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Question 243-1 : Which statement about negative tail stall is correct ? [ Question security ]
When negative tail stall occurs the aeroplane will show an uncontrollable pitch down moment
.negative tail stall is a sudden reduction in the downward aerodynamic force on the tailplane it means that previously the tail was producing a downward force cg is forward of cp . /com en/com080 699 jpg.
Question 243-2 : An aeroplane has static directional stability if when in a sideslip with the relative airflow coming from the left initially the ?
Nose of the aeroplane tends to yaw left
.a side slip to 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.directional stability is accomplished by placing a vertical stabilizer or fin to the rear of the centre of gravity on the upper portion of the tail section
Question 243-3 : As the stability of an aeroplane decreases ?
Its manoeuvrability increases
Question 243-4 : Aeroplane manoeuvrability increases for a given control surface deflection when ?
Ias increases
.the capability of an airplane to respond to the pilot's control greatly depends on the airflow speed on the control surface
Question 243-5 : Static lateral stability will be decreased by ?
The use of a low rather than high wing mounting
.an aircraft's stability is expressed in relation to each axis .lateral stability stability in roll directional stability stability in yaw and longitudinal stability stability in pitch .rolling is the rotation of the aeroplane about the longitudinal axis . 684.static stability refers to the aircraft's initial response to a disturbance a statically unstable aircraft will uniformly depart from a condition of equilibrium .mounting the wings above the centre of gravity aids lateral stability because the weight of the aircraft will act as a pendulum to restore level flight therefore the use of a low wing mounting will decrease the static lateral stability
Question 243-6 : Static lateral stability will be decreased by ?
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 243-7 : 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 243-8 : 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 243-9 : 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 243-10 : 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 243-11 : 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 243-12 : 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 leftt 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 243-13 : Static directional stability is mainly provided by ?
The fin
Question 243-14 : Longitudinal stability is directly influenced by ?
Centre of gravity position
Question 243-15 : 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 243-16 : 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 243-17 : 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 243-18 : 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 243-19 : 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 243-20 : 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 243-21 : Assuming no pilot input the motion of the aeroplane in the diagram shows . err a 081 1013 ?
Dynamic longitudinal stability
Question 243-22 : 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 243-23 : 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 243-24 : 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 243-25 : 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 243-26 : 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 243-27 : 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 243-28 : 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 243-29 : 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 243-30 : Static lateral stability will be increased by ?
The use of a high rather than low wing mounting
Question 243-31 : 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 totallift the vertical component must be large enough to maintain level flight while the horizontalcomponent is large enough to produce the required centripetal force
Question 243-32 : During a short period oscillation the altitude ?
Remains approximately constant whereas during a phugoid it varies significantly
Question 243-33 : The purpose of a dorsal fin is to ?
Maintain static directional stability at large sideslip angles
Question 243-34 : 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 243-35 : 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 243-36 : 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 243-37 : 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 243-38 : 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
Img /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 243-39 : 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.
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