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Static and dynamic longitudinal stability 19
The aft CG limit can be determined by the: - ANSWER>>minimum acceptable static longitudinal stability.
What happens if the CG is located beyond the forward CG limit? - ANSWER>>This can lead to an unacceptably high value of manoeuvre stability.
The neutral point of an aeroplane is the point where: - ANSWER>>the aeroplane becomes longitudinally unstable when the CG is moved beyond it in an aft direction.
The max aft position of the centre of gravity is amongst others limited by the: - ANSWER>>minimum value of the stick force per g.
How can a pilot recognise static stick force stability in an aeroplane during flight? - ANSWER>>To maintain a speed above the trim speed requires a push force.
A phugoid refers to: - ANSWER>>dynamic longitudinal stability.
The stick force stability and the manoeuvre stability are positively affected by: - ANSWER>>A forward CG movement in case of the stick force stability and a forward CG movement in case of the manoeuvre stability.
Given an aeroplane in steady, straight and level flight at low speed and considering the effects of centre of gravity (CG) location and thrust, the highest value of wing lift occurs at: - ANSWER>>forward CG and low thrust.
If an aeroplane exhibits insufficient stick force per g, this problem can be resolved by installing: - ANSWER>>a bobweight in the control system which pulls the stick forwards.
Phugoid - ANSWER>>oscillations of a high amplitude
When an aeroplane with the centre of gravity forward of the centre of pressure of the combined wing/fuselage is in straight and level flight, the vertical load on the tailplane will be: - ANSWER>>downwards.
The purpose of the horizontal stabilizer is to: - ANSWER>>give the aeroplane sufficient longitudinal stability.
curva para abajo - ANSWER>>mayor estabilidad
The short period mode is an: - ANSWER>>oscillation about the lateral axis.
Which statement on dynamic longitudinal stability of a conventional aeroplane is correct? - ANSWER>>Damping of the phugoid is normally very weak.
- A requirement for positive static longitudinal stability of an aeroplane is, that the neutral point is behind the centre of gravity.
- A wing with positive camber provides a positive contribution to static longitudinal stability, when the centre of gravity of the aeroplane is in front of the aerodynamic centre of the wing. - ANSWER>>1) is correct,
- is correct.
A longitudinal dynamic oscillation can take two forms. One of these, the "long period oscillation", involves slow changes in: - ANSWER>>altitude and speed.
The contribution of the wing to the static longitudinal stability of an aeroplane: - ANSWER>>depends on CG location relative to the wing aerodynamic centre.
The air loads on the horizontal tailplane (tail load) of an aeroplane in straight and level cruise flight are generally directed: - ANSWER>>downwards and will reduce in magnitude as the CG moves aft.
Longitudinal static stability is created by the fact that the: - ANSWER>>centre of gravity is located in front of the neutral point of the aeroplane.
How does positive camber of an aerofoil affect static longitudinal stability? - ANSWER>>No effect, because camber of the aerofoil produces a constant pitch down moment coefficient, independent of angle of attack.
When you pull the yoke backwards, what happens? - ANSWER>>The elevator deflects up and increases the tailplanes negative angle of attack
An aeroplane exhibits static longitudinal stability, if, when the angle of attack increases: - ANSWER>>the change in total aeroplane lift acts aft of the CG.
An aircraft which has a higher static longitudinal stability, the longitudinal manoeuvrability is (1) _____, because the necessary elevator deflections are (2) _____. - ANSWER>>(1) reduced; (2) increased
Given an aeroplane in steady, straight and level flight at low speed and considering the effects of CG location and thrust, the lowest value of wing lift occurs at: - ANSWER>>aft CG and high thrust.
The CG of an aeroplane is in a fixed position forward of the neutral point. Which of these statements about the stick force stability is correct? - ANSWER>>An increase of 10 kt from the trimmed position at high speed has less effect on the stick force than an increase of 10 kt from the trimmed position at low speed.
If the centre of gravity moves forward, the stick force per g (1) _____ and the elevator authority (2) _____. - ANSWER>>(1) increases; (2) decreases
- insufficient in-flight manoeuvrability The combination that regroups all of the correct statements is: - ANSWER>>1, 3.
The aerodynamic centre of a wing is the point relative to which.. - ANSWER>>assuming no flow separation, the pitching moment coefficient does not change with varying Angle Of Attack.
Positive static longitudinal stability means that a: - ANSWER>>nose down moment occurs after encountering an upgust.
An aeroplane exhibits static longitudinal stability, if, when the angle of attack changes: - ANSWER>>the change in total aeroplane lift acts aft of the centre of gravity.
Longitudinal stability is directly influenced by: - ANSWER>>centre of gravity position.
Whilst in straight and level flight with the autopilot engaged, the aircraft begins to pick up some autopilot-induced oscillations. Which of the following will happen if the pilot does not intervene? - ANSWER>>Unwanted pitch and/or roll.
When an aircraft's Centre of Gravity (CG) is at the forward limit, the longitudinal static stability is (1) _____ and the pitch control forces are (2) _____ than when the CG is at the aft limit. - ANSWER>>(1) highest; (2) higher
A large jet aircraft is designed to be operated with a positive longitudinal stability and is equipped with a Fly-By-Wire (FBW) system. Prior to each flight, the pilots input the aircraft mass and CG location into the Flight Management System (FMS). The aircraft's FMS then informs the FBW system of this data, allowing for the correct control forces and limitations to be used, giving flight envelope protection and ensuring stability is maintained. Consider what will happen to the aircraft's high altitude handling characteristics if the pilot inputs the INCORRECT CG position into the FMS, located forward of the actual CG position. Which of the following statements is correct? - ANSWER>>The actual longitudinal stability is lower than calculated by the FBW system, and the system may allow for control surface deflections that result in instability.
Stick force per g: - ANSWER>>is dependent on CG location.
When is the airplane longitudinal stable? - ANSWER>>When the CG is in front of the CP/Neutral point
The maximum aft position of the centre of gravity is, amongst others, limited by the: - ANSWER>>required minimum value of the stick force per g.
The point between the aerodynamic centres of the wing and tail, where the... - ANSWER>>wing and tail moments are equal, is called Neutral Point.
An aft CG shift: - ANSWER>>increases longitudinal manoeuvrability.
Given an aeroplane in steady, straight and level flight at low speed and considering the effects of CG location and thrust, the highest value of wing lift occurs at: - ANSWER>>forward CG and low thrust.
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.
- ANSWER>>I is incorrect, II is correct.
A CG location beyond the forward limit can cause: - ANSWER>>an unacceptably high value of manoeuvre stability.
Long-period oscillation about the aeroplane's lateral axis with variations in pitch attitude, altitude and airspeed, with an aircraft constant angle of attack, is known as: - ANSWER>>Phugoid
During the initial climb-out an airplane has its trim in the neutral position. As the aircraft continues to climb, the pilot realises that the aircraft's elevator trim is stuck in the low speed range. Knowing that the aircraft is climbing with trimmed thrust, the pilot may expect the stick forces to ... - ANSWER>>decrease
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: - ANSWER>>upwards.
How can a pilot recognise static stick force stability in an aeroplane during flight? - ANSWER>>To maintain a speed below the trim speed requires a pull force.
The Cm (pitching moment) vs alpha (angle of attack) graph is mainly determined by aerofoil and aircraft design, and dictates aircraft longitudinal stability. Which of the following factors can the pilot influence whilst in flight?
- The centre of pressure, by changing the flap setting.
- The neutral point, by varying alpha.
- The centre of pressure, by varying alpha.
- The centre of gravity, which influences the degree of pitching moment. - ANSWER>>1 and 3
A forward CG shift: - ANSWER>>decreases longitudinal manoeuvrability.
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? - ANSWER>>(1) reduces, (2) reduces.
Aircraft certified under CS-23 and CS25 have to be able to show that they can avoid upset situations and unusual attitudes, as well as withstand and recover from them. Consider two identical aeroplanes, one with its CG at the FWD limit, the other with its CG at the AFT limit; which of the following statements is true regarding stability and manoeuvrability? - ANSWER>>Manoeuvrability reduces slightly with a FWD CG compared to an AFT CG.
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 longitudinal stability, when the centre of gravity of the aeroplane is in front of the aerodynamic centre of the wing. - ANSWER>>I is correct, II is correct.
For a statically stable aeroplane, the relationship between the neutral point and centre of gravity (CG) is such that the neutral point is located:
Choose the correct statement: - ANSWER>>The short period oscillation should always be heavily damped.
Pilot is trimming the aircraft during climb-out. At some point the trim gets stuck. Speed and power remain constant. What happens to stick force with increasing altitude? - ANSWER>>Decreases
The "short period mode" is an: - ANSWER>>oscillation about the lateral axis.
The most forward CG location may be limited by:
- insufficient flare capability.
- excessive in-flight manoeuvrability.
- insufficient in-flight manoeuvrability. The combination that regroups all of the correct statements is: - ANSWER>>1, 3
Which statement about stick force per g is correct? - ANSWER>>The stick force per g must have both an upper and lower limit in order to ensure acceptable control characteristics.
Consider a conventional aircraft with normal manoeuvring stability characteristics which does NOT require any augmentation. During initial climb, the elevator trim system remains stuck in the low speed regime with the aircraft's control surfaces trimmed in the neutral position. The aircraft continues to climb at the same speed with the throttles fixed on the trimmed thrust setting. How will the stick force be experienced by the pilot during climb if the load factor is kept constant? The pilot will...
- ANSWER>>experience a decrease in stick force for a similar control surface deflection.
Which part of an aeroplane provides the greatest positive contribution to static longitudinal stability? - ANSWER>>The horizontal tailplane.
The aerodynamic contribution to the static longitudinal stability of the nacelles of aft fuselage-mounted engines is.. - ANSWER>>always positive.
A pilot is performing a flight in an aeroplane with mechanical flight controls. The aeroplane makes one flight at its MTOM of 1900 kg with a CG near the aft limit. On the following flight, the pilot is the only occupant on board; the aeroplane is approximately 400 kg lighter and the CG has moved forward. How will this change the feel of the aircraft as experienced by the pilot? - ANSWER>>The stick force per g is
