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Question 242-1 : What is the effect of an aft shift of the centre of gravity on 1 static longitudinal stability and 2 the required control deflection for a given pitch change ? [ Question security ]

1 reduces 2 reduces

.you will have less static stability and less control deflection for a given response exemple 342 (1) reduces (2) reduces.

Question 242-2 : When an aeroplane has zero static longitudinal stability the cm versus angle of attack line ?

Is horizontal

.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 346 Is horizontal.

Question 242-3 : What is the effect of elevator trim tab adjustment on the static longitudinal stability of an aeroplane ?

No effect

.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 350 No effect.

Question 242-4 : Which statement concerning sweepback is correct ?

Sweepback provides a positive contribution to static lateral stability

.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 354 Sweepback provides a positive contribution to static lateral stability.

Question 242-5 : Which three aerodynamic means decrease manoeuvring stick forces ?

Servo tab horn balance spring tab

exemple 358 Servo tab - horn balance - spring tab.

Question 242-6 : Which statement is correct .i stick force per g is independent of altitude .ii stick force per g increases when the centre of gravity moves forward ?

I is incorrect ii is correct

.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 362 I is incorrect, ii is correct.

Question 242-7 : Which statement is correct ?

The short period oscillation should always be heavily damped

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 366 The short period oscillation should always be heavily damped.

Question 242-8 : Which statement is correct ?

During a phugoid altitude varies significantly but during a short period oscillation it remains approximately constant

Img /com en/com080 483a jpg. /com en/com080 483 jpg.vdo927 exemple 370 During a phugoid altitude varies significantly, but during a short period oscillation it remains approximately constant.

Question 242-9 : During a phugoid the speed ?

Varies significantly whereas during a short period oscillation it does not

. /com en/com080 483a jpg. /com en/com080 483 jpg. exemple 374 Varies significantly, whereas during a short period oscillation it does not.

Question 242-10 : An aeroplane exhibits static longitudinal stability if when the angle of attack changes ?

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

exemple 378 The change in total aeroplane lift acts aft of the centre of gravity.

Question 242-11 : A negative contribution to the static longitudinal stability of conventional jet transport aeroplanes is provided by ?

The fuselage

. 686.generally the contributions of the wing fuselage and nacelles is de stabilizing together these components generate nonrestoring pitching moments when changes in lift coefficient occur if the airplane is to possess static longitudinal stability the horizontal tail must be designed to overcome the destabilizing influence of the remainder of the airplane's components the contribution of the horizontal tail to static longitudinal stability is powerful and almost always strongly stabilizing exemple 382 The fuselage.

Question 242-12 : A jet transport aeroplane exhibits pitch up when thrust is suddenly increased from an equilibrium condition because the thrust line is below the ?

Cg

. /com en/com080 526 jpg.thrust line is below the center of gravity if thrust is suddenly increased it creates a pitching moment exemple 386 Cg.

Question 242-13 : The aeroplane motion schematically illustrated in the annex is an example of a dynamically . err a 081 529 ?

Unstable periodic motion

exemple 390 Unstable periodic motion.

Question 242-14 : The aerodynamic contribution to the static longitudinal stability of the nacelles of aft fuselage mounted engines is ?

Positive

. 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 . longitudinal lateral and directional stability . /com en/com080 547a jpg.here we are talking about aft fuselage mounted nacelles . /com en/com080 547b jpg.and they are not a symmetrical body they are curved like aerofoils airflow around them produce aerodynamic forces it generates a nose up moment the plan area of the engines stub mountings and so on acts like an extra horizontal tail that aerodynamic force is stabilising it is the same as having a larger tailplane which gives positive longtitudinal stability exemple 394 Positive.

Question 242-15 : Stick force per g ?

Is dependent on cg location

.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 .when the centre of gravity moves forward the stick force per g increases exemple 398 Is dependent on cg location.

Question 242-16 : Static lateral stability should not be too large because ?

Too much aileron deflection would be required in a crosswind landing

High lateral stability results in high stick forces with the aircraft attempting to maintain a wing level attitude during a crosswind landing the aircraft will tend to yaw and sideslip .the sideslip component will result in lateral stability attempting to level the wing you therefore have to hold this roll off by applying aileron which if the stability is too high will require a larger aileron deflection exemple 402 Too much aileron deflection would be required in a crosswind landing.

Question 242-17 : Positive static stability of an aeroplane means that following a disturbance from the equilibrium condition ?

The initial tendency is to return towards its equilibrium condition

exemple 406 The initial tendency is to return towards its equilibrium condition.

Question 242-18 : Positive static longitudinal stability means that a ?

Nose down moment occurs after encountering an up gust

exemple 410 Nose-down moment occurs after encountering an up-gust.

Question 242-19 : Static lateral stability should not be too small because ?

The aeroplane would show too strong a tendency to spiral dive

exemple 414 The aeroplane would show too strong a tendency to spiral dive.

Question 242-20 : The effect on static lateral stability of an aeroplane with a high wing as compared with a low wing is ?

A positive dihedral effect

.an aircraft that tends to return to wings level flight after it has been disturbed is considered to be laterally stable 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 .'positive dihedral effect' 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 418 A positive dihedral effect.

Question 242-21 : The effect of the wing downwash on the static longitudinal stability of an aeroplane is ?

Negative

. /com en/com080 557a jpg.the downwash behind the wing will have a negative contribution on the static longitudinal stability because it tends to push the tail down as angle of attack increases you will have a more important nose up attitude .longitudinal stability is on the lateral axis . 686.note a t tail aircraft keeps the tail out of downwash and of propeller wash but in extreme nose high attitudes t tail aircraft pitches up viciously when stalled because if the horizontal tail surfaces become buried in the wing's wake the elevator may lose all effectiveness making it impossible to reduce pitch attitude and break the stall exemple 422 Negative.

Question 242-22 : The effect of a wing with sweepback on static directional stability is as follows ?

Stabilizing effect

.wing sweepback aids in directional stability if the aircraft is rotated about the vertical axis the aircraft will be forced sideways into the relative wind .because of sweepback this causes the leading wing to present more frontal area to the relative wind than the trailing wing this increased frontal area creates more drag which tends to force the aircraft to return to its original direction of flight . /com en/com080 558 jpg. exemple 426 Stabilizing effect.

Question 242-23 : If the nose of an aeroplane yaws left this causes ?

A roll to the left

If the nose yaw left a part of the left wing will be shadowed by the fuselage you will have more lift on the right wing inducing a roll to the left . /com en/com080 567 jpg.this phenomenon is increasing to an airplane with dihedral the right wing has a slightly increased angle of attack and therefore higher lift which causes more roll to the left exemple 430 A roll to the left.

Question 242-24 : If the elevator trim tab is deflected up the cockpit trim indicator shows ?

Nose down

exemple 434 Nose down.

Question 242-25 : If an aeroplane exhibits insufficient stick force per g this problem can be resolved by installing ?

A bobweight in the control system which pulls the stick forwards

.when you pull the stick back and if the stick force is judge to weak you may quickly suffer from g force with a risk of lost consciousness or even worse destroying the airplane .by installing a bobweight in the control system it will be subjected to acceleration g force and it pulls the stick forwards .the more the g force is the more the effect will be important exemple 438 A bobweight in the control system which pulls the stick forwards.

Question 242-26 : How can the designer of an aeroplane with straight wings increase the static lateral stability ?

By increasing the aspect ratio of the vertical stabiliser whilst maintaining a constant area

.by making the tail fin taller while keeping the same area you are moving the cp of the fin further away from the aircraft cg giving more moment arm and thus more correcting roll force exemple 442 By increasing the aspect ratio of the vertical stabiliser, whilst maintaining a constant area.

Question 242-27 : If the total sum of moments about one of its axes is not zero an aeroplane would ?

Experience an angular acceleration about that axis

exemple 446 Experience an angular acceleration about that axis.

Question 242-28 : The manoeuvre stability of a large jet transport aeroplane is 280 n/g what stick force is required if the aeroplane is pulled to the limit manoeuvring load factor from a trimmed horizontal straight and steady flight cruise configuration ?

420 n

.limitation for transport aircraft is 2 5 g .difference between 2 5 g and 1 g is 1 5 g .to reach the limit manoeuvring load factor force to be applied will be 280 x 1 5 = 420 n exemple 450 420 n.

Question 242-29 : Which of the following provides a positive contribution to static directional stability ?

A dorsal fin

exemple 454 A dorsal fin

Question 242-30 : The primary purpose of dihedral is to ?

Increase 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 458 Increase static lateral stability.

Question 242-31 : A conventional stabiliser on a stable aeroplane in a normal cruise condition .1 always provides negative lift.2 contributes to the total lift of the aeroplane.3 may stall before the wing in icing conditions with large flap settings unless adequate design and/or operational precautions are ?

2 3 and 4

exemple 462 2, 3 and 4.

Question 242-32 : During a take off roll with a strong crosswind from the right 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 right 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 right in order to counteract this tendency you must apply rudder to the left now if the right outboard engine fails thrust from the left engines will combined and it might be impossible to counteract the turning moment . /com en/com080 646 jpg. exemple 466 The right outboard engine.

Question 242-33 : In general directional controllability with one engine inoperative on a multi engine aeroplane is adversely affected by .1 high temperature.2 low temperature.3 aft cg location.4 forward cg location.5 high altitude.6 low altitude.the combination that regroups all of the correct statements is ?

2 3 6

It's because thrust is lower in the less dense air high temperature and high altitude so the asymmetric effect is lessened .now with regards to the centre of gravity we have to take into account the perpendicular distance whether forward or aft the position of the centre of gravity doesn't affect the perpendicular distance from the thrust line created by the live engine to the aircraft's longitudinal axis about which the centre of gravity moves .if we look at the perpendicular distance from the lift force generated by the rudder as the force is at an angle to the longitudinal axis assuming the rudder is deflected to counteract the moment from the live engine an aft centre of gravity would reduce the perpendicular distance and so reduce the moment created by the rudder .vmca speed is cas based so engine thrust is reduced but control forces and effects on the rudder remain unaffected in a less dense atmosphere

Question 242-34 : The most aft cg location may be limited by .1 insufficient stick force stability.2 insufficient flare capability.3 excessive in flight manoeuvrability.4 insufficient in flight manoeuvrability.the combination that regroups all of the correct statements is ?

1 3

.because an aft cg equals less longitudinal stability makes the aircraft respond too rapidly which is the same thing as having too low a stick force per g and is the same thing as having too much manoeuvre ability and vice versa where a forward cg makes a sluggish aircraft and for example may leave you unable to raise the nose for landing exemple 474 1, 3.

Question 242-35 : An example of a combined lateral and directional aperiodic motion is a ?

Spiral dive

.a spin may be defined as an aggravated stall that results in what is termed 'autorotation' wherein the airplane follows a downward corkscrew path as the airplane rotates around a vertical axis the rising wing is less stalled than the descending wing creating a.rolling yawing and pitching motion the airplane is basically being forced downward by gravity rolling yawing and pitching in a spiral path . /com en/com080 684 jpg.'periodic' means recurring at regular intervals 'aperiodic' adds the greek prefix 'a' meaning 'not' or 'without' .'dutch roll' 'phugoid' and 'short period oscillation' are continuous oscillations with a period of oscillation a spiral dive is a continuous divergence exemple 478 Spiral dive.

Question 242-36 : An aeroplane's bank angle is defined as the angle between its ?

Lateral axis and the horizontal plane

exemple 482 Lateral axis and the horizontal plane.

Question 242-37 : Low speed pitch up can be caused by a significant thrust ?

Increase with podded engines located beneath a low mounted wing

. /com en/com080 690 jpg.low speed flight means an increasing angle of attack the centre of pressure moves forward the cg and the horizontal stabilizer must produce lift instead of producing a downforce in normal cruise flight .lift generates by the horizontal stabilizer is affected by the disturbed flow from the wing and if you increase thrust additional arm moment comes in force due to the podded engines located beneath the cg exemple 486 Increase with podded engines located beneath a low-mounted wing.

Question 242-38 : 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 up position for take off ?

Rotation will be normal using the normal rotation technique

.the forward cg limit is defined as the most nose heavy loading condition that will allow the aircraft to be rotated on takeoff and flared upon landing futhermore if trimmable horizontal stabiliser ths is positioned at the maximum allowable nose up position for take off rotation will be normal using the normal rotation technique exemple 490 Rotation will be normal using the normal rotation technique.

Question 242-39 : When a jet transport aeroplane takes off with the cg at the aft limit and the trimmable horizontal stabiliser ths is positioned at the maximum allowable nose up position for take off ?

Early nose wheel raising will take place

exemple 494 Early nose wheel raising will take place.

Question 242-40 : Negative tail stall is ?

A sudden reduction in the downward aerodynamic force on the tailplane

exemple 498 A sudden reduction in the downward aerodynamic force on the tailplane.


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