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Longitudinal static stability is created by the fact that the ? [ Formation assignment ]

Question 234-1 : Centre of gravity is located in front of the neutral point of the aeroplane centre of gravity is located in front of the leading edge of the wing wing surface is greater than the horizontal tail surface aeroplane possesses a large trim speed range

exemple 334 Centre of gravity is located in front of the neutral point of the aeroplane.Centre of gravity is located in front of the neutral point of the aeroplane.

Following a disturbance an aeroplane oscillates about the lateral axis at a ?

Question 234-2 : Statically stable dynamically neutral statically unstable dynamically stable statically stable dynamically unstable statically unstable dynamically neutral

. static stability .static stability refers to the initial tendency or direction of movement back to equilibrium in aviation it refers to the aircraft's initial response when disturbed from a given aoa slip or bank .positive static stability is the initial tendency of the aircraft to return to the original state of equilibrium after being disturbed . dynamic stability .dynamic stability refers to the aircraft response over time when disturbed from a given aoa slip or bank .neutral dynamic stability means once displaced the displaced object neither decreases nor increases in amplitude a worn automobile shock absorber exhibits this tendency .for information . positive dynamic stability means over time the motion of the displaced object decreases in amplitude and because it is positive the object displaced returns toward the equilibrium state . negative dynamic stability means over time the motion of the displaced object increases and becomes more divergent exemple 338 Statically stable - dynamically neutralStatically stable - dynamically neutral

Which statement on dynamic longitudinal stability of a conventional aeroplane ?

Question 234-3 : Damping of the phugoid is normally very weak speed remains constant during one period of the phugoid period time of the phugoid is normally 5 s damping of the short period oscillation is normally very weak

. /com en/com080 483a jpg.since the pitch rate is quite low and only negligible changes in angle of attack take place damping of the phugoid is weak however such weak damping does not necessarily have any great consequence since the period of oscillation is so great long period oscillation is easily controlled by the pilot exemple 342 Damping of the phugoid is normally very weak.Damping of the phugoid is normally very weak.

The 'short period mode' is an ?

Question 234-4 : Oscillation about the lateral axis oscillation about the normal axis oscillation about the longitudinal axis unstable movement of the aeroplane induced by the pilot

.oscillation about the lateral axis 'short period mode' is movement in the longitudinal axis . 686.the short period mode is a usually heavily damped oscillation with a period of only a few seconds the motion is a rapid pitching of the aircraft about the center of gravity the period is so short that the speed does not have time to change so the oscillation is essentially an angle of attack variation the change could be caused by a sudden gust or by a longitudinal displacement of the stick . short period mode . /com en/com080 84 jpg.for information the longer period mode is called the 'phugoid' exemple 346 Oscillation about the lateral axis.Oscillation about the lateral axis.

An aeroplane that has positive static stability ?

Question 234-5 : Can be dynamically stable neutral or unstable is always dynamically stable is never dynamically stable is always dynamically unstable

exemple 350 Can be dynamically stable, neutral or unstable.Can be dynamically stable, neutral or unstable.

A statically unstable aeroplane is ?

Question 234-6 : Never dynamically stable always dynamically stable sometimes dynamically stable sometimes dynamically unstable

exemple 354 Never dynamically stable.Never dynamically stable.

One of the requirements for positive dynamic stability is ?

Question 234-7 : Positive static stability a large deflection range of the stabiliser trim a small cg range an effective elevator

exemple 358 Positive static stability.Positive static stability.

Which of the following statements about dihedral is correct ?

Question 234-8 : The 'effective dihedral' of an aeroplane component means the contribution of that component to the static lateral stability effective dihedral is the angle between the 1/4 chord line and the lateral axis of the aeroplane dihedral contributes to dynamic but not to static lateral stability dihedral is necessary for the execution of slip free turns

.the dihedral is the angle between the wings and the horizontal looked at from the front where the wingtips are higher than the roots .it is an angle that raises the centerline of the wing tip above the centreline of the root . /com en/com080 208 jpg.effective dihedral is pretty much what it sounds like effective dihedral is the effect of other aspects of the aircraft configuration that produce an effect similar to geometric dihedral many aspects of an aircraft's configuration can effect its effective dihedral but two major components are wing sweep and the wing location with respect to the fuselage such as a low wing or high wing .as a rough estimation 10° of sweepback on a wing provides about 1° of effective dihedral while a high wing configuration can provide about 5° of effective dihedral over a low wing configuration .when a wing goes down dihedral effect will tend to decrease bank angle and roll the wing back up this is a positive contribution to the static lateral stability exemple 362 The 'effective dihedral' of an aeroplane component means the contribution of that component to the static lateral stability.The 'effective dihedral' of an aeroplane component means the contribution of that component to the static lateral stability.

Which design features improve static lateral stability .1 high wing.2 low ?

Question 234-9 : 1 3 2 4 1 4 2 3

.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. exemple 366 1, 3.1, 3.

Which wing design feature decreases the static lateral stability of an aeroplane ?

Question 234-10 : Anhedral dihedral high wing increased wing span

. first static stability .static stability refers to the initial tendency or direction of movement back to equilibrium in aviation it refers to the aircraft's initial response when disturbed from a given aoa slip or bank . second static lateral stability of an aeroplane .an aircraft that tends to return to wings level flight after it has been disturbed is considered to be laterally stable . now what is anhedral and dihedral wing design features .this is the upward and outward slope of the wing if the wing tip is higher than the wing root relative to the horizontal plane the aircraft has positive dihedral negative dihedral is termed anhedral . /com en/com080 94 jpg.when an aircraft rolls the aircraft will begin to sideslip the lower wing presents a larger span as seen from the direction of the approaching air the effect is to roll the aircraft back towards the horizontal .this will always be a restoring moment for a dihedral wing but it's the opposite for an anhedral wing . what about high wing .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 . and why increased wing span do not decrease the static lateral stability .without dihedral if the restoring moment is insufficient to restore level flight the aircraft will begin to sideslip .in a sideslip the lower wing has in increased angle of attack while the upper wing has a reduced angle of attack the greater lift on the lowered wing will restore level flight and this effect is increase with an increased wing span exemple 370 Anhedral.Anhedral.

The manoeuvrability of an aeroplane is best when the ?

Question 234-11 : Cg is on the aft cg limit speed is low cg position is on the forward cg limit flaps are down

.manoeuvrability is the ability of a pilot to increase the load factor of the aircraft which is of course accomplished through turning climbing or descending .however manoeuvre stability is the aircrafts ability to resist such a change .thus a forward cg will increase the stability but reduce controllability manoeuvrability where as an aft cg will be just the opposite exemple 374 Cg is on the aft cg limit.Cg is on the aft cg limit.

The effect of a ventral fin on the static stability of an aeroplane is as ?

Question 234-12 : 1 no effect 2 negative 3 positive 1 positive 2 negative 3 negative 1 negative 2 positive 3 positive 1 no effect 2 positive 3 negative

. static stability .static stability refers to the initial tendency or direction of movement back to equilibrium in aviation it refers to the aircraft's initial response when disturbed from a given aoa slip or bank .a dorsal or ventral fine will increase directional stability the fin acts like a weathercock to keep the aircraft straight if it yaws the surface is struck more from the side to force the nose back while decreasing lateral stability the ventral fin makes you roll when hit by a gust from the side .ventral fin has no effect on pitching longitudinal axis exemple 378 1 : no effect, 2 : negative, 3 : positive1 : no effect, 2 : negative, 3 : positive

Which of the following statements about static lateral and directional ?

Question 234-13 : An aeroplane with an excessive static directional stability in relation to its static lateral stability will be prone to spiral dive spiral instability the effects of static lateral and static directional stability are completely independent of each other because they take place about different axes an aeroplane with an excessive static directional stability in relation to its static lateral stability will be prone to 'dutch roll' static directional stability can be increased by installing more powerful engines

.spiral divergence will exist when static directional stability is very large when compared to the static lateral stability dihedral effect when a wing goes down dihedral effect will tend to decrease bank angle and roll the wing back up .the character of spiral divergence is not violent the aeroplane when disturbed from the equilibrium of level flight begins a slow spiral which gradually increases to a spiral dive when a small sideslip is introduced the strong directional stability tends to restore the nose into the wind while the relatively weak 'dihedral effect' lags in restoring the aeroplane laterally the rate of divergence in the spiral motion is usually so gradual that the pilot can control the tendency without difficulty exemple 382 An aeroplane with an excessive static directional stability in relation to its static lateral stability, will be prone to spiral dive (spiral instability).An aeroplane with an excessive static directional stability in relation to its static lateral stability, will be prone to spiral dive (spiral instability).

Which moments or motions interact in a dutch roll ?

Question 234-14 : Rolling and yawing pitching and yawing pitching and rolling pitching and adverse yaw

exemple 386 Rolling and yawing.Rolling and yawing.

Ignoring downwash effects on the tailplane extension of fowler flaps will ?

Question 234-15 : A nose down pitching moment a nose up pitching moment a force which reduces drag no pitching moment

exemple 390 A nose-down pitching moment.A nose-down pitching moment.

Which one of the following systems suppresses the tendency to 'dutch roll' ?

Question 234-16 : Yaw damper roll spoilers spoiler mixer rudder limiter

exemple 394 Yaw damper.Yaw damper.

Which aeroplane behaviour will be corrected by a yaw damper ?

Question 234-17 : Dutch roll flutter spiral dive buffeting

exemple 398 Dutch roll.Dutch roll.

If the sum of all the moments in flight is not zero the aeroplane will rotate ?

Question 234-18 : Centre of gravity neutral point of the aeroplane aerodynamic centre of the wing centre of pressure of the wing

exemple 402 Centre of gravity.Centre of gravity.

Wing dihedral ?

Question 234-19 : Contributes to static lateral stability is the only way of ensuring static lateral stability is particularly applied on aeroplanes with high mounted wings does not affect static lateral stability

.when a wing goes down dihedral effect will tend to decrease bank angle and roll the wing back up this is a positive contribution to the static lateral stability the dihedral effect is an increase in angle of attack on the lower wing compared to the upper wing exemple 406 Contributes to static lateral stability.Contributes to static lateral stability.

A c g location beyond the aft limit leads to ?

Question 234-20 : An unacceptable low value of the manoeuvre stability stick force per g fe/g a too high pulling stick force during rotation in the take off an increasing static longitudinal stability a better recovery performance in the spin

exemple 410 An unacceptable low value of the manoeuvre stability (stick force per g, fe/g).An unacceptable low value of the manoeuvre stability (stick force per g, fe/g).

What should be usually done to perform a landing with the stabiliser jammed in ?

Question 234-21 : Choose a higher landing speed than normal and/or use a lower flapsetting for landing choose a lower landing speed than normal if possible relocate as many passengers as possible to the front of the cabin use the mach trimmer until after landing

exemple 414 Choose a higher landing speed than normal and/or use a lower flapsetting for landing.Choose a higher landing speed than normal and/or use a lower flapsetting for landing.

The pitch up effect of an aeroplane with swept back wing in a stall is due to ?

Question 234-22 : Wing tip stalling first aft movement of the centre of gravity forward movement of the centre of gravity wing root stalling first

exemple 418 Wing tip stalling first.Wing tip stalling first.

How does positive camber of an aerofoil affect static longitudinal stability ?

Question 234-23 : No effect because camber of the aerofoil produces a constant pitch down moment coefficient independent of angle of attack positive effect because the centre of pressure shifts rearward at increasing angle of attack negative effect because the lift vector rotates forward at increasing angle of attack positive effect because the lift vector rotates backward at increasing angle of attack

The aerofoil will always pitch about the aerodynamic center and it depends where the average forces of the top surface are acting through compared to where the average forces of the bottom surfaces are acting through .with a symmetrical aerofoil the forces of the top and bottom surfaces act through the same position so it has no pitching moment .a cambered aerofoil will have the top surface forces acting through a point further back along the chord than the bottom forces so it will pitch nose down exemple 422 No effect, because camber of the aerofoil produces a constant pitch down moment coefficient, independent of angle of attack.No effect, because camber of the aerofoil produces a constant pitch down moment coefficient, independent of angle of attack.

Which statement about a primary control surface controlled by a servo tab is ?

Question 234-24 : The position is undetermined during taxiing in particular with tailwind the servo tab can also be used as a balance tab the control effectiveness of the primary surface is increased by servo tab deflection due to the effectiveness of the servo tab the control surface area can be smaller

.the function of a servo tab is to assist in moving large control surfaces rather than holding them in one position servo tabs move in the opposite direction to the surfaces they are attached to trough a mechanism on the port elevator torque tube .the system requires airflow from leading edge to trailing edge when taxiing in a tailwind a servo tab is ineffective so the control surface just flops around throw in a tailwind and it can end up anywhere .servo tab . /com en/com080 350a jpg.anti servo tab . /com en/com080 350b jpg.the control column is directly connected to the control surface but a tab is geared to the movement of the control surface so that it either assists the movement of the control or counters the movement of the control thus the controls can be made to feel heavier anti servo tab or lighter servo tab than they would otherwise exemple 426 The position is undetermined during taxiing, in particular with tailwind.The position is undetermined during taxiing, in particular with tailwind.

Sensitivity for spiral dive will occur when ?

Question 234-25 : The static directional stability is positive and the static lateral stability is relatively weak the static directional stability is negative and the static lateral stability is positive the static lateral and directional stability are both negative the dutch roll tendency is too strongly suppressed by the yaw damper

.the effects of static lateral stability and static directional stability do interact if an aeroplane is in a sideslip to the right for example static directional stability will generate a yawing moment to the right but static lateral stability will generate a rolling moment to the left the net result on the aeroplane can be decided by which type of static stability is dominant .if the yawing moment from static directional stability is larger than the rolling moment from static lateral stability the aeroplane would roll further to the right and sideslip more the aeroplane will enter a spiral dive to the right spiral instability .on the other hand if the rolling moment from static lateral stability is larger than the yawing moment from static directional stability the lower wing will have more lift and more induced drag and the aeroplane will not only initially roll to the left but will then yaw to the right and so on this is known as dutch roll .the way to remember which type of dynamic stability will result if the aeroplane has a dominance of static directional stability it will tend to suffer spiral instability whereas if the aeroplane has a dominance of static lateral stability it will tend to suffer from dutch roll exemple 430 The static directional stability is positive and the static lateral stability is relatively weak.The static directional stability is positive and the static lateral stability is relatively weak.

Which part of an aeroplane provides the greatest positive contribution to ?

Question 234-26 : The horizontal tailplane the engine the fuselage the wing

exemple 434 The horizontal tailplane.The horizontal tailplane.

An advantage of locating the engines at the rear of the fuselage in comparison ?

Question 234-27 : Less influence of thrust changes on longitudinal control less influence on lateral/directional stability characteristics such as dutch roll easier maintenance of the engines a wing which is less sensitive to flutter

exemple 438 Less influence of thrust changes on longitudinal control.Less influence of thrust changes on longitudinal control.

The tendency to dutch roll increases when ?

Question 234-28 : The static lateral stability increases the static directional stability increases the centre of gravity moves forward the anhedral increases

exemple 442 The static lateral stability increases.The static lateral stability increases.

Which statement is correct ?

Question 234-29 : Dynamic stability is possible only when the aeroplane is statically stable about the relevant axis static stability means that the aeroplane is also dynamically stable about the relevant axis dynamic stability about the lateral axis implies that after being displaced from original equilibrium condition the aeroplane will return to that condition without oscillation a dynamically stable aeroplane would be almost impossible to fly manually

.static and dynamic stability .static stability refers to the initial response of the aeroplane to displacement example if the aircraft pitches up due to a gust of wind then without any input from the pilot it returns back to where it was it has displayed positive static stability since this was in pitch it would be longitudinal stability if after pitching up the aircraft stayed pitched up that would be neutral static stability if the aircraft were to pitch up further away from where it was that would be negative static stability .dynamic stability refers to what the aircraft does over time using the example above the aircraft pitches up then pitches back down .positive static stability as the aircraft pitches down it is subjected to a angular velocity it has mass and its momentum might make it swing past its initial position but since it has positive static stability it will then pitch back up and after a few oscillations settle back to where it was initially that is positive dynamic stability if after say 2 minutes the aircraft is still pitching up and down at the same rate that would be an example of neutral dynamic stability if the aircraft swings further and further away over time that would be an example of negative dynamic stability .you cannot have an aircraft which is dynamic stable on an axis if it is not stable statically on this axis exemple 446 Dynamic stability is possible only when the aeroplane is statically stable about the relevant axis.Dynamic stability is possible only when the aeroplane is statically stable about the relevant axis.

Positive static lateral stability is the tendency of an aeroplane to ?

Question 234-30 : Roll to the left in the case of a sideslip with the aeroplane nose pointing to the left of the incoming flow roll to the left in the case of a sideslip angle with the aeroplane nose pointing to the right of the incoming flow roll to the right in a right turn roll to the left in a right turn

.rolling is the rotation of the aeroplane about the longitudinal axis . 684.a side slip to the right is the slip of the tail to the right the nose goes left .when a sideslip 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 exemple 450 Roll to the left in the case of a sideslip (with the aeroplane nose pointing to the left of the incoming flow).Roll to the left in the case of a sideslip (with the aeroplane nose pointing to the left of the incoming flow).

What is the effect of an aft shift of the centre of gravity on 1 static ?

Question 234-31 : 1 reduces 2 reduces 1 increases 2 reduces 1 increases 2 increases 1 reduces 2 increases

.you will have less static stability and less control deflection for a given response exemple 454 (1) reduces (2) reduces.(1) reduces (2) reduces.

When an aeroplane has zero static longitudinal stability the cm versus angle of ?

Question 234-32 : Is horizontal is vertical has a negative slope has a positive slope

.pitching moment coefficient cm versus angle of attack diagram . /com en/com080 426 jpg.by 'zero' they mean 'neutral' the response after encountering an up gust will always be same regardless of the angle of attack exemple 458 Is horizontal.Is horizontal.

What is the effect of elevator trim tab adjustment on the static longitudinal ?

Question 234-33 : No effect depends on the value of stick force/g aeroplane nose up trim increases the static longitudinal stability aeroplane nose down trim increases the static longitudinal stability

.the elevator trim tab adjustment is take out stick forces at one particular attitude none of the basic factors that determine stability has changed exemple 462 No effect.No effect.

Which statement concerning sweepback is correct ?

Question 234-34 : Sweepback provides a positive contribution to static lateral stability sweepback increases speed stability at mach numbers above mcrit sweepback is mainly intended to increase static directional stability a disadvantage of sweepback is that it decreases mcrit

.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 exemple 466 Sweepback provides a positive contribution to static lateral stability.Sweepback provides a positive contribution to static lateral stability.

Which three aerodynamic means decrease manoeuvring stick forces ?

Question 234-35 : Servo tab horn balance spring tab servo tab trim tab balance tab spring tab trim tab mass balancing weight spring tab horn balance bobweight

Which statement is correct .i stick force per g is independent of altitude .ii ?

Question 234-36 : I is incorrect ii is correct i is correct ii is correct i is correct ii is incorrect i is incorrect ii is incorrect

.stick force per g is dependent of altitude rho changes with altitude pressure on the control surface will change .if the cg moves forward static longitudinal stability increases and controllability decreases stick force increases a very high stick forces are required to pitch because the aircraft is very stable the magnitude of the stick force required to pitch for an aircraft with manual controls is determined by the distance the cg is forward of the neutral point exemple 474 I is incorrect, ii is correct.I is incorrect, ii is correct.

Which statement is correct ?

Question 234-37 : The short period oscillation should always be heavily damped the phugoid should always be heavily damped when the phugoid is slightly unstable an aeroplane becomes uncontrollable a slightly unstable short period oscillation is no problem for an aeroplane

Img /com en/com080 483a jpg. /com en/com080 483 jpg.vdo925.the short period oscillation should always be heavily damped short period oscillation is dangerous because structural failure usually results if the oscillation is not damped immediately short period oscillations affect airplane and control surfaces alike and reveal themselves as 'porpoising' in the airplane or as in 'buzz' or 'flutter' in the control surfaces exemple 478 The short period oscillation should always be heavily damped.The short period oscillation should always be heavily damped.

Which statement is correct ?

Question 234-38 : During a phugoid altitude varies significantly but during a short period oscillation it remains approximately constant during both a phugoid and a short period oscillation altitude remains approximately constant during both a phugoid and a short period oscillation altitude varies significantly during a phugoid altitude remains approximately constant but during a short period oscillation it varies significantly

Img /com en/com080 483a jpg. /com en/com080 483 jpg.vdo927 exemple 482 During a phugoid altitude varies significantly, but during a short period oscillation it remains approximately constant.During a phugoid altitude varies significantly, but during a short period oscillation it remains approximately constant.

During a phugoid the speed ?

Question 234-39 : Varies significantly whereas during a short period oscillation it does not remains approximately constant as during a short period oscillation varies significantly as during a short period oscillation remains approximately constant whereas during a short period oscillation it varies significantly

. /com en/com080 483a jpg. /com en/com080 483 jpg. exemple 486 Varies significantly, whereas during a short period oscillation it does not.Varies significantly, whereas during a short period oscillation it does not.

An aeroplane exhibits static longitudinal stability if when the angle of attack ?

Question 234-40 : The change in total aeroplane lift acts aft of the centre of gravity the change in total aeroplane lift acts through the centre of gravity the resulting moment is positive the change in wing lift is equal to the change in tail lift

exemple 490 The change in total aeroplane lift acts aft of the centre of gravity.The change in total aeroplane lift acts aft of the centre of gravity.

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