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Question 244-1 : Which kind of 'tab' is commonly used in case of manual reversion of fully powered flight controls ? [ Question security ]
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 244-2 : 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 244-3 : 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 244-4 : 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 244-5 : 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..
Question 244-6 : Flaperons are controls which combine the function of ?
Ailerons and flaps.
Question 244-7 : In general transport aeroplanes with power assisted flight controls are fitted with an adjustable stabiliser instead of trim tabs on the elevator. this is because ?
Effectiveness of trim tabs is insufficient for those aeroplanes.
Question 244-8 : A jet aeroplane equipped with inboard and outboard ailerons is cruising at its normal cruise mach number. in this case ?
Only the inboard ailerons are active.
.the ailerons are normally situated at the wing tip, to give the greatest moment for the force produced. however this also means that they cause the maximum twisting and bending loads on the wing. this can cause a loss of effectiveness or even reversal of the aileron..to reduce these effects the ailerons can be mounted further inboard. alternatively, two sets of ailerons may be fitted, one set at the wing tip for use at low speeds when the forces involved are low, and one set inboard for use at high speeds when the forces are greater and could cause greater structural distortion. in summary, outboard ailerons are low speed ailerons and inboard ailerons are high speed ailerons and only the inboard ailerons are used when the flaps are retracted.
Question 244-9 : Which of the following statements concerning control is correct ?
In a differential aileron control system the control surfaces have a larger upward than downward maximum 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 244-10 : When are outboard ailerons if present de activated ?
Flaps and slats retracted or speed above a certain value.
Question 244-11 : Which statement about stick force per g is correct ?
The stick force per g must have both an upper and lower limit in order to ensure acceptable control characteristics.
Question 244-12 : Examples of aerodynamic balancing of control surfaces are ?
Servo tab, spring tab, seal between the wing trailing edge and the leading edge of control surface.
Illustration of a seal between the wing trailing edge and the leading edge of control surface. 2762.when you move the control surface, it generates an area of high pressure and an area of low pressure...this differential pressure creates a compensation force acting in the same way of the pilot's action.
Question 244-13 : Which phenomenon is counteracted with differential aileron deflection ?
Adverse yaw.
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....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.
Question 244-14 : An aeroplane has a servo tab controlled elevator. what will happen if the elevator jams during flight ?
Pitch control sense is reversed.
. /com en/com080 378.jpg..only the tab is left functioning. it is not connected to the elevator but works in the unnatural sense to drive the elevator in the natural sense, so with the elevator locked you only have very limited control from the tab only and in the unnatural sense and, of course, you have no trim or balance fuction left.
Question 244-15 : A horn balance in a control system has the following purpose ?
To decrease stick forces.
.a horn balance is a method of aerodynamic balancing for the ailerons, elevators and rudders, and is used to produce a balancing moment in order to reduce amount of force required to move the controls..flutter is prevented by the use of mass balancing by adding weights to the control surface to move their cg , not by horn balancing...example of horn balance. 1537
Question 244-16 : An increase in geometric dihedral in a steady sideslip condition at constant speed would ?
Increase the required lateral control force.
Stability is the ability of the aircraft to return to equalibrium without input from the pilot..equalibrium is where all the forces are zero...it does not mean that the aircraft returns to the same heading, or altitude, but that the relative airflow is in such a position that the aircraft will be balanced. in the question, we are trying to hold the aircraft in a steady side slip, which means we are holding the aircraft out of equalibrium..a stable aircraft with geometric dihedral will try to oppose this...so we will be required to hold greater forces to maintain the angle which is opposing the natural tendency of the aircraft..if we increase the geometric dihedral even further, we will need more effort to hold that sideslip as stability will be increased.
Question 244-17 : When a jet transport aeroplane takes off with the cg at the forward limit and the trimmable horizontal stabiliser ths is positioned at the maximum allowable nose down position for take off ?
Rotation will require a higher than normal stick force.
Question 244-18 : Which statement is correct.i. on fully hydraulic powered flight controls there is no need for mass balancing.ii. on fully hydraulic powered flight controls there is no need for trim tabs. ?
I is incorrect, ii is correct
.flight control force balance can normally be achieved hydraulically as part of the actuator sizing. you have to remember that even though fly by wire aircraft recieve their control inputs electronically, the control surfaces are still powered by the hydraulic system s which are sized to overcome mass balance and flight loads. but, to prevent flutter, mass balancing is required, and also in case of manual reversion total hydraulic failure...and with a fully hydraulic powered flight controls there is no need for trim tabs, you can move the controls where you like and use an artificial trim.
Question 244-19 : An aeroplane performs a right turn, the slip indicator is left of neutral. one way to co ordinate the turn is to apply ?
More left rudder.
.in a skidding turn the ball will be displaced in the opposite direction of turn in the direction of turn for a slipping turn.. /com en/com080 593.jpg..one way to co ordinate the turn is to apply more left rudder.
Question 244-20 : When roll spoilers are extended, the part of the wing on which they are mounted ?
Experiences a reduction in lift, which generates the desired rolling moment. in addition there is a local increase in drag, which suppresses adverse yaw.
Question 244-21 : When power assisted controls are used for pitch control ?
A part of the aerodynamic forces is still felt on the column.
Question 244-22 : The pitch angle is defined as the angle between the ?
Longitudinal axis and the horizontal plane.
. 682..the angle of attack should not be confused with the pitch angle or attitude of aircraft, which are angles relative to the horizontal while the angle of attack is in respect to the relative airflow.
Question 244-23 : Which statement in respect of a trimmable horizontal stabiliser is correct ?
An aeroplane with a forward c.g. requires the stabiliser leading edge to be lower than for one with an aft c.g. in the same trimmed condition.
.if the cg is moved aft, it results in a larger nose down pitching moment which has to be compensated for by placing a download on the tailplane. this can be achieved by deflecting the elevator up, although this results in high trim drag at higher airspeeds. on large aircraft small movements of the variable incidence stabiliser allow the trimming to be carried out, but with reduced trim drag...an upward deflection of the elevator is required to trim the aircraft, so think of the stabiliser as a large elevator with its trailing edge moving in the same direction as the elevator. to achieve this you must therefore lower the leading edge of the stabiliser to produce the necessary download...note once in a trimmed condition on fully powered flying controls the elevator will then align itself with the stabiliser to reduce the tail load and also the loads acting on the hinges and servo actuator. on power assisted controls there is however no guarantee that this occurs due to downwash and configuration effects that can alter the flow over the surface. it is also fair to say that trim drag also increases fuel consumption.
Question 244-24 : An example of differential aileron deflection during initiation of left turn is ?
Left aileron 5° up. right aileron 2° down.
. /com en/com080 510.jpg.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 244-25 : An aeroplane is provided with spoilers and both inboard and outboard ailerons. roll control during cruise is provided by ?
Inboard ailerons and roll spoilers.
Question 244-26 : Mass balancing of control surfaces is used to ?
Prevent flutter of control surfaces.
.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 244-27 : In what phase of flight are the outboard ailerons if fitted not active ?
Cruise.
Question 244-28 : The most important factor determining the required position of the trimmable horizontal stabiliser ths for take off is the ?
Position of the aeroplane's centre of gravity.
Question 244-29 : What is the position of the elevator in relation to the trimmable horizontal stabiliser of an aeroplane with fully hydraulically operated flight controls that is in trim ?
Elevator deflection is zero.
.a fully hydraulically operated flight controls is an irreversible system, and the trim is a redatum, as there is no physical connection between the stick and control. therefore there will be no elevator deflection when trimmed.
Question 244-30 : In straight flight, as speed is increased, whilst trimming to keep the stick force zero ?
The elevator is deflected further downwards and the trim tab further upwards.
. /com en/com080 641.jpg..
Question 244-31 : Rotation around the longitudinal axis is called ?
Rolling.
Img /com en/com080 547a.jpg..
Question 244-32 : Rotation around the normal axis is called ?
Yawing.
Question 244-33 : Which of these statements about a trimmable horizontal stabiliser is correct ?
A trimmed aeroplane with an aft cg requires the stabiliser leading edge to be higher than in the case of a forward cg in the same condition.
. /com fr/com080 298.jpg.with a forward cg, the tailplane must produce a high downward force to stabilise the aircraft. if the cg moves aft closer to the centre of lift the downward force is reduced, the.trimmable horizontal stabiliser leading edge is higher than in the case of a forward cg, to keep the balance of lift and total weight constant.
Question 244-34 : When comparing an elevator trim system with a stabiliser trim system, which of these statements is correct ?
An elevator trim is more sensitive to flutter.
.on a stabiliser trim system, the whole tailplane is moving. this large surface is less sensitive to flutter than an elevator trim system. the elevator trim tab system is a small auxiliary control surface hinged at the trailing edge of the elevators.
Question 244-35 : When comparing a stabiliser trim system with an elevator trim system, which of these statements is correct ?
An elevator trim is less suitable for aeroplanes with a large cg range.
.a horizontal trimmable stabiliser enables a larger cg range, and is more suitable to cope with the large trim changes generated by the high lift devices on most jet transport aeroplanes..on a stabiliser trim system, the whole tailplane is moving. this large surface is less sensitive to flutter than an elevator trim system. the elevator trim tab system is a small auxiliary control surface hinged at the trailing edge of the elevators.
Question 244-36 : Comparing the differences between a horizontal trimmable stabiliser and an elevator trim tab, which of these statements are correct or incorrect.i. the effects of a stabiliser trim runaway are more serious..ii. a jammed trim tab causes less control difficulty. ?
I is correct, ii is correct.
.the effects of a trim tab runaway are more serious > wrong...the effects of a stabiliser trim runaway are more serious > correct..a jammed stabiliser trim causes less control difficulty > wrong...a jammed trim tab causes less control difficulty > correct..stabiliser trim runaway is more serious because it requires more force to be exerted by the pilot to overcome the movement of the stabiliser trim. because stabilisers pivot around a central hinge point, they are extremely sensitive to control inputs and aerodynamic loads. antiservo tabs are incorporated on the trailing edge to decrease sensitivity. they deflect in the same direction as the stabilisator. this results in an increase in the force required to move the stabiliser...whereas a jammed trim tab is less serious because it requires less force to be exerted by the pilot in order to overcome it.
Question 244-37 : Which aerodynamic design features can be used to reduce control forces ?
Horn balance, balance tab, servo tab.
Question 244-38 : In general, control forces are reduced by ?
A horn balance, servo tab and spring tab.
Question 244-39 : What are the primary roll controls on a conventional aeroplane ?
The ailerons.
Question 244-40 : Artificial feel is required ?
With fully powered flight controls.
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