opposite direction to the roll and this is called adverse yaw.. /com en/com080 300a.jpg..with differential ailerons, one aileron is raised a greater distance than the other aileron is lowered for a given movement of the control wheel. this produces an increase in drag on the descending wing. the greater drag results from deflecting the up aileron on the descending wing to a greater angle than the down aileron on the rising wing. while adverse yaw is reduced, it is not eliminated completely.. /com en/com080 300b.jpg..
Question 266-36 : Which kind of tab is commonly used in case of manual reversion of fully powered flight controls ?
Servo tab.
.on fully powered controls, a fail/safe system is included such that if the power fails or there is a fault, the control of one or more primary control surface reverts to manual control. conventional trailing edge tabs are not included in this system because the aeroplane is trimmed by adjusting the zero position of the artificial feel mechanism. although powered controls do not require balance tabs some aeroplanes do have them fitted to relieve the servo and hinge loads. in the case of manual reversion of fully powered flight controls a servo tab is commonly used together with control surface mass balancing to make the aeroplane easier to control.
Question 266-37 : One advantage of a movable stabiliser system compared with an elevator trim system is that ?
It is a more effective means of trimming.
.the trimming stabiliser is a very powerful trimming system and its other advantage is that when you are trimmed out the elevator sits more or less in line with the stabilizer giving less trim drag.
Question 266-38 : Which statement is correct about a spring tab ?
At high ias it behaves like a servo tab.
. /com en/com080 276.jpg.servo tabs rely on airflow over them in order to fly the control surface into the desired position. very handy for reducing stick forces. unfortunately the higher the airspeed, the more effective the tab, so that gives us a system that get more effective as ias increases, so the controls get lighter. not a good situation...the spring tab.the easiest way to visualise this is to look at two extremes, in the context of the strength of the spring compared to the aerodynamic forces present...case 1 very low ias.if ias is low, then aerodynamic forces are low. so, relatively, the spring is strong. now imagine its really strong... by replacing it with a rigid link...now, when you move the control column, the flying control is directly moved, and the tab doesn't do anything, so this is now a basic control surface...case 2 very high ias.if ias is high, the aerodynamic forces are high. relatively speaking, the spring is weak. now imagine its really weak... by removing it altogether. now, when you move the column, you are only moving the tab and that flies the control surface into position, so this is now a servo tab system.
Question 266-39 : How is adverse yaw compensated for during entry into and roll out from a turn ?
Differential aileron deflection.
.to generate lift we have to move air downwards, and to roll into a banked attitude to turn we have to lift one wing while dropping the other. to lift a wing we have to generate more lift and so we lower the aileron on that side, we don't get something for nothing and so this extra lift increases the drag, meanwhile dropping the other wing by moving the aileron upwards reduces the drag. the increased drag generated by the down going aileron causes the nose to yaw in the opposite direction to the roll and this is called adverse yaw.. /com en/com080 300a.jpg..with differential ailerons, one aileron is raised a greater distance than the other aileron is lowered for a given movement of the control wheel. this produces an increase in drag on the descending wing. the greater drag results from deflecting the up aileron on the descending wing to a greater angle than the down aileron on the rising wing. while adverse yaw is reduced, it is not eliminated completely.. /com en/com080 300b.jpg..
Question 266-40 : One method to compensate adverse yaw is ?
A differential aileron.
.to generate lift we have to move air downwards, and to roll into a banked attitude to turn we have to lift one wing while dropping the other. to lift a wing we have to generate more lift and so we lower the aileron on that side, we don't get something for nothing and so this extra lift increases the drag, meanwhile dropping the other wing by moving the aileron upwards reduces the drag. the increased drag generated by the down going aileron causes the nose to yaw in the opposite direction to the roll and this is called adverse yaw.. /com en/com080 300a.jpg..with differential ailerons, one aileron is raised a greater distance than the other aileron is lowered for a given movement of the control wheel. this produces an increase in drag on the descending wing. the greater drag results from deflecting the up aileron on the descending wing to a greater angle than the down aileron on the rising wing. while adverse yaw is reduced, it is not eliminated completely.. /com en/com080 300b.jpg..
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